Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 110130
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
930 PM EDT WED SEP 10 2014

.SYNOPSIS...
A COLD FRONT WILL APPROACH THE AREA FROM THE WEST THURSDAY. THE
BOUNDARY WILL MOVE THROUGH THE MID-ATLANTIC BY THURSDAY NIGHT
BEFORE STALLING OUT TO THE SOUTH FRIDAY THROUGH SATURDAY. A
REINFORCING COLD FRONT WILL PASS THROUGH THE AREA SATURDAY NIGHT
AND HIGH PRESSURE WILL RETURN FOR SUNDAY.

&&

.NEAR TERM /THROUGH THURSDAY/...
HIGH PRESSURE RESIDES ALONG THE MID-ATLANTIC COAST THIS
EVENING...WITH SOUTHERLY FLOW ESTABLISHED ACROSS THE MID-ATLANTIC.
HIGH CLOUDS HAVE ALREADY MOVED IN WITH WARM ADVECTION AHEAD OF A
MIDWEST SHORTWAVE. MAY ALSO SEE SOME STRATUS DEVELOPMENT LATE AT
NIGHT. THUS MOSTLY CLOUDY SKIES FOR THE OVERNIGHT. SHOWERS LIKELY
STAY TO THE NORTH TONIGHT...BUT MAY APPROACH THE POTOMAC HIGHLANDS
BY DAYBREAK.

THE SHORTWAVE AND A COLD FRONT APPROACH THE POTOMAC HIGHLANDS BY
THURSDAY MORNING. SOUTHERLY FLOW WILL CONTINUE AT THE SFC AND
CONTINUE TO DRAW IN MOISTURE WITH DEWPTS RISING INTO THE LOW 70S
BY AFTERNOON. FCST MAX TEMPS WILL RANGE FROM THE MID TO UPPER 80S
EAST OF THE BLUE RIDGE TO THE UPPER 70S IN THE MTNS. CLOUD COVER
ACROSS THE REGION WILL LIMIT INSTABILITY AND SBCAPE OF 800-1500
J/KG IS EXPECTED DEPENDING ON THE CLOUD COVER. AS THE WIND FIELD
INCREASES ALOFT 20-30KTS OF EFF 0-6KM SHEAR IS EXPECTED. DUE TO
THE HIGH DEWPTS AND MARGINAL SHEAR/INSTABILITY...STRONG TO SEVERE
THUNDERSTORMS ARE POSSIBLE THURSDAY AFTERNOON AND EVENING. THE
COLD FRONT IS EXPECTED TO BE NEAR THE BLUE RIDGE BY EARLY
AFTERNOON AND THE I-95 CORRIDOR BY EARLY EVENING. SOME STORMS
AHEAD OF THE COLD FRONT MAY PRODUCE DAMAGING WINDS. PWATS ALONG
AND AHEAD OF THE COLD FRONT ARE PROGGED TO BE NEAR 2-2.25 INCHES
AND HEAVY RAIN IS EXPECTED. AT THIS TIME...DUE TO THE PROGGED
QUICKER STORM MOTION FLASH FLOODING IS NOT EXPECTED AT THIS TIME.

&&

.SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
THE COLD FRONT IS EXPECTED TO MOVE ACROSS THE REGION THURSDAY
NIGHT. THE LATEST 12Z MODEL SOLUTIONS FROM THE GFS...NAM AND THE 9Z
SREF MEAN HAVE THE FRONT MOVING INTO THE TIDEWATER REGION OF VA BY
EARLY FRIDAY MORNING. NORTHERLY WINDS BEHIND THE FRONT WILL LEAD
TO DRIER COOLER AIR ENTERING THE MID-ATLANTIC FRIDAY. FCST MAX
TEMPS WILL RANGE FROM THE LOW TO MID 70S NEAR THE PA/MD BORDER TO
THE MID TO UPPER 70S IN THE NRN PIEDMONT/SRN MD.

