Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 310754 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 353 AM EDT FRI OCT 31 2014 .SYNOPSIS...AN ARCTIC AIRMASS WILL SPILL SOUTHWARD FROM CANADA INTO THE CENTRAL UNITED STATES TONIGHT AS A POTENT UPPER LEVEL DISTURBANCE DIGS SOUTHEAST THROUGH THE UPPER GREAT LAKES. MULTIPLE WAVES OF LOW PRESSURE WILL DEVELOP ALONG THE CAROLINA COAST IN ADVANCE OF THE UPPER LEVEL DISTURBANCE FRIDAY INTO FRIDAY NIGHT. AN EARLY SEASON NOR EASTER WILL DEVELOP ON SATURDAY AS THE UPPER LEVEL DISTURBANCE TRACKS INTO THE CAROLINAS. && .NEAR TERM /THROUGH TONIGHT/...
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AS OF 330 AM FRIDAY... RELATIVE CALM BEFORE THE STORM TODAY. A NARROW RIDGE OF 1018 MB HIGH PRESSURE WAS ANALYZED AT 07Z OVER THE MIDDLE ATLANTIC AND WESTERN CAROLINAS THIS MORNING...IN BETWEEN A DEVELOPING COASTAL LOW ALONG THE OLD FRONTAL ZONE A FEW HUNDRED MILES OFF THE COAST OF THE CAROLINAS AND A TRIO OF FLATTER WAVES OVER NORTHERN MS; WESTERN KY; AND NORTHERN MI. ALOFT...THREE DISTINCT SHORTWAVE TROUGHS ARE EVIDENT IN WV IMAGERY IN ASSOCIATION WITH THE SURFACE WAVES - ONE OFF THE SE COAST...ANOTHER OVER THE MID-SOUTH...AND THE MOST POTENT ONE OVER THE WESTERN GREAT LAKES. THE LATEST SUITE OF NWP GUIDANCE IS SLIGHTLY FARTHER SOUTH WITH THE SHARPLY AMPLIFYING SHORTWAVE TROUGH AND ASSOCIATED CLOSED LOW EVOLUTION THROUGH THE CAROLINAS...AND THE ACCOMPANYING PRIMARY SURFACE LOW FORECAST TO CROSS THE CAROLINAS TONIGHT. THE STRONGEST LOW LEVEL CAA AND ALREADY-ONLY MARGINAL OPPORTUNITY FOR ANY WET FLAKES HAS CONSEQUENTLY SHIFTED SOUTH TO THE SOUTHERN NC PIEDMONT. THE RELATIVE HIGHEST CHANCES OF RAIN...AND PRECIPITATION AMOUNTS...WILL ALSO ACCORDINGLY BE FOCUSED IN AN ARC FROM WESTERN NC TO NORTHERN SC TO EASTERN NC...AS THE SURFACE LOW AND DEFORMATION ZONE EVOLVE IN A REGION OF STRONG ASCENT FUELED BY BOTH THE "DYNAMICS" ALOFT AND STRONG LOW-MID LEVEL FGEN. THE WEAK LEAD SURFACE WAVES OVER NORTHERN MS AND WESTERN KY ARE FORECAST TO CONTINUE EAST...BENEATH THE PARENT SHORTWAVE TROUGH...AND MERGE INTO A SINGLE LOW IN THE LEE OF THE APPALACHIANS THIS AFTERNOON. THIS LEE LOW WILL THEN REMAIN RELATIVELY STATIONARY AS THE STRONGEST HEIGHT FALLS ACCOMPANYING THE POTENT SHORTWAVE AMPLIFYING SHARPLY SSE FROM THE WESTERN GREAT LAKES TO THE SOUTHERN APPALACHIANS CAUSES ALLOWS THE TRAILING SURFACE LOW OVER NORTHERN MI AND ASSOCIATED PRESSURE FALLS TO CATCH UP TO AND "CAPTURE" THE LEAD LEE LOW...WITH THE THEN MERGED SURFACE LOW FORECAST TO MOVE DUE EAST INVOF THE SC/NC BORDER TONIGHT. SHALLOW CONVECTION...INCLUDING