FXUS62 KRAH 250710


AFDRAH





AREA FORECAST DISCUSSION


NATIONAL WEATHER SERVICE RALEIGH NC


308 AM EDT SUN APR 25 2010





.SYNOPSIS...


A STRONG STORM SYSTEM OVER THE MID MISSISSIPPI VALLEY WILL DRIFT 


EAST ACROSS THE OHIO VALLEY TO PENNSYLVANIA THROUGH TUESDAY... 


KEEPING THE WEATHER UNSETTLED OVER THE AREA. DURING THIS TIME... A 


SERIES OF WEAK COLD FRONTS CROSSING THE AREA WILL GRADUALLY PUSH 


TEMPERATURES BACK TO NEAR TO BELOW NORMAL. ANOTHER DISTURBANCE 


PASSING OVER NORTH CAROLINA TUESDAY NIGHT WILL BRING DRIER AIR AND 


MORE SUNSHINE FOR WEDNESDAY.





$$





.NEAR TERM /THROUGH TONIGHT/...


AS OF 255 AM SUNDAY...





THROUGH TODAY: A CHALLENGING FORECAST. THE NAM/GFS/ECMWF FAILED TO 


PROPERLY INITIALIZE THE WIDESPREAD RAIN CURRENTLY FALLING OVER 


CENTRAL AND EASTERN NC... A DISCONCERTING FACTOR CONSIDERING THAT 


THIS PRECEDING PRECIP WILL IMPACT THE ATMOSPHERIC RECOVERY AHEAD OF 


THE CONVECTION NOW OCCURRING FROM THE TN/NC BORDER DOWN THROUGH 


AL/GA. THE 4 KM WRF DEPICTS THIS CONVECTION (IN PARTICULAR THE BAND 


FROM SW NC TO CENTRAL AL) HOLDING TOGETHER AND CROSSING NC THIS 


MORNING THROUGH MID AFTERNOON... A REASONABLE SCENARIO... AND THE 


NAM SHOWS MLCAPE INCREASING TO 1200+ J/KG OVER OUR AREA BY MIDDAY 


AND TRANSLATING EAST THROUGH THE COASTAL PLAIN IN THE AFTERNOON. 


WHILE THESE VALUES ARE IN SOME DOUBT AS OUR AREA HAS LOWER SURFACE 


DEW POINTS AND WEAKER LAPSE RATES... THE STEADY LOW LEVEL MOISTURE 


TRANSPORT INTO NC SHOULD YIELD A CONTINUED SLOW RISE IN DEW POINTS 


THIS MORNING AND DESTABILIZATION IS STILL POSSIBLE. THE UPPER JET 


CORE NOW OVER SRN MS/AL WILL BE WEAKENING BUT WILL STILL BRING AN 


AREA OF (WANING) UPPER DIVERGENCE OVER CENTRAL NC THIS MORNING... 


AND THE EFFECTIVE DEEP LAYER SHEAR OVER 60 KTS HEADING OVER THE 


CAROLINAS IS MORE THAN SUFFICIENT FOR LONG HODOGRAPHS AND A 


POTENTIAL FOR BOWING SEGMENTS PRODUCING DAMAGING WINDS FROM DAYBREAK 


THROUGH MID AFTERNOON TODAY. THE NAM/GFS/CANADIAN/ ECMWF ALL SHOW 


CAPE IN THE MIXED-PHASE -10C TO -30C LAYER TO BE 500-700 J/KG 


FAVORING A HAIL THREAT... AND MID LEVEL WET BULB LAPSE RATES ARE 


LIKELY TO BE INCREASING WITH THE ARRIVAL OF THE MID LEVEL DRY PUNCH 


NOSING INTO SOUTHWEST NC. WILL CONTINUE TO HIGHLIGHT THIS RISK OF 


DAMAGING WINDS AND LARGE HAIL IN THE HAZARDOUS WEATHER OUTLOOK. WITH 


LIMITED SUNSHINE THROUGH THE MAJORITY OF THE DAY... HAVE BUMPED 


HIGHS DOWN A BIT TO 77-82. 





FOR TONIGHT: WITH MID LEVEL DRY AIR MOVING IN AND LOWER PRECIP WATER 


AIR PUSHING IN FROM THE WEST... RAIN CHANCES WILL BE DECREASING WEST 


TO EAST STARTING IN THE LATE AFTERNOON... HOWEVER THEY ARE UNLIKELY 


TO DROP TO ZERO. A WEAK SURFACE FRONT SWEEPS EAST THROUGH CENTRAL NC 


OVERNIGHT (ALBEIT WITH ONLY WEAK MASS CONVERGENCE) WITH THE SLOWLY 


DEPARTING LOW LEVEL JET PUSHES VERY SLOWLY EASTWARD OVER EASTERN NC. 


