Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 211956 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 256 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 /TONIGHT/... NO PROBS FORESEEN IN THE MID ATLC TNGT. 12Z IAD SNDG REALLY SUMMED IT UP - 0.11" PWAT. HIGH PRES OVR THE AREA SHOULD LEAD TO CLR SKIES. THIS COMBINED W/ LGT WINDS WL ALLOW TEMPS TO DROP OFF AFTR SUNSET. U20S IN THE CITIES...A20 MAJORITY OF THE FCST AREA...TEENS IN THE HIGHLANDS. && .SHORT TERM /SATURDAY 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 THURSDAY/... 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 /18Z FRIDAY THROUGH WEDNESDAY/... VFR CONDS XPCTD TNGT THRU SAT NGT. 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. && .MARINE... SCA IN EFFECT...BUT XPCT WINDS WL BE DIMINISHING TO BLO SCA LVLS BY SHORTLY AFTR SUNSET. NO PROBS ON THE WATERS XPCTD SAT OR SAT NGT. 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. && .TIDES/COASTAL FLOODING... WATER LVLS WERE SLTLY OVR ONE FT BLO NRML DURG THE LATE MRNG HIGH TIDE CYCLE. AS WIND SPEEDS DIMINISH WATER LVLS SHOULD REBOUND AS TEH NEXT HIGH TIDE CYCLE APRCHS. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EST THIS EVENING FOR ANZ530>543. && $$ PRODUCTS...WOODY!/ADS/CEM

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