Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 201827
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
227 PM EDT MON OCT 20 2014

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFFSHORE THIS AFTERNOON. 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.

&&

.NEAR TERM /THROUGH TONIGHT/...
HIGH PRESSURE RESIDES OVER EASTERN VA/NC THIS AFTERNOON. SURFACE
AND UPPER LOW PRESSURE HAS MOVED INTO THE UPPER GREAT
LAKES...WITH A TRAILING SURFACE COLD FRONT OVER THE WESTERN OHIO
VALLEY. BOTH AN UPPER TROUGH AND SURFACE COLD FRONT WILL APPROACH
FROM THE WEST THROUGH TONIGHT. SOME LIGHT RETURNS HAVE MOVED INTO
THE POTOMAC HIGHLANDS...AND ISOLATED RAIN HAS BEEN NOTED ON
SURFACE OBS OVER ERN WV. WITH RELATIVELY DRY AIR AT LOW LEVELS AND
DEW POINT DEPRESSIONS AROUND 10-15 DEGREES...RAIN WILL HAVE
DIFFICULTY MAKING IT TO THE GROUND. FCST CALLS FOR ISOLATED
SHOWERS OVER THE POTOMAC HIGHLANDS INITIALLY...SPREADING EWD INTO
THE SHENANDOAH VALLEY BY LATE AFTERNOON AND INTO THE I-95 CORRIDOR
BY THIS EVENING. ANY RAIN SHOULD BE ISOLATED TO SCATTERED WITH
LIKELY JUST A FEW HUNDREDTHS OF AN INCH ACCUMULATION FOR THOSE
AREAS THAT DO SEE RAIN.

IN TERMS OF TEMPS AND WINDS...HIGHS LATE THIS AFTERNOON GENERALLY IN
THE 60S UNDER SOUTHERLY FLOW WITH SOME GUSTS TO 2O MPH. WINDS BECOME
LIGHT TONIGHT. LOW TEMPS WILL BE AROUND 50 ALONG AND EAST OF
I-95...AND IN THE 40S ELSEWHERE.

&&

.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
SURFACE COLD FRONT MOVES THROUGH TUESDAY. AN UPPER LOW WILL DROP
FROM THE GREAT LAKES INTO PA AND NORTHERN PORTIONS OF WV/MD/VA BY
TUESDAY AFTERNOON...AND THEN OVER THE MID-ATLANTIC TUESDAY NIGHT. WITH
SOME INSTABILITY AND PERIODS OF VORTICITY ADVECTION...POTENTIAL
FOR SCATTERED RAIN/SHOWERS WILL CONTINUE.

TEMPS AROUND 10 DEGREES BELOW NORMAL TUESDAY...WITH HIGHS
PRIMARILY IN THE 50S. LOWS TUESDAY NIGHT IN THE 40S AGAIN...AND
AROUND 50 IN URBAN AREAS AND BY CHESAPEAKE BAY.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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.

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.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
VFR CONTINUES THROUGH TODAY AS THE HIGH SHIFTS OFFSHORE WITH RETURN
SLY/SWLY FLOW GUSTING UP TO 18 KT THIS AFTERNOON. 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.

&&

.MARINE...
SCA IN EFFECT FOR GUSTY SOUTHERLY WINDS. GUSTS OVER MOST ZONES
WILL DECREASE LATE THIS AFTERNOON AND EARLY EVENING. SCA EXPIRES
AT 8 PM FOR MOST ZONES...EXCEPT FOR THE MD CHES BAY SOUTH OF POOLES
ISLAND AND THE LOWER TIDAL POTOMAC WHERE SOUTHERLY CHANNELING IS
EXPECTED TO CONTINUE 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.


&&

.TIDES/COASTAL FLOODING...
ANOMALIES BACK ON THE RISE...APPROACHING 1 FT LATE THIS AFTERNOON
UNDER SOUTHERLY WINDS. FORECASTS FOR WASHINGTON
CHANNEL...BALTIMORE AND ANNAPOLIS SHOW LIKELIHOOD TO REACH ACTION
STAGES IN THE NEXT TWO HIGH TIDE CYCLES LATE TODAY AND
OVERNIGHT...BUT AT THIS TIME FALL SHORT OF MINOR INUNDATION.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR
     ANZ530>533-535-536-538>542.
     SMALL CRAFT ADVISORY UNTIL 2 AM EDT TUESDAY FOR ANZ534-537-543.

&&

$$
SYNOPSIS...KCS
NEAR TERM...KCS
SHORT TERM...KCS
LONG TERM...CEB
AVIATION...KCS/CEB
MARINE...KCS/CEB
TIDES/COASTAL FLOODING...KCS






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