SPORADIC LIGHTNING IN AN ENVIRONMENT CHARACTERIZED BY MUCAPE OF UP TO A FEW HUNDRED J/KG...WILL EASE EAST FROM THE SC UPSTATE AND NC FOOTHILLS...INTO THE NC SOUTHERN AND WESTERN PIEDMONT ROUGHLY BETWEEN 7-10 PM. THESE SHOWERS AND ISOLATED STORMS WILL MAKE ONLY SLOW EASTWARD PROGRESS ACROSS THOSE AREAS THROUGH MIDNIGHT...BEFORE THE CHARACTER OF THE PRECIPITATION ASSUMES AN INCREASINGLY STRATIFORM PRECIPITATION SHIELD WITH EMBEDDED SHALLOW CONVECTIVE ELEMENTS LINGERING OWING TO STRONG MID LEVEL CAA ATOP A WARM/MOIST TONGUE WRAPPED CYCLONICALLY BENEATH THE COLD POOL ALOFT...AROUND THE DEVELOPING LOW LEVEL CYCLONE. RAIN...WITH ASSOCIATED AMOUNTS BETWEEN ONE HALF AND ONE INCH...WILL CONSEQUENTLY GRADUALLY PIVOT ACROSS THE SANDHILLS AND CENTRAL PIEDMONT THROUGH DAYBREAK...WITH MUCH OF THE COASTAL PLAIN AND FAR NE PIEDMONT LIKELY TO EXPERIENCE ONLY OCCASIONAL LIGHT RAIN AND AMOUNTS LESS THAN A TENTH OF AN INCH. FORECAST PARTIAL THICKNESS VALUES HOLD IN THE INDETERMINATE RANGE THROUGHOUT CENTRAL NC FROM EVEN THE COLDEST EC/NAM GUIDANCE...AND BUFR SOUNDINGS EVEN IN THE SOUTHERN AND WESTERN PIEDMONT LIKEWISE MAINTAIN A COUPLE OF THOUSAND FT ABOVE FREEZING BOUNDARY LAYER. LOWS GENERALLY IN THE UPPER 30S TO MIDDLE 40S FROM WEST TO EAST...AFTER HIGHS TODAY IN THE UPPER 50S TO MIDDLE 60S.
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&& .SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
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AS OF 350 AM FRIDAY... WIDESPREAD RAIN WILL CONTINUE TO PIVOT EAST ACROSS THE SOUTHERN AND EASTERN RAH CWFA...WHILE THE NORTHERN PIEDMONT REMAINS IN A RELATIVE MINIMUM OF OF JUST SPOTTY LIGHT RAIN...AND THE MOUNTAIN SHADOW/DOWNSLOPE FLOW ERODE THE RAIN AND CLOUDS OVER THE WESTERN PIEDMONT. NORTHERLY WINDS WILL GRADUALLY RAMP UP SAT...FIRST OVER THE WESTERN PIEDMONT AS THE MIXED LAYER DEEPENS WITH DOWNSLOPE FLOW...THEN OVER THE COASTAL PLAIN AND NE PIEDMONT OWING TO A TIGHTENING PRESSURE GRADIENT AROUND WHAT WILL BECOME A RAPIDLY DEEPENING PRIMARY COASTAL LOW OFF THE NC COAST. WINDS OF 15-25 MPH WITH GUSTS BETWEEN 30-35 MPH ARE LIKELY IN BOTH AREAS...WITH SLIGHTLY WEAKER WINDS OVER THE TRIANGLE. WINDS WILL VEER TO NW SAT NIGHT...BUT CONTINUE IN THE 15-25 MPH RANGE WITH GUSTS OF 30-35 MPH OVER EASTERN SECTIONS...AND GRADUALLY LESSENING WINDS TO THE WEST. IF A WIND ADVISORY WERE TRULY NEEDED...IT WOULD LIKELY BE FOR THE LATE SAT-SAT NIGHT TIME FRAME OVER THE EASTERN THIRD OF THE CWFA. NEAR STEADY...TO SLOWLY RISING TEMPERATURES WITH PARTIAL CLEARING IN THE WESTERN PIEDMONT SAT...THEN CAA-DRIVEN LOWS IN THE 30S SAT NIGHT.
