WFO RAH Text Data |
FXUS62 KRAH 270350 CCA AFDRAH AREA FORECAST DISCUSSION...CORRECTION. NATIONAL WEATHER SERVICE RALEIGH NC 1015 PM EST SAT FEB 26 2005 .SYNOPSIS... WEAK HIGH PRESSURE WAS CENTERED OVER NE NC AT 00Z/27. A REINFORCING SHOT OF DRIER AIR WAS PUSHING SOUTH THROUGH N VA DRIVEN BY A 1030 MB SURFACE HIGH OVER MICHIGAN. DEW POINTS IN THE TEENS OVER N VA COMPARED TO 30S FROM RICHMOND SOUTHWARD. && SATELLITE INFORMATION... AT 00Z/27 FEB THE WATER VAPOR LOOP WAS INDICATING AN INCREASINGLY ACTIVE SUBTROPICAL JET EXTENDING FROM MEXICO NE ACROSS NW-N GULF AND OVER THE SOUTHEASTERN STATES. A CYCLONIC CIRCULATION WAS CENTERED OVER CENTRAL TEXAS MOVING NE. IR LOOP INDICATED CIRRUS THICKENING ACROSS GA-SC AND HEADING TOWARD SE NC. THE FORECAST OVERNIGHT INTO SUNDAY MORNING IS FOR THE SURFACE HIGH OVER MI TO GRADUALLY BUILD DOWN INTO NC. MUCH OF THE DRIER AIR IS NOT EXPECTED TO PUSH INTO CENTRAL NC UNTIL DURING THE DAY SUNDAY. THUS, LIGHT WINDS AND MAINLY CLEAR SKIES (SCATTERED TO THIN BROKEN CIRRUS AT TIMES)... WILL LEAD TO READINGS BY DAYBREAK CLOSE TO THE CURRENT DEW POINTS IN THE UPPER 20S TO AROUND 30. NO CHANGES NEEDED TO THE SHORT TERM. AS FOR THE IMPENDING STORM FOR SUNDAY NIGHT INTO MONDAY... THE 12Z/18Z MODEL MAJORITY DEPICTS A "MILLER TYPE A" SURFACE LOW THAT MOVES FROM THE NORTHERN GULF COAST SUNDAY TO A POSITION NEAR CHARLESTON SC AROUND 06Z/29 MON. THE 18Z GFS WAS STRONGEST... DEVELOPING A COASTAL BOMB MONDAY...(992 MB CAPE LOOKOUT 12Z/28... TO 987 OFF VA 18Z/28). THE NAM (OUTLIER ON THE LEFT SIDE OF ALL MODEL TRACKS (UP THE MOUNTAINS - PUTTING RDU IN THE SURFACE WARM SECTOR)... WAS DISCARDED... THE NAM H5 HEIGHTS WERE INITIALIZED MUCH TOO HIGH AT 12Z TODAY OVER TX AND NE MEXICO POSSIBLY CONTRIBUTING TO IT BEING AN OUTLIER SOLUTION. THUS... THE GFS CONTINUES TO TREND TOWARD THE MODEL MAJORITY (CANADIAN... ECMWF... UKMET) IN EMPHASIZING A STRONGER MILLER TYPE A COASTAL LOW... INCREASING THE THREAT OF SIGNIFICANT FROZEN PRECIPITATION OVER THE CLIMATOLOGICALLY PREFERRED PIEDMONT OF NC WITH THIS EVENT. WE DEFERRED UNTIL AFTER THE 00Z/27 RUNS ARE ALL IN BEFORE THE ISSUANCE OF A WINTER STORM WATCH NW... BUT IF THE MODEL TRENDS CONTINUE THIS AFOREMENTIONED SCENARIO FOCUSING DEVELOPMENT OF A PRIMARY COASTAL LOW TRACKING JUST OFFSHORE OF CHS TO CAPE LOOKOUT... THEN HEAVY WET SNOW OVER THE NW-N PIEDMONT WILL BE POSSIBLE. ONE MAJOR FACTOR FOR HEAVY SNOW MAY BE THE LACK OF SUPPLY OF LOW LEVEL COLD AIR... AS ALL MODELS INDICATE THE PARENT HIGH TO BE ON THE WEAK SIDE (1028 MB) AND TRANSIENT (MOVES OFFSHORE QUICKLY AS THE STORM APPROACHES). THUS... THE DYNAMICS OF THE SYSTEM WILL HAVE TO GENERATE COLD AIR... AND THE DEEPENING STORM WILL HAVE TO TAP INTO THE COLD AIR THAT WILL BE IN PLACE JUST TO OUR NORTH. THE 18Z GFS INDICATED THE H85 LOW TRACK OVER E SC AND SE NC... AND THE H7 TRACK FROM SE OF CLT TO NEAR OR JUST SE OF RALEIGH TO ROANOKE RAPIDS. THE H7 LOW BEGAN TO CLOSE OFF NEAR RDU AROUND 12Z MONDAY... INDICATING THE POTENTIAL FOR HEAVY SNOW BANDING NORTHWEST AND NORTH OF RDU. A DESTINCTIVE COLD NOSE DEVELOPS IN THE NW PIEDMONT JUST ABOVE SURFACE LEVEL... WITH SOME COOLING FORECAST IN THE MID LAYERS. THE MID LEVEL WARMING OCCURS OVER EASTERN NC. PARTIAL THICKNESSES FOR GSO ON THE 18Z/GFS INDICATED 1000/850 AND 850/700 THICKNESSES (AROUND 1290 TO 1295/ 1540-1544)... BETWEEN 06Z-15Z/28 SUPPORTING ACCUMULATING SNOW AND SLEET DURING THE HEART OF THE EVENT. PARTIALS INDICATED A NARROW TRANSITION ZONE FROM FROZEN TO LIQUID OVER THE E-S PIEDMONT... TO RAIN ELSEWHERE. QPF FORECASTS INDICATE 0.50 TO POTENTIALLY 1.25 INCHES (LIQUID EQUIVALENT) OVER CENTRAL NC. FOR NOW... THE MODEL MODEL MAJORITY / GFS TRACK AND STRENGTH ARE FAVORED. THUS, A WINTER STORM WATCH IS BEING CONSIDERED FOR THE PIEDMONT TRIAD REGION... AND AS FAR SOUTH AS ALBEMARLE... HIGH ROCK... ASHEBORO... BURLINGTON... AND ROXBORO FOR ACCUMULATING SNOW AND SLEET SUNDAY NIGHT INTO EARLY MONDAY. A COLD RAIN APPEARS LIKELY ELSEWHERE... WITH A NARROW TRANSITION ZONE SOMEWHERE OVER THE EASTERN PIEDMONT DURING THE EVENT. MUCH MORE TO COME.... && .PREVIOUS DISCUSSION... (ISSUED 230 PM EST SAT FEB 26 2005) SUN NGT-MON...THE GFS/CANADIAN/UKMET/ECMWF ARE NOW CONVERGING MORE TOWARD A MAIN COASTAL LOW MILLER-A CYCLOGENESIS SOLUTION. WE WILL BE LEANING TOWARD THE DETAILS OF THE GFS MOISTURE AND THERMAL STRUCTURE...NOTING THIS IS THE COLDEST RUN OF THE LAST THREE BUT IN LINE WITH UKMET/ECMWF BULK THICKNESS (1000-500). THIS SUGGESTS MIXED P-TYPES IN THE NW QUADRANT AND AT THE ONSET IN THE NORTHEAST PDMT. A STATEMENT WILL BE ISSUED CALLING FOR A 1-2 INCH POTENTIAL OF SNOW/SLEET MIX WITH RAIN IN THE NW PDMT...AN UP TO A HALF INCH BEFORE CHANGEOVER TO RAIN IN THE NE PDMT. LOWS 33-35 IN THE NW THIRD GRADUATING UP TO 42 IN SAMPSON-WAYNE. HEAVIEST PCPN SHOULD EBB AROUND 10 AM AS THE 850 LOW MOVES NORTH OF CAPE LOOKOUT AND THE EASTERLY LOW LEVEL JET TRANSLATES NORTH OF THE CWA. A LOOSE PRESSURE TROUGH IN THE WAKE OF THE LOW SHOULD ALLOW LOW CLOUDS AND DRIZZLE OR SPRINKLES TO LINGER INTO LATE AFTERNOON HOLDING TEMPERATURES NEAR 40 NW TO NEAR 50 SE. MON NGT-TUE...COLD DRY NW FLOW SETS IN WITH MOSTLY CLEAR SKIES AND BELOW NORMAL TEMPERATURES. 