Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 100250 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 1050 PM EDT WED JUL 9 2014 .SYNOPSIS...
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CYCLONIC FLOW ALOFT WILL PREVAIL OVER THE REGION THROUGH FRIDAY. MEANWHILE...A STALLED FRONT WILL PERSIST ACROSS THE CAROLINAS THROUGH FRIDAY.
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&& .NEAR TERM /OVERNIGHT/...
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AS OF 1045 PM WEDNESDAY... CYCLONIC FLOW ALOFT WILL PREVAIL ACROSS THE REGION OVERNIGHT... FOSTERING A POTENTIAL FOR DPVA ASSOCIATED WITH SMALL AMPLITUDE DISTURBANCES TRACKING EAST FROM THE TN/OH VALLEY INTO THE MID- ATLANTIC AND NORTH CAROLINA. GIVEN THE PRESENCE OF MARGINAL NOCTURNAL INSTABILITY (500-1000 J/KG MUCAPE) AND THE PRESENCE OF A SHORTWAVE JUST UPSTREAM OVER TN/KY (PER RAP DATA AND WV IMAGERY)... WILL CONTINUE TO INDICATE A SLIGHT CHANCE OF SHOWERS/STORMS THROUGHOUT THE NIGHT. EXPECT LOWS IN THE LOWER 70S. -VINCENT
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&& .SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
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AS OF 230 PM WEDNESDAY... SCATTERED SHOWERS AND THUNDERSTORMS WILL OCCUR AGAIN ON THURSDAY AS A SERIES OF WEAK DISTURBANCES MOVE NE ACROSS OUR AREA IN ADVANCE OF THE MID-LEVEL TROUGH AXIS TO OUR WEST. AT THE SFC...THE COLD FRONT CURRENTLY TO OUR NW WILL DROP SOUTH AND MERGE WITH THE PIEDMONT TROUGH...PROVIDING A LOW LEVEL FOCUS FOR CONVECTION INITIATION. NOTED THAT GUIDANCE SHOWS AN AXIS OF HIGH PWAT (AROUND 2 INCHES) WILL PERSIST ACROSS THE EASTERN 2/3 OF OUR CWA DURING THE AFTERNOON INTO THE EVENING...TRENDING LOWER TO AROUND 1.5 INCHES ACROSS THE TRIAD. MEANWHILE...DEEP LAYER SHEAR WILL BE SIMILAR TO TODAY...25KT OR LESS. THUS...WHILE WE CAN`T RULE OUT THE POTENTIAL FOR AN ISOLATED STRONG WIND GUST OR TWO...THE MAIN IMPACTS MAY INSTEAD BE HEAVY RAIN INVOF OF THE BELT OF HIGH PWAT...AND THE POTENTIAL FOR LOCALIZED POOR DRAINAGE FLOODING WITH ANY OF THE SLOWER CELLS OR LOCATIONS THAT SEE REPETITIVE DOWNPOURS. GIVEN THIS MOISTURE PROFILE...LOOK FOR THE BEST COVERAGE AND THUS HIGHEST POPS TO BE EAST OF THE TRIAD. SIMILAR TO TODAY...HIGHS WILL BE DEPENDENT ON CLOUD COVERAGE...WHICH MAY BE MORE WIDESPREAD ACROSS OUR CWA TOMORROW COMPARED TO TODAY. HIGHS IN THE MID-UPR 80S AND LOWS THURSDAY NIGHT IN THE UPPER 60S TO AROUND 70.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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AS OF 245 PM WEDNESDAY... FOR FRI THROUGH SAT NIGHT: THE WEAKENING MID LEVEL TROUGH AXIS SHIFTS EAST OF THE SRN APPALACHIANS FRI... BEFORE SWEEPING OVERHEAD FRI NIGHT AND TO OUR EAST SAT. THE WEAK SURFACE TROUGH WILL ROUGHLY FOLLOW THIS PACE AS WELL... SETTLING OVER THE COASTAL CAROLINAS BY SAT MORNING BEFORE LARGELY DISSIPATING. THE EASTERN HALF OF NC WILL REMAIN WITHIN SUFFICIENTLY DEEP MOISTURE FRI FOR MAINLY AFTERNOON/EVENING SHOWERS AND STORMS... WHILE A DRIER COLUMN... SLIGHT RISE IN HEIGHTS ALOFT... AND DOWNSLOPE LOW LEVEL FLOW OVER THE WEST WILL LIMIT CONVECTION THERE... A PATTERN SUPPORTED BY THE LATEST SREF PROBABILITIES OF CONVECTIVE PRECIP. THE GFS SHOWS MUCAPE PEAKING AT 1500-2000 J/KG BUT SUBPAR DEEP LAYER SHEAR OF JUST AROUND 20 KTS OR SO... SO EXPECT ANOTHER ROUND OF WEAKLY FORCED AND SLOW MOVING MULTICELL CLUSTER WITH SUPPRESSED SEVERITY BUT THE POTENTIAL FOR TRAINING CELLS AND LOCALLY HEAVY RAIN GIVEN THE PW HOLDING NEAR 2.0 INCHES EAST OF HIGHWAY 1. THE SHEAR AXIS BROADENS AND WEAKENS FURTHER ON SAT WITH MINOR RISES IN HEIGHTS ALOFT. ANY TRACE OF THE SURFACE TROUGH IS TOUGH TO DETECT ON THE MODEL OUTPUT WITH A FAIRLY UNIFORM LIGHT LOW LEVEL FLOW FROM