WEAK MID LEVEL DPVA IS NOTED AS A SHEARED LOBE OF VORTICITY TRACKS 


UP THROUGH THE NC COASTAL PLAIN... AND ADDITIONAL FORCING FOR ASCENT 


MAY ARRIVE IF ANOTHER SMALL 100+ KT UPPER SPEED MAX - PROJECTED TO 


STREAK ACROSS GA INTO SC LATE TONIGHT - BRINGS SUFFICIENT UPPER 


DIVERGENCE OVER NC. MODELS DEPICT A FEW HUNDRED J/KG OF MLCAPE 


LINGERING THROUGH MUCH OF THE NIGHT OVER THE EASTERN CWA WHERE DEW 


POINTS SHOULD REMAIN ELEVATED AS COMPARED TO EXPECTED DRIER AIR 


MOVING INTO THE WESTERN CWA. WILL KEEP IN A SMALL CHANCE OF SHOWERS 


(AND A POSSIBLE STORM MAINLY IN THE EVENING EAST)... WITH PRECIP 


CHANCES PUSHING EAST OF HIGHWAY 1 LATE. THE AIR UPSTREAM IS NOT 


MARKEDLY COOLER SO WILL CONTINUE WITH LOWS JUST ABOVE STATISTICAL 


GUIDANCE... 60-67. -GIH





&&





.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/....


AS OF 245 AM SUNDAY...





MONDAY AND MONDAY NIGHT:


SURFACE COLD FRONT/TROUGH IS EXPECTED TO BE EXITING THE COASTAL 


PLAIN BY AROUND 12Z MONDAY... ALLOWING DRIER AIR AT THE SURFACE TO 


FILTER INTO THE AREA. THIS WILL KEEP CONDITIONS DRY ACROSS THE AREA 


THROUGH AT LEAST EARLY AFTERNOON. HOWEVER... AS THE CLOSED MID/UPPER 


LOW (EXPECTED TO BE LOCATED ACROSS THE OH VALLEY AT 12Z MONDAY) 