850 TEMPERATURES REMAIN MINUS 5-MINUS 10 ON TUE. LOWS 30-35. HIGHS MID-UPPER 40S. LONG TERM (MONDAY NIGHT THROUGH SATURDAY)... UPPER TROF REMAINS IN PLACE THROUGH WEDNESDAY AND CAA ACCOMPANYING THE SHORT WAVE ROTATING THROUGH TUESDAY NIGHT INTO WEDNESDAY SHOULD BE ENOUGH TO INDUCE CONSIDERABLE STRATOCUMULUS...ESPECIALLY ACROSS THE NORTHERN TIER. HIGHS WEDNESDAY 45 TO 50. SUNNY THURSDAY AS WEAK RIDGING BUILDS IN BRIEFLY FROM THE WEST...A BIT OF REBOUND ON THE AFTERNOON HIGHS TO 50 TO 55. WILL NOT BITE ON POPS THIS EARLY FOR THE POTENTIAL SYSTEM WHICH IS DIGGING SOUTHEAST ACROSS THE MOUNTAINS LATE FRIDAY AS TIMING THE UPPER IMPULSES IN NORTHWEST IS NOT A HIGH OR EVEN A MEDIUM CONFIDENCE EVENT AT THAT RANGE. FAIR AMOUNTS OF MID/HIGH CLOUDINESS DO LOOK TO BE IN THE STREAM FOR BOTH DAYS. AVIATION... CLEAR SKIES AND LIGHT TO CALM WINDS EARLY TONIGHT MAY LEAD TO BRIEF MVFR VISIBILITIES IN THE 11-13Z TIME FRAME. THINK THAT PROGRESSIVELY THICKENING HIGH CLOUDINESS OVERNIGHT SHOULD DELAY THE RADIATION PROCESS...HOWEVER...SO WILL FORECAST VFR THROUGH THE TAF PERIOD. INCREASING/THICKENING MID CLOUDINESS WILL BE ON TAP TOMORROW AFTERNOON...JUST BEYOND THE TAFS 18Z ENDING TIME. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS... SHORT TERM...BADGETT/HARTFIELD/TDP FXUS62 KRAH 270729 AFDRAH AREA FORECAST DISCUSSION...PRELIMINARY. NATIONAL WEATHER SERVICE RALEIGH NC 220 AM EST SUN FEB 27 2005 .SHORT TERM (TODAY THROUGH MONDAY)... .SYNOPSIS... WEAK HIGH PRESSURE WAS CENTERED OVER NC AT 06Z/27. A REINFORCING SHOT OF DRIER AIR WAS PUSHING SOUTH THROUGH VA DRIVEN BY A 1030 MB SURFACE HIGH OVER MICHIGAN. A DEVELOPING STORM SYSTEM WAS LOCATED OVER THE WESTERN GULF OF MEXICO. && .TODAY THROUGH MONDAY... THE REAL CONCERN BEGINS AROUND SUNSET TONIGHT AS THE MODEL MAJORITY/ GFS TRACK AND STRENGTH ARE STILL FAVORED AFTER THIS EVENINGS MODEL RUN... WITH THE DEVELOPING GULF OF MEXICO STORM. A WINTER STORM WATCH WILL BE ISSUED FOR THE PIEDMONT TRIAD REGION... NORTHEAST TO ROXBORO FOR ACCUMULATING SNOW TONIGHT INTO MONDAY MORNING. A COLD RAIN APPEARS LIKELY ELSEWHERE... WITH A NARROW TRANSITION ZONE SOMEWHERE OVER THE EASTERN PIEDMONT DURING THE EVENT. IT IS STRESSED THAT A STORM TRACK DEVIATION OF 50 MILES OR SO FARTHER EAST COULD BRING ACCUMULATING SNOW TO THE RALEIGH-DURHAM AREA. THIS IS STILL POSSIBLE GIVEN THE RECENT COLDER TRENDS IN THE MODEL RUNS. THE LATEST DATA ANALYSIS AND 00Z/27 FEBRUARY MODEL RUNS CONTINUE TO POINT TO A "MILLER A" TYPE SFC COASTAL CYCLOGENESIS TODAY THROUGH MONDAY FROM THE GULF OF MEXICO... NE ACROSS THE FL PANHANDLE... AND UP THE COAST OF SC/NC. THE 00Z/27 NAM TRACK CONTINUED TO BE ON THE LEFT SIDE OF ALL GUIDANCE... BUT CONTINUED TO TREND TOWARD THE MODEL MAJORITY OF A SIGNIFICANT COASTAL STORM. HPC CONTINUED TO SUPPORT THE GFS WITH THIS SYSTEM AS IT HAS BEEN THE MOST CONSISTENT RUN TO RUN IN THE PAST 24 HOURS. A LITTLE QUICKER ACCELERATION OF THE STORM IS ALSO PREFERRED AS TRENDED BY THE LAST SEVERAL GFS RUNS. WITH THE GFS BEING THE PREFERRED MODEL FOR THIS DEVELOPING STORM... THE FORECAST STORM TRACK STRONGLY SUGGESTS ACCUMULATING SNOW OVER PORTIONS OF THE NORTHWEST-NORTH PIEDMONT... ESPECIALLY OVER THE PIEDMONT TRIAD REGION EAST TO NEAR ROXBORO. THE FORECAST H85 AND H7 LOW PRESSURE CENTER TRACKS FROM NEAR CHARLOTTE TO RALEIGH AND ROANOKE RAPIDS TONIGHT AND MONDAY MORNING... IMPLYING THE P-TYPE TRANSITION ZONE WILL BE IN THAT GENERAL AREA... WITH ACCUMULATING SNOW JUST WEST-NORTH OF THE TRACK. THE 00Z/28 GFS H7 LOW FORECAST TRACK WAS SLIGHTLY WEST OF THE PREVIOUS TRACK... BUT STILL INDICATING THE MID LEVEL WARM NOSE TO MAINLY RUN UP THE COASTAL PLAIN OR FAR EASTERN PIEDMONT... WITH A PIVOT POINT AROUND RALEIGH... IMPLYING A VERY TIGHT NARROW P-TYPE TRANSITION ZONE TO BE IN THAT GENERAL LOCATION. TO THE NW... THE COLD AIR IS DEEPER WITH THE LATEST GFS RUNS INDICATING A SIGNIFICANT LOW LEVEL COLD NOSE AROUND 925 MB EXTENDING FROM CENTRAL VIRGINIA S-SW TOWARD GSO/INT... WITH CORRESPONDING LOW LEVEL THICKNESSES FALLING TO BETWEEN 1288 AND 1295 DURING THE 03Z-12Z MON TIME FRAME (DURING THE MAXIMUM QPF). CORRESPONDING MID LEVEL THICKNESSES AT GSO TO ROX DROP BELOW 1535. THE ONLY MISSING INGREDIENT FOR A