Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 210054
AFDLWX

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

.SYNOPSIS...
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 TUESDAY/...
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.

&&

.SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY/...
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.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
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 /01Z TUESDAY THROUGH SATURDAY/...
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...
SOUTHERLY CHANNELING WILL CONTINUE ACROSS THE MD CHESAPEAKE BAY
SOUTH OF POOLES ISLAND/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.

&&

.TIDES/COASTAL FLOODING...
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.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 AM EDT TUESDAY FOR ANZ531>534-537-
     539>541-543.

&&

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







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