TRACKS ACROSS THE OH VALLEY AND INTO THE NORTHERN MID ATLANTIC 


MONDAY AFTERNOON INTO MONDAY EVENING THE MID/UPPER TROUGH AXIS WILL 


SEND A REINFORCING SURFACE COLD FRONT/TROUGH THROUGH THE AREA. GIVEN 


LI ARE EXPECTED TO BE AROUND 0 TO -2 IN ADVANCE OF THE SURFACE 


TROUGH AND MUCAPE VALUES RANGING ANYWHERE FROM A COUPLE HUNDRED J/KG 


ACROSS THE WEST TO NEAR 500 J/KG ACROSS THE EAST EXPECT WE MAY SEE 


SOME ISOLATED SHOWERS AND/OR THUNDERSTORMS DEVELOP ON MONDAY 


AFTERNOON AS THE SURFACE TROUGH MOVES THROUGH THE AREA COUPLED WITH 


DAYTIME HEATING. GIVEN DEEP LAYER SHEAR IS EXPECTED TO BE IN THE 30 


TO 40 KT RANGE AND STEEP LOW LEVEL LAPSE RATES WITH INVERTED V 


SOUNDINGS... THINK WE COULD SEE A FEW STRONG STORMS OR EVEN AN 


ISOLATED SVR STORM MONDAY AFTERNOON WITH THE MAIN THREAT FROM STRONG 


TO DAMAGING WIND GUSTS FROM EVAPORATIVE COOLING ENHANCED 


DOWNDRAFTS... WITH THE HIGHEST LIKELIHOOD OF A STRONG TO SVR STORM 


GENERALLY EAST OF RALEIGH WHERE THE GREATEST INSTABILITY IS EXPECTED 


TO RESIDE. IN ADDITION TO THE POSSIBILITY OF STRONG WIND GUSTS IN 


STORMS... WINDS NEAR THE TOP OF THE MIXED LAYER A FORECAST TO 


APPROACH 30 KTS OR SO ON MONDAY AFTERNOON. GIVEN THE SHARPENING 


SURFACE TROUGH CROSSING THE AREA AND DEEP MIXED LAYER MONDAY 


AFTERNOON... EXPECT WE COULD SEE SUSTAINED WINDS IN THE 15 TO 20 MPH 


RANGE... WITH WIND GUSTS OF UP TO 25 TO PERHAPS 30 MPH.  WITH REGARD 


TO TEMPS... SHOULD SEE A RANGE IN AFTERNOON HIGHS ON MONDAY GIVEN 


THE REINFORCING COLD FRONT/SURFACE TROUGH IS EXPECTED TO MOVE INTO 


THE WESTERN CWA BY EARLY AFTERNOON... WITH EASTERN LOCALES NOT 


SEEING THE FRONT UNTIL CLOSER TO 00Z TUESDAY. THUS... EXPECT TO SEE 


PARTLY SUNNY TO MOSTLY CLOUDY SKIES AND HIGH TEMPS RANGING FROM THE 


LOWER TO MID 70S IN THE NORTHWEST TO LOWER TO MID 80S IN THE 


SOUTHEAST.





MONDAY NIGHT... EXPECT BRIEF MID LEVEL RIDGING AS THE MID/UPPER 


LEVEL S/W TROUGH DEPARTS AND BEFORE THE NEXT S/W TROUGH AFFECTS THE 


REGION ON TUESDAY AFTERNOON/EVENING. THIS SHOULD ALLOW SKIES TO 


BECOME AT LEAST MOSTLY CLEAR TO PARTLY CLOUDY OVERNIGHT. HOWEVER... 


EXPECT BREEZY CONDITIONS TO CONTINUE OVERNIGHT AS A 990 MB SURFACE 


LOW SHIFTS OFFSHORE OF THE NORTHERN MID ATLANTIC COAST AND BEGINS TO 


LIFTS OFF TO THE NORTHEAST. THIS SHOULD KEEP A FAIRLY TIGHT PRESSURE 


GRADIENT ACROSS THE AREA OVERNIGHT... WITH SURFACE WINDS EXPECTED TO 


REMAIN AT LEAST IN THE 7 TO 12 MPH RANGE OVERNIGHT MONDAY/TUESDAY 


MORNING. THIS SHOULD HELP TO KEEP OVERNIGHT LOW TEMPS UP A BIT. 


EXPECT LOW TEMPS ON TUESDAY MORNING TO RANGE FROM THE UPPER 40S TO 


AROUND 50 ACROSS THE NORTH AND WEST TO THE MID 50S IN THE SOUTHEAST.





TUESDAY AND TUESDAY NIGHT:


NEXT AND LAST MID/UPPER LEVEL SHORTWAVE IS FORECAST TO TRACK THROUGH 


THE EAST COAST TROUGH ON TUESDAY AFTERNOON INTO TUESDAY EVENING. 


INSTABILITY LOOKS TO BE SIMILAR OR MAYBE EVEN LESS WITH THIS SYSTEM 


AS MID LEVEL FLOW IN ADVANCE OF THIS SYSTEM REMAIN PRIMARILY 


WESTERLY. THUS... WILL CONTINUE TO MENTION ISOLATED SHOWERS AND 


THUNDERSTORMS POSSIBLE TUESDAY AFTERNOON INTO TUESDAY NIGHT. 


HOWEVER... EVEN WITH THIS S/W TRACKING A BIT FURTHER TO THE SOUTH 


THAN THE ONE ON MONDAY... EXPECT WE SEE A VERY LITTLE IN THE WAY OF 


A SEVERE THREAT... WITH PERHAPS AN OUTSIDE CHANCE FOR AN ISOLATED 


STRONG OR SVR WIND GUSTS. WITH AFTERNOON LOW LEVEL THICKNESS VALUES 


ONLY TOPPING OUT IN THE 1350S TO 1360S... EXPECT HIGH TEMPS WILL BE 


ON THE COOL SIDE OF GUIDANCE... MID TO UPPER 60S ACROSS THE 


NORTHWEST TO THE LOWER 70S SOUTHEAST. PARTLY TO MOSTLY CLOUDY SKIES 


WILL BECOME MOSTLY CLEAR TO PARTLY CLOUDY BY 12Z WEDNESDAY... AS THE 


S/W LIFTS OFF TO THE NORTHEAST. EXPECT OVERNIGHT LOWS TO BOTTOM OUT 


IN THE MID TO UPPER 40S.  





&&





.LONG TERM/WEDNESDAY THROUGH SATURDAY/...


