Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 181747 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 145 PM EDT THU SEP 18 2014 .SYNOPSIS...HIGH PRESSURE CENTERED OVER THE NORTHERN GREAT LAKES WILL EXTEND DOWN THROUGH VIRGINIA AND THE CAROLINAS THROUGH THE WEEKEND... AS IT SLIDES EAST. A COLD FRONT WILL APPROACH FROM THE NORTHWEST LATE SUNDAY... THEN MOVE SOUTHEAST THROUGH THE REGION MONDAY. && .NEAR TERM /THROUGH TONIGHT/... AS OF 1035 AM THURSDAY... REST OF TODAY: STILL APPEARS MOSTLY DRY WITH SEASONABLE TEMPS. THIS MORNING`S AREAS OF LOW CLOUDS HAVE MIXED OUT OVER ALL BUT THE FAR WRN CWA... WHERE THE LOW LEVEL TERRAIN UPGLIDE IS HIGHER AND WHERE LOW LEVEL MASS CONVERGENCE IS TAKING PLACE ALONG A WEAK INVERTED SURFACE TROUGH. THE LATEST CONVECTION-ALLOWING MODELS GENERALLY AGREE ON ISOLATED SHALLOW SHOWERS FORMING OVER THE MOUNTAINS AND FOOTHILLS EARLY-MID AFTERNOON... AND SUBSEQUENTLY DRIFTING EASTWARD INTO THE FAR WRN PIEDMONT THROUGH EVENING BEFORE DISSIPATING. THE 12Z GSO SOUNDING REVEALS PLENTIFUL MOISTURE BELOW 775 MB CAPPED BY THE INVERSION ALOFT... SUFFICIENT TO SUPPORT A FEW SHOWERS. WILL RETAIN ISOLATED SHOWERS FROM MID AFTERNOON THROUGH THIS EVENING IN THE FAR WRN AND EXTREME SW CWA. OTHERWISE... THE WARM CAP ALOFT AND DRY MID LEVELS ALONG WITH BELOW NORMAL PW WILL MAKE FOR DRY CONDITIONS OVER THE REST OF THE CWA... WITH FLAT CUMULUS MAXIMIZED IN THE AFTERNOON. THE PACE OF TEMP RISE SO FAR THIS MORNING SUPPORTS HIGHS OF 77-81. -GIH TONIGHT...AVAILABLE LOW LEVEL MOISTURE IN THE WESTERN PIEDMONT... POOLING ALONG THE SFC TROUGH...MAY MAINTAIN A FEW SHOWERS THROUGH THE LATE EVENING HOURS. OTHERWISE AVAILABLE LOW LEVEL MOISTURE MAY CAUSE THE FORMATION OF FOG AND/OR LOW CLOUDS... ESPECIALLY OVER THE PIEDMONT. MIN TEMPS NEAR 60-LOWER 60S. -WSS && .SHORT TERM /FRIDAY AND FRIDAY NIGHT/... AS OF 310 AM THURSDAY... DRY AIR RIDGE WILL BUILD INTO AND EXTEND ACROSS CENTRAL NC THIS PERIOD. THE DRIEST AIR WILL ENCOMPASS THE NE PIEDMONT AND MOST OF THE COASTAL PLAIN. THE LOW LEVEL EASTERLY FLOW MAY CAUSE MOISTURE TO BANK UP AGAINST THE HIGHER TERRAIN OF WESTERN NC WHICH MAY SPILL INTO OUR FAR WESTERN COUNTIES. THE MOISTURE APPEARS TOO SHALLOW TO SUPPORT ANY SHOWER ACTIVITY PLUS LIFT IS MINIMAL THIS PERIOD. MAX TEMPS SIMILAR TO TODAY IN THE UPPER 70S TO THE LOWER 80S. MIN TEMPS FRIDAY NIGHT IN THE UPPER 50S TO THE LOWER 60S. && .LONG TERM /FRIDAY THROUGH WEDNESDAY/... AS OF 330 AM THURSDAY... A PORTION OF THE LONGWAVE TROUGH INITIALLY ALONG THE EAST COAST WILL BE LEFT BEHIND AND SUPPORT WEAK FRONTAL WAVE DEVELOPMENT OFFSHORE THE SE US COAST THIS WEEKEND...BUT THE OTHERWISE DEAMPLIFYING/LIFTING TROUGH WILL YIELD TO RISING HEIGHTS ALOFT OVER THE CAROLINAS...AS A FLAT MID LEVEL RIDGE RIDGE NOSES EASTWARD FROM THE SOUTHERN PLAINS AND LOWER MS VALLEY. THE RE-ESTABLISHMENT AND AMPLIFICATION OF A WESTERN NOAM RIDGE WILL THEN RESULT IN DOWNSTREAM TROUGH AMPLIFICATION FROM SOUTH-CENTRAL CANADA TO THE EAST-CENTRAL US THIS WEEKEND-EARLY NEXT WEEK. THE WESTERN RIDGE...IN