Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 110946 AAA
AFDLWX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
546 AM EDT THU SEP 11 2014

.SYNOPSIS...
A COLD FRONT WILL APPROACH THE AREA FROM THE WEST TODAY BEFORE
PASSING THROUGH THE AREA TONIGHT. THE FRONT WILL STALL OUT TO THE
SOUTH FRIDAY...BUT IT WILL RETURN NORTH AS A WARM FRONT FRIDAY
NIGHT INTO SATURDAY. A REINFORCING COLD FRONT WILL PASS THROUGH
THE AREA SATURDAY NIGHT AND HIGH PRESSURE WILL RETURN FOR SUNDAY.
ANOTHER COLD FRONT MAY PASS THROUGH THE AREA EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
ANALYSIS EARLY THIS MORNING SHOWS LOW PRESSURE TRACKING THROUGH
ONTARIO WHILE ITS ASSOCIATED COLD FRONT MOVES INTO THE OHIO VALLEY
AS WELL AS PENNSYLVANIA. SHOWERS ASSOCIATED WITH THIS SYSTEM CAN
BE SEEN ON RADAR ACROSS THESE LOCATIONS.

THE COLD FRONT WILL CONTINUE TO TRACK THROUGH THE OHIO VALLEY THIS
MORNING BEFORE MOVING INTO NORTHWESTERN PORTIONS OF OUR CWA THIS
AFTERNOON. SHOWERS AND AND A FEW THUNDERSTORMS AHEAD OF THE FRONT
WILL MOVE INTO OUR AREA DURING THIS TIME. A SOUTHERLY FLOW AHEAD
OF THE FRONT WILL ALLOW FOR WARM AND HUMID CONDITIONS TODAY. MAX
TEMPS WILL RANGE FROM THE LOWER 70S IN THE ALLEGHENY HIGHLANDS TO
THE MID AND UPPER 80S NEAR WASHINGTON AND BALTIMORE. THE WARM AND
HUMID AIRMASS WILL LEAD TO AN UNSTABLE ATMOSPHERE...WHICH MEANS
THERE IS THE POTENTIAL FOR A FEW THUNDERSTORMS TO BECOME SEVERE
THIS AFTERNOON/EARLY EVENING WITH LOCALLY DAMAGING WINDS BEING
THE PRIMARY THREAT. DO FEEL THAT THE HIGHER INSTABILITY WILL BE
SEPARATED FROM THE STRONGER SHEER PROFILES...WHICH MEANS THAT THE
COVERAGE OF SEVERE THUNDERSTORMS SHOULD BE ISOLATED. THE BEST
CHANCE FOR STRONGER STORMS WILL BE WHERE THE HIGHER AMOUNTS OF
INSTABILITY ARE FROM THE SHENANDOAH VALLEY EASTWARD THROUGH THE
WASHINGTON AND BALTIMORE METROPOLITAN AREAS AS WELL AS THE VIRGINIA
PIEDMONT AND SOUTHERN MARYLAND. PWATS WILL ALSO BE QUITE HIGH FOR
THIS TIME OF YEAR...NEARLY TWO STANDARD DEVIATIONS ABOVE CLIMO.
THIS DOES POSE A THREAT FOR HEAVY RAINFALL...BUT CURRENT FEELING
IS THAT STORMS SHOULD HAVE ENOUGH MOTION TO PREVENT ANY WIDESPREAD
THREAT FOR HEAVY RAINFALL. ALSO FLASH FLOOD GUIDANCE IS
HIGH...OVER 2 INCHES PER HOUR FOR MOST LOCATIONS.

THE COLD FRONT WILL PASS THROUGH THE ENTIRE AREA LATER THIS
EVENING INTO THE OVERNIGHT HOURS. COOLER AND DRIER AIR WILL FILTER
IN FROM THE NORTH LATE TONIGHT. HOWEVER...THERE IS STILL SOME
UNCERTAINTY AS TO HOW FAR SOUTH OF THE AREA THE FRONT WILL MAKE
IT. SHOULD THE BOUNDARY GET HUNG UP OVER CENTRAL VIRGINIA...THEN
OVERRUNNING MAY BE DEEP ENOUGH FOR MORE CLOUDS AND PERHAPS A FEW
SHOWERS ACROSS CENTRAL VIRGINIA AND SOUTHERN MARYLAND.
HOWEVER...IF THE FRONT PUSHES FARTHER SOUTH THAN THESE AREAS WILL
END UP DRY. EITHER WAY...ANY SHOWERS THAT DO OCCUR WILL BE LIGHT
AND MOST OF THE TIME SHOULD BE DRY.

