Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 210026 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 826 PM EDT MON OCT 20 2014 .SYNOPSIS...
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A COLD FRONT WILL APPROACH FROM THE WEST TONIGHT AND MOVE THROUGH THE REGION TUESDAY. LOW PRESSURE WILL PERSIST NEAR THE MID- ATLANTIC COAST INTO THURSDAY. HIGH PRESSURE WILL RETURN FOR THE END OF THE WORKWEEK AND INTO THE WEEKEND.
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&& .NEAR TERM /THROUGH TUESDAY/...
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A UPPER LEVEL TROUGH WILL MOVE ACROSS THE GREAT LAKES AND NEW ENGLAND TONIGHT. LOW PRESSURE AND AN ASSOCIATED COLD FRONT WILL APPROACH THE REGION TONIGHT. AN AREA OF VORTICITY ADVECTION IS MOVING AHEAD OF AN ADVANCING SHORTWAVE TROUGH THIS EVENING. SHOWERS HAVE MOVED ACROSS THE POTOMAC HIGHLANDS AND BLUE RIDGE AND WILL CONTINUE TO MOVE EASTWARD. THESE SHOWERS ARE MOVING INTO A DRY AIRMASS AND ONLY HUNDREDTHS ARE EXPECTED IN PLACES THAT RECIEVE RAIN THIS EVENING. A COLD FRONT ACROSS THE OHIO VALLEY WILL ALSO CONTINUE TO MOVE EASTWARD TONIGHT. SHOWERS ARE EXPECTED TAPER OFF OVERNIGHT AND INTO TUESDAY MORNING WITH THE EXCEPTION OF THE HIGHLANDS. WESTERLY FLOW AGAINST THE MTNS WILL LEAD TO ENHANCED LIFT AND SHOWERS ARE EXPECTED THROUGH TUESDAY. FCST MIN TEMPS ARE IN THE 40S AND NEAR 50 IN THE METROS. THE COLD FRONT IS EXPECTED TO CROSS THE REGION TUESDAY AS THE UPPER LOW MOVES OVER HEAD. COLD AIR ALOFT WILL LEAD TO STEEPENING LAPSE RATES AND THEREFORE SOME INSTABILITY. ADDED ISOLATED TSTMS TO AREAS EAST OF THE BLUE RIDGE TUESDAY AFTERNOON. LITTLE WIND FIELD WILL LIMIT GUSTY WINDS TUESDAY AFTERNOON. FCST MAX TEMPS ARE IN THE 60S TUESDAY AFTERNOON.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/...
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UPPER LEVEL LOW PRESSURE WILL REMAIN OCCLUDED AND STRENGTHEN NEAR THE MID-ATLANTIC THROUGH THE DAY WEDNESDAY AND WEDNESDAY NIGHT. THE ASSOCIATED SURFACE LOW WILL DEEPEN DUE TO BAROCLINIC ENHANCEMENT AS IT MOVES OVER RELATIVELY WARM OCEAN WATERS OFF OF THE MID-ATLANTIC COAST DURING THIS TIME. POPS WILL REMAIN FOCUSED OVER THE NORTHEASTERN HALF OF THE CWA AS STORMS PRECIP SHIELDS SLOWLY STAGGERS NORTHEASTWARD WITH THE LOW. WE SHOULD SEE A RESPECTABLE QPF GRADIENT WITH THE AREAS ALONG AND JUST WEST OF THE BAY RECEIVING ONLY A COUPLE OF TENTHS OF AN INCH OF RAINFALL WHILE LOCATIONS ON THE THE DELMARVA PENINSULA WILL SEE SIGNIFICANTLY MORE DUE TO THEIR PROXIMITY OT THE LOW.
