Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 250701 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 301 AM EDT MON APR 25 2016 .SYNOPSIS...
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SOUTHERLY RETURN FLOW WILL RESULT IN A GENERAL WARMING TREND THROUGH MID-WEEK. A WEAKENING COLD FRONT WILL APPROACH THE AREA FROM THE NORTH TUESDAY NIGHT...STALL NEAR THE VIRGINIA BORDER ON WEDNESDAY... THEN LIFT NORTHWARD INTO THE DELMARVA AS A WARM FRONT ON THURSDAY.
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&& .NEAR TERM /TODAY AND TONIGHT/...
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AS OF 255 AM MONDAY... THOUGH SOUTHWESTERLY RETURN FLOW HAS COMMENCED...MOISTURE IS EXPECTED TO REMAIN INSUFFICIENT TO SUPPORT CONVECTION THIS AFTERNOON (ESP. GIVEN SOUTHWESTERLY LOW-LEVEL FLOW OVER LAND IN LIEU OF SOUTHERLY FLOW OFF THE ATLANTIC) AND LITTLE (IF ANY) FORCING. ISOLD CONVECTION CANNOT BE RULED OUT ON THE WESTERN RIDGE OF THE MTNS NEAR THE NC/TN BORDER WHERE RETURN FLOW /LOW-LEVEL MOISTURE/ WILL BE SOMEWHAT BETTER ESTABLISHED AND UPSLOPE FLOW/DIFFERENTIAL HEATING MAY BE SUFFICIENT TO SUPPORT DIURNAL CONVECTION. ALTHOUGH ~25 KT WESTERLY MID-LEVEL FLOW WOULD SUPPORT EASTWARD PROPAGATION/ADVECTION OF ISOLD CONVECTION FROM THE MOUNTAINS TOWARD THE FOOTHILLS...AN INCREASINGLY HARSH THERMODYNAMIC ENVIRONMENT /LACK OF FORCING/ WITH EASTWARD EXTENT SUGGESTS CONVECTION (SHOULD IT DEVELOP) WOULD DISSIPATE OVER THE BLUE RIDGE WITH SCT MID-LEVEL CONVECTIVE DEBRIS (AT BEST) SURVIVING INTO THE FOOTHILLS. WITH THE ABOVE IN MIND...EXPECT MOSTLY SUNNY SKIES ASIDE FROM SCT DIURNAL CU AT ~5000 FT AGL...PRIMARILY IN THE WESTERN PIEDMONT. SW LOW-LEVEL WARM ADVECTION (~925 MB) WILL ALLOW TEMPS TO REBOUND SEVERAL DEGREES FROM YESTERDAY WITH HIGHS NEAR 79-82F. AIRMASS MODIFICATION AND A LIGHT SOUTHWEST BREEZE WILL RESULT IN LOWS MUCH WARMER THAN YESTERDAY MORNING...IN THE MID/UPPER 50S TO NEAR 60F...COOLEST SE COASTAL PLAIN AND WARMEST WEST OF HWY 1. -VINCENT
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&& .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... AS OF 235 AM MONDAY... A COLD FRONT WILL BE PUSHING AT THE NORTHERN DOOR STEP BY 12Z/WED. THERE MAY BE PLENTY OF RESIDUAL CLOUDS ASSOCIATED WITH THE PREVIOUS OVERNIGHT CONVECTION ALONG THE NORTHERN TIER OF NC. HOWEVER... AS THE FRONT MOVES SOUTH INTO THE CENTRAL COASTAL PLAIN AND NORTHERN PIEDMONT (GENERALLY A NW TO SE AXIS FROM DANVILLE TO WILSON) BY 18Z... CLUSTERS OF THUNDERSTORMS ARE EXPECTED TO DEVELOP IN THE AIR MASS CLASSIFIED AS MODERATELY UNSTABLE WITH TEMPERATURES IN THE MID TO UPPER 80S... DEW POINTS 60-65... MU CAPES NEARING 1500-2000 J/KG... ALONG WITH THE FRONT BECOMING NEARLY STATIONARY OVER THE REGION. UNIDIRECTIONAL WIND PROFILES FROM THE NW WITH SPEEDS OF 40KT OR SO SUGGEST CLUSTERS AND LINE SEGMENTS WITH THE POTENTIAL FOR MARGINAL SEVERE HAIL AND WIND. WE WILL CONTINUE TO CARRY 50 POP FOR THE NW... NORTH CENTRAL AND EASTERN ZONES WITH LESS CHANCE IN THE SW PIEDMONT WHERE THE FRONT WILL BE FARTHER AWAY. HIGHS NEAR 90 S-SW PIEDMONT WITH LOWER 80S FAR NE PIEDMONT. THE CHANCE OF THUNDERSTORMS WILL LINGER INTO THE LATE EVENING WEDNESDAY... THEN LESSEN WITH SKIES BECOMING PARTLY CLOUDY. THE STATIONARY FRONT WILL BECOME WARM AND