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Data updated Mon Apr 17 2006
FXUS62 KRAH 240719


AFDRAH





AREA FORECAST DISCUSSION


NATIONAL WEATHER SERVICE RALEIGH NC


315 AM EDT SAT APR 24 2010





.SYNOPSIS...


A STORM SYSTEM OVER THE CENTRAL STATES AND LOWER MISSISSIPPI VALLEY 


WILL MOVE NORTHEAST TOWARD THE GREAT LAKES THIS WEEKEND. DEEP 


SOUTHWEST FLOW DEVELOPING OVER THE SOUTHEAST AND MIDATLANTIC REGION 


WILL BRING IN INCREASINGLY MOIST AND UNSTABLE AIR... KEEPING THE 


WEATHER UNSETTLED THROUGH SUNDAY NIGHT. A COLD FRONT WILL SWEEP 


THROUGH THE AREA MONDAY... USHERING IN COOLER AND DRIER AIR.





$$





.NEAR TERM /THROUGH TONIGHT/...


AS OF 255 AM SATURDAY...





THROUGH THIS MORNING: MID LEVEL CLOUDINESS CONTINUES TO STREAM INTO 


WESTERN AND CENTRAL NC. SCATTERED SHOWERS ARE DEVELOPING OVER NORTH 


CENTRAL/NE NC IN APPARENT ASSOCIATION WITH A BAND OF ENHANCED MOIST 


UPGLIDE ALONG THE SLOWLY RETREATING 850 MB WARM FRONT. THE LATEST 


MODEL GUIDANCE EASES THIS UPGLIDE SLOWLY NORTHEAST THIS MORNING AS 


THE 850 MB WARM FRONT BECOMES MORE DIFFUSE AND SHIFTS TO OUR 


NORTHEAST... BUT WILL MENTION SCATTERED SHOWERS ACROSS THE NORTHEAST 


CWA INTO MID MORNING. FORECAST SOUNDINGS SHOW MINOR INSTABILITY 


EARLY THIS MORNING WITH DECENT DEEP LAYER SHEAR ON THE IMMEDIATE 


NORTHEAST SIDE OF THE MID LEVEL RIDGE AXIS... AND SPC MESOANALYSES 


SHOW A POCKET OF UPPER DIVERGENCE HERE IN THE RIGHT ENTRANCE REGION 


OF A JETLET JUST TO OUR NORTHEAST. AS SUCH... SHOWERS COULD BECOME 


TALL/PERSISTENT ENOUGH FOR A FEW LIGHTNING STRIKES. AS THIS UPPER 


FORCING AND FAVORABLE SHEAR SHIFT TO OUR NORTHEAST THIS MORNING 


WHILE THE MID LEVEL RIDGE SHIFTS OVERHEAD... PRECIP CHANCES WILL 


DIMINISH. TEMPS SHOULD WARM NICELY INTO THE UPPER 60S TO LOWER 70S 


BY NOON EVERYWHERE DESPITE THE LIMITED SUNSHINE ESPECIALLY OVER THE 


PIEDMONT. 





FOR THIS AFTERNOON: THE LARGE AREA OF CONVECTION JUST TO OUR WEST 


COVERING MUCH OF TN INTO AL/GA APPEARS TO BE LARGELY SUPPORTED BY 


STRONG UPPER DIVERGENCE (WITH THE 110+ KT JET OVER SRN TX/LA/AR) IN 


A CONDITIONALLY UNSTABLE AIR MASS. BUT THIS CONVECTION IS OUTRUNNING 


THIS FORCING AS IT MOVES EAST AND ENCOUNTERS LIGHTER UPPER LEVEL 


WINDS AND WEAKER LAPSE RATES BENEATH THE MID LEVEL RIDGE THAT COVERS 


MUCH OF THE SOUTHEAST INCLUDING THE CAROLINAS. THIS CONVECTION IS 


LIKELY TO CONTINUE TO DISSIPATE THIS MORNING AND BY THE TIME ITS 


REMNANTS ARRIVE IN CENTRAL NC... ONLY A FEW SHOWERS ARE EXPECTED. 


