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 FXUS62 KRAH 130712
 AFDRAH
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE RALEIGH NC
 310 AM EDT WED APR 13 2011
 
 .SYNOPSIS...
 AN UPPER LEVEL LOW PRESSURE AREA WILL DRIFT OVERHEAD THIS MORNING 
 AND DEPART TO THE NORTHEAST LATER TODAY. WEAK HIGH PRESSURE WILL 
 BUILD IN FROM THE WEST WEDNESDAY NIGHT THROUGH THURSDAY NIGHT... AND 
 SHIFT OFF THE COAST FRIDAY. A STORM SYSTEM WILL APPROACH FROM THE 
 WEST FRIDAY NIGHT.
 
 &&
 
 .NEAR TERM /TODAY THROUGH TONIGHT/...
 AS OF 240 AM WEDNESDAY...
 
 THE STACKED LOW OVER CENTRAL VA THIS MORNING WILL MOVE TOWARD THE 
 NNE OVER ERN PA TODAY BEFORE WEAKENING TO AN OPEN WAVE AND CROSSING 
 NEW ENGLAND AND CANADIAN MARITIMES TONIGHT. SURFACE LOW PRESSURE 
 LOCATED JUST EAST OF THE MID LEVEL VORTEX... OVER EASTERN VA 
 ACCORDING TO THE LATEST SURFACE ANALYSIS... HAS A WEAK SURFACE 
 TROUGH EXTENDING DOWN THROUGH CENTRAL NC EARLY THIS MORNING (ONE OF 
 SEVERAL TROUGHS ROTATING ABOUT THE SURFACE LOW). AS THIS LOW ALSO 
 TRACKS TO THE NNE AWAY FROM NC... CYCLONIC SURFACE FLOW WILL BECOME 
 UNIFORM NORTHWESTERLY ACROSS THE AREA THIS MORNING... INITIALLY A 
 BIT BREEZY AND GUSTY WITH A DECENT MSLP GRADIENT ACROSS THE STATE... 
 HOWEVER THIS WILL SLACKEN THIS AFTERNOON AND WINDS SHOULD DIMINISH. 
 PATCHY LIGHT SPRINKLES PERSIST OVER THE FAR NRN CWA EARLY THIS 
 MORNING WHERE LOW LEVEL MOISTURE IS POOLING ALONG THE 925-850 MB 
 TROUGH... BUT THIS MASS CONVERGENCE WILL DECREASE THIS MORNING AND 
 WILL TREND OUT THESE PATCHY SPRINKLES TOWARD A DRY FORECAST. 
 SCATTERED (OCCASIONALLY BROKEN ACROSS THE NORTHERN AND NE CWA) 
 STRATOCUMULUS CLOUDS ARE EXPECTED AT THE TOP OF THE MIXED LAYER FROM 
 MIDDAY INTO THE AFTERNOON... YIELDING PARTLY TO MOSTLY SUNNY SKIES. 
 HIGHS 67-72 FIT WILL WITH LOW LEVEL THICKNESSES AND AN AVERAGE OF 
 STATISTICAL GUIDANCE. EXPECT CLEAR SKIES TONIGHT WITH DIMINISHING 
 WINDS AS WEAK HIGH PRESSURE NOW OVER THE GREAT LAKES REGION BUILDS 
 IN FROM THE NNW. LOWS 42-47. -GIH
 
 &&
 
 .SHORT TERM /THURSDAY THROUGH FRIDAY/...
 AS OF 255 AM WEDNESDAY...
 
 FOR THURSDAY: A PLEASANT AND WARM DAY. WEAK SURFACE HIGH PRESSURE 
 SITS OVERHEAD... AND MODELS AGREE ON DRY AND STABLE AIR IN PLACE 
 THROUGH THE COLUMN WITH A FLAT FLOW ALOFT IN THE WAKE OF THE QUICKLY 
 DEPARTING AND DISSIPATING SHORTWAVE TROUGH TO OUR NE. EXPECT PLENTY 
 OF SUNSHINE... AND AS THICKNESSES WARM SLIGHTLY FROM TODAY... HIGHS 
 SHOULD REACH INTO THE 72-76 RANGE. 
 
