Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 210801 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 400 AM EDT THU MAY 21 2015 .SYNOPSIS...LOW PRESSURE WILL TRACK EAST ALONG A QUASI-STATIONARY FRONT OVER NC TODAY. WEAK HIGH PRESSURE WILL FOLLOW FOR TONIGHT AND FRI. && .NEAR TERM /THROUGH TONIGHT/... AS OF 345 PM WEDNESDAY... OVERVIEW: MINOR SHORTWAVE ENERGY TRACKING INTO CENTRAL NC FROM THE WEST LATE TONIGHT WILL PROGRESS EAST TO THE NC/VA COAST BY 18Z THU AFTERNOON AND OFFSHORE SHORTLY THEREAFTER. MEANWHILE...POTENT SHORTWAVE ENERGY DIGGING INTO THE UPPER MS RIVER VALLEY TONIGHT WILL TRACK INTO THE OH VALLEY DURING THE DAY THU...PROGRESSING TO THE MID- ATLANTIC COAST THU NIGHT. A SFC LOW CENTERED IN VICINITY OF CHARLOTTE AT 12Z THU WILL TRACK EAST ALONG A NORTHWARD MOVING WARM FRONT (FRONT WILL STALL NEAR THE HWY 64 CORRIDOR)...PROGRESSING TO KINSTON/KENANSVILLE BY 18Z AND OFFSHORE BY 00Z...THOUGH A WEAK SFC TROUGH WILL LIKELY PERSIST OVER CENTRAL NC IN RESPONSE TO HEIGHT FALLS ATTENDANT POTENT SHORTWAVE ENERGY TRACKING EASTWARD THROUGH THE OH VALLEY INTO THE MID-ATLANTIC. MORNING: PRECIPITATION ASSOC/W WARM ADVECTION AND ELEVATED INSTABILITY ON THE EASTERN PERIPHERY OF THE SFC-H85 LOW THU MORNING WILL LIFT NORTHWARD INTO VA BY 15-18Z. ELEVATED SHOWERS MAY PERSIST ACROSS THE NORTHERN PIEDMONT AND NE COASTAL PLAIN IN VICINITY OF THE VA BORDER EARLY THU AFTERNOON...HOWEVER...WIDESPREAD ELEVATED CONVECTION WILL LIFT NORTHWARD THROUGH CENTRAL VA TO THE DELMARVA COAST BY MID AFTERNOON...IN CONCERT WITH THE BEST WARM ADVECTION AND IN CLOSER VICINITY TO STRONGER DPVA/HEIGHT FALLS ASSOC/W SHORTWAVE ENERGY TRACKING EASTWARD THROUGH THE OH VALLEY. AFTERNOON: PRIMARY FCST PROBLEM REVOLVES AROUND WHETHER OR NOT CONVECTION WILL RE-DEVELOP THU AFTERNOON...AND IF SO...COVERAGE/ INTENSITY...IN ADDITION TO HIGH TEMPS. RICH LOW-LEVEL MOISTURE WILL ADVECT NORTHWARD INTO CENTRAL NC ALONG THE EASTERN PERIPHERY OF THE SFC LOW THU AFTERNOON AS THE BOUNDARY STALLED TO THE SOUTH LIFTS NORTHWARD TO THE HWY 64 CORRIDOR AS A WARM FRONT...PARTICULARLY IN THE SANDHILLS AND SE COASTAL PLAIN WHERE DEWPOINTS WILL APPROACH UPPER 60S TO NEAR 70F AND FCST SOUNDINGS SUGGEST MODERATE DIURNAL DESTABILIZATION. WITH DPVA EXITING BY EARLY AFTERNOON AND ADDITIONAL SHORTWAVE ENERGY TOO FAR REMOVED FROM CENTRAL NC (OH VALLEY)... FORCING FOR ASCENT WILL LARGELY BE CONFINED TO LOW-LEVEL CONVERGENCE INVOF THE SFC LOW TRACKING EAST ALONG OR JUST SOUTH OF THE HWY 64 CORRIDOR. THOUGH WEAK/SHALLOW LOW-LEVEL CONVERGENCE ATTENDANT SFC TROUGHING WILL PERSIST THROUGH THE AFTERNOON...12Z GUIDANCE SUGGESTS THE BEST LOW-LEVEL