CLASSICAL WINTER STORM IS THE LACK OF A STRONG PARENT SFC HIGH PRESSURE TO OUR N-NE. THERE IS A RATHER WEAK SURFACE HIGH (1028 MB) TODAY AND TONIGHT IN A FAVORED LOCATION TO DELIVER COLD DRY LOW LEVEL AIR... BUT THE HIGH IS FORECAST TO MOVE QUICKLY EAST TONIGHT AS THE PRECIP ROLLS IN. THUS... THIS IS NOT A CLASSICAL COLD AIR DAMMING SET UP. WE WILL HAVE TO RELY ON DYNAMICAL COOLING WITH THE STRENGTHENING MID LEVEL SYSTEM... AND THE TAPPING OF COLDER AIR OVER VIRGINIA INTO THE NC PIEDMONT REGION AS THE SFC STORM STRENGTHENS... AND MOVES UP THE SC/NC COAST TONIGHT ... THIS SUPPORTS THE SIGNIFICANT SNOW IN THE CLIMATOLOGICALLY PREFERRED NW-N PIEDMONT REGIONS. PARTIAL THICKNESS NOMOGRAMS ALSO SUPPORT THE MEASURABLE AND SIGNIFICANT SNOW THEME NW-N WITH A NARROW TRANSITION ZONE TO RAIN MIXED WITH SNOW OVER THE EASTERN AND SOUTHERN PIEDMONT... WITH ALL RAIN EAST AND SOUTH OF RDU. IF THE H7 LOW CLOSES OFF BEFORE EXITING TO THE NE EARLY MONDAY MORNING... THERE SHOULD BE HEAVY SNOW JUST NW OF ITS TRACK. LOOKING BACK INTO THE DOCUMENTED CASE STUDIES OF PREVIOUS WINTER WEATHER EVENTS (KEETER FILES)... THE CURRENT FORECAST PARTIAL THICKNESSES SUPPORT MEASURABLE SNOWFALL AT GSO. RDU HAS HAD MOSTLY RAIN EVENTS... SOME MIXED WITH MEASURABLE SNOW... GIVEN SIMILAR PARTIALS. QPF SHOULD AVERAGE AT LEAST 0.50 TO 1.00 INCHES WITH THIS EVENT... GIVEN THE FORECAST STRENGTH AND TRACK. MOST SHOULD OCCUR BETWEEN 02Z-15Z TONIGHT AND MONDAY. SNOWFALL ACCUMULATIONS SHOULD REACH 3-6 INCHES IN THE WATCH AREA... POSSIBLY AS HIGH AS 8 INCHES IN LOCAL AREAS. THE GROUND TEMPS HAVE COOLED IN RECENT DAYS DUE TO THE RECENT SOAKING RAIN EVENT... AND THE COLDER NIGHTS IN THE 20S. THE SOIL TEMPS WERE STILL IN THE LOWER 40S OVER THE NW PIEDMONT... INDICATING THAT SNOW ACCUMULATIONS WOULD MELT SOME FROM BELOW. ROAD TEMPS ARE ALSO LIKELY TO BE ABOVE 32 UNTIL WELL AFTER THE PRECIP BEGINS... INDICATING WET ROADS BECOMING SLUSHY AS THE SNOW EVENT UNFOLDS. FOR NOW... A WINTER STORM WATCH WILL BE ISSUED FOR 3-6 INCHES OF SNOW ACCUMULATION TONIGHT THROUGH 15Z/MONDAY FOR FORSYTH... GUILFORD... DAVIDSON... RANDOLPH... ALAMANCE... ORANGE... AND PERSON COUNTIES... (THE CLIMATOLOGICALLY PREFERRED AREA WITH THIS STORM TRACK). PRECIP MAY BEGIN AS LIGHT RAIN... BUT QUICKLY CHANGE TO WET SNOW AS THE STRONG DYNAMICAL COOLING DEVELOPS. A ONE-TWO COUNTY TRANSITION BUFFER ZONE WILL COVER AREAS JUST EAST AND SOUTH OF THESE COUNTIES INCLUDING AREAS FROM ALBEMARLE TO SANFORD... RALEIGH... AND ROANOKE RAPIDS... WHERE RAIN WILL LIKELY OCCASIONALLY MIX WITH SNOW... SOME ACCUMULATION WILL BE POSSIBLE AND A WINTER WEATHER ADVISORY MAY BE NEEDED TONIGHT. RAIN IS EXPECTED EAST AND SOUTH OF RALEIGH. THE RAIN MAY CHANGE TO SNOW BEFORE THE STEADY PRECIP TAPERS OFF FROM SW TO NE MONDAY MORNING... FOLLOWED BY COLD WINDY WEATHER MONDAY NIGHT AND TUESDAY. IT SHOULD BE STRESSED THAT IF THE FORECAST STORM TRACK DEVIATES ONLY 25 TO 50 MILES IN EITHER DIRECTION... IT WILL HAVE HUGE IMPLICATIONS ON THE LOCATION OF THE P-TYPE TRANSITION ZONE SET UP AND SNOW ACCUMULATIONS. A TRACK FARTHER EAST WILL LIKELY BRING SIGNIFICANT SNOW TO RALEIGH-DURHAM... AND A TRACK MORE LIKE THE NAM WILL LIMIT SNOW TO THE BLUE RIDGE MOUNTAINS ONLY. STAY TUNED ON THIS ONE AS IT HAS THE POTENTIAL TO BRING A MAJOR WET SNOW EVENT OVER MUCH OF THE W-N PIEDMONT... WHICH MAY EXTEND FURTHER SOUTH AND EAST THAN WHAT IS CURRENTLY FORECAST. && .LONG TERM (MONDAY NIGHT THROUGH SATURDAY)... MID LEVEL LOW CLOSES OFF OVER THE MIDWEST EARLY IN THE PERIOD AS DEEP COLD AIR FILTERS INTO THE STATE. VORT AXIS SWINGS THROUGH BY TUE MORNING & WITH LOW LEVEL FLOW REMAINING STRONG FROM THE WSW... THIS ENERGY MAY BE ENOUGH TO SQUEEZE OUT A SPRINKLE OR SNOW SHOWER... IF THE LIFT CAN SATURATE THE PRIME DEDRITE GROWTH REGION ALOFT. THE CLOSED VORTEX MOVES TOWARD NEW ENGLAND WHEN A SECOND STRONG VORT MAX DROPS INTO THE TROUGH BASE... THROUGH NC... ON WED. AGAIN MOISTURE WILL BE LIMITED... THUS WILL KEEP CONDITIONS DRY... BUT IT REMAINS QUITE CHILLY WITH LOW LEVEL THICKNESSES PROGGED BY THE NAM & GFS TO BE IN THE 1260S-1270S ALL DAY WED. EXPECT A DRY NORTHWEST LOW LEVEL FLOW THEN THU-SAT AS THE LOW ALOFT MOVES INTO THE CANADIAN MARITIMES & THE HIGH PRESSURE AREA BUILDING INTO NC FROM THE WNW MODERATES SOMEWHAT. && .AVIATION... TERMINAL FORECASTS DEPICT A THICKENING AND LOWERING OF THE HIGH AND MID CLOUDS TONIGHT INTO SUN MORNING. HAVE BROUGHT CIGS DOWN TO MVFR BY 18Z (SOUTH) TO 21Z (NORTH) AND SPED UP PRECIP ONSET TO 21Z-00Z SOUTH TO NORTH... AS CIGS/VSBYS GO IFR. && .RAH WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FOR NCZ007- 021>024-038-039 FROM 6 PM SUNDAY TO 10AM MONDAY. && $$ SHORT TERM...BADGETT/GIH/RHJ/RLH