Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 281332 AFDLWX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC 932 AM EDT TUE OCT 28 2014 .SYNOPSIS... HIGH PRESSURE WILL REMAIN OFFSHORE THROUGH TONIGHT. A COLD FRONT WILL PASS THROUGH THE AREA WEDNESDAY AND HIGH PRESSURE WILL RETURN FOR THURSDAY. LOW PRESSURE AND ITS ASSOCIATED COLD FRONT WILL PASS THROUGH THE AREA FRIDAY INTO SATURDAY BEFORE CANADIAN HIGH PRESSURE BUILDS OVERHEAD EARLY NEXT WEEK. && .NEAR TERM /THROUGH TONIGHT/...
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A COLD FRONT IS LOCATED ALONG THE OHIO RIVER THIS MORNING AND THE MID-ATLANTIC IS IN A SOUTHERLY FLOW REGIME. CIRRUS HAVE BLANKETED MOST OF THE MID-ATLANTIC THIS MORNING AS THE COLD FRONT APPROACHES. A MTN WAVES WAS OBSERVED IN THE IR SAT IMAGERY THIS MORNING AND LED TO OVERCAST CONDITIONS ACROSS NRN MD. PER THE 12Z IAD RAOB...A STRONG INVERSION EXISTS ABOVE THE SFC. SFC HEATING AND MIXING WILL ALLOW THIS TO BREAK BUT NOT COMPLETELY DUE TO THE TIME OF YEAR AND SUN ANGLE. A MIX OF CIRRUS AND SUNSHINE IS EXPECTED TODAY LEADING TO WARMER THAN USUAL CONDITIONS. FCST MAX TEMPS IN THE UPPER 70S TO NEAR 80 ARE EXPECTED. PREV DISCUSSION... THE COLD FRONT WILL MOVE INTO THE ALLEGHENY HIGHLANDS LATE TONIGHT. CLOUDS WILL INCREASE AHEAD OF THE BOUNDARY AND A FEW SHOWERS ARE LIKELY OVERNIGHT ACROSS THE POTOMAC HIGHLANDS AND POSSIBLY INTO THE SHENANDOAH VALLEY TOWARD MORNING. MOISTURE WILL BE LIMITED WITH THE BOUNDARY...SO RAINFALL AMOUNTS WILL BE LIGHT. MIN TEMPS WILL BE QUITE MILD DUE TO THE SOUTHERLY FLOW AHEAD OF THE BOUNDARY...RANGING FROM THE 40S IN THE ALLEGHENY HIGHLANDS TO THE LOWER AND MIDDLE 60S IN DOWNTOWN WASHINGTON AND BALTIMORE.
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&& .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... THE COLD FRONT WILL SLOWLY PASS THROUGH THE REGION WEDNESDAY...MOST LIKELY MOVING THROUGH THE SHENANDOAH VALLEY DURING THE MORNING HOURS BEFORE PASSING THROUGH THE WASHINGTON AND BALTIMORE METROPOLITAN AREAS AS WELL AS SOUTHERN MARYLAND DURING THE AFTERNOON AND EVENING HOURS. THERE WILL BE PLENTY OF CLOUDS AHEAD OF THE FRONT ALONG WITH SOME SHOWERS...BUT SKIES WILL GIVE WAY TO SOME SUNSHINE ACROSS WESTERN PORTIONS OF THE CWA WEDNESDAY AFTERNOON BEHIND THE FRONT. THE UPPER-LEVEL SUPPORT WILL BE WEAK AND WELL OFF TO THE NORTH AND WEST OF THE BOUNDARY. MOISTURE WITH THE BOUNDARY WILL BE LIMITED AS WELL...SO RAINFALL AMOUNTS WILL BE LIGHT. WEDNESDAY WILL TURN OUT NOTICEABLY COOLER COMPARED TO TUESDAY DUE TO THE CLOUD COVER AND SHOWERS. MAX TEMPS WILL RANGE FROM THE 50S IN THE ALLEGHENY HIGHLANDS...TO THE UPPER 60S/NEAR 70 IN WASHINGTON AND BALTIMORE...TO THE LOWER AND MIDDLE 70S IN SOUTHERN MARYLAND INTO THE VIRGINIA PIEDMONT. THE BOUNDARY WILL MOVE OFF TO THE EAST WEDNESDAY NIGHT. THERE MAY BE A FEW SHOWERS ACROSS SOUTHERN MARYLAND AND THE VIRGINIA PIEDMONT THAT HANG AROUND INTO THE EVENING HOURS...BUT DRIER AIR WILL SPREAD ACROSS ALL AREAS AS HIGH PRESSURE APPROACHES FROM THE MIDWEST. MIN TEMPS WILL BE SEASONABLY CHILLY BEHIND THE FRONT...RANGING FROM THE UPPER 20S AND LOWER 30S ALONG THE RIDGE TOPS OF THE ALLEGHENY HIGHLANDS TO NEAR 50 IN DOWNTOWN WASHINGTON AND BALTIMORE. && .LONG TERM /THURSDAY THROUGH MONDAY/... THURSDAY WILL BE A RELATIVELY TRANQUIL DAY AS HIGH PRESSURE BUILDS IN FROM THE WEST. COLD ADVECTION BEHIND A DEPARTING COLD FRONT WILL LIMIT HIGH TEMPERATURES TO THE UPPER 50S TO LOWER 60S. HIGH PRESSURE WILL BEGIN TO BREAK DOWN ON FRIDAY AS THE NEXT SYSTEM TAKES SHAPE TO THE NORTHWEST. THIS SYSTEM WILL BE THE DOMINANT WEATHER FEATURE OF THE EXTENDED PERIOD...AS THE UPPER AIR PATTERN AMPLIFIES AND TROUGH...OR PERHAPS CLOSED LOW...DIGS OVER THE NORTHEASTERN