Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 201840 AFDRAH AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE RALEIGH NC 240 PM EDT SUN APR 20 2014 .SYNOPSIS...LOW PRESSURE OFF THE SE COAST WILL CONTINUE MOVING EAST AND OUT INTO THE ATLANTIC...LEAVING BEHIND A COOL WEDGE OF HIGH PRESSURE ON MONDAY. A COLD FRONT WILL CROSS THE REGION ON TUESDAY...WITH HIGH PRESSURE RETURNING FOR MIDWEEK. && .NEAR TERM /THROUGH MONDAY NIGHT/... AS OF 220 PM SUNDAY... TODAY: VERTICALLY STACKED LOW WILL DRIFT SLOWLY EASTWARD AND AWAY FROM SHORE THROUGH TONIGHT. EXPECT VERY DELIBERATE...IN FACT SLOTH-LIKE IMPROVEMENT TO SPREAD EASTWARD THROUGH TONIGHT WITH WESTERN PORTIONS UNDER THE INFLUENCE OF THE DRY AIR RIDGE FROM THE NORTH...YIELDING DRY CONDITIONS WITH FULL COMPLIMENTS OF SUN TODAY. MEANWHILE...EASTERN PORTIONS OF THE FORECAST AREA WILL REMAIN MOSTLY CLOUDY FOR A GOOD PART OF THE DAY WITH WANING ONSHORE CONVERGENT FLOW SUPPORTIVE OF PATCHY AND MOSTLY TRACE AMOUNTS OF PRECIP. THIS WEST TO EAST CLOUD GRADIENT WILL GOVERN HIGHS TODAY...WITH STRONGER ISOLATION OUT WEST SUPPORTING SOME OF THE WARMEST READINGS. HIGHS RANGING FROM UPPER 60S WEST TO LOWER 60S SOUTHEAST. WITH THE MSLP GRADIENT STAYING TIGHT ESPECIALLY FROM THE TRIANGLE SOUTH AND EAST... EXPECT THE STEADY BRISK AND OCCASIONALLY GUSTY WINDS TO CONTINUE TODAY... MOST MARKEDLY IN THE ERN CWA. TONIGHT: THERE REMAINS SOME UNCERTAINTY WITH RESPECT TO THE DEVELOPMENT OF LOW STRATUS TONIGHT. WHILE NOT AS MOIST AS LAST NIGHTS CYCLE...12Z/20 NAM BUFR SOUNDINGS STILL SUGGEST THAT AS THE BOUNDARY LAYER COOLS...LOW STRATUS WILL BE APT TO FORM OWING TO THE RELATIVELY DEEP NELY ONSHORE FLOW. THE GFS IS MUCH DRIER IN THE LOWER LEVELS...SUGGESTING LITTLE IN THE WAY OF SUB-VFR CEILINGS. EXPECT WE WILL SEE AT LEAST SOME RETURN OF CLOUDS INTO THE COASTAL PLAIN...AND AS POSSIBLY FAR INLAND AS SAY THE EASTERN/CENTRAL PIEDMONT. WILL INDICATE THIS IN THE FORECAST WITH BROKEN MVFR CEILINGS AT KRWI AND KFAY. LOWS IN THE LOWER 40 TO MID 40S...COOLEST ACROSS THE NW. FOR MONDAY/MONDAY NIGHT: STRONG PARENT HIGH OVER THE NORTHEAST WILL RETREAT OUT INTO THE ATLANTIC...LEAVING BEHIND THE RESIDUAL DRY AIR SURFACE RIDGE WHICH WILL WEAKEN/BREAK DOWN THROUGHOUT THE DAY. ALOFT...MID LEVEL SHORTWAVE RIDGE WILL BUILD OVER THE AREA IN ADVANCE OF THE PROGRESSIVE POSITIVE-TILT LONG-WAVE TROUGH PROGRESSING EASTWARD THROUGH THE CENTRAL US. ALL OF THE FORECAST AREA WILL FINALLY GET TO ENJOY MOSTLY