THE S AND SE. MODELS SHOW CENTRAL AND WRN NC WITHIN A RELATIVE PW MINIMUM... BETWEEN THE 1.5+ INCH VALUES OVER COASTAL NC AND ERN SC... AND THE HIGHER VALUES PUSHING INTO THE OH VALLEY ASSOCIATED WITH WHAT WILL LIKELY BE AN MCS CROSSING THE MIDWEST AND SOUTHERN END OF THE GREAT LAKES SAT/SAT NIGHT. BUT ANY AMOUNT OF ATLANTIC-SOURCE LOW LEVEL INFLOW COMBINED WITH HEATING COULD GENERATE DISORGANIZED ISOLATED TO SCATTERED PULSE CONVECTION IN THE AFTERNOON. WILL HAVE POPS ON THE LOW END... 20-30% ORIENTED NW TO SE RESPECTIVELY...SAT AFTERNOON/EVENING. THICKNESSES BOTH FRI AND SAT STAY SLIGHTLY BELOW NORMAL...WITH A BIT MORE SUNSHINE ANTICIPATED SAT THAN FRI... SO WILL HOLD ONTO HIGHS FROM THE MID 80S TO NEAR 90 WITH LOWS IN THE UPPER 60S TO LOWER 70S. FOR SUN-WED: DEEP LAYER WIND FIELDS REMAIN VERY WEAK SUNDAY WITH ONLY A SUBTLE SURFACE TROUGH EVIDENT THROUGH THE PIEDMONT... HOWEVER WE WILL START TO SEE PW VALUES RECOVER BACK UP ABOVE SEASONAL NORMALS... SUGGESTING A TREND BACK TO MORE SEASONALLY TYPICAL COVERAGE OF AFTERNOON PULSE CONVECTION FOR SUNDAY. AN ANOMALOUSLY STRONG MID LEVEL VORTEX (MID LEVEL HEIGHTS AS LOW S 2-3 STANDARD DEVIATIONS BELOW NORMAL) AS LOW AS WILL WOBBLE EASTWARD ACROSS SRN ONTARIO AND THE NRN GREAT LAKES SUN-TUE THEN INTO QUEBEC WED... AND THIS BROAD TROUGHING OVER ERN NOAM WILL MEAN INCREASINGLY UNSETTLED WEATHER FOR NC... WITH SW LOW LEVEL AHEAD OF THE SLOWLY APPROACHING SURFACE COLD FRONT... AND STRENGTHENING MID LEVEL WESTERLY FLOW FOSTERING BETTER STORM ORGANIZATION. WILL PLACE GOOD CHANCES OF SHOWERS AND STORMS FOCUSED ON EACH AFTERNOON/EVENING MON-TUE... WITH PERHAPS A SOUTHEASTWARD SHIFT OF THE HIGHER POPS WED TO LEVERAGE THE POSSIBILITY THAT THE SURFACE FRONT MIGHT DROP SE INTO THE CWA AND PUSH THE BETTER MOISTURE INTO SRN/ERN NC. SEE NOTHING TO INDICATE A MAJOR DEPARTURE FROM CLIMATOLOGICAL TEMPS... AS GREATER-THAN-USUAL CLOUD COVER WITH HEATING EACH DAY WILL MODULATE SLIGHTLY ABOVE- NORMAL THICKNESSES... SO WILL STICK WITH DAILY HIGHS IN THE UPPER 80S TO LOWER 90S... AND DAILY LOWS NEAR 70 TO THE LOWER 70S. -GIH
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&& AVIATION /00Z THURSDAY THROUGH MONDAY/... AS OF 700 PM WEDNESDAY... 24 HOUR TAF PERIOD: SHOWERS AND THUNDERSTORMS CURRENTLY AFFECTING THE TRIAD WILL MOVE EASTWARD OVER THE NEXT SEVERAL HOURS. ANOTHER BOUNDARY IN THE EXTREME EASTWARD SIDE OF THE AREA IS ALSO PRODUCING CONVECTION BUT SHOULD MOVE OFF TO THE EAST. ALL IN ALL CONVECTION SEEMS TO BE WINDING DOWN WITH THE EXCEPTION BEING MAYBE ACROSS THE NORTH AND EAST. WILL CONTINUE TO MENTION SHOWERS IN THE TAFS AT KRDU AND KRWI AS THEY ARE THE MOST LIKELY TO BE AFFECTED OVER THE NEXT SEVERAL HOURS. EXPECT LIGHT SOUTHWESTERLY WINDS OVERNIGHT AT 5-10 KTS. THERE COULD BE POCKETS OF FOG OR LOW STRATUS OVERNIGHT..ESPECIALLY WHERE THERE HAS BEEN CONVECTION BUT CONFIDENCE IN THIS IS LOW AND IT WILL BE LEFT OUT OF THE TAFS AT THIS TIME. THERE MAY BE SOME IMPROVED CONDITIONS AROUND DAYBREAK BUT THESE WILL QUICKLY GO DOWN HILL DURING THE AFTERNOON AS CONVECTION IS EXPECTED TO BE FAIRLY WIDESPREAD AS A COLD FRONT MOVES IN FROM THE NORTHWEST. WILL COVER WITH A PROB 30 GROUP AFTER 18Z BUT A GOOD CHANCE FOR PROLONGED MVFR CONDITIONS AT ALL SITES TOMORROW AFTERNOON WITH CEILINGS NEAR 3 KFT AND 5 SM VISIBILITIES POSSIBLE. THIS IS EXPECTED TO CONTINUE THROUGH THE END OF THE TAF PERIOD. LONG TERM: THERE WILL BE CONTINUED CHANCES FOR SUB-VFR CONDITIONS THROUGH MONDAY WITH THE LEAST COVERAGE SATURDAY AND SUNDAY BUT STILL A CHANCE FOR DIURNAL CONVECTION...ESPECIALLY IN THE EAST. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...NP LONG TERM...HARTFIELD AVIATION...ELLIS

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