THE COLD FRONT WILL STALL ACROSS THE CAROLINAS WHILE A SHORTWAVE
TROUGH MOVES INTO THE UPPER MID-WEST. THE STALLED BOUNDARY IS
EXPECTED TO MOVE NORTHWARD DUE TO LOW PRESSURE MOVING INTO THE
GREAT LAKES REGION. SHOWERS ARE POSSIBLE ACROSS THE CENTRAL
FOOTHILLS BY SATURDAY MORNING. SHOWERS MAY OVERSPREAD THE REGION
SATURDAY RESULTING IN A CLOUDY DAY WITH SCT SHOWERS. FCST MAX
TEMPS WILL RANGE FROM THE UPPER 60S WEST OF THE BLUE RIDGE TO THE
LOW 70S ALONG THE I-95 CORRIDOR. TEMPS IN THE MID 60S ARE EXPECTED
AT HIGHER ELEVATIONS.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
ECMWF 500MB HAS WEAK TROUGH CROSSING THE CWA SATURDAY NIGHT THEN
ZONAL FLOW THROUGH TUESDAY. SURFACE HIGH PRESSURE BUILDING ACROSS
CWA SATURDAY NIGHT WILL MOVE OFFSHORE BY MONDAY EVENING. SLIGHT
CHANCE OF SHOWERS EAST OF THE BLUE RIDGE. MOIST CONDITIONS WILL
RETURN ON SOUTH TO SOUTHWEST FLOW AROUND THE BACK OF HIGH MONDAY
AFTERNOON. INCREASING CHANCE OF RAIN IN THE VIRGINIA PIEDMONT AND THE
CENTRAL SHENANDOAH VALLEY MONDAY AFTERNOON WILL SPREAD ACROSS THE
REST OF CWA MONDAY NIGHT. A BOUNDARY WILL CROSS THE CWA EARLY
TUESDAY TAKING THE PRECIPITATION OFFSHORE. HIGH PRESSURE AND MUCH
DRIER CONDITIONS WILL RETURN FOR MUCH OF TUESDAY AND WEDNESDAY.

&&

.AVIATION /01Z THURSDAY THROUGH MONDAY/...
HIGH CLOUDS HAVE MOVED IN ALREADY. MODELS SUGGEST SOME STRATUS
DEVELOPING LATE TONIGHT TOO. MVFR IS LIKELY...CONFIDENCE A LITTLE
LOWER IN IFR AT THE HUBS BUT PLAUSIBLE.

A COLD FRONT WILL CROSS THE REGION LATE THURSDAY. SHRA AND TSRA
ARE EXPECTED AND WILL LIKELY REDUCE TAF SITES TO IFR IN ACTIVITY.
GUSTY WINDS AND HEAVY RAIN ARE LIKELY. WINDS WILL BECOME NRLY
BEHIND THE FRONTAL BOUNDARY AS IT MOVES WEST TO EAST ACROSS THE
REGION THURSDAY AFTERNOON AND EVENING.

THE FRONTAL BOUNDARY WILL LIKELY MOVE NORTHWARD FRIDAY NIGHT AND
SATURDAY AND SHRA ARE POSSIBLE. MVFR/IFR CONDITIONS POSSIBLE DURING
THIS TIME.

&&

.MARINE...
SCA MUCH OF THE CHESAPEAKE BAY/LOWER TIDAL POTOMAC RIVER
BEGINNING AT MIDNIGHT TONIGHT AND CONTINUING INTO THURSDAY
MORNING. FLOW LOOKS TO TURN NEARLY DUE SOUTH AND CHANNELLING WILL
LIKELY ENHANCE SPEEDS INTO SCA CRITERIA PARTICULARLY UP THE MAIN
CHANNEL OF THE BAY.

A COLD FRONT WILL CROSS THE WATERS THURSDAY EVENING AND NRLY
WINDS WILL MOVE INTO THE REGION. SCA CONDITIONS ARE POSSIBLE IN
POST- FRONTAL CONDITIONS. AT THIS TIME DUE TO UNCERTAINTY IN THE
TIMING OF THE FRONTAL BOUNDARY...NO SCA IS IN EFFECT. SHOWERS AND
THUNDERSTORMS ARE EXPECTED NEAR THE FRONT AND GUSTY WINDS MAY LEAD
TO SMW`S ON THE LATE THURS AFTERNOON TO LATE THURS NIGHT.

&&

.TIDES/COASTAL FLOODING...
TIDAL ANOMALIES WERE GENERALLY 1-1.