Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 100504 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 105 AM EDT THU JUL 10 2014 .SYNOPSIS...A WEAKENING COLD FRONT WILL MOVE INTO THE AREA TODAY THEN DRIFT TOWARD THE COAST FRIDAY. WEAK HIGH PRESSURE WILL SETTLE OVER THE REGION SATURDAY. && .NEAR TERM /OVERNIGHT/... 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 && .SHORT TERM /THURSDAY AND THURSDAY NIGHT/... 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. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... 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 && AVIATION /06Z THURSDAY THROUGH MONDAY/... AS OF 105 AM THURSDAY... A MOIST AND UNSTABLE AIR MASS WILL SUPPORT THE DEVELOPMENT OF SCATTERED TO NUMEROUS SHOWERS AND THUNDERSTORMS OVERNIGHT THROUGH THURSDAY NIGHT AS AN UPPER LEVEL TROUGH AND ATTENDANT SURFACE BOUNDARY MOVES ACROSS THE AREA. THE SHOWERS AND STORMS WILL BE MOST NUMEROUS DURING THE AFTERNOON AND EARLY EVENING HOURS. EXPECT MVFR/IFR VISIBILITIES AND CEILINGS IN VICINITY OF THE HEAVIER SHOWERS AND STORMS. AWAY FROM THE CONVECTION...EXPECT VFR CONDITIONS WITH SFC WINDS PREDOMINATELY WEST-SOUTHWEST AT LESS THAN 10 KTS. IMPROVING AVIATION CONDITIONS ANTICIPATED FRIDAY THROUGH SATURDAY AS A SLIGHTLY DRIER MORE STABLE AIR MASS COVERS MOST OF THE REGION. SCATTERED AFTERNOON-EARLY EVENING CONVECTION WILL STILL BE PROBABLE IN VICINITY OF KFAY AND KRWI FRIDAY WHERE AVAILABLE MOISTURE AND LOW LEVEL INSTABILITY WILL BE BEST COMPARED TO THE PIEDMONT. ANY CONVECTION SATURDAY IS EXPECTED TO BE ISOLATED. BY SUNDAY AND MONDAY ...REMNANTS OF DECAYING THUNDERSTORM COMPLEXES ORIGINATING IN THE MIDWEST MAY BEGIN TO AFFECT CENTRAL NC...LEADING TO A SLIGHTLY BETTER CHANCE FOR SCATTERED CONVECTION AND ASSOCIATED MVFR CONDITIONS. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...WSS NEAR TERM...VINCENT SHORT TERM...NP LONG TERM...HARTFIELD AVIATION...WSS

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