CONUS AND A STRONG COLD FRONT SURGES SOUTHEASTWARD. AFTER SHOWING SOME SIMILARITIES IN RECENT RUNS...THE 00Z MODELS DIVERGED AGAIN...WITH THE ECMWF SHOWING A MUCH DEEPER/SLOWER SOLUTION. WHILE ENSEMBLES SUPPORT THE NOTION OF A DEEP TROUGH...THERE IS SPREAD ON THE AMPLITUDE. THE PATTERN IS TRICKY SINCE IT INVOLVES DOWNSTREAM AMPLIFICATION BUT IS ALSO SOMEWHAT PROGRESSIVE. THE DEEPER SOLUTION IS PLAUSIBLE...SO CANNOT RULE OUT THE ECMWF. IN TERMS OF SENSIBLE WEATHER...WHAT INITIALLY APPEARED TO BE A LOW POP EVENT EAST OF THE MOUNTAINS COULD BECOME MORE SHOWERY WITH AN AMPLIFIED SOLUTION. BUMPED POPS UP A LITTLE...BUT STILL TOO EARLY TO MAKE WHOLESALE CHANGES. THE POTOMAC HIGHLANDS DO STAND THE CHANCE OF SEEING SOME SNOW SHOWERS ON THE BACK SIDE OF THE SYSTEM. TEMPERATURES IN THE FRIDAY NIGHT-SATURDAY TIME FRAME WILL DEPEND ON THE SPEED OF THE SYSTEM...BUT THE PATTERN IS SETTING UP THIS WEEKEND FOR SOME OF THE COOLEST AIR THIS FALL TO EVENTUALLY MAKE IT IN...WITH HIGH TEMPERATURES IN THE 40S AND LOWS NEAR OR BELOW FREEZING. SATURDAY COULD ALSO BE BREEZY IF A STRONG SURFACE CYCLONE DEVELOPS OFFSHORE. HIGH PRESSURE WILL BUILD IN SUNDAY AND MONDAY BUT TEMPERATURES WILL REMAIN BELOW NORMAL. && .AVIATION /14Z TUESDAY THROUGH SATURDAY/... VFR CONDITIONS ARE EXPECTED THROUGH THIS EVENING. SOUTHERLY WINDS WILL INCREASE THIS AFTERNOON WITH GUSTS AROUND 15 TO 20 KNOTS. WINDS WILL DIMINISH AS THE MIXING LAYER DECREASES THIS EVENING. A COLD FRONT WILL APPROACH THE TERMINALS TONIGHT BEFORE PASSING THROUGH WEDNESDAY. A FEW SHOWERS ARE EXPECTED AND CIGS/VSBYS MAY APPROACH MVFR LEVELS DURING THIS TIME. HIGH PRESSURE WILL RETURN FOR WEDNESDAY NIGHT THROUGH THURSDAY. LOW PRESSURE AND ITS ASSOCIATED COLD FRONT MAY IMPACT THE TERMINALS FRIDAY INTO SATURDAY. && .MARINE... HIGH PRESSURE WILL REMAIN OVER THE ATLANTIC WHILE A COLD FRONT APPROACHES FROM THE WEST TODAY. THIS WILL ALLOW FOR SOUTHERLY WINDS TO INCREASE. A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE WATERS TODAY...BUT IT WILL BE MARGINAL DUE TO THE RELATIVELY COOLER WATERS DECREASING THE MIXING LAYER A BIT. THE COLD FRONT WILL CONTINUE TO APPROACH THE WATERS FROM THE WEST TONIGHT. THE SMALL CRAFT ADVISORY CONTINUES THROUGH TONIGHT FOR MIDDLE PORTIONS OF THE MARYLAND CHESAPEAKE BAY AND THE LOWER TIDAL POTOMAC RIVER AS SOUTHERLY WINDS ARE EXPECTED TO CHANNEL ACROSS THESE AREAS. THE COLD FRONT WILL PASS THROUGH THE WATERS LATE WEDNESDAY. ANOTHER PRESSURE SURGE BEHIND THE FRONT MAY CAUSE WINDS TO EXCEED SCA CRITERIA OVERNIGHT WEDNESDAY INTO THURSDAY. A STRONGER COLD FRONT MAY IMPACT THE WATERS FRIDAY INTO SATURDAY. && .TIDES/COASTAL FLOODING... A SOUTHERLY FLOW WILL CAUSE TIDAL ANOMALIES TO INCREASE TODAY. WATER LEVELS MAY APPROACH MINOR FLOODING THRESHOLDS FOR SENSITIVE AREAS NEAR HIGH TIDE TONIGHT. ANOMALIES WILL DECREASE WEDNESDAY AS THE FLOW TURNS OFFSHORE. && .CLIMATE...
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MAX TEMPS TODAY WILL BE UNUSUALLY WARM FOR THIS TIME OF YEAR. THE RECORD AT DULLES MAY BE TIED OR BROKEN TODAY. BELOW IS A LIST OF THE PREVIOUS RECORDS AT IAD...DCA AND BWI. IAD...83 IN 1984 DCA...87 IN 1919 BWI...87 IN 1919.
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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 6 PM EDT THIS EVENING FOR ANZ530- 531-535-536-538-539. SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ542. SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ532>534- 537-540-541-543.
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&& $$ SYNOPSIS...BJL NEAR TERM...BJL/HAS SHORT TERM...BJL LONG TERM...AS AVIATION...BJL/AS MARINE...BJL/AS TIDES/COASTAL FLOODING...BJL CLIMATE...BJL

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