LONG TERM...HARTFIELD AVIATION...HARTFIELD/RLH FXUS62 KRAH 270818 AAA AFDRAH AREA FORECAST DISCUSSION...FINAL. NATIONAL WEATHER SERVICE RALEIGH NC 319 AM EST SUN FEB 27 2005 .SHORT TERM (TODAY THROUGH MONDAY)... .SYNOPSIS... WEAK HIGH PRESSURE WAS CENTERED OVER NC AT 06Z/27. A REINFORCING SHOT OF DRIER AIR WAS PUSHING SOUTH THROUGH VA DRIVEN BY A 1030 MB SURFACE HIGH OVER MICHIGAN. A DEVELOPING SFC STORM SYSTEM WAS LOCATED OVER THE CENTRAL GULF OF MEXICO. && .TODAY THROUGH MONDAY... THE WATER VAPOR LOOP/UPPER AIR ANALYSIS INDICATE A STRONG SOUTHERN BRANCH JET OVER NRN MEXICO/S TX EXTENDING ACROSS NC. A MID LEVEL VORTEX WAS OVER THE RED RIVER. A POLAR VORTEX WAS DIGGING SOUTH INTO ND FROM CANADA. THE CURRENT INDICATIONS ARE THAT THE SOUTHERN BRANCH SYSTEM OVER THE RED RIVER WILL RACE EAST AHEAD OF THE DIGGING POLAR VORTEX... FAVORING THE LATEST GFS/ECMWF/UKMET FOR THE SE COASTAL STORM. TODAY... EXPECT LOWERING AND THICKENING CLOUDS WITH TEMPS IN THE LOWER TO MID 40S. THE REAL CONCERN BEGINS AROUND SUNSET TONIGHT AS THE MODEL MAJORITY/ GFS TRACK AND STRENGTH ARE STILL FAVORED AFTER THIS EVENINGS MODEL RUN... WITH THE DEVELOPING GULF OF MEXICO STORM. A WINTER STORM WATCH WILL BE ISSUED FOR THE PIEDMONT TRIAD REGION... NORTHEAST TO ROXBORO FOR ACCUMULATING SNOW TONIGHT INTO MONDAY MORNING. A COLD RAIN APPEARS LIKELY ELSEWHERE... WITH A NARROW TRANSITION ZONE SOMEWHERE OVER THE EASTERN PIEDMONT DURING THE EVENT. IT IS STRESSED THAT A STORM TRACK DEVIATION OF 50 MILES OR SO FARTHER EAST COULD BRING ACCUMULATING SNOW TO THE RALEIGH-DURHAM AREA. THIS IS STILL POSSIBLE GIVEN THE RECENT COLDER TRENDS IN THE MODEL RUNS. THE LATEST DATA ANALYSIS AND 00Z/27 FEBRUARY MODEL RUNS CONTINUE TO POINT TO A "MILLER A" TYPE SFC COASTAL CYCLOGENESIS TODAY THROUGH MONDAY FROM THE GULF OF MEXICO... NE ACROSS THE FL PANHANDLE... AND UP THE COAST OF SC/NC. THE 00Z/27 NAM TRACK CONTINUED TO BE ON THE LEFT SIDE OF ALL GUIDANCE... BUT CONTINUED TO TREND TOWARD THE MODEL MAJORITY OF A SIGNIFICANT COASTAL STORM. HPC CONTINUED TO SUPPORT THE GFS WITH THIS SYSTEM AS IT HAS BEEN THE MOST CONSISTENT RUN TO RUN IN THE PAST 24 HOURS. A LITTLE QUICKER ACCELERATION OF THE STORM IS ALSO PREFERRED AS TRENDED BY THE LAST SEVERAL GFS RUNS. WITH THE GFS BEING THE PREFERRED MODEL FOR THIS DEVELOPING STORM... THE FORECAST STORM TRACK STRONGLY SUGGESTS ACCUMULATING SNOW OVER PORTIONS OF THE NORTHWEST-NORTH PIEDMONT... ESPECIALLY OVER THE PIEDMONT TRIAD REGION EAST TO NEAR ROXBORO. THE FORECAST H85 AND H7 LOW PRESSURE CENTER TRACKS FROM NEAR CHARLOTTE TO RALEIGH AND ROANOKE RAPIDS TONIGHT AND MONDAY MORNING... IMPLYING THE P-TYPE TRANSITION ZONE WILL BE IN THAT GENERAL AREA... WITH ACCUMULATING SNOW JUST WEST-NORTH OF THE TRACK. THE 00Z/28 GFS H7 LOW FORECAST TRACK WAS SLIGHTLY WEST OF THE PREVIOUS TRACK... BUT STILL INDICATING THE MID LEVEL WARM NOSE TO MAINLY RUN UP THE COASTAL PLAIN OR FAR EASTERN PIEDMONT... WITH A PIVOT POINT AROUND RALEIGH... IMPLYING A VERY TIGHT NARROW P-TYPE TRANSITION ZONE TO BE IN THAT GENERAL LOCATION. TO THE NW... THE COLD AIR IS DEEPER WITH THE LATEST GFS RUNS INDICATING A SIGNIFICANT LOW LEVEL COLD NOSE AROUND 925 MB EXTENDING FROM CENTRAL VIRGINIA S-SW TOWARD GSO/INT... WITH CORRESPONDING LOW LEVEL THICKNESSES FALLING TO BETWEEN 1288 AND 1295 DURING THE 03Z-12Z MON TIME FRAME (DURING THE MAXIMUM QPF). CORRESPONDING MID LEVEL THICKNESSES AT GSO TO ROX DROP BELOW 1535. THE ONLY MISSING INGREDIENT FOR A CLASSICAL WINTER STORM IS THE LACK OF A STRONG PARENT SFC HIGH PRESSURE TO OUR N-NE. THERE IS A RATHER WEAK SURFACE HIGH (1028 MB) TODAY AND TONIGHT IN A FAVORED LOCATION TO DELIVER COLD DRY LOW LEVEL AIR... BUT THE HIGH IS FORECAST TO MOVE QUICKLY EAST TONIGHT AS THE PRECIP ROLLS IN. THUS... THIS IS NOT A CLASSICAL COLD AIR DAMMING SET UP. WE WILL HAVE TO RELY ON DYNAMICAL COOLING WITH THE STRENGTHENING MID LEVEL SYSTEM... AND THE TAPPING OF COLDER AIR OVER VIRGINIA INTO THE NC PIEDMONT REGION AS THE SFC STORM STRENGTHENS... AND MOVES UP THE SC/NC COAST TONIGHT ... THIS SUPPORTS THE SIGNIFICANT SNOW IN THE CLIMATOLOGICALLY PREFERRED NW-N PIEDMONT REGIONS. PARTIAL THICKNESS NOMOGRAMS ALSO SUPPORT THE MEASURABLE AND SIGNIFICANT SNOW THEME NW-N WITH A NARROW TRANSITION ZONE TO RAIN MIXED WITH SNOW OVER THE EASTERN AND SOUTHERN PIEDMONT... WITH ALL RAIN EAST AND SOUTH OF RDU. IF THE H7 LOW CLOSES OFF BEFORE EXITING TO THE NE EARLY MONDAY MORNING... THERE SHOULD BE HEAVY SNOW JUST NW OF ITS TRACK. LOOKING BACK INTO THE DOCUMENTED CASE STUDIES OF PREVIOUS WINTER WEATHER EVENTS (KEETER FILES)... THE CURRENT FORECAST PARTIAL THICKNESSES SUPPORT MEASURABLE SNOWFALL AT GSO. RDU HAS HAD MOSTLY RAIN EVENTS... SOME MIXED