AS OF 3 AM SUNDAY...





MID/UPPER RIDGE BUILDS BACK ACROSS THE AREA DURING THIS TIME FRAME 


ALONG WITH SURFACE HIGH PRESSURE... ALLOWING QUIET WEATHER AND TEMPS 


TO REBOUND... WITH AFTERNOON HIGHS BACK ABOVE NORMAL BY FRIDAY AND 


SATURDAY (IN THE 80S FOR FRI AND SAT). THE ONLY POTENTIAL FOR ANY 


SHOWERS... WOULD BE LATE IN THE FORECAST PERIOD IF AT ALL... AS THE 


MID LEVEL RIDGE AXIS BEGINS SHOW SIGNS OF POSSIBLY SHIFTING TO THE 


EAST OF THE AREA. HOWEVER... MEDIUM RANGE MODELS DIFFER WITH THE 


AMPLIFICATION OF THE RIDGE AND THUS TIMING OF THIS HAPPENING. 


THUS... WILL KEEP THE FORECAST DRY FOR NOW.





&&





AVIATION /06Z SUNDAY THROUGH THURSDAY/...


AS OF 150 AM SUNDAY...





MVFR TO IFR CONDITIONS WILL DOMINATE AT CENTRAL NC TERMINAL FORECAST 


SITES THIS MORNING... ALTHOUGH REPEATED CATEGORY CHANGES ARE LIKELY 


AND PERIODS OF VFR CONDITIONS ARE LIKELY. A LARGE AREA OF RAIN 


COVERING THE CENTRAL AND EASTERN CAROLINAS WILL CONTINUE DRIFTING 


EAST BUT STILL AFFECT CENTRAL NC AIRPORTS THROUGH THE REST OF THE 


NIGHT. SURFACE WINDS FROM THE SOUTH AND SOUTHWEST WILL CONTINUE TO 


INCREASE TO 13-20 KTS SUSTAINED THROUGH 12Z... AND GUSTS OVER 25 KTS 


ARE LIKELY AS A 40+ KT LOW LEVEL JET TRAVERSES THE AREA THROUGH 


EARLY AFTERNOON. A BRIEF LULL IN NOTABLE PRECIPITATION IS EXPECTED 


BEHIND THIS AREA OF RAIN THIS MORNING... BUT MULTIPLE CLOUD LAYERS 


MAY CAUSE FREQUENT CIG DROPS TO MVFR. A BAND OF SHOWERS AND STORMS 


NOW STRETCHING FROM EASTERN TN THROUGH NRN GA AND AL IS EXPECTED TO 


ARRIVE LATER THIS MORNING... REACHING INT/GSO AFTER 11Z... RDU AFTER 


12Z... AND RWI/FAY AFTER 14Z. AS THIS BAND CROSSES CENTRAL NC THIS 


MORNING INTO EARLY AFTERNOON... EXPECT 2-4 HOURS OF OCCASIONALLY 


HEAVY RAIN... ENHANCED WIND GUSTS OVER 35 KTS GENERATING VIGOROUS 


LOW LEVEL TURBULENCE... AND FREQUENT LIGHTNING STRIKES. CIGS/VSBYS 


WILL IMPROVE TO VFR BEHIND THIS LINE STARTING EARLY TO MID AFTERNOON 


TODAY... BUT AN ISOLATED SHOWER WILL REMAIN POSSIBLE INTO TONIGHT. 


SOUTHWEST TO WEST-SOUTHWEST WINDS WILL HOLD ABOVE 10 KTS AFTER DARK 


WITH OCCASIONAL GUSTS OVER 20 KTS.





LOOKING BEYOND TONIGHT... UNSETTLED WEATHER WITH PERIODS OF VFR CIGS 


AND A LINGERING RISK OF ISOLATED SHOWERS WILL HOLD FOR MONDAY 


THROUGH TUESDAY NIGHT. WINDS WILL CONTINUE BRISK AND GUSTY MAINLY 


FROM THE WEST. A COLD FRONT SWEEPING THROUGH TUESDAY NIGHT WILL 


BRING DRIER AIR AND VFR CONDITIONS FOR WEDNESDAY/THURSDAY. -GIH





&&





.RAH WATCHES/WARNINGS/ADVISORIES...


NONE.





&&





$$





SYNOPSIS...HARTFIELD


NEAR TERM...HARTFIELD


SHORT TERM...BSD


LONG TERM...BSD


AVIATION...HARTFIELD