Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 181810
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
210 PM EDT THU SEP 18 2014

.SYNOPSIS...
A WEAK COLD FRONT WILL PASS THROUGH THIS AFTERNOON AND EVENING.
HIGH PRESSURE WILL BUILD OVERHEAD FOR LATE TONIGHT THROUGH
SATURDAY. THE HIGH WILL MOVE OFF THE COAST SUNDAY AND A STRONGER
COLD FRONT WILL PASS THROUGH THE AREA SUNDAY NIGHT INTO MONDAY.
HIGH PRESSURE WILL RETURN FOR THE MIDDLE PORTION OF NEXT WEEK.

&&

.NEAR TERM /THROUGH FRIDAY/...
A BROAD UPPER-LEVEL TROUGH WILL REMAIN OVER THE REGION THROUGH
LATE THIS AFTERNOON AND EVENING WHILE A WEAK UPPER-LEVEL
DISTURBANCE PASSES THROUGH IN THE FLOW ALOFT. A WEAK COLD FRONT
ASSOCIATED WITH THIS SYSTEM WILL ALSO MOVE THROUGH DURING THIS
TIME. DESPITE LIMITED MOISTURE AND FORCING...THERE HAS BEEN ENOUGH
WARM AIR FOR A LITTLE INSTABILITY AHEAD OF THE BOUNDARY...CAUSING
A FEW SHOWERS TO DEVELOP NEAR THE INTERSTATE 95 CORRIDOR INTO
CENTRAL VIRGINIA. THE THREAT FOR SHOWERS WILL CONTINUE INTO EARLY
THIS EVENING...BUT COVERAGE WILL BE ISOLATED WITH MOST AREAS
REMAINING DRY.

THE COLD FRONT WILL DROP TO OUR SOUTH LATE TONIGHT AND HIGH
PRESSURE WILL BUILD OVER NEW ENGLAND...ALLOWING FOR THE SURFACE
RIDGE AXIS ASSOCIATED WITH THIS HIGH TO BUILD INTO OUR AREA. THIS
SHOULD BRING DRY CONDITIONS OVERNIGHT...BUT CLOUDS MAY GET HUNG UP
ACROSS CENTRAL VIRGINIA INTO THE POTOMAC HIGHLANDS WHERE
OVERRUNNING WILL OCCUR BEHIND THE COLD FRONT.

HIGH PRESSURE WILL CONTINUE TO WEDGE INTO THE MID-ATLANTIC THROUGH
FRIDAY...BRINGING MAINLY DRY CONDITIONS ALONG WITH BELOW NORMAL
TEMPERATURES. HOWEVER...THE FLOW WILL TURN ONSHORE AND THIS MAY
CAUSE CLOUDS TO GET TRAPPED UNDERNEATH THE SUBSIDENCE INVERSION.
THE DEEPEST MOISTURE WILL BE ACROSS SOUTHERN MARYLAND...CENTRAL
VIRGINIA AND THE POTOMAC HIGHLANDS WHERE A FEW SPRINKLES CANNOT BE
RULED OUT. MAX TEMPS WILL RANGE FROM THE LOWER TO MIDDLE 60S IN
THE POTOMAC HIGHLANDS TO THE LOWER AND MIDDLE 70S NEAR WASHINGTON
AND BALTIMORE.

&&

.SHORT TERM /FRIDAY NIGHT THROUGH SUNDAY/...
HIGH PRESSURE WILL MOVE OFF THE NEW ENGLAND COAST AND THE SURFACE
RIDGE AXIS WILL CONTINUE TO EXTEND SOUTH AND WEST TOWARD THE MID-
ATLANTIC COAST FRIDAY NIGHT THROUGH SATURDAY. AN ONSHORE FLOW WILL
CONTINUE DURING THIS TIME...AND IT MAY LEAD TO SOME LOW CLOUDS
ALONG WITH PATCHY FOG...ESPECIALLY LATE FRIDAY NIGHT INTO SATURDAY
MORNING. CLOUDS SHOULD GIVE WAY TO SUNSHINE SATURDAY...AND THAT
WILL CAUSE MAX TEMPS TO BE A BIT WARMER COMPARED TO
FRIDAY...RANGING FROM THE 70S IN THE MOUNTAINS TO NEAR 80 ACROSS
WASHINGTON AND BALTIMORE.

A STRONGER COLD FRONT WILL APPROACH THE AREA SATURDAY NIGHT...BUT
THE SURFACE RIDGE AXIS SHOULD REMAIN IN PLACE. AREAS OF LOW CLOUDS
AND FOG ARE POSSIBLE OVERNIGHT SATURDAY INTO SUNDAY MORNING. THE
COLD WILL MOVE INTO THE AREA SUNDAY AFTERNOON. A SOUTHERLY FLOW
AHEAD OF THE FRONT WILL CAUSE WARM AND HUMID CONDITIONS. A FEW
SHOWERS AND THUNDERSTORMS ARE POSSIBLE SUNDAY AFTERNOON AHEAD OF
THE COLD FRONT.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
A COLD FRONT WILL MOVE ACROSS THE REGION TO THE EAST COAST SUNDAY
NIGHT. THERE IS A CHANCE FOR SHOWERS ALONG THE FRONT...MAINLY FROM
THE SHENANDOAH VALLEY EAST TO THE CHESAPEAKE BAY.

AN UPPER LEVEL TROUGH OF LOW PRESSURE WILL SWEEP ACROSS THE REGION
MONDAY. THERE COULD BE A FEW INSTABILITY SHOWERS THAT DEVELOP
ENLIGHTEN TO THIS TROUGH. FOR THE MOST PART...MOST AREAS SHOULD BE
DRY. HIGH PRESSURE WILL GRADUALLY BUILD INTO THE REGION MONDAY NIGHT.