 FOR THURSDAY NIGHT/FRIDAY: THE ELONGATED NEGATIVELY TILTED MID LEVEL 
 TROUGH STRETCHING FROM OFF THE BC COAST TOWARD CO/NM EARLY THURSDAY 
 IS STILL EXPECTED TO CLOSE OFF A POTENT LOW OVER KS BY THURSDAY 
 EVENING... RESULTING IN WEAK BROAD RIDGING UPSTREAM FROM THE GREAT 
 LAKES TO THE SOUTHEAST STATES. THE WEAK HIGH OVERHEAD SHIFTS TO OUR 
 EAST BUT BECOMES OVERTAKEN BY A STRONGER (AND COOLER) RIDGE CENTERED 
 WELL TO OUR NORTH OVER JAMES BAY. THE MODELS DIFFER SLIGHTLY ON 
 WHETHER OR NOT THIS IS TRULY A BACKDOOR FRONTAL ZONE DROPPING INTO 
 NRN AND NE NC FROM THE NORTH... AS THE GFS SHOWS A MARKED DROP IN 
 BOUNDARY LAYER THETA-E INTO THE NRN AND ERN CWA ON FRIDAY ALONG WITH 
 A STRONGER PUSH OF HIGHER PRESSURES FROM THE NORTH AS COMPARED TO 
 THE NAM. THE GFS'S RESULTING STRONGER 850 MB FLOW FROM THE ESE DOES 
 BRING IN A FEW MORE STRATOCUMULUS ON FRIDAY MORNING... AND ITS 
 SLIGHTLY FASTER EASTWARD MOVEMENT OF THE KS VORTEX INTO MO FRIDAY 
 ALLOWS THE MID/HIGH CLOUDS TO SPREAD EASTWARD INTO NC MUCH FASTER. 
 WITH NO CLEAR WINNER HERE AND ONLY MINOR DIFFERENCES WITH RESPECT TO 
 OUR SENSIBLE WEATHER... WILL SHOW A SLOW BUT STEADY INCREASE IN 
 CLOUDS WEST TO EAST FRIDAY... WITH TEMPS SIMILAR TO THURSDAY'S 
 HIGHS... BUT WILL NUDGE THEM DOWN A DEGREE OR TWO IN THE NORTHEAST 
 AS A NOD TOWARD THE POSSIBILITY OF A SLIGHTLY COOLER/DRIER AIR MASS 
 WORKING IN HERE FROM THE NORTH. -GIH
 
 &&
 
 .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
 AS OF 310 AM WEDNESDAY...
 
 PACIFIC JET ENERGY DIGGING ACROSS THE ROCKIES WILL DEEPEN A SYSTEM 
 FROM THE LEE OF THE ROCKIES TO THE MID MS RIVER VALLEY REGION ON 
 FRIDAY. THERE HAS BEEN GOOD GENERAL AGREEMENT BETWEEN THE GFS/ECMWF 
 ON AN UPPER WAVE CUTTING OFF AND THE SYSTEM BECOMING VERTICALLY 
 STACKED AS THE A ~995MB SURFACE LOW LIFTS NE FROM MO TO THE 
 GREAT LAKES BY SATURDAY MORNING.  AN ONGOING QLCS FRIDAY IN A 
 MODERATELY UNSTABLE AIRMASS OVER THE DEEP SOUTH...FURTHER SUPPORTED 
 BY THE SURFACE COLD FRONT/PREFRONTAL TROUGH AND INCREASINGLY 
 DIFLUENT UPPER LEVEL FLOW AS A SPEED MAX SURGES INTO THE BASE OF THE 
 UPPER LOW...SHOULD BE APPROACHING THE SOUTHERN APPALACHIANS BY 06Z 
 SATURDAY.  MODELS HAVE SLOWED ARRIVAL TIME OF THE CONVECTIVE LINE BY 
 6-12 HOURS...MORE TOWARD THE DAYTIME HOURS SATURDAY.  THIS MAY SPELL 
 A GREATER SEVERE THREAT AS MODEST DESTABILIZATION WILL BE POSSIBLE 
 VIA DAYTIME HEATING AND A SURGE OF 60F+ DEWPOINT AIR FROM THE SOUTH. 
 AS THE UPPER TROUGH BECOMES NEGATIVELY TILTED...DEEP LAYER SHEAR IN 
 EXCESS OF 50KT AND AND LOW LEVEL VEERING PROFILE/HODOGRAPH 
 SIGNATURES ARE A BIT CONCERNING.  TIMING AND DESTABILIZATION WILL BE 
 KEY WITH THIS SYSTEM...AND THOSE DETAILS WILL HOPEFULLY BECOME MORE 
 CLEAR IN SUBSEQUENT FORECASTS.  GIVEN THE AMOUNT OF MID LEVEL 
 FORCING AND STRENGTH OF THE LOW LEVEL JET... RELATIVELY QPF AMOUNTS 
 ARE FORECAST TO RANGE FROM 0.5-1.0" ON AVERAGE...WITH HIGHER AMOUNTS 
 CERTAINLY POSSIBLE.
 