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&& .LONG TERM /SUNDAY THROUGH THURSDAY/... AS OF 314 AM FRIDAY... STRONG COASTAL STORM WILL BE MOVING NORTHEASTWARD OFF THE COAST... WITH A STRONG 1032 MB HIGH BUILDING IN TO THE OHIO VALLEY. GUSTY WINDS WILL STILL BE POSSIBLE UNTIL THE PRESSURE GRADIENT RELAXES LATE IN THE DAY SUNDAY AS THE HIGH BEGINS TO MOVE INTO THE AREA. SKIES WILL BE CLEAR ON SUNDAY... WITH DRY NORTHWESTERLY FLOW. THE HIGH WILL MOVE OVER THE AREA SUNDAY NIGHT... SETTING THE STAGE FOR EXCELLENT RADIATIONAL COOLING... AND LIKELY FROST/FREEZE CONDITIONS MONDAY MORNING. MOSTLY SUNNY CONDITIONS WILL CONTINUE THROUGH MONDAY... WITH HIGHS NEAR 60. HIGH PRESSURE WILL MOVE OFF THE EAST COAST ON TUESDAY... AND TEMPERATURES WILL CONTINUE TO MODERATE INTO THE 60S AS FLOW BECOMES SOUTHWESTERLY. NORTHERN STREAM SHORTWAVE ENERGY WILL MOVE ALONG THE CANADIAN BORDER... AND THE ASSOCIATED WEAK COLD FRONT WILL ENTER THE AREA LATE THURSDAY/EARLY FRIDAY. THE STRONGEST FORCING WILL REMAIN NORTH AND MOISTURE LOOKS TO BE LIMITED... AND MODEL QPF IS CONSEQUENTLY NEAR 0 ACROSS THE AREA. WILL KEEP POPS TO SLIGHT CHANCE AT THIS TIME... BUT IF THE CURRENT TREND FOR A DRY FRONTAL PASSAGE CONTINUES... EVEN THIS MAY BE OVERDONE. && .CLIMATE... RECORD LO-MAX TEMPERATURES FOR NOVEMBER 1ST LO-MAX RDU 50/1925 GSO 45/1925 FAY 48/1988 && .AVIATION /06Z THURSDAY THROUGH TUESDAY/... AS OF 145 AM FRIDAY... VFR CONDITIONS ARE GENERALLY EXPECTED TO CONTINUE THROUGH AROUND 00Z SATURDAY... AS SURFACE HIGH PRESSURE LOCATED TO THE NORTH OF THE REGION THIS MORNING WILL EXTEND INTO OUR AREA WHILE SHIFTING EASTWARD TODAY. THE ONE EXCEPTION COULD BE A BRIEF PERIOD OF IFR/MVFR VISBYS AT FOG PRONE KRWI. OTHERWISE... WINDS ARE GENERALLY EXPECTED TO BE LIGHT AND VARIABLE THIS MORNING THROUGH TODAY. MEANWHILE... A POTENT MID/UPPER LEVEL DISTURBANCE WILL APPROACH THE AREA TODAY... ALLOWING FOR VFR CLOUD COVER TO INCREASE GENERALLY IN A WEST TO EAST FASHION TODAY WITH PRECIP AND SUB-VFR CONDITIONS SPREADING INTO THE WESTERN PIEDMONT BY AROUND 03Z FOR SO. MVFR CONDITIONS LATE THIS EVENING WILL LIKELY FALL QUICKLY TO IFR/LIFR BY AROUND 06Z SATURDAY. OUTLOOK: CONDITIONS WILL CONTINUE TO RAPIDLY DETERIORATE ACROSS THE ENTIRE AREA TONIGHT INTO SATURDAY MORNING AS AN ANOMALOUSLY STRONG UPPER LOW SWINGS THROUGH THE REGION. SUB-VFR CONDITIONS IN PERIODS OF RAIN AND BLUSTERY NW WINDS WILL IMPACT THE AREA TONIGHT THROUGH SATURDAY. A RETURN TO VFR CONDITIONS ARE EXPECTED BY SUNDAY AS THE POTENT SYSTEM LIFTS OFF TO THE NORTHEAST. VFR CONDITIONS ARE THEN EXPECTED TO CONTINUE ACROSS THE REGION AS SURFACE HIGH PRESSURE BUILDS ACROSS THE AREA. && .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...VINCENT NEAR TERM...MWS SHORT TERM...MWS LONG TERM...SEC CLIMATE...CBL AVIATION...BSD/CBL

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