&&

.SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
THE COLD FRONT WILL REMAIN STALLED TO OUR SOUTH FRIDAY AND A
NORTHERLY FLOW WILL CONTINUE TO USHER IN COOLER AND DRIER AIR
ACROSS MOST LOCATIONS. HOWEVER...MORE CLOUDS AND PERHAPS A FEW
SHOWERS ARE POSSIBLE ACROSS CENTRAL VIRGINIA AND SOUTHERN
MARYLAND. EVEN ACROSS THESE AREAS...MOST OF THE TIME WILL TURN OUT
DRY. MAX TEMPS FRIDAY WILL RANGE FROM THE 60S IN THE MOUNTAINS TO
THE MIDDLE 70S NEAR WASHINGTON AND BALTIMORE.

HIGH PRESSURE WILL RETREAT TO THE NORTH AND EAST ACROSS NORTHERN NEW
ENGLAND WHILE AN AREA OF LOW PRESSURE/TROUGH APPROACH FROM THE SOUTH
FRIDAY NIGHT INTO SATURDAY. LIFT ASSOCIATED WITH THIS SYSTEM WILL
BRING ABOUT A CHANCE OF SHOWERS DURING THE DAY WITH IMPROVING
CONDITIONS SATURDAY NIGHT. UNDER CLOUD COVER...HIGH TEMPERATURES
WILL ONLY REACH THE UPPER 60S OVER THE HIGHER TERRAIN OUT WEST TO
THE LOWER AND POSSIBLY MIDDLE 70S EAST OF THE BLUE RIDGE AND ACROSS
THE METRO AREAS. OVERNIGHT LOWS FROM THE UPPER 40S WEST TO THE UPPER
50S EAST CAN BE EXPECTED.

&&

.LONG TERM /SUNDAY THROUGH WEDNESDAY/...
HIGH PRESSURE WILL BUILD OVER THE MIDDLE ATLANTIC REGION TO CLOSE
THE WEEKEND. PLEASANT WEATHER IS EXPECTED SUNDAY WITH HIGH
TEMPERATURES MOSTLY IN THE 70S. ANOTHER TROUGH OF LOW PRESSURE WILL
APPROACH THE REGION MONDAY BRINGING INCREASING CLOUDS AND A CHANCE
FOR SHOWERS LATER MONDAY INTO TUESDAY. HIGH PRESSURE IS PROGGED BY
LONG RANGE GUIDANCE TO RETURN TO THE MIDDLE ATLANTIC FOR THE MIDDLE
PART OF NEXT WEEK.

&&

.AVIATION /10Z THURSDAY THROUGH MONDAY/...
A SOUTHERLY FLOW WILL CONTINUE TO USHER IN PLENTY OF MOISTURE
ACROSS THE AREA THIS MORNING. THIS MOISTURE MAY GET TRAPPED
UNDERNEATH THE NOCTURNAL INVERSION...RESULTING IN SOME LOW CLOUDS.
HAVE ALLOWED FOR MVFR CIGS EARLY THIS MORNING.

SHOWERS AND A FEW THUNDERSTORMS ARE LIKELY THIS AFTERNOON AND
EARLY EVENING. THUNDERSTORMS WILL HAVE THE POTENTIAL TO PRODUCE
GUST WINDS AND LOCALLY HEAVY RAINFALL THAT COULD BRIEFLY REDUCE
CIGS/VSBYS TO IFR LEVELS. DRIER AIR WILL MOVE IN BEHIND A COLD
FRONT LATER TONIGHT.

MOSTLY VFR EXPECTED FRIDAY NIGHT. INCREASING CLOUDS EXPECTED
SATURDAY WITH SOME VSBY RESTRICTIONS IN SHOWERS EXPECTED. VFR WILL
RETURN FOR SUNDAY THEN SUB-VFR CONDITIONS RETURN LATER MONDAY INTO
TUESDAY WITH INCREASING CHANCES FOR SHOWERS. HIGH PRESSURE WILL
RETURN FOR THE MIDDLE OF NEXT WEEK.