WITH MEASURABLE SNOW... GIVEN SIMILAR PARTIALS. QPF SHOULD AVERAGE AT LEAST 0.50 TO 1.00 INCHES WITH THIS EVENT... GIVEN THE FORECAST STRENGTH AND TRACK. MOST SHOULD OCCUR BETWEEN 02Z-15Z TONIGHT AND MONDAY. SNOWFALL ACCUMULATIONS SHOULD REACH 3-6 INCHES IN THE WATCH AREA... POSSIBLY AS HIGH AS 8 INCHES IN LOCAL AREAS. THE GROUND TEMPS HAVE COOLED IN RECENT DAYS DUE TO THE RECENT SOAKING RAIN EVENT... AND THE COLDER NIGHTS IN THE 20S. THE SOIL TEMPS WERE STILL IN THE LOWER 40S OVER THE NW PIEDMONT... INDICATING THAT SNOW ACCUMULATIONS WOULD MELT SOME FROM BELOW. ROAD TEMPS ARE ALSO LIKELY TO BE ABOVE 32 UNTIL WELL AFTER THE PRECIP BEGINS... INDICATING WET ROADS BECOMING SLUSHY AS THE SNOW EVENT UNFOLDS. FOR NOW... A WINTER STORM WATCH WILL BE ISSUED FOR 3-6 INCHES OF SNOW ACCUMULATION TONIGHT THROUGH 15Z/MONDAY FOR FORSYTH... GUILFORD... DAVIDSON... RANDOLPH... ALAMANCE... ORANGE... AND PERSON COUNTIES... (THE CLIMATOLOGICALLY PREFERRED AREA WITH THIS STORM TRACK). PRECIP MAY BEGIN AS LIGHT RAIN... BUT QUICKLY CHANGE TO WET SNOW AS THE STRONG DYNAMICAL COOLING DEVELOPS. A ONE-TWO COUNTY TRANSITION BUFFER ZONE WILL COVER AREAS JUST EAST AND SOUTH OF THESE COUNTIES INCLUDING AREAS FROM ALBEMARLE TO SANFORD... RALEIGH... AND ROANOKE RAPIDS... WHERE RAIN WILL LIKELY OCCASIONALLY MIX WITH SNOW... SOME ACCUMULATION WILL BE POSSIBLE AND A WINTER WEATHER ADVISORY MAY BE NEEDED TONIGHT. RAIN IS EXPECTED EAST AND SOUTH OF RALEIGH. THE RAIN MAY CHANGE TO SNOW BEFORE THE STEADY PRECIP TAPERS OFF FROM SW TO NE MONDAY MORNING... FOLLOWED BY COLD WINDY WEATHER MONDAY NIGHT AND TUESDAY. IT SHOULD BE STRESSED THAT IF THE FORECAST STORM TRACK DEVIATES ONLY 25 TO 50 MILES IN EITHER DIRECTION... IT WILL HAVE HUGE IMPLICATIONS ON THE LOCATION OF THE P-TYPE TRANSITION ZONE SET UP AND SNOW ACCUMULATIONS. A TRACK FARTHER EAST WILL LIKELY BRING SIGNIFICANT SNOW TO RALEIGH-DURHAM... AND A TRACK MORE LIKE THE NAM WILL LIMIT SNOW TO THE BLUE RIDGE MOUNTAINS ONLY. STAY TUNED ON THIS ONE AS IT HAS THE POTENTIAL TO BRING A MAJOR WET SNOW EVENT OVER MUCH OF THE W-N PIEDMONT... WHICH MAY EXTEND FURTHER SOUTH AND EAST THAN WHAT IS CURRENTLY FORECAST. && .LONG TERM (MONDAY NIGHT THROUGH SATURDAY)... MID LEVEL LOW CLOSES OFF OVER THE MIDWEST EARLY IN THE PERIOD AS DEEP COLD AIR FILTERS INTO THE STATE. VORT AXIS SWINGS THROUGH BY TUE MORNING & WITH LOW LEVEL FLOW REMAINING STRONG FROM THE WSW... THIS ENERGY MAY BE ENOUGH TO SQUEEZE OUT A SPRINKLE OR SNOW SHOWER... IF THE LIFT CAN SATURATE THE PRIME DEDRITE GROWTH REGION ALOFT. THE CLOSED VORTEX MOVES TOWARD NEW ENGLAND WHEN A SECOND STRONG VORT MAX DROPS INTO THE TROUGH BASE... THROUGH NC... ON WED. AGAIN MOISTURE WILL BE LIMITED... THUS WILL KEEP CONDITIONS DRY... BUT IT REMAINS QUITE CHILLY WITH LOW LEVEL THICKNESSES PROGGED BY THE NAM & GFS TO BE IN THE 1260S-1270S ALL DAY WED. EXPECT A DRY NORTHWEST LOW LEVEL FLOW THEN THU-SAT AS THE LOW ALOFT MOVES INTO THE CANADIAN MARITIMES & THE HIGH PRESSURE AREA BUILDING INTO NC FROM THE WNW MODERATES SOMEWHAT. && .AVIATION... TERMINAL FORECASTS DEPICT A THICKENING AND LOWERING OF THE HIGH AND MID CLOUDS TONIGHT INTO SUN MORNING. HAVE BROUGHT CIGS DOWN TO MVFR BY 18Z (SOUTH) TO 21Z (NORTH) AND SPED UP PRECIP ONSET TO 21Z-00Z SOUTH TO NORTH... AS CIGS/VSBYS GO IFR. && .RAH WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FOR NCZ007- 021>024-038-039 FROM 6 PM SUNDAY TO 10AM MONDAY. && $$ SHORT TERM...BADGETT/GIH/RHJ/RLH LONG TERM...HARTFIELD AVIATION...HARTFIELD/RLH FXUS62 KRAH 271544 AAA AFDRAH AREA FORECAST DISCUSSION...UPDATE NATIONAL WEATHER SERVICE RALEIGH NC 1045 AM EST SUN FEB 27 2005 .SHORT TERM (REST OF TODAY THROUGH MONDAY)... INCREASED SKY COVERAGE TO OVERCAST DUE TO CIRRUS CANOPY CURRENTLY OVERHEAD AND GRADUALLY INCREASE IN MID LAYER DECK FROM THE SOUTH THIS AFTERNOON. 15Z TEMPS CURRENTLY 4-6 DEGREES FROM FORECAST MAX TEMPS...SO LITTLE CHANGE REQUIRED IN THAT DEPARTMENT. FOR TONIGHT AND MONDAY....WHILE STILL AWAITING THE 12Z GFS...CALLED AROUND REGION TO GET A FEEL FOR SOIL AND ROAD TEMPS. IN NW PIEDMONT SOIL TEMPS AROUND 40 TOT HE LOWER 40S WHILE ROAD SURFACE TEMPS IN THE MID 40S. FARTHER E AND S....SOIL TEMPS WARM TO THE MID 40S WHILE ROAD SURFACE TEMPS ARE IN THE UPPER 40S TO LOWER 50S. THUS APPEARS THAT THERE IS THE POTENTIAL FOR SNOW TO STICK/ACCUMULATE ON GROUND AND ROAD SURFACE IN THE NW PIEDMONT...ESPECIALLY IF HEAVY BANDS OF PRECIP OCCUR WHICH IS HIGHLY PROBABLE DUE TO CLOSED H7 CYCLONE JUST SE OF AREA OVERNIGHT/EARLY MON. ROADS OVER THE REMAINDER OF THE PIEDMONT MAY INITIALLY BE WET WITH SLUSH DEVELOPING IN AREAS THAT EXPERIENCE HEAVY BANDS. AT THIS TIME PLAN WILL LET WATCH RIDE AS IS FOR NOW. PRESENT