PROGRESSIVE FLOW ALOFT...WILL BUILD EAST ACROSS THE MID-LATITUDES OF THE CENTRAL AND EASTERN STATES MID TO LATE NEXT WEEK. BENEATH THE CONTINUED RISING HEIGHTS ALOFT SAT...A CANADIAN SFC HIGH (AROUND 1030 MB) WILL BUILD FROM CENTRAL CANADA TO THE CANADIAN MARITIMES AND RIDGE SOUTH/SOUTHWESTWARD THROUGH THE EASTERN STATES THROUGH THE FIRST HALF OF THE WEEKEND...BEFORE YIELDING - AMIDST FALLING HEIGHTS DOWNSTREAM OF THE AFOREMENTIONED REDEVELOPING TROUGH ALOFT HEADED FOR THE EAST-CENTRAL US - TO APPALACHIAN-LEE SFC TROUGH DEVELOPMENT SUN...AND A PASSING COLD FRONT MON. ANOTHER STRONG CANADIAN HIGH WILL EXPAND AND STRENGTHEN ACROSS MUCH OF THE CENTRAL AND EASTERN CONUS IN THE WAKE OF THE PASSING COLD FRONT...WHICH GUIDANCE SUGGESTS WILL CLEAR ALL BUT PERHAPS SOUTHERN FL BY MID NEXT WEEK. WITH THE BRUNT OF THE COOLER AND DRIER AIR ASSOCIATED WITH THE LEAD HIGH LIKELY TO HOLD OVER THE NORTHERN MIDDLE ATLANTIC AND NORTHEAST STATES THIS WEEKEND...CENTRAL NC TEMPERATURES ARE APT TO WARM TO ABOVE AVG...IN THE LOWER TO MIDDLE 80S - WARMEST SUNDAY. ANY SIGNIFICANT LOW-MID LEVEL CLOUD COVER ATTENDING THE OFFSHORE FRONTAL WAVE IS FORECAST AT THIS TIME TO HOLD ALONG COASTAL AREAS...WITH MORE OF A NORTHWESTERLY FLOW COMPONENT OVER CENTRAL NC...INTO THE OFFSHORE LOW/FRONTAL ZONE. FRONTAL PASSAGE TIMING HAS SPED FOR MON...SUCH THAT A FEW LINGERING SHOWERS FROM UPSTREAM CONVECTION MAY DRIFT INTO THE NW PIEDMONT SUN NIGHT...AND LEAVE MAINLY THE FAR SOUTHEAST CWFA IN THE WARM SECTOR THROUGH EARLY AFTERNOON...WITH EARLIER/UNFAVORABLE DIURNAL FRONTAL TIMING ACROSS THE REMAINDER OF THE AREA. SHOWER CHANCES WILL BE RELATIVELY LOW...THROUGHOUT THIS PERIOD...HOWEVER...AS GULF MOISTURE RETURN WILL BE LIMITED. COOLER TUE-WED...WITH HIGHS IN THE 70S IN THE POST-FRONTAL CANADIAN HIGH...WITH SFC DEWPOINTS IN THE 40S-50S. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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AS OF 145 PM THURSDAY... VFR CONDITIONS ARE LIKELY TO HOLD THROUGH THE TAF FORECAST PERIOD. EARLIER MVFR CIGS AT INT/GSO HAVE MIXED OUT TO SCATTERED... ALTHOUGH THESE MAY STILL GO BROKEN BRIEFLY PRIOR TO 20Z. OTHERWISE... ANY CLOUDS THROUGH TONIGHT AND FRI MORNING SHOULD BE BASED ABOVE 3 000 FT AGL... MORE LIKELY TO BE BROKEN AT INT/GSO WITH LESS COVERAGE AT RDU/RWI/FAY. LIGHT AND VARIABLE WINDS MAINLY FROM THE NE WILL CONTINUE TONIGHT AT SPEEDS MAINLY UNDER 6 KTS... THEN SHOULD INCREASE TO 7-10 KTS FROM THE ENE AFTER 14Z FRI. LOOKING BEYOND 18Z FRI... VFR CONDITIONS SHOULD DOMINATE THROUGH AT LEAST SUNDAY... ALTHOUGH MVFR FOG IS POSSIBLE EARLY SAT MORNING AS THE LIGHT ONSHORE LOW LEVEL FLOW PERSISTS. A PERIOD OF MVFR CIGS IS POSSIBLE LATE SUN INTO SUN NIGHT AHEAD OF A COLD FRONT. VFR CONDITIONS SHOULD THEN RETURN FOR MON/TUE WITH HIGH PRESSURE BUILDING IN FROM THE NW. -GIH
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...HARTFIELD NEAR TERM...HARTFIELD/WSS SHORT TERM...WSS LONG TERM...MWS AVIATION...HARTFIELD

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