Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 221917 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 315 PM EDT WED APR 22 2015 .SYNOPSIS...A COLD FRONT WILL PUSH SOUTH THROUGH THE REGION LATE TODAY THROUGH TONIGHT. HIGH PRESSURE WILL THEN BUILD IN BEHIND THE FRONT FOR THE END OF THE WORK WEEK. UNSETTLED WEATHER IS EXPECTED FOR THE WEEKEND. && .NEAR TERM /TONIGHT THROUGH THURSDAY NIGHT/... AS OF 250 PM WEDNESDAY... THROUGH TONIGHT: GUSTY WINDS ARE THE PRIMARY CONCERN FOR THE NEXT SEVERAL HOURS... AS SUSTAINED WINDS FROM THE SW AT 10-20 MPH WILL CONTINUE TO GUST TO AROUND 30-33 MPH THROUGH THE REST OF THE AFTERNOON. AS THE COLD FRONT APPROACHES FROM THE NNW ON SCHEDULE LATE... ISOLATED SHOWERS ARE EXPECTED. THE "BETTER" COVERAGE (STILL WELL UNDER 30%) WILL BE IN THE FAR NORTH THROUGH LATE AFTERNOON... AS AGREED UPON BY THE LATEST HRRR/RAP AND SREF PROBABILITIES... BUT A CONSIDERABLE DOWNSLOPE-DIRECTED LOW LEVEL FLOW JUST OFF THE SURFACE UP TO THE MID LEVELS ALONG WITH PW VALUES THAT ARE AT OR JUST BELOW NORMAL WILL GREATLY LIMIT COVERAGE OVER MOST OF THE CWA. WILL MAINTAIN AN ISOLATED MENTION OF SHOWERS AS IS CURRENTLY CONFIGURED... GENERALLY NORTH OF HWY 64 UNTIL 7 PM THEN S OF HWY 64 FROM MID EVENING UNTIL SHORTLY AFTER MIDNIGHT. BUT THE VAST MAJORITY OF CENTRAL NC WILL REMAIN DRY. GIVEN THE INVERTED-V APPEARANCE ON FORECAST SOUNDINGS AND STEEP LOW LEVEL LAPSE RATES OF 9-9.5 C/KM... EVAPORATIVE COOLING MAY LEAD TO ENHANCED WIND GUSTS IN AND AROUND ANY OF THESE SHOWERS... POTENTIALLY CAUSING BRIEF LOCAL GUSTS OVER 40 MPH... BUT THESE WILL NOT BE COMMONPLACE. CANNOT RULE OUT AN ISOLATED LIGHTNING STRIKE OR TWO GIVEN SUCH STEEP LAPSE RATES AND MODEL PROJECTIONS OF MUCAPE PEAKING AT 100-300 J/KG... BUT THE LACK OF MOISTURE AND DYNAMIC FORCING FOR ASCENT SHOULD MAKE ANY SUCH OCCURRENCE A RARITY. OTHERWISE... EXPECT A PERIOD OF VARIABLY TO MOSTLY CLOUDY SKIES JUST AHEAD OF AND WITH THE FRONT... FOLLOWED BY CLEARING SKIES OVERNIGHT NORTH TO SOUTH... AND DECREASING WIND SPEEDS FROM THE NW. LOWS FROM 43 NORTH TO AROUND 50 SOUTH... IN LINE WITH STATISTICAL GUIDANCE. FOR THU/THU NIGHT: EXPECT PLENTY OF SUNSHINE TOMORROW AS WEAK HIGH PRESSURE BUILDS IN FROM THE NW BEHIND THE FRONT. LOW LEVEL FLOW WILL BACK SLIGHTLY TO BE FROM THE WNW... AND WITH A DECENT HEIGHT GRADIENT JUST ALOFT AT 925 MB AND GOOD MIXING WITH HEATING... SUSTAINED WIND SPEEDS FROM MID MORNING ONWARD ARE LIKELY TO REBOUND TO 10-20 KTS... ALBEIT WITH MUCH LOWER GUSTS (IF ANY) THAN WE`VE SEEN TODAY. LOW LEVEL THICKNESSES ARE EXPECTED TO BE 30-40 M BELOW NORMAL THU MORNING... BUT WITH STRONG HEATING AND A NEARLY DRY ADIABATIC LOW LEVEL THERMAL PROFILE... EXPECT HIGHS IN THE MID 60S TO LOWER 70S... STILL SEVERAL DEGREES BELOW NORMAL. A WEAK REINFORCING TROUGH WILL DROP SE THROUGH NC LATE THU... WITH HIGH PRESSURE CONTINUING TO BUILD IN FROM THE NW... ITS CENTER EXPECTED TO BE JUST NW OF THE AREA BY SUNRISE FRI MORNING. WINDS WILL DIMINISH THURSDAY NIGHT WITH DECOUPLING LIKELY... AND FORECAST SOUNDINGS ARE SUFFICIENTLY DRY FOR CLEAR SKIES AND GOOD RADIATIONAL COOLING. WITH THICKNESSES DROPPING TO UNDER 1325 M OVER MUCH OF THE AREA THU NIGHT... EXPECT CHILLY LOWS FROM 36-42... WITH THESE COOLER READINGS IN THE RURAL OUTLYING AREAS. LOW DEWPOINTS SHOULD LIMIT THE FORMATION OF FROST... HOWEVER WILL TAKE A CLOSER LOOK AT THIS IN LATER FORECASTS. BUT AT THIS TIME IT LOOKS LIKE THIS WOULDN`T BE A WIDESPREAD EVENT ANYWAY. -GIH && .SHORT TERM /FRIDAY THROUGH SATURDAY/...