THINKING IS TO UPGRADE WATCH TO A WARNING SOME TIME EARLY THIS AFTERNOON (ONCE 12Z GFS IS IN AND HOPEFULLY CONSISTENT WITH PREVIOUS RUNS)...HOPEFULLY BEFORE 3 PM. BASED ON STORM TRACK AND PARTIAL THICKNESSES...MAY NEED TO EXTEND WATCH/WARNING A LITTLE FARTHER SOUTH AND EAST. WILL NEED TO COORDINATE THIS WITH WFO NEIGHBORS W AND N OF RAH. IF CURRENT PATTERN AND STRONG DYNAMICS AND PLENTIFUL MOISTURE CONTINUE...POTENTIAL FOR HEAVY SNOW (EXCESS OF 6 INCHES)OVER NW PIEDMONT APPEARS LIKELY. FINAL NOTE...THE MAIN CONCERN/FLY IN THE OINTMENT ITO THE ABOVE SCENARIO IS THE LACK OF A COLD AIR SOURCE. POTENTIAL FOR LOW/MID LEVEL FLOW TO PUMP ENOUGH WARM AIR INTO THE NW PIEDMONT TO KEEP P-TYPE A SNOW/RAIN MIX...CUTTING DOWN ON SNOW ACCUMULATION TOTALS. && .PREVIOUS DISCUSSION... (ISSUED 319 AM EST SUN FEB 27 2005) SHORT TERM (TODAY THROUGH MONDAY)... SYNOPSIS... WEAK HIGH PRESSURE WAS CENTERED OVER NC AT 06Z/27. A REINFORCING SHOT OF DRIER AIR WAS PUSHING SOUTH THROUGH VA DRIVEN BY A 1030 MB SURFACE HIGH OVER MICHIGAN. A DEVELOPING SFC STORM SYSTEM WAS LOCATED OVER THE CENTRAL GULF OF MEXICO. TODAY THROUGH MONDAY... THE WATER VAPOR LOOP/UPPER AIR ANALYSIS INDICATE A STRONG SOUTHERN BRANCH JET OVER NRN MEXICO/S TX EXTENDING ACROSS NC. A MID LEVEL VORTEX WAS OVER THE RED RIVER. A POLAR VORTEX WAS DIGGING SOUTH INTO ND FROM CANADA. THE CURRENT INDICATIONS ARE THAT THE SOUTHERN BRANCH SYSTEM OVER THE RED RIVER WILL RACE EAST AHEAD OF THE DIGGING POLAR VORTEX... FAVORING THE LATEST GFS/ECMWF/UKMET FOR THE SE COASTAL STORM. TODAY... EXPECT LOWERING AND THICKENING CLOUDS WITH TEMPS IN THE LOWER TO MID 40S. THE REAL CONCERN BEGINS AROUND SUNSET TONIGHT AS THE MODEL MAJORITY/ GFS TRACK AND STRENGTH ARE STILL FAVORED AFTER THIS EVENINGS MODEL RUN... WITH THE DEVELOPING GULF OF MEXICO STORM. A WINTER STORM WATCH WILL BE ISSUED FOR THE PIEDMONT TRIAD REGION... NORTHEAST TO ROXBORO FOR ACCUMULATING SNOW TONIGHT INTO MONDAY MORNING. A COLD RAIN APPEARS LIKELY ELSEWHERE... WITH A NARROW TRANSITION ZONE SOMEWHERE OVER THE EASTERN PIEDMONT DURING THE EVENT. IT IS STRESSED THAT A STORM TRACK DEVIATION OF 50 MILES OR SO FARTHER EAST COULD BRING ACCUMULATING SNOW TO THE RALEIGH-DURHAM AREA. THIS IS STILL POSSIBLE GIVEN THE RECENT COLDER TRENDS IN THE MODEL RUNS. THE LATEST DATA ANALYSIS AND 00Z/27 FEBRUARY MODEL RUNS CONTINUE TO POINT TO A "MILLER A" TYPE SFC COASTAL CYCLOGENESIS TODAY THROUGH MONDAY FROM THE GULF OF MEXICO... NE ACROSS THE FL PANHANDLE... AND UP THE COAST OF SC/NC. THE 00Z/27 NAM TRACK CONTINUED TO BE ON THE LEFT SIDE OF ALL GUIDANCE... BUT CONTINUED TO TREND TOWARD THE MODEL MAJORITY OF A SIGNIFICANT COASTAL STORM. HPC CONTINUED TO SUPPORT THE GFS WITH THIS SYSTEM AS IT HAS BEEN THE MOST CONSISTENT RUN TO RUN IN THE PAST 24 HOURS. A LITTLE QUICKER ACCELERATION OF THE STORM IS ALSO PREFERRED AS TRENDED BY THE LAST SEVERAL GFS RUNS. WITH THE GFS BEING THE PREFERRED MODEL FOR THIS DEVELOPING STORM... THE FORECAST STORM TRACK STRONGLY SUGGESTS ACCUMULATING SNOW OVER PORTIONS OF THE NORTHWEST-NORTH PIEDMONT... ESPECIALLY OVER THE PIEDMONT TRIAD REGION EAST TO NEAR ROXBORO. THE FORECAST H85 AND H7 LOW PRESSURE CENTER TRACKS FROM NEAR CHARLOTTE TO RALEIGH AND ROANOKE RAPIDS TONIGHT AND MONDAY MORNING... IMPLYING THE P-TYPE TRANSITION ZONE WILL BE IN THAT GENERAL AREA... WITH ACCUMULATING SNOW JUST WEST-NORTH OF THE TRACK. THE 00Z/28 GFS H7 LOW FORECAST TRACK WAS SLIGHTLY WEST OF THE PREVIOUS TRACK... BUT STILL INDICATING THE MID LEVEL WARM NOSE TO MAINLY RUN UP THE COASTAL PLAIN OR FAR EASTERN PIEDMONT... WITH A PIVOT POINT AROUND RALEIGH... IMPLYING A VERY TIGHT NARROW P-TYPE TRANSITION ZONE TO BE IN THAT GENERAL LOCATION. TO THE NW... THE COLD AIR IS DEEPER WITH THE LATEST GFS RUNS INDICATING A SIGNIFICANT LOW LEVEL COLD NOSE AROUND 925 MB EXTENDING FROM CENTRAL VIRGINIA S-SW TOWARD GSO/INT... WITH CORRESPONDING LOW LEVEL THICKNESSES FALLING TO BETWEEN 1288 AND 1295 DURING THE 03Z-12Z MON TIME FRAME (DURING THE MAXIMUM QPF). CORRESPONDING MID LEVEL THICKNESSES AT GSO TO ROX DROP BELOW 1535. THE ONLY MISSING INGREDIENT FOR A CLASSICAL WINTER STORM IS THE LACK OF A STRONG PARENT SFC HIGH PRESSURE TO OUR N-NE. THERE IS A RATHER WEAK SURFACE HIGH (1028 MB) TODAY AND TONIGHT IN A FAVORED LOCATION TO DELIVER COLD DRY LOW LEVEL AIR... BUT THE HIGH IS FORECAST TO MOVE QUICKLY EAST TONIGHT AS THE PRECIP ROLLS IN. THUS... THIS IS NOT A CLASSICAL COLD AIR DAMMING SET UP. WE WILL HAVE TO RELY ON DYNAMICAL COOLING WITH THE STRENGTHENING MID LEVEL SYSTEM... AND THE TAPPING OF COLDER AIR OVER VIRGINIA INTO THE NC PIEDMONT REGION AS THE SFC STORM STRENGTHENS... AND MOVES UP THE SC/NC COAST TONIGHT .. THIS SUPPORTS THE SIGNIFICANT