 AS FOR TEMPS....WIDESPREAD MID AND HIGH CLOUDS WILL BE POSSIBLE AS 
 THE SYSTEM APPROACHES SATURDAY...BUT MILD MID 60 LOWS SATURDAY 
 MORNING AND PREFRONTAL WARM ADVECTION SHOULD BE SUFFICIENT TO PUSH 
 HIGHS INTO THE MID TO UPPER 70S OVER THE EASTERN CWA...COOLER IN THE 
 WEST WITH EARLIER ARRIVAL OF PRECIP. 
 
 AS THE SYSTEM DEPARTS THE REGION LATE SATURDAY...MODELS INDICATE A 
 BRIEF PERIOD OF ZONAL FLOW ALOFT WHILE SURFACE HIGH PRESSURE BUILDS 
 QUICKLY ACROSS THE SOUTHERN US TO THE CAROLINA COAST BY MONDAY.  
 TEMPS AROUND NORMAL SUNDAY WILL BEGIN TO REBOUND BACK ABOVE NORMAL 
 MONDAY AND TUESDAY AS SOUTHWESTERLY FLOW ALOFT DEVELOPS AHEAD OF THE 
 MEAN TROUGH BECOMING ESTABLISHED OVER THE CENTRAL US.  THERE AS SOME 
 LONGWAVE AMPLIFICATION DIFFERENCES AMONG MEDIUM RANGE MODELS... 
 WHICH LEADS TO LESS CONFIDENCE IN WHEN THE NEXT SYSTEM WILL IMPACT 
 CENTRAL NC...AND A SLOWER APPROACH PER ECMWF WOULD NOT BRING POPS IN 
 UNTIL LATE WEDNESDAY OR THURSDAY.
 
 &&
 
 .AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
 AS OF 150 AM WEDNESDAY...
 
 EXPECT VFR CONDITIONS THROUGH TONIGHT. CURRENT CIGS WITH BASES ABOVE 
 5 THOUSAND FEET WILL PERSIST OVER THE NORTHERN TERMINAL FORECAST 
 SITES (INT/GSO/RDU/RWI) UNTIL AROUND DAYBREAK. THESE ARE ASSOCIATED 
 WITH AN UPPER LEVEL LOW PRESSURE AREA CENTERED JUST TO OUR NORTH 
 OVER VA. AS THIS LOW DRIFTS TOWARD THE NNE AND AWAY FROM THE AREA 
 TODAY... SKIES WILL GRADUALLY CLEAR OUT WITH UNRESTRICTED SKIES AND 
 VSBYS INTO TONIGHT AS WEAK HIGH PRESSURE BUILDS INTO THE AREA FROM 
 THE NW. WINDS WILL HOLD FROM THE NW TODAY (AND WILL VEER TO NWRLY AT 
 RDU/RWI/FAY) AT SPEEDS OF 8-13 KTS WITH OCCASIONAL GUSTS TO 15-20 
 KTS FROM 13Z-22Z... MAINLY AT INT/GSO. WINDS BECOME LIGHT FROM THE 
 NORTH THIS EVENING.
 
 LOOKING BEYOND 06Z EARLY THURSDAY MORNING... VFR CONDITIONS WILL 
 DOMINATE THROUGH FRIDAY WITH HIGH PRESSURE NOSING IN FROM THE NW 
 THEN NORTH. AN APPROACHING STORM SYSTEM FROM THE WEST WILL BRING 
 THICKENING AND LOWERING MID CLOUDS AND LOW IFR STRATUS STARTING 
 FRIDAY EVENING WITH AN INCREASING RISK OF LOW LEVEL WIND SHEAR. GOOD 
 CHANCE OF IFR CIGS WITH WIDESPREAD SHOWERS AND STORMS SATURDAY... 
 THEN IMPROVING CONDITIONS BACK TO VFR ON SUNDAY. -GIH
 
 &&
 
 .RAH WATCHES/WARNINGS/ADVISORIES...
 NONE.
 
 &&
 
 $$
 
 SYNOPSIS...SMITH
 NEAR TERM...HARTFIELD
 SHORT TERM...HARTFIELD
 LONG TERM...SMITH
 AVIATION...HARTFIELD