CONVERGENCE (CENTER OF SFC LOW) WILL PROGRESS EAST OF THE I-95 CORRIDOR PRIOR TO PEAK HEATING (~18Z). FURTHERMORE...FCST SOUNDINGS INDICATE SIGNIFICANT DRYING AOA 700 MB FROM WEST-EAST THU AFTERNOON. GIVEN A TEMPORAL DISCONNECT BETWEEN THE BEST LOW-LEVEL FORCING/ DIURNAL DESTABILIZATION AND THE PRESENCE OF AN INCREASINGLY HOSTILE THERMODYNAMIC ENVIRONMENT (ENTRAINMENT OF DRY AIR AOA 700 MB)... IT IS POSSIBLE THAT AFTERNOON DEVELOPMENT WILL BE LIMITED TO SCATTERED SHOWER ACTIVITY OR POSSIBLY PRECLUDED ALTOGETHER. HOWEVER... UNCERTAINTY PERSISTS WITH REGARD TO THE PRECISE EVOLUTION OF THE APPROACHING SHORTWAVE/ATTENDANT SFC- LOW...AND A NARROW TEMPORAL/ SPATIAL WINDOW FAVORING THE DEVELOPMENT OF DEEP CONVECTION CANNOT BE ENTIRELY RULED OUT BETWEEN ~18-21Z IN THE SE COASTAL PLAIN. DEEP LAYER SHEAR WOULD BE SUFFICIENT FOR SUPERCELLULAR ORGANIZATION AND AN ATTENDANT POTENTIAL FOR SEVERE WIND/HAIL...SHOULD DEEP CONVECTION DEVELOP. WITH THE ABOVE IN MIND...OVERALL SVR THREAT (AND ANY TOR POTENTIAL) IS EXPECTED TO BE CONFINED TO COASTAL NC WHERE SFC-BASED CONVECTION IS MOST LIKELY TO OCCUR AND WHERE LOW-LEVEL SHEAR WILL BE MOST FAVORABLE ON THE EASTERN PERIPHERY OF THE SFC-H85 LOW. EXPECT HIGHS RANGING FROM THE LOWER/MID 70S N/NW TO MID 80S SE. THURSDAY NIGHT: EXPECT CLEARING SKIES AS A DRIER AIRMASS ADVECTS INTO THE REGION IN THE WAKE OF THE DEPARTING LOW. LOWS IN THE LOWER 50S. && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 355 AM THURSDAY... A TROUGH ALOFT WILL AMPLIFY ACROSS THE NORTHEAST AND MIDDLE ATLANTIC STATES FRI...THEN OFFSHORE FRI NIGHT. DESPITE THE AMPLIFICATION OF THE TROUGH...HEIGHT RISES ALOFT AND ASSOCIATED SUBSIDENCE WILL BE UNDERWAY OVER VA AND THE CAROLINAS...IN THE WAKE OF A LEAD SHORTWAVE TROUGH FORECAST TO CROSS THE MIDDLE ATLANTIC STATES TONIGHT. SURFACE HIGH PRESSURE WILL CONSEQUENTLY BUILD EAST FROM THE TN VALLEY ON FRI IN ASSOCIATION WITH THE LEAD MIDDLE ATLANTIC SHORTWAVE TROUGH... FOLLOWED BY THE PASSAGE OF A DRY COLD FRONT RESULTING FROM THE LARGER SCALE TROUGH AMPLIFICATION OVER THE NORTHEAST. TEMPERATURES WILL BE IN THE 70S ON FRI...WITH LOWER HUMIDITY VALUES OWING TO SURFACE DEWPOINTS IN THE 40S. TEMPERATURES FRI NIGHT WILL LIKELY VARY WILDLY...WITH PE-FRONTAL RADIATIONAL COOLING INITIALLY; THEN MIXING AND ASSOCIATED WARMING WITH FROPA; AND ENDING WITH CAA LATE...WITH LOWS BY THE END OF THE NIGHT IN THE 50S. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... AS OF 220 AM THURSDAY... SATURDAY THROUGH WEDNESDAY: VERY LITTLE SIGNIFICANT WEATHER IS EXPECTED DURING THE LONG TERM PERIOD WITH HIGH PRESSURE DOMINATING THE PATTERN FOR MUCH OF THE PERIOD. INITIALLY...SURFACE HIGH PRESSURE WILL BE TO THE NORTH OF THE AREA BRINING COOLER NORTHEASTERLY FLOW TO CENTRAL NC FOR SATURDAY BEFORE THE HIGH SLIDES OFFSHORE AND SETS UP EAST OF THE AREA. THIS WILL SHIFT WINDS TO SOUTHERLY (ALTHOUGH LIGHT) AND BEGIN A WARMING TREND THAT WILL CONTINUE THROUGH WEDNESDAY. INITIALLY...EXPECT TEMPERATURES IN THE UPPER 70S TO NEAR 80 DEGREES ON SATURDAY BUT STEADILY RISING A FEW DEGREES EACH DAY UP TO NEAR 90 DEGREES BY WEDNESDAY AFTERNOON. LOWS WILL FOLLOW A SIMILAR PATTERN...RISING A COUPLE DEGREES EACH DAY FROM THE UPPER 50S ON SATURDAY NIGHT UP TO THE UPPER 60S BY TUESDAY NIGHT/WEDNESDAY MORNING. MUCH OF THE PERIOD LOOKS DRY AS HIGH PRESSURE KEEPS MUCH OF THE PRECIPITATION THREAT WELL AWAY FROM THE AREA. LATE IN THE PERIOD...A FRONTAL SYSTEM WILL APPROACH FROM THE WEST AND THERE IS A LITTLE DISCREPANCY ON TIMING BUT MODELS THIS MORNING LOOK TO HOLD OFF PRECIPITATION WITH THIS FRONT A LITTLE LONGER THAN THE PREVIOUS DAYS RUNS AND THEREFORE HAVE CUT BACK POPS ON TUESDAY AND WEDNESDAY...INTRODUCING A SLIGHT CHANCE IN THE WEST ON TUESDAY AFTERNOON AND THEN CHANCE IN THE WEST...SLIGHT CHANCE IN THE EAST ON WEDNESDAY AFTERNOON. && .AVIATION /06Z THURSDAY THROUGH MONDAY/... AS OF 230 AM THURSDAY... A WARM FRONT AND ASSOCIATED LIFT AND FOCUS FOR THE DEVELOPMENT OF BOTH MVFR-IFR CEILINGS AND SCATTERED ELEVATED SHOWERS/STORMS WILL CONTINUE TO RETREAT NORTH INTO CENTRAL NC THIS MORNING...WITH THE RELATIVE BEST CHANCE OF SHOWERS AND STORMS AT GSO/INT/RDU THROUGH 15Z. A WAVE OF LOW PRESSURE WILL TRACK EAST ALONG THE FRONT...WHICH IS EXPECTED TO STALL IN THE VICINITY OF A LINE FROM NEAR RDU TO RWI. THE LOW PRESSURE WILL BE ACCOMPANIED BY A BAND OF THUNDERSTORMS THAT WILL LIKELY DEVELOP NEAR THE TRIAD TERMINALS BETWEEN 15-17Z AND GAIN STRENGTH AS IT MOVES EAST INTO AN INCREASINGLY UNSTABLE AIR MASS DOWNSTREAM...PARTICULARLY SOUTH OF THE WARM FRONT -AT FAY- WHERE DESTABILIZATION WILL BE MAXIMIZED. OTHERWISE...THE FRONT WILL ALSO SERVE AS THE BOUNDARY BETWEEN CONTINUED MVFR-IFR CEILINGS TO THE NORTH AND VFR CEILINGS AND A GUSTY S TO SW SURFACE WIND TO THE SOUTH. WHILE THE ASSOCIATED SUB-VFR CEILINGS MAY LINGER AT NORTHERN TAF SITES INTO HE AFTERNOON...OR EVENING EARLY EVENING AT RWI...DRIER AIR WILL EVENTUALLY SETTLE SOUTH INTO OUR AREA IN THE WAKE OF THE PASSING LOW PRESSURE SYSTEM...WITH AN ASSOCIATED RETURN TO VFR CONDITIONS FOR TONIGHT. OUTLOOK: VFR...UNDER THE INFLUENCE OF HIGH PRESSURE. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...26 NEAR TERM...BRV SHORT TERM...26 LONG TERM...ELLIS AVIATION...26

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