Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 220151 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 851 PM EST FRI NOV 21 2014 .SYNOPSIS... HIGH PRESSURE WILL BUILD OVERHEAD TONIGHT...AND THEN SHIFT OFFSHORE SATURDAY. A DEEPENING LOW PRESSURE SYSTEM OVER THE GREAT LAKES WILL LIFT A WARM FRONT THROUGH THE AREA MONDAY. AN ASSOCIATED COLD FRONT IS EXPECTED TO MOVE THROUGH MONDAY NIGHT. THE FRONT STALLS JUST OFFSHORE AS HIGH PRESSURE BUILDS IN THE WAKE AS THE AREA REMAINS POSITIONED BETWEEN AREAS OF LOW PRESSURE. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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CENTER OF SURFACE HIGH RESIDES OVER THE CWA THIS EVENING...AND WILL DRIFT TO THE EAST AND WIND UP ALONG THE COAST BY DAYBREAK SATURDAY. CLEAR SKIES WERE OVERHEAD...AND WILL HOLD THROUGH THE NIGHT. DECENT RADIATIONAL COOLING ALREADY UNDERWAY...PAVING THE WAY FOR A COLD NIGHT. USED BC ADJMET/SREFS TO RE-POPULATE MINIMA...WHICH RESULTED IN A 1 TO 2 DEG F REDUCTION FOR SOME LOCATIONS COMPARED TO PREV FORECAST.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/... THE HIGH WL CONTINUE TO BE IN CONTROL OF AREA WX SAT AND SAT NGT. THE HIGH WL BE MIGRATING OFFSHORE...HENCE WINDS WL TURNING TO THE S. THIS WL ALLOW FOR A WARMER DAY SAT THAN TDA...AND ALSO WARMER SAT NGT THAN THE UPCOMING NGT. HIGHS 45-50 MOST OF THE AREA...LOWS SAT NGT CLOSER TO FRZG. && .LONG TERM /SUNDAY THROUGH FRIDAY/... UPPER FLOW PATTERN SPLIT ON SUNDAY MORNING WITH A NORTHERN WAVE OVER THE DAKOTAS AND SOUTHERN WAVE OVER TEXAS. AHEAD OF THESE FEATURES...UPPER FLOW WILL BE ZONAL OVER THE MID ATLANTIC. SURFACE HIGH PRESSURE WILL BE MOVING OFF THE ATLANTIC COAST WITH SOUTHERLY LOW LEVEL FLOW IN PLACE. MODELS ARE IN GOOD AGREEMENT OF DRY CONDITIONS THROUGH THE MORNING HOURS. PARTLY TO MOSTLY CLOUDY TO START THE DAY...BUT MAINLY OF THE MID/HIGH VARIETY. DESPITE WARM ADVECTION ALOFT...MIXING WILL BE POOR AND HIGHS WILL BE HELD IN THE LOWER TO MID 50S. HAVE SLOWED RAIN CHANCES A BIT MORE FOR THE AFTERNOON...BUT PERHAPS NOT ENOUGH. DEW POINTS WILL STILL BE RATHER LOW...AND STRONG FORCING DOES NOT ARRIVE UNTIL EVENING. THE SOUTHERN WAVE WILL TRACK INTO THE OHIO VALLEY TO BEGIN PHASING WITH THE NORTHERN WAVE...WITH A LLJ AND FAVORABLE ISENTROPIC LIFT DEVELOPING OVER THE MID ATLANTIC. AN AREA OF MODERATE RAIN WILL PUSH NORTH THROUGH THE AREA DURING THE EVENING NIGHT...WITH GOOD AGREEMENT OF THIS OCCURRING DURING THE 00-09Z TIME PERIOD. WITH A SOUTHEASTERLY SURFACE WIND DEVELOPING...COULD SEE SOME RAIN TOTALS OVER A HALF INCH FOCUSED ON THE EAST FACING SLOPES. WITH THE SURFACE WARM FRONT PUSHING THROUGH OVERNIGHT...EXPECT TO SEE TEMPERATURES AND DEW POINTS RISING NONDIURNALLY. RAIN WILL TAPER TO SHOWERS BY DAYBREAK MONDAY. UPPER LEVEL TROUGH OVER THE MISSISSIPPI VALLEY WILL MOVE EAST THROUGH THE PERIOD. JET MAX WILL PASS FROM SOUTHWEST TO NORTH OF THE MID ATLANTIC REGION MONDAY NIGHT THROUGH TUESDAY. SHORTWAVE WILL REACH THE ATLANTIC COAST BY WEDNESDAY NIGHT. THE TROUGH WILL REACH THE COAST BY EARLY FRIDAY. SURFACE BOUNDARY SETTING UP FROM NORTH TO SOUTH ACROSS THE AREA EAST OF THE BLUE RIDGE EARLY MONDAY. DRY SLOT TAKING OVER MONDAY NIGHT THROUGH TUESDAY. DEVELOPING LOW OFF SOUTH ATLANTIC COAST WILL MOVE NORTHWARD ALONG THE COAST TRANSPORTING MOISTURE INTO MID ATLANTIC REGION AT MID WEEK. ECMWF TREND IS SIMILAR TO HPC GUIDANCE. FOLLOWING HPC GUIDANCE WITH SOME VERY MINOR TWEAKS IN POP GRID. && .AVIATION /01Z SATURDAY THROUGH WEDNESDAY/...
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VFR CONDS XPCTD TNGT THRU SAT NGT. HIGH PRESSURE WILL BE OVERHEAD TONIGHT...THEN OFFSHORE FOR SAT FOR INCREASING SOUTHERLY WINDS DURING THE DAYTIME. SUB-VFR CONDITIONS ARE LIKELY FROM SUNDAY EVENING UNTIL EARLY MONDAY MORNING...WITH IFR POSSIBLE DURING THE PERIOD OF HEAVIER RAIN. A STRONG LOW LEVEL JET WILL ALSO BE IN PLACE SUNDAY NIGHT...BUT LLWS ISSUES MAY BE MITIGATED BY LACK OF A NEAR-SURFACE INVERSION AND SOME MIXING OF THE WINDS. SOUTHERLY WIND GUSTS OF 20-25 KT POSSIBLE ON MONDAY. THE PROBABILITY OF AVIATION HAZARDS IS LOW THROUGH THE REMAINDER OF THE FORECAST PERIOD.
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&& .MARINE...
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WITH THE SETTING OF THE SUN AND HIGH PRESSURE BUILDING IN FROM THE WEST...WINDS HAVE DIMINISHED AND SCA WAS ALLOWED TO EXPIRE. HIGH PRESSURE MOVES OFFSHORE FOR SATURDAY...SOUTHERLY WINDS INCREASE DURING THE EVENING AND CHANNELLING WILL ENHANCE SPEEDS UP THE BAY BUT CURRENT FORECAST IS TO REMAIN JUST BELOW SCA. SOUTHERLY WINDS ON SUNDAY MAY REACH MARGINAL CONDITIONS FOR A SMALL CRAFT ADVISORY. WINDS WILL INCREASE SUNDAY EVENING AND NIGHT...WITH GUSTS UP TO 30 KT POSSIBLE. STRONG SOUTHERLY WIND GUSTS ABOVE 20 KT CONTINUE MONDAY...BECOMING WESTERLY MONDAY NIGHT BEFORE GRADUALLY DIMINISHING TUESDAY MORNING. AT THIS TIME WINDS ARE FORECAST TO REMAIN BELOW SMALL CRAFT CRITERIA THROUGH THURSDAY.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...NONE.
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&& $$ BPP/WOODY!/ADS/CEM

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