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AS OF 315 PM WEDNESDAY... FRIDAY... S/W RIDGE OVER THE CENTRAL U.S. AND A DEEP LOW PRESSURE SYSTEM OVER NORTHERN NEW ENGLAND WILL MAINTAIN A NW FLOW ALOFT OVER CENTRAL NC. AT THE SURFACE...AN AREA OF HIGH PRESSURE WILL EXTEND ACROSS THE FORECAST AREA. THIS SET-UP WILL PROVIDE FOR MOSTLY SUNNY/PARTLY CLOUDY SKIES AND TEMPS A FEW DEGREES BELOW NORMAL. HIGH TEMPS FRIDAY MID 60S FAR NORTH-NW TO NEAR 70 FAR SOUTH-SE. FRIDAY NIGHT AND SATURDAY...A S/W IN THE SOUTHERN STREAM WILL ADVANCE EAST FROM THE SOUTHERN PLAINS...AND THROUGH THE LOWER MS VALLEY LATE FRIDAY AND FRIDAY NIGHT. AS THIS SYSTEM APPROACHES THE CONFLUENT NW FLOW OVER OUR AREA...THE S/W WILL GRADUALLY WEAKEN. STILL...THIS SYSTEM WILL ADVECT ENOUGH MOISTURE INTO CENTRAL NC WHILE SPEED CONVERGENCE AT 700MB ALONG WITH WARM AIR ADVECTION AT 850MB WILL SUPPLY THE LIFT TO CAUSE SCATTERED TO NUMEROUS SHOWERS TO DEVELOP. BASED ON MODEL TIMING...SHOULD SEE MOSTLY CLEAR-PARTLY CLOUDY SKIES FRIDAY EVENING GIVE WAY TO MOSTLY CLOUDY -OVERCAST SKIES BY DAYBREAK SATURDAY. CANNOT RULE OUT A STRAY SHOWER ALONG OUR WESTERN FRINGE BY DAYBREAK SATURDAY BUT PROBABILITY APPEARS TOO LOW AT THIS TIME TO MENTION IN THE FORECAST. AFTER 12Z...SHOWERS DEVELOP IN THE MORNING HOURS ACROSS THE SOUTHERN-WESTERN PIEDMONT...OVERSPREADING THE REMAINDER OF CENTRAL NC SATURDAY AFTERNOON. MIN TEMPS FRIDAY NIGHT WILL BE MORE MILD COMPARED TO THE PREVIOUS NIGHT`S LOW TEMPS DUE TO THE INCREASING/THICKENING CLOUD COVER. MIN TEMPS NEAR 40/LOWER 40S FAR NE TO THE LOWER 50S FAR SOUTH-SW. OVERCAST SKIES AND INCREASING SHOWER COVERAGE WILL LEAD TO MUCH COOLER AFTERNOON TEMPS. HIGHS SATURDAY NEAR 60 FAR NORTH-NW TO THE MID-UPPER 60S SOUTH.
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&& .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
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AS OF 315 PM WEDNESDAY... SATURDAY NIGHT-SUNDAY...THE SOUTHERN STREAM S/W WILL GRADUALLY WEAKEN AS IT MOVES EAST ACROSS THE SOUTHEAST U.S. SATURDAY NIGHT. THIS SYSTEM WILL MAINTAIN A THREAT FOR SHOWERS...ESPECIALLY DURING THE EVENING HOURS. SHOWER CHANCES SHOULD DECREASE LATE SATURDAY NIGHT-EARLY SUNDAY. A SECOND S/W...THIS ONE IN THE NORTHERN STREAM...WILL TRACK EAST-SE ACROSS THE CENTRAL APPALACHIANS INTO CENTRAL NC SUNDAY. THIS SYSTEM INTERACTING WITH AVAILABLE MOISTURE WILL SPARK A FEW SHOWERS...SPECIALLY DURING THE AFTERNOON-EARLY EVENING HOURS. COOLER THAN NORMAL TEMPERATURES WILL CONTINUE SUNDAY. MIN TEMPS SATURDAY NIGHT 45-50 NORTH...AND 50-54 SOUTH. HIGH TEMPS MID-UPPER 60S SUNDAY. MONDAY THROUGH WEDNESDAY... THE WEATHER PATTERN WILL REMAIN UNSETTLED THIS PERIOD. A WEAK HIGH PRESSURE SYSTEM WILL SETTLE INTO OUR REGION MONDAY IN THE WAKE OF THE EXITING NORTHERN STREAM S/W. A DEEP LOW PRESSURE OVER THE SOUTHERN PLAINS WILL DRIFT SLOWLY EAST TUESDAY INTO WEDNESDAY. AS THE SFC HIGH OVER OUR REGION MONDAY DRIFTS EAST TUESDAY...LOW LEVEL RETURN SLY FLOW WILL INCREASE MOISTURE OVER CENTRAL NC. THE APPROACH OF DISTURBANCES ROTATING OUT OF THE DEEP LOW WILL INCREASE THE THREAT FOR SHOWERS ACROSS THE CAROLINAS LATE TUESDAY INTO WEDNESDAY. HIGH TEMPERATURES THROUGH THIS PERIOD WILL AVERAGE 4-8 DEGREES BELOW NORMAL.