SUNNY SKIES ON MONDAY...WITH TEMPERATURES MODERATING INTO THE UPPER 60S NE TO LOWER 70S JUST ABOUT EVERYWHERE ELSE. EXPECT AN INCREASE IN MID/HIGH LEVEL CLOUDS LATE MONDAY NIGHT WITH THE APPROACH OF THE TROUGH INTO THE SOUTHERN/CENTRAL APPALACHIANS. EARLIER ARRIVAL AND THICKER CLOUD COVER ACROSS THE WEST WILL HINDER RADIATIONAL COOLING AND SUPPORT SOME OF THE WARMEST OVERNIGHT TEMPERATURES. LOWS RANGING FROM LOWER 50S NW TO MID/UPPER 40S EAST. && .SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
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AS OF 230 PM SUNDAY... SHORTWAVE ENERGY CURRENTLY IN THE CENTRAL PLAINS WILL PROGRESS EASTWARD THROUGH THE APPALACHIANS TO THE EASTERN SEABOARD ON TUESDAY...WHILE ADDITIONAL SHORTWAVE ENERGY (CURRENTLY IN FAR WESTERN CANADA) DIGS SOUTHEAST THROUGH THE GREAT LAKES AND INTO THE NORTHERN MID-ATLANTIC. AN ATTENDANT SFC LOW WILL STRENGTHEN ACROSS THE MID-ATLANTIC AND NEW ENGLAND ON TUE...WITH AN ASSOCIATED COLD FRONT APPROACHING FROM THE NW LATE TUE/TUE NIGHT. ONLY BRIEF MOISTURE RECOVERY IS EXPECTED IN ASSOC/W THIS SYSTEM AND SFC DEWPOINTS MAY STRUGGLE TO EXCEED THE 50S. HOWEVER...RELATIVELY STEEP MID-LEVEL LAPSE RATES AND INSOLATION MAY ALLOW FOR MARGINAL DIURNAL DESTABILIZATION (~500 J/KG MLCAPE) TUE AFT/EVE. GIVEN DPVA JUXTAPOSED WITH LOW LEVEL CONVERGENCE AND MARGINAL INSTABILITY... EXPECT A CHANCE OF SHOWERS AND ISOLD STORMS...THOUGH CHANCES WILL BE CAPPED AT 50% DUE TO UNCERTAINTY IN THE EVOLUTION OF THE UPPER LEVEL PATTERN AND WHETHER OR NOT THE AFOREMENTIONED FACTORS WILL BE FAVORABLE ALIGNED. DO NOT ANTICIPATE ANY CHANCE FOR SEVERE WEATHER GIVEN MARGINAL MOISTURE/INSTABILITY AND DEEP LAYER SHEAR LESS THAN 25 KT (SUPPORTIVE OF MULTICELL ORGANIZATION)...THOUGH PERHAPS SLIGHTLY STRONGER (CLOSER TO 30 KT) NEAR THE VA BORDER. HIGHS TUE IN THE MID/UPPER 70S TO NEAR 80F IN THE FAR SE...WITH LOWS TUE NIGHT RANGING FROM THE UPPER 40S (N/NW) TO LOWER/MID 50S (S/SE). -VINCENT
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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AS OF 240 PM SUNDAY... WED-THU: EXPECT DRY CONDITIONS TO PREVAIL IN THIS PERIOD DUE TO SYNOPTIC SUBSIDENCE ASSOC/W RISING HEIGHTS ATTENDANT AN UPPER LEVEL RIDGE BUILDING OVER THE EASTERN CONUS. EXPECT TEMPS NEAR OR SLIGHTLY BELOW NORMAL (HIGHS IN THE LOWER/MID 70S) ASSOC/W HIGH PRESSURE BUILDING INTO THE REGION FROM THE NORTH. FRI-SUN: EXPECT SOME POTENTIAL FOR CONVECTION ACTIVITY FRI AFTERNOON INTO FRI NIGHT AS THE UPPER LEVEL PATTERN GRADUALLY SHIFTS TO BROAD CYCLONIC FLOW ALOFT IN THE PRESENCE OF A MORE SEASONABLE MOISTURE RETURN. AT THIS TIME...EXPECT NEAR CLIMO TEMPS AND PRECIP CHANCES IN ASSOC/W A RELATIVELY FLAT /UNIDIRECTIONAL/ UPPER LEVEL PATTERN OVER THE REGION NEXT WEEKEND. -VINCENT