THIS IS REFLECTED FAIRLY WELL IN THE 00Z 4KM WRF... ALTHOUGH IT DOES 


SHOW CONVECTION FIRING IN THE SANDHILLS/COASTAL PLAIN VERY LATE THIS 


AFTERNOON. WHILE THIS IS NOT IMPLAUSIBLE... OTHER MODELS SHOW 


MINIMAL INSTABILITY THROUGH THIS AFTERNOON AND THEY SUPPRESS THE 


BEST LOW LEVEL MOISTURE TRANSPORT TO OUR WEST THROUGH 00Z. THE MID 


LEVEL RIDGE AXIS HOLDS OVER EASTERN NC TODAY... LIMITING ANY DPVA... 


AND THE BEST UPPER DIVERGENCE REDEVELOPS OVER KY/TN/MS/AL THIS 


AFTERNOON... AN AREA LIKELY TO SEE WIDESPREAD STRONG TO SEVERE  


STORMS ALONG A 50-60 KT LOW LEVEL JET... MEANING A BETTER CHANCE OF 


SUBSIDENCE DOWNSHEAR OVER NC. WILL KEEP POPS ON THE LOW SIDE THIS 


AFTERNOON WITH A STEEP INCREASE IN THE EXTREME WESTERN CWA TOWARD 


00Z. HIGHS 73-82.





FOR TONIGHT: INSTABILITY INCREASES OVERNIGHT OVER CENTRAL NC WITH 


NAM/GFS MLCAPE RISING TO 300-600 J/KG... OKAY BUT NOT NEARLY AS 


IMPRESSIVE AS THE 1500+ J/KG EXPECTED OVER THE GULF STATES BY THIS 


EVENING. THE 50+ KT LOW LEVEL JET CORE HOWEVER DOES SWEEP EAST 


ACROSS CENTRAL NC OVERNIGHT... AND DEEP LAYER SHEAR SITS IN EXCESS 


OF 45 KTS WITH AN AREA OF UPPER DIVERGENCE PROJECTED TO SLIDE OVER 


THE STATE. WITH THIS IMPROVING FORCING AND PRECIP WATER INCREASING 


OVER 1.5 INCHES... WILL BUMP UP POPS TO CATEGORICAL IN THE WESTERN 


CWA THIS EVENING... THEN EXPECT HIGH POPS TO SHIFT INTO THE EASTERN 


CWA LATE TONIGHT AS THE LOW LEVEL JET MOVES INTO EASTERN NC. A FEW 


STORMS MAY BECOME STRONG TO SEVERE WITH DAMAGING WINDS AS THE MAIN 


THREAT GIVEN THE LONG FAIRLY STRAIGHT HODOGRAPH (HAIL IS A LESSER 


POSSIBILITY WITH THE FORECAST CAPE IN THE MIXED PHASE LAYER HOLDING 


UNDER 100 J/KG)... BUT THE MID LEVEL LAPSE RATES REMAIN MARGINAL 


OVERNIGHT WITH THE MID LEVEL FLOW REMAINING ANTICYCLONIC BEFORE 


FLATTENING OUT VERY LATE... SO ANY SEVERE STORMS SHOULD BE ISOLATED. 


WITH STRONG LOW LEVEL WARM ADVECTION... EXPECT VERY MILD LOWS ABOVE 


STATISTICAL GUIDANCE... MAINLY IN THE MID 60S. WITH THE LOW LEVELS 


REMAINING MIXED OVERNIGHT... WINDS WILL BE VERY BLUSTERY FROM THE 


SOUTH-SOUTHWEST... SUSTAINED OVER 12 KTS WITH FREQUENT GUSTS OVER 25 


KTS LIKELY. -GIH





&&





.SHORT TERM /SUNDAY AND SUNDAY NIGHT/....