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&& .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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THE MAJOR FORECAST CHALLENGE ON THE BACKSIDE OF THE LOW IS THE UPSLOPE PRECIP THREAT. THE HIGHEST ELEVATIONS ALONG THE POTOMAC HIGHLANDS WILL SEE LOW TEMPS THAT MAY DIP INTO THE MID 30S WEDNESDAY NIGHT...AND GIVEN THE FETCH OF THE NORTHERLY WINDS OVER THE GREAT LAKES UPSTREAM OF THE ALLEGHENY FRONT THE OPTION TO INCLUDE SNOW AS A PRECIP TYPE WAS TEMPTING. BUT IT LOOKS LIKE THE LAYER OF ABOVE-FREEZING AIR NEAR THE SURFACE WILL BE A BIT TOO THICK FOR ANY SNOWFALL. THIS MAY CHANGE IN UPCOMING FORECASTS AS CONFIDENCE IN LOW TEMPS INCREASES...BUT EVEN IF A FEW FLAKES DO FALL NO ACCUMULATION WILL OCCUR. HIGH PRESSURE CENTERED OVER THE SOUTHEASTERN UNITED STATES WILL NOSE INTO THE AREA FRIDAY AND CONTINUE TO STRENGTHEN THROUGH THE WEEKEND. OVERALL...SATURDAY AND SUNDAY SHOULD BE BEAUTIFUL FALL DAYS WITH DRY CONDITIONS AND HIGHS IN THE MID-60S. HIGH PRESSURE WILL BEGIN TO SHIFT OFF OF THE MID-ATLANTIC COAST EARLY NEXT WORKWEEK AND OUR NEXT THREAT FOR ADVERSE WEATHER SHOULD NOT PRESENT ITSELF UNTIL THE MIDDLE OF NEXT WEEK.
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&& .AVIATION /00Z TUESDAY THROUGH SATURDAY/...
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A COLD FRONT WILL APPROACH FROM THE WEST TONIGHT AND MOVE THROUGH THE REGION TUESDAY. PERIODIC SHOWERS AND SUB-VFR POSSIBLE...BUT CONFIDENCE TOO LOW TO INCLUDE AT THE END OF THE TAF PERIOD AT THIS TIME. LIGHT W WINDS TUESDAY. CONFIDENCE IS LOW IN THE OCCURRENCE OF AVIATION HAZARDS THROUGH THE LONG TERM PERIOD.
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&& .MARINE...
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SOUTHERLY CHANNELING WILL CONTINUE ACROSS THE MD CHESAPEAKE BAY SOUTH OF DRUM PT/TANGIER SOUND AND LOWER TIDAL POTOMAC UNTIL 2 AM. WLY FLOW TUESDAY AS LOW PRESSURE APPROACHES FROM THE NORTHWEST. LIGHT S WINDS EXPECTED LATE TONIGHT...TRENDING TOWARDS THE WEST AND EVENTUALLY NW DURING THE DAY TUESDAY. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED WEDNESDAY AND WEDNESDAY NIGHT AS LOW PRESSURE DEEPENS JUST OFF OF THE MID-ATLANTIC COAST. A SMALL CRAFT ADVISORY MAY ALSO BE NEEDED THURSDAY THROUGH FRIDAY NIGHT AS BREEZY NORTHERLY WINDS FILL IN BEHIND LOW PRESSURE DEPARTING OFF TO THE NORTHEAST.
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&& .TIDES/COASTAL FLOODING...
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ANOMALIES BACK ON THE RISE...APPROACHING 1 FT TONIGHT UNDER SOUTHERLY WINDS. FORECASTS FOR WASHINGTON CHANNEL...BALTIMORE AND ANNAPOLIS SHOW LIKELIHOOD TO REACH ACTION STAGES IN THE NEXT TWO HIGH TIDE CYCLES TONIGHT AND OVERNIGHT...BUT AT THIS TIME FALL SHORT OF MINOR INUNDATION.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...NONE. MD...NONE. VA...NONE. WV...NONE. MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT TUESDAY FOR ANZ534-537-543.
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&& $$ SYNOPSIS...KS NEAR TERM...HAS SHORT TERM...KS LONG TERM...CEB AVIATION...KS/CEB/HAS MARINE...KS/CEB/HAS TIDES/COASTAL FLOODING...HAS

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