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&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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AS OF 120 PM SUNDAY... WEDGE OF COOL DRY AIR ACROSS THE PIEDMONT WILL SECURE VFR CONDITIONS AT KGSO...KINT...AND KRDU THROUGH THE PERIOD...WHILE THE LOW OFF THE SOUTHEAST COAST WILL THREATEN TO PRODUCE PERIODS OF SUB-VFR CONDITIONS ACROSS EASTERN TERMINALS THROUGH MONDAY MORNING. EXPECT PREDOMINATELY BKN VFR STRATUS LAYER BETWEEN TO 3.5-5KFT ACROSS EASTERN TERMINALS THROUGH 00Z IN ASSOCIATION WITH THE SLOW EASTWARD MOVING VERTICALLY STACKED LOW OFF THE SOUTHEAST COAST...WITH THE POTENTIAL FOR A BRIEF PERIOD OF MVFR CEILINGS ACCOMPANYING SOME OF THE LAST RAIN BANDS MOVING ONSHORE. BREEZY NELY WINDS WILL PERSIST AT ALL TERMINALS...GUSTING TO 25 TO 27KTS AT TIMES. NAM BUFR SOUNDINGS SUGGEST THAT AS THE BOUNDARY LAYER COOLS...LOW STRATUS WILL BE APT TO FORM OVERNIGHT DUE TO THE RELATIVELY DEEP NELY ONSHORE FLOW. THE GFS IS MUCH DRIER IN THE LOWER LEVELS...SUGGESTING LITTLE IN THE WAY OF SUB-VFR CEILINGS. EXPECT WE WILL SEE AT LEAST SOME RETURN OF CLOUDS INTO THE COASTAL PLAIN...AND AS POSSIBLY FAR INLAND AS SAY THE EASTERN/CENTRAL PIEDMONT. WILL INDICATE THIS IN THE FORECAST WITH BROKEN MVFR CEILINGS AT KRWI AND KFAY. LOOKING BEYOND 12Z MONDAY MORNING... AS THE OFFSHORE LOW MOVES AWAY AND OUT TO SEA... VFR CONDITIONS ARE EXPECTED TO DOMINATE MONDAY AND MONDAY NIGHT. THE NEXT SYSTEM WILL IMPACT THE AREA ON TUESDAY... BRINGING ANOTHER CHANCE FOR RAIN AND ASSOCIATED ADVERSE AVIATION CONDITIONS. HOWEVER... THIS WILL BE A MUCH MORE PROGRESSIVE SYSTEM THAN THE CURRENT ONE... WITH CONDITIONS IMPROVING TO VFR LATE TUESDAY NIGHT INTO WEDNESDAY. VFR CONDITIONS SHOULD THEN PERSIST THROUGH THURSDAY AS HIGH PRESSURE RETURNS WITH THE NEXT CHANCE FOR SUB-VFR CONDITIONS ARRIVING BY FRIDAY AS A COLD FRONT APPROACHES FROM THE WEST.
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&& .RAH WATCHES/WARNINGS/ADVISORIES... NONE. && $$ SYNOPSIS...CBL NEAR TERM...CBL SHORT TERM...VINCENT LONG TERM...VINCENT AVIATION...CBL

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