AS OF 245 AM SATURDAY:





SUNDAY AND SUNDAY NIGHT:


TRICKY FORECAST FOR SUNDAY. DRIER AIR ALOFT IF FORECAST TO SPREAD 


ACROSS THE AREA ON SUNDAY. HOWEVER... WITH A CONTINUED MOIST 


SOUTHWESTERLY LOW LEVEL FLOW AND MLCAPE VALUES OF UPWARDS OF 500 TO 


1200 J/KG IN THE AFTERNOON THINK WE SHOULD SEE SOME CONVECTION ON 


SUNDAY AFTERNOON. IN ADDITION... DEEP LAYER SHEAR IS EXPECTED TO BE 


IN THE 50 TO 60 KTS RANGE. INSTABILITY LOOKS TO BE THE BEST ACROSS 


EASTERN PORTIONS OF THE AREA... GENERALLY RALEIGH EASTWARD. 


HOWEVER... OVERALL LACK OF DEEP MOISTURE OR A WELL DEFINED LOW LEVEL 


TRIGGER (OUTSIDE OF MESOSCALE BOUNDARIES) SHOULD LIMIT COVERAGE OF 


STORMS GREATLY. THUS... PLAN ON KEEPING POPS IN THE CHANCE RANGE ON 


SUNDAY AFTERNOON INTO THE EVENING. WITH THAT SAID... SPC HAS PLACED 


ALL OF CENTRAL NC IN A SLIGHT RISK FOR SEVERE THUNDERSTORMS ON 


SUNDAY AFTERNOON INTO THE EVENING... WITH THE HIGHEST PROBABILITY OF 


SVR STORMS ACROSS THE EASTERN PORTION OF THE AREA.... WITH THE MAIN 


THREAT DAMAGING WINDS AND HAIL. AFTER SUNSET EXPECT COVERAGE WILL 


BEGIN TO DWINDLE. HOWEVER... WOULD NOT BE SURPRISED IF STRONG TO 


SEVERE THUNDERSTORMS PERSIST A BIT ACROSS THE EAST AFTER SUNSET... 


AS OUTFLOW DRIVEN STORMS CONTINUE TO FIRE UNTIL THE BL STABILIZES. 


HIGHS ON SUNDAY LOOK TO BE IN THE LOWER TO PERHAPS MID 80S. WITH DEW 


POINTS LIKELY IN THE LOWER TO MID 60S AT LEAST... IT WILL FEEL QUITE 


SUMMER LIKE OUT. IN ADDITION TO THIS AND THE STORMS... IT WILL BE 


QUITE WINDY AS WELL AS MODEL SOUNDING SHOW WINDS NEAR THE TOP OF THE 


MIXED LAYER NEAR 40 KTS. THUS... EXPECT WINDS ON SUNDAY OF 20 TO 25 


MPH... WITH GUSTS OF 30 TO POSSIBLY 35 MPH.





SUNDAY NIGHT... TEMPS SHOULD REMAIN MILD ON SUNDAY NIGHT... IN 


ADVANCE OF AN APPROACHING COLD FRONT. AS THE MID/UPPER LOW SLOWLY 


MOVES EASTWARD ACROSS THE OH VALLEY ON SUNDAY NIGHT A S/W TROUGH IS 


EXPECTED TO TRACK THROUGH THE L/W PATTERN AND ACROSS CAROLINAS. 


THUS... HAVE ADDED A SLIGHT CHANCES OF SHOWERS AFTER MIDNIGHT. GIVEN 


THE COLD FRONT IS EXPECTED TO REMAIN TO THE WEST OF THE AREA... 


ALLOWING FOR BREEZY SOUTHWESTERLY WINDS TO CONTINUE OVERNIGHT... 