SURGE NORTHWARD INTO VA LATE WED NIGHT AND EARLY THURSDAY. && .LONG TERM /THURSDAY THROUGH SUNDAY/... AS OF 235 AM MONDAY... THERE WILL BE A CHANCE OF SHOWERS AND THUNDERSTORMS THURSDAY AFTERNOON INTO THURSDAY EVENING AS THE NEXT WAVE TRACKS EAST FROM THE OHIO VALLEY TO THE MID-ATLANTIC. THIS WILL PULL A COLD FRONT THROUGH THE REGION LATE THURSDAY NIGHT OR EARLY FRIDAY. THE BEST CHANCE OF THUNDERSTORMS WILL OCCUR DURING THE AFTERNOON IN THE NW... THEN PROGRESS SE DURING THE LATE AFTERNOON/EVENING IN THE EAST. FORECAST SOUNDINGS AND WIND PROFILES ALONG WITH SEVERE PARAMETERS SUGGEST A MARGINAL RISK OF SEVERE. WE WILL CONTINUE TO REVISIT THIS POSSIBILITY AS THURSDAY NEARS. HIGHS GENERALLY 80-85 NE TO UPPER 80S SOUTH. A CHANCE OF SHOWERS MAY LINGER IN THE SE FRIDAY MORNING IN THE EAST... OTHERWISE PARTLY SUNNY FRIDAY. THERE MAY BE ANOTHER CHANCE IN THE AFTERNOON FRIDAY... MAINLY IN THE NE ZONES WITH HEATING AND A POTENTIAL DISTURBANCE ALOFT IN THE NW FLOW. HIGHS GENERALLY 75-80 NORTH AND 80-85 SOUTH. SATURDAY AND SATURDAY NIGHT SHOULD BE QUIET... DRY AND COOLER BEHIND THE FRONT. WEAK HIGH PRESSURE TO THE NORTH WILL EXTEND INTO THE REGION INTO EARLY SUNDAY BEFORE MOVING OFFSHORE. TEMPERATURES WILL BE ONLY IN THE 70S SATURDAY WITH SOME LOWER 80S NEAR THE SC BORDER. SUNDAY... EXPECT INCREASING CLOUDS OUT AHEAD OF ANOTHER ENERGETIC SYSTEM APPROACHING FROM THE WEST LATE SUNDAY. THIS WILL BRING A CHANCE OF SHOWERS MAINLY IN THE WEST LATER IN THE AFTERNOON OR SUNDAY NIGHT. HIGHS SUNDAY AGAIN IN THE MID 70S TO LOWER 80S. WIDESPREAD SHOWERS/STORMS ARE EXPECTED BY MONDAY. && .AVIATION /06Z MONDAY THROUGH FRIDAY/... AS OF 200 AM MONDAY... 24-HOUR TAF PERIOD: VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD...HOWEVER...HAZARDOUS AVIATION CONDITIONS IN THE FORM OF STRONG (35-40 KT) LOW-LEVEL WIND SHEAR (400-800 FT AGL) WILL BE PRESENT AT ALL TERMINALS UNTIL ~12Z THIS MORNING...ABRUPTLY ENDING SHORTLY AFTER THE ONSET OF DIURNAL HEATING /MIXING/. THIS PARTICULAR PATTERN...I.E. THE ONSET OF SOUTHERLY RETURN FLOW AS HIGH PRESSURE MOVES OFFSHORE...IS ESPECIALLY HAZARDOUS BECAUSE IT OFTEN OCCURS WHEN CONDITIONS ARE OTHERWISE VFR/BENIGN...BECAUSE THE GREATEST SHEAR IS LOCATED CLOSER TO THE GROUND (ATOP THE NOCTURNAL INVERSION)...AND BECAUSE MODEL GUIDANCE IS NOTORIOUS IN UNDER- REPRESENTING THE STRENGTH OF THE LOW-LEVEL JET (COMPARE GFS/NAM/RAP FCST SOUNDINGS WITH KRAX VELOCITY DATA THIS MORNING). OTHERWISE... EXPECT SCATTERED VFR CEILINGS AT 4000-5000 FT AGL THIS AFTERNOON AND SSW/SW WINDS AT 10-15 KT AFTER SUNRISE...PERHAPS GUSTING TO ~20 KT AS THE NOCTURNAL INVERSION MIXES OUT THIS MORNING AND AGAIN LATER THIS AFTERNOON AS THE MSLP GRADIENT TIGHTENS FROM THE WEST. LOOKING AHEAD: VFR CONDITIONS WILL PREVAIL UNTIL MID-WEEK WHEN A WEAKENING COLD FRONT IS PROGGED TO STALL OVER THE REGION...IN THE PRESENCE OF INCREASING MOISTURE VIA PERSISTENT SOUTHERLY RETURN FLOW. SUB-VFR CONDITIONS ASSOC/W CONVECTION WILL BE POSSIBLE AT ALL TERMINALS MID/LATE WEEK...WITH PRE-DAWN FOG/STRATUS POSSIBLE AS WELL...ESP. IN AREAS AFFECTED BY AFT/EVE CONVECTION. -VINCENT && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...VINCENT SHORT TERM...BADGETT LONG TERM...BADGETT AVIATION...VINCENT

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