HIGH PRESSURE SHOULD HANG ON TO THE MID ATLANTIC COAST TUESDAY
BEFORE IT MOVES OFFSHORE AND A SURFACE COLD FRONT SAGS IN FROM THE
NORTHWEST AND NORTH LATE TUESDAY INTO TUESDAY NIGHT. WITH LIMITED
MOISTURE IN PLACE...MOST AREAS WILL BE RAINFREE.

A SECOND AREA OF HIGH PRESSURE WILL BUILD IN BEHIND THE FRONT AND
USHER IN COLDER THAN NORMAL AIR INTO THE REGION WEDNESDAY THROUGH
THURSDAY.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
VFR CONDITIONS ARE EXPECTED THIS AFTERNOON AND EVENING. A STRAY
SHOWER CANNOT BE RULED OUT...BUT MOST AREAS WILL BE DRY. AN
ONSHORE FLOW WILL DEVELOP LATE TONIGHT THROUGH FRIDAY...AND THIS
MAY LEAD TO LOW CLOUDS ACROSS KCHO. ALSO PATCHY BR IS POSSIBLE
LATE TONIGHT INTO FRIDAY MORNING FOR KMRB AND KCHO.

VFR CONDITIONS ARE EXPECTED FOR MOST OF THE TERMINALS FRIDAY...BUT
LOW CLOUDS MAY PERSIST ACROSS KCHO WHICH COULD LEAD TO MVFR
CONDITIONS. LOW CLOUDS MAY BECOME MORE WIDESPREAD LATE FRIDAY
NIGHT INTO SATURDAY...AND AGAIN LATE SATURDAY NIGHT INTO SUNDAY AS
AN ONSHORE FLOW PERSISTS. A COLD FRONT WILL MOVE INTO THE
TERMINALS SUNDAY AFTERNOON...AND A FEW SHOWERS AND THUNDERSTORMS
ARE POSSIBLE.

&&

.MARINE...
A WEAK COLD FRONT WILL PASS THROUGH THE WATERS LATE THIS AFTERNOON
AND EVENING. A COUPLE SHOWERS ARE POSSIBLE...BUT MOST AREAS WILL
BE DRY. A PRESSURE SURGE IS EXPECTED TO DEVELOP BEHIND THE COLD
FRONT LATE TONIGHT THROUGH FRIDAY MORNING. THIS WILL CAUSE WINDS
TO INCREASE AND A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE
MARYLAND CHESAPEAKE BAY AND LOWER TIDAL POTOMAC RIVER.
HOWEVER...IT WILL BE MARGINAL WITH GUSTS NEAR 20 KNOTS.

AN EAST TO SOUTHEAST FLOW WILL CONTINUE FRIDAY THROUGH SATURDAY AS
HIGH PRESSURE BUILDS OFF THE NEW ENGLAND COAST. WIND GUSTS MAY
APPROACH SCA CRITERIA AT TIMES...BUT THE GUSTS HAVE BEEN CAPPED AT
15 KNOTS FOR NOW DUE TO A RELATIVELY WEAK PRESSURE GRADIENT.

A COLD FRONT WILL APPROACH THE WATERS SUNDAY. A FEW SHOWERS AND
THUNDERSTORMS ARE POSSIBLE LATE IN THE DAY INTO SUNDAY NIGHT.
WINDS WILL SHIFT TO THE NORTHWEST BEHIND THE FRONT...AND A SMALL
CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE WATERS SUNDAY
NIGHT INTO MONDAY.

&&

.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES HAVE INCREASED TO ABOUT 1 TO 1.5 FEET ABOVE NORMAL
FROM THE SOUTHERLY FLOW WEDNESDAY. THE FLOW WILL BE CONTINUE TO BE
LIGHT THROUGH THIS EVENING...BEFORE INCREASING AND TURNING
TOWARD THE NORTHEAST LATE TONIGHT. WITH NO OFFSHORE FLOW TO PUSH
THE WATER OUT OF THE BAY...THESE TIDAL ANOMALIES ARE LIKELY TO
CONTINUE THROUGH TONIGHT. A COASTAL FLOOD ADVISORY IS IN EFFECT
FOR THE HIGH TIDE CYCLE LATE TONIGHT INTO EARLY FRIDAY FOR ANNE
ARUNDEL COUNTY THROUGH ST MARYS COUNTY.

ELSEWHERE...MINOR TIDAL FLOODING IS POSSIBLE NEAR HIGH TIDE LATE
TONIGHT INTO EARLY FRIDAY. HOWEVER...CONFIDENCE IS NOT HIGH ENOUGH
FOR A COASTAL FLOOD ADVISORY AT THIS POINT.

AN ONSHORE FLOW IS EXPECTED TO CONTINUE THROUGH SUNDAY...CAUSING
ELEVATED WATER LEVELS AND THE POSSIBILITY OF MINOR TIDAL FLOODING.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...COASTAL FLOOD ADVISORY FROM 8 PM THIS EVENING TO 2 AM EDT
     FRIDAY FOR MDZ017-018.
     COASTAL FLOOD ADVISORY UNTIL 5 AM EDT FRIDAY FOR MDZ014.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 2 AM TO NOON EDT FRIDAY FOR
     ANZ530>534-537-539>541-543.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL
SHORT TERM...BJL
LONG TERM...BJL/KLW
AVIATION...BJL/KLW
MARINE...BJL/KLW
TIDES/COASTAL FLOODING...BJL







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