WILL GO WITH OVERNIGHT LOWS ON THE WARM SIDE OF GUIDANCE. THIS 


YIELDS LOW TEMPS IN THE LOWER TO MID 60S. -BSD





&&





.LONG TERM/MONDAY THROUGH THURSDAY/...


AS OF 310 AM SATURDAY...





MONDAY THROUGH WEDNESDAY:


AS THE MID/UPPER LOW BEGINS TO LIFT OUT OF THE OH VALLEY AND INTO 


THE NORTHEAST AND PHASE WITH THE A MID/UPPER LOW OVER EASTERN 


CANADA... A COLD FRONT WILL MOVE THROUGH OUR AREA ON MONDAY. EVEN 


WITH LESS IN THE WAY OF INSTABILITY ON MONDAY... EXPECT WE WILL SEE 


AT LEAST ISOLATED SHOWERS AND THUNDERSTORMS ON MONDAY AFTERNOON AS 


THE FRONT CROSSES THE AREA... WITH THE BEST CHANCES ACROSS THE EAST. 


THUS... FOR NOW WILL MAINTAIN LOW END CHANCE POPS. GIVEN THE LOWER 


INSTABILITY... SPC ONLY HAS A SEE TEXT FOR EXTREME EASTERN PORTIONS 


OF NORTH CAROLINA. THUS... IF WE DO SEE ANY STRONG STORMS WOULD 


EXPECT THEM TO BE IN THE COASTAL PLAIN. HIGHS ON MONDAY WILL DEPEND 


ON THE TIMING OF THE FRONT... WHICH LOOKS TO BE IN THE LATE MORNING 


INTO THE AFTERNOON. THUS... FOR NOW WILL GO HIGHS RANGING FROM THE 


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





DRY WEATHER SHOULD PREVAIL ON MONDAY NIGHT... WITH WEST TO WEST 


NORTHWESTERLY FLOW THROUGH THE COLUMN. THIS SHOULD RESULT IN OVERNIGHT 


LOWS FALLING INTO THE UPPER 40S ACROSS THE NORTH AND WEST TO LOWER 


TO MID 50S ACROSS THE SOUTHEAST.





TUESDAY THROUGH WEDNESDAY... A COUPLE MORE SHORTWAVE TROUGHS ARE 


EXPECTED TO CROSS THE AREA IN THE CONTINUED CYCLONIC FLOW ALOFT 


ACROSS THE EASTERN U.S. THIS WILL RESULT IN POSSIBLY SOME ISOLATED 


SHOWERS BOTH AFTERNOONS. OTHERWISE EXPECT TRANQUIL WEATHER DURING 


THIS TIME WITH HIGH A BIT BELOW NORMAL IN THE UPPER 60S TO MID 


70S... AND LOWS IN THE MID TO UPPER 40S ON WEDNESDAY MORNING.





WEDNESDAY NIGHT THROUGH FRIDAY:


UPPER RIDGE BUILDS BACK ACROSS THE AREA DURING THIS TIME FRAME... 


ALLOWING QUIET WEATHER AND TEMPS TO REBOUND... WITH AFTERNOON 


HIGHS BACK ABOVE NORMAL BY FRIDAY.








&&





AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...


AS OF 210 AM SATURDAY...





AREAS OF MVFR FOG ARE POSSIBLE MAINLY AT INT/GSO THROUGH DAYBREAK... 


AND RWI IS LIKELY TO DROP TO LIFR AS IS CLIMATOLOGICALLY FAVORED... 


BUT OTHERWISE VFR CONDITIONS WILL DOMINATE THROUGH MUCH OF TODAY. 


BUT THIS WILL BE FOLLOWED BY A QUICK DETERIORATION TO MVFR/IFR AFTER 


23Z THIS EVENING.