&&

.MARINE...
THE PRESSURE GRADIENT WILL TIGHTEN OVER THE WATERS THROUGH EARLY
THIS AFTERNOON AHEAD OF A COLD FRONT. THIS WILL CAUSE SOUTH TO
SOUTHWEST WINDS TO STRENGTHEN. A SMALL CRAFT ADVISORY IS IN EFFECT
FOR THE WATERS TODAY. THERE MAY BE A BREAK IN THE GRADIENT WINDS
LATER THIS AFTERNOON AND EARLY EVENING...BUT SHOWERS AND
THUNDERSTORMS WILL BE AROUND DURING THIS TIME. SOME THUNDERSTORMS
WILL BE CAPABLE OF PRODUCING GUSTY WINDS. A COLD FRONT WILL PASS
THROUGH THE WATER LATE THIS EVENING INTO THE OVERNIGHT HOURS AND A
PRESSURE SURGE BEHIND THE BOUNDARY WILL CAUSE NORTHERLY WINDS TO
INCREASE. THEREFORE...THE SMALL CRAFT ADVISORY CONTINUES THROUGH
TONIGHT FOR THE WATERS.

THE FLOW WILL GRADUALLY WEAKEN FRIDAY AS THE FRONT STALLS TO OUR
SOUTH AND THE PRESSURE GRADIENT WEAKENS. HOWEVER...A SMALL CRAFT
ADVISORY IS IN EFFECT FRIDAY MORNING FOR THE MARYLAND CHESAPEAKE
BAY SOUTH OF POOLES ISLAND AND THE LOWER TIDAL POTOMAC RIVER.

SMALL CRAFT CONDITIONS MAY RETURN SATURDAY NIGHT INTO SUNDAY OVER A
PORTION OF THE WATERS ALONG WITH REDUCED VISIBILITY IN SHOWERS. SCA
CONDITIONS MAY BE POSSIBLE AT LEAST OVER THE LOWER WATERS TUESDAY
NIGHT INTO WEDNESDAY OF NEXT WEEK.

&&

.TIDES/COASTAL FLOODING...
SOUTHERLY FLOW HAS CAUSED TIDAL ANOMALIES TO INCREASE TO AROUND 1
TO 1.5 FEET ABOVE NORMAL. THIS WILL CAUSE MINOR TIDAL FLOODING ALONG
THE WESTERN SHORE OF THE MARYLAND CHESAPEAKE BAY AND ALONG THE
UPPER TIDAL POTOMAC RIVER DURING THE HIGH TIDE CYCLE THIS MORNING
INTO EARLY THIS AFTERNOON. THE COASTAL FLOOD ADVISORY REMAINS IN
EFFECT FOR THESE AREAS DURING THIS TIME. A COASTAL FLOOD ADVISORY
IS ALSO IN EFFECT FOR THE MARYLAND CHESAPEAKE BAY FROM ANNE
ARUNDEL COUNTY THROUGH ST MARYS COUNTY FOR THE HIGH TIDE CYCLE
LATE THIS AFTERNOON AND EVENING. WATER LEVELS MAY NOT BE AS HIGH
AS THIS MORNING SINCE THE FLOW WILL TURN MORE WESTERLY...BUT WATER
LEVELS ARE STILL EXPECTED TO EXCEED MINOR FLOODING THRESHOLDS.

CERTAINTY FOR MINOR FLOODING THIS EVENING FOR BALTIMORE AND
HARFORD COUNTIES ALONG THE WESTERN SHORE OF THE MARYLAND
CHESAPEAKE BAY AND THE SHORE OF THE UPPER TIDAL POTOMAC RIVER IS
LOWER. THEREFORE...A COASTAL FLOOD ADVISORY HAS NOT BEEN EXTENDED
TO INCLUDE THIS TIDE CYCLE...BUT THIS WILL HAVE TO BE MONITORED
LATER TODAY.

THE OFFSHORE FLOW WILL STRENGTHEN OVERNIGHT BEHIND A COLD FRONT
AND TIDAL ANOMALIES WILL DROP SHARPLY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...COASTAL FLOOD ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR
     DCZ001.
MD...COASTAL FLOOD ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR
     MDZ007-013.
     COASTAL FLOOD ADVISORY UNTIL 10 PM EDT THIS EVENING FOR MDZ014-
     017-018.
     COASTAL FLOOD ADVISORY UNTIL 11 AM EDT THIS MORNING FOR MDZ011.
VA...COASTAL FLOOD ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR
     VAZ054.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT FRIDAY FOR ANZ531>534-537-
     539>541-543.
     SMALL CRAFT ADVISORY UNTIL 6 AM EDT FRIDAY FOR ANZ530-536-538-
     542.
     SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 6 AM EDT
     FRIDAY FOR ANZ535.

&&

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






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