SNOW IN THE CLIMATOLOGICALLY PREFERRED NW-N PIEDMONT REGIONS. PARTIAL THICKNESS NOMOGRAMS ALSO SUPPORT THE MEASURABLE AND SIGNIFICANT SNOW THEME NW-N WITH A NARROW TRANSITION ZONE TO RAIN MIXED WITH SNOW OVER THE EASTERN AND SOUTHERN PIEDMONT... WITH ALL RAIN EAST AND SOUTH OF RDU. IF THE H7 LOW CLOSES OFF BEFORE EXITING TO THE NE EARLY MONDAY MORNING... THERE SHOULD BE HEAVY SNOW JUST NW OF ITS TRACK. LOOKING BACK INTO THE DOCUMENTED CASE STUDIES OF PREVIOUS WINTER WEATHER EVENTS (KEETER FILES)... THE CURRENT FORECAST PARTIAL THICKNESSES SUPPORT MEASURABLE SNOWFALL AT GSO. RDU HAS HAD MOSTLY RAIN EVENTS... SOME MIXED WITH MEASURABLE SNOW... GIVEN SIMILAR PARTIALS. QPF SHOULD AVERAGE AT LEAST 0.50 TO 1.00 INCHES WITH THIS EVENT... GIVEN THE FORECAST STRENGTH AND TRACK. MOST SHOULD OCCUR BETWEEN 02Z-15Z TONIGHT AND MONDAY. SNOWFALL ACCUMULATIONS SHOULD REACH 3-6 INCHES IN THE WATCH AREA... POSSIBLY AS HIGH AS 8 INCHES IN LOCAL AREAS. THE GROUND TEMPS HAVE COOLED IN RECENT DAYS DUE TO THE RECENT SOAKING RAIN EVENT... AND THE COLDER NIGHTS IN THE 20S. THE SOIL TEMPS WERE STILL IN THE LOWER 40S OVER THE NW PIEDMONT... INDICATING THAT SNOW ACCUMULATIONS WOULD MELT SOME FROM BELOW. ROAD TEMPS ARE ALSO LIKELY TO BE ABOVE 32 UNTIL WELL AFTER THE PRECIP BEGINS... INDICATING WET ROADS BECOMING SLUSHY AS THE SNOW EVENT UNFOLDS. FOR NOW... A WINTER STORM WATCH WILL BE ISSUED FOR 3-6 INCHES OF SNOW ACCUMULATION TONIGHT THROUGH 15Z/MONDAY FOR FORSYTH... GUILFORD... DAVIDSON... RANDOLPH... ALAMANCE... ORANGE... AND PERSON COUNTIES... (THE CLIMATOLOGICALLY PREFERRED AREA WITH THIS STORM TRACK). PRECIP MAY BEGIN AS LIGHT RAIN... BUT QUICKLY CHANGE TO WET SNOW AS THE STRONG DYNAMICAL COOLING DEVELOPS. A ONE-TWO COUNTY TRANSITION BUFFER ZONE WILL COVER AREAS JUST EAST AND SOUTH OF THESE COUNTIES INCLUDING AREAS FROM ALBEMARLE TO SANFORD... RALEIGH... AND ROANOKE RAPIDS... WHERE RAIN WILL LIKELY OCCASIONALLY MIX WITH SNOW... SOME ACCUMULATION WILL BE POSSIBLE AND A WINTER WEATHER ADVISORY MAY BE NEEDED TONIGHT. RAIN IS EXPECTED EAST AND SOUTH OF RALEIGH. THE RAIN MAY CHANGE TO SNOW BEFORE THE STEADY PRECIP TAPERS OFF FROM SW TO NE MONDAY MORNING... FOLLOWED BY COLD WINDY WEATHER MONDAY NIGHT AND TUESDAY. IT SHOULD BE STRESSED THAT IF THE FORECAST STORM TRACK DEVIATES ONLY 25 TO 50 MILES IN EITHER DIRECTION... IT WILL HAVE HUGE IMPLICATIONS ON THE LOCATION OF THE P-TYPE TRANSITION ZONE SET UP AND SNOW ACCUMULATIONS. A TRACK FARTHER EAST WILL LIKELY BRING SIGNIFICANT SNOW TO RALEIGH-DURHAM... AND A TRACK MORE LIKE THE NAM WILL LIMIT SNOW TO THE BLUE RIDGE MOUNTAINS ONLY. STAY TUNED ON THIS ONE AS IT HAS THE POTENTIAL TO BRING A MAJOR WET SNOW EVENT OVER MUCH OF THE W-N PIEDMONT... WHICH MAY EXTEND FURTHER SOUTH AND EAST THAN WHAT IS CURRENTLY FORECAST. LONG TERM (MONDAY NIGHT THROUGH SATURDAY)... MID LEVEL LOW CLOSES OFF OVER THE MIDWEST EARLY IN THE PERIOD AS DEEP COLD AIR FILTERS INTO THE STATE. VORT AXIS SWINGS THROUGH BY TUE MORNING & WITH LOW LEVEL FLOW REMAINING STRONG FROM THE WSW... THIS ENERGY MAY BE ENOUGH TO SQUEEZE OUT A SPRINKLE OR SNOW SHOWER... IF THE LIFT CAN SATURATE THE PRIME DEDRITE GROWTH REGION ALOFT. THE CLOSED VORTEX MOVES TOWARD NEW ENGLAND WHEN A SECOND STRONG VORT MAX DROPS INTO THE TROUGH BASE... THROUGH NC... ON WED. AGAIN MOISTURE WILL BE LIMITED... THUS WILL KEEP CONDITIONS DRY... BUT IT REMAINS QUITE CHILLY WITH LOW LEVEL THICKNESSES PROGGED BY THE NAM & GFS TO BE IN THE 1260S-1270S ALL DAY WED. EXPECT A DRY NORTHWEST LOW LEVEL FLOW THEN THU-SAT AS THE LOW ALOFT MOVES INTO THE CANADIAN MARITIMES & THE HIGH PRESSURE AREA BUILDING INTO NC FROM THE WNW MODERATES SOMEWHAT. AVIATION... TERMINAL FORECASTS DEPICT A THICKENING AND LOWERING OF THE HIGH AND MID CLOUDS TONIGHT INTO SUN MORNING. HAVE BROUGHT CIGS DOWN TO MVFR BY 18Z (SOUTH) TO 21Z (NORTH) AND SPED UP PRECIP ONSET TO 21Z-00Z SOUTH TO NORTH... AS CIGS/VSBYS GO IFR. && .RAH WATCHES/WARNINGS/ADVISORIES... WINTER STORM WATCH FOR NCZ007-021>024-038-039 FROM 6 PM SUNDAY TO 9 AM MONDAY. && $$ SHORT TERM...WSS FXUS62 KRAH 272212 AFDRAH AREA FORECAST DISCUSSION... RETRANSMISSION NATIONAL WEATHER SERVICE RALEIGH NC 308 PM EST SUN FEB 27 2005 .SHORT TERM (TONIGHT THROUGH MONDAY NIGHT)... MAIN FORECAST CHALLENGE REMAINS ON AMOUNT OF SNOW TO EXPECT OVER THE SECTIONS OF NORTHERN PIEDMONT LATE TONIGHT/EARLY MON. FIRST THE FACTS: ANTECEDENT CONDITIONS SUCH AS GROUND AND PAVEMENT TEMPS MARGINAL TO QUITE WARM. REPORTS FROM PTI AIRPORT AUTHORITY HAVE PAVEMENT AND GROUND SURFACE TEMPS RANGING IN THE 45 TO 50 DEGREE RANGE. IN ADDITION...CURRENT TEMPS IN THE MID 40S WILL ONLY FALL SLOWLY THROUGH THIS EVENING...THUS MAY SEE TEMPS AT PRECIP