WE CONTINUE TO WATCH A STRONG MID LEVEL LOW PRESSURE SYSTEM OVER THE 


CENTRAL U.S. WITH A TRAILING WARM FRONT EXTENDING SOUTHEAST ACROSS 


THE GULF STATES... WHILE A MID LEVEL RIDGE AXIS SITS OVER THE 


SOUTHEAST COAST INCLUDING THE CAROLINAS. HIGH RELATIVE HUMIDITY AND 


WEAK WINDS OVER CENTRAL NC ARE DUE IN PART TO A WEAK PRESSURE 


GRADIENT WITH A WEAK BOUNDARY ACROSS NC... AND THESE FACTORS MAY 


LEAD TO FOG DEVELOPMENT THIS MORNING... ALTHOUGH THE VEIL OF MID 


CLOUDS MAY BE JUST THICK ENOUGH TO INHIBIT FULL COOLING DOWN TO THE 


DEW POINT. PATCHY SHOWERS - ASSOCIATED WITH THE 850 MB WARM FRONT - 


WILL CONTINUE TO STREAM OVER NORTHEAST NC EARLY THIS MORNING... 


AFFECTING MAINLY RWI AND RDU... AND A LIGHTNING STRIKE OR TWO IS 


ALSO POSSIBLE. MUCH MORE WIDESPREAD SHOWERS AND STORMS CURRENTLY 


COVERING MUCH OF IL/TN THROUGH NORTHERN MS/AL INTO WESTERN GA ARE 


EXPECTED TO WEAKEN AND BREAK APART BY DAYBREAK AS THEY HEAD TOWARD 


CENTRAL NC... RESULTING IN JUST RESIDUAL PATCHY SHOWERS AND 


THICKENING MID CLOUDINESS OVER CENTRAL NC. THE ARRIVAL OF A LOW 


LEVEL JET VERY LATE THIS AFTERNOON THROUGH TONIGHT WILL BRING 


WIDESPREAD SHOWERS AND A FEW STORMS TO ALL TAF SITES... STARTING 


FIRST AT INT/GSO BY EARLY EVENING THEN SPREADING TO RDU/RWI/FAY 


THROUGH THE EVENING AND OVERNIGHT. THESE WILL LIKELY BRING MVFR/IFR 


CONDITIONS ALONG WITH BRISK AND GUSTY WINDS FROM THE SOUTH AND 


SOUTHWEST TONIGHT. WIND PROFILES WILL BE FAIRLY UNIDIRECTIONAL WITH 


A STEADY INCREASE IN SPEED WITH HEIGHT FROM THE SURFACE ON UP... SO 


THE RISK OF TRUE LOW LEVEL WIND SHEAR IS SMALL... BUT THIS WILL 


CERTAINLY INCREASE THE RISK OF VIGOROUS MECHANICAL TURBULENCE 


BEGINNING LATE THIS EVENING. 





LOOKING BEYOND TONIGHT... THE SHOWERS/STORMS SHOULD BECOME MORE 


SCATTERED TOWARD SUNDAY MORNING BUT MVFR/IFR CONDITIONS WILL HOLD 


INTO THE MORNING ALONG WITH BLUSTERY GUSTY SOUTHWEST WINDS. CIGS 


SHOULD CLIMB UP TO VFR BY MIDDAY SUNDAY BUT A GOOD CHANCE OF STORMS 


WILL LINGER THROUGH SUNDAY AFTERNOON ESPECIALLY EAST OF HIGHWAY 1. 


ANOTHER ROUND OF MVFR SCATTERED SHOWERS IS EXPECTED MONDAY AFTERNOON 


AND EVENING WITH A COLD FRONT PASSAGE. THEN... ANY CIGS MONDAY NIGHT 


THROUGH WEDNESDAY ARE EXPECTED TO BE VFR WITH LITTLE RISK OF FOG. 


-GIH 





&&





.RAH WATCHES/WARNINGS/ADVISORIES...


NONE.





&&





$$





SYNOPSIS...HARTFIELD


NEAR TERM...HARTFIELD


SHORT TERM...BSD


LONG TERM...BSD


AVIATION...HARTFIELD