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&& .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... AS OF 150 PM WEDNESDAY... VFR CONDITIONS WILL HOLD OVER THE NEXT 24 HOURS OVER ALL OF CENTRAL NC... WITH HIGH CLOUD BASES (IF ANY) AND UNRESTRICTED VSBYS. OF MOST IMMEDIATE CONCERN TO AVIATION INTERESTS WILL BE THE WIND THROUGH 23Z... MAINLY FROM THE SW AT 15-22 KTS GUSTING AS HIGH AS 27-32 KTS. A COLD FRONT WILL BE DROPPING THROUGH THE AREA TOWARD THE SSE BETWEEN 23Z AND 05Z... RESULTING IN A SHIFT OF WINDS TO INITIALLY A WNW DIRECTION AND REDUCED SPEEDS DOWN TO 9-14 KTS WITH INFREQUENT GUSTS. ISOLATED SHOWERS ARE EXPECTED AHEAD OF AND ALONG THE FRONT... HOWEVER THESE WILL BE FAR TOO SPARSE TO MENTION IN THE TAFS. WIND GUSTS MAY BE LOCALLY ENHANCED NEAR SHOWERS... WHERE AN ISOLATED GUST OVER 40 KTS MAY OCCUR... BUT THESE SPEEDS WILL NOT BE COMMON. THE FRONT AND ANY SHOWER CHANCES WILL SETTLE TO OUR SOUTH AFTER MIDNIGHT WITH CLEARING SKIES... LASTING THROUGH THU MORNING. AFTER MID MORNING THU... WINDS WILL PICK UP FROM THE WNW AT AROUND 10-15 KTS SUSTAINED. LOOKING BEYOND 18Z THU... WINDS WILL DIMINISH TOWARD EARLY EVENING. VFR CONDITIONS ARE LIKELY TO HOLD THROUGH FRIDAY NIGHT AS A RIDGE OF HIGH PRESSURE EXTENDS OVER THE AREA. THE APPROACH OF AN UPPER LEVEL DISTURBANCE AND A WARM FRONT FROM THE SW WILL BRING A GOOD CHANCE OF RAIN AND SUB-VFR CONDITIONS (LIKELY IFR) STARTING SAT MORNING... LASTING THROUGH AT LEAST SAT NIGHT... AND PERHAPS THROUGH SUNDAY AS LOW PRESSURE SKIRTS BY JUST TO OUR SOUTH. IMPROVING CONDITIONS TO VFR ARE EXPECTED MONDAY AS COOLER HIGH PRESSURE BUILDS IN FROM THE NW. -GIH && .FIRE WEATHER...
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AS OF 250 PM WEDNESDAY... WILL MAINTAIN THE INCREASED FIRE DANGER THROUGH THE REST OF THE DAY. RECENT RAINFALL HAS ALLOWED FOR MOISTENING OF FINE FUELS OVER MUCH OF THE AREA... BUT WITH TODAY`S WIND SPEEDS SUSTAINED AS HIGH AS 10- 20 KTS GUSTING UP TO AROUND 30 KTS... AND RH VALUES BOTTOMING OUT IN THE 25-29% RANGE... DRYING OF TOP-LAYER FUELS SHOULD CONTINUE TODAY... AND OUTDOOR BURNING IS NOT ADVISED THROUGH SUNDOWN. A COOL DRY AIR MASS WILL OVERSPREAD CENTRAL NC OVERNIGHT AND PERSIST INTO THURSDAY. MIN RH VALUES MID-LATER AFTERNOON THURSDAY WILL DIP INTO THE 22-27 PERCENT RANGE. SFC WINDS WILL ALSO BE BREEZY WITH GUSTS 15-20 MPH LIKELY IN THE AFTERNOON.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD SHORT TERM...WSS LONG TERM...WSS AVIATION...HARTFIELD FIRE WEATHER...DJF/HARTFIELD

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