ONSET LATE TONIGHT NEAR 40 DEGREES. ALSO SURFACE DEWPOINTS IN THE UPPER 20S TO LOWER 30S WITH THE MUCH LOWER DEWPOINTS CONFINED TO FAR NORTHERN VA (MID/UPPER TEENS). GFS FAIRLY CONSISTENT FROM PREVIOUS RUNS AND FAVORED WITH THIS FORECAST PACKAGE WITH SLIGHT MODIFICATIONS. DID NOTE THAT GFS PARTIAL THICKNESS WERE WARMER IN THE LOWER PARTIALS IN THE CRITICAL 06-12Z TIME FRAME COMPARED TO THE 06Z RUN. NAM/ETA HAS COME INTO SLIGHTLY BETTER AGREEMENT WITH THE GFS BUT IS STILL NOTABLY FARTHER TO THE WEST WITH THE 850/700MB FEATURES. ALL SHORT TERM MODELS DEPICT STRONG MID/UPPER LEVEL FORCING LATE TONIGHT AS CENTRAL NC IN LEFT EXIT REGION OF 300 MB JET WHICH THE MODELS APPEAR 10-20 KTS TOO WEAK IN THEIR INITIALIZATION. ALSO...ACCORDING TO QPF DISCUSSION FROM HPC...APPEARS THAT MID LEVEL CIRCULATION CENTER DEVELOPING FARTHER TO THE NW THAN PROJECTED BY MODELS. IF THIS TREND CONTINUES (MID LEVEL CIRCULATION MOVING FARTHER INLAND THAN MODEL INDICATES)...THEN VAST MAJORITY OF CWA WILL SEE ALL LIQUID PRECIP OVERNIGHT/EARLY MON WITH PROBABILITY OF CONVECTION OVER THE SE COUNTIES. DUE TO THE STRONG DYNAMICS...MODERATE HEAVY PRECIP SHOULD BE ENOUGH TO COOL THE COLUMN TO SUPPORT WET SNOW MIXED AT TIMES WITH RAIN OVER THE NW COUNTIES. AT THIS TIME...APPEARS UNLIKELY THAT CENTRAL NC WILL NOT BE ABLE TO TAP THE COOLER/DRIER AIR OVER NORTHERN VA (THIS WILL BE SOMETHING THAT THE FOLLOWING SHIFTS WILL HAVE TO MONITOR). IF ABLE TO TAP THIS AIRMASS...THEN GREATER POTENTIAL FOR SNOW AND HEAVIER AMOUNTS. WHEN CONSIDERING THE ANTECEDENT CONDITIONS...THE MORE LIKELY SCENARIO THAT COOLER AIR TO THE NORTH WILL NOT BE TAPPED...AND THAT THE MID LEVEL CIRCULATION MAY TREND TO GO FURTHER INLAND...WILL MAINTAIN SNOW MIXED AT TIMES WITH RAIN OVER THE NW PIEDMONT. DUE TO POTENTIAL FOR HEAVY PRECIP BANDS...COULD SEE SNOW AMOUNTS ON GRASSY AREAS 2-4 INCHES OVER THE CURRENT WATCH AREA WITH ISOLATED HEAVIER AMOUNTS. DUE TO RELATIVELY WARM ROAD SURFACES...EXPECT MAIN ROADS TO VARY FROM WET TO SLUSHY. THUS WILL UPGRADE WATCH AREA TO A WARNING. IMMEDIATELY EAST OF WARNING...MAINLY CHATHAM...DURHAM AND GRANVILLE...COULD SEE ENOUGH SLUSHY WET SNOW TO WARRANT AN ADVISORY (1-2 INCHES). FOR THE REMAINDER OF THE NE PIEDMONT AND THE SOUTHERN PIEDMONT COUNTIES...EXPECT RAIN MIXED AT TIMES WITH SNOW WITH LITTLE IF ANY ACCUMULATION. COULD SEE SOME ISOLATED THUNDERSTORMS IN THE SE OVERNIGHT/EARLY MON BUT APPEARS SEVERE WEATHER THREAT MORE APPLICABLE CLOSER TO THE COAST. EXPECT PRECIP TO RAPIDLY END SW-NE BETWEEN 12Z-16Z MON. WITH SOME RESIDUAL DRIZZLE/LIGHT RAIN FAR N. MAY SEE WIDELY SCATTERED SHOWERS WITH PASSAGE OF MID LEVEL DISTURBANCE MON EVENING BUT CONFIDENCE NOT HIGH ENOUGH AT THIS TIME TO WARRANT MENTIONING. && .LONG TERM (TUESDAY THROUGH SUNDAY)... TROF OVER THE EASTERN UNITED STATES CONTINUES TO DIG WITH VARIOUS IMPULSES REINFORCING THE COOL TREND THROUGH WEDNESDAY NIGHT. THUS EXPECT PREVALENT CAA STRATOCUMULUS THROUGH THE PERIOD. HIGHS TUE AND WED IN THE MID 40S. COOL HIGH PRESSURE BUILDING IN THURSDAY...MOSTLY SUNNY...AROUND 50. CONTINUED MOSTLY SUNNY WITH SOME AIRMASS MODERATION FRIDAY...LOW AND MID 50S. WEEKEND IS STILL SOMEWHAT IN QUESTION WITH A PAIR OF FAIRLY STRONG SHORT WAVES IN THE NORTHWEST FLOW AFFECTING THE AREA. A FAST FROPA LOOKS LIKELY FRIDAY NIGHT/EARLY SATURDAY WHICH MIGHT DIG FAR ENOUGH SOUTH TO TAP SOUTHERN STREAM MOISTURE AND KICK OFF SHOWERS. WILL WAIT FOR LATER MODEL PERSISTENCE BEFORE INTRODUCING POPS AT THIS TIME. THE LATER SHORT WAVE REMAINS WELL NORTH...OVER THE GREAT LAKES...WHICH WOULD PRODUCE MAINLY MID CLOUDINESS. THUS...WILL CONTINUE DRY THROUGH THE WEEKEND WITH SLIGHTLY BELOW CLIMATOLOGICAL TEMPS... MOSTLY MID 50S. && .AVIATION... VFR CEILINGS WILL BE LOWERING EARLY TONIGHT AS THE PRECIPITATION SHIELD GRADUALLY EDGES IN FROM THE SOUTH. IFR CEILINGS SHOULD BE IN PLACE FOR THE DURATION BY 06Z. EXPECT RAIN IN THE FAYETTEVILLE AREA AROUND SUNSET...THEN A COUPLE OF HOURS LATER...PREDOMINANT RAIN AT RWI AND RDU OVERNIGHT WITH SOME SNOW MIXED IN...ESPECIALLY RDU AFTER MIDNIGHT. A MIX INITIALLY AT GSO AND INT BY 02Z...CHANGING TO PREDOMINANTLY SNOW AFTER MIDNIGHT. WINDS WILL BE PICKING UP SIGNIFICANTLY AFTER SUNSET AS THE SURFACE LOW MOVES UP THE COAST. NORTHEAST WINDS INCREASING TO 10 TO 15 KT WITH GUSTS TO 20 TO 25 KT AROUND 03Z WILL SWING AROUND MORE NORTHERLY TOWARDS SUNRISE AND GRADUALLY DIMINISH...ESPECIALLY AT GSO AND INT...DURING THE MORNING. && .RAH WATCHES/WARNINGS/ADVISORIES... WINTER STORM WARNING FOR NCZ007-021>024-038-039 FROM TONIGHT THROUGH 10 AM MONDAY. WINTER WEATHER ADVISORY TONIGHT THROUGH 10 AM MONDAY FOR CHATHAM...DURHAM AND GRANVILLE. && $$ SHORT TERM...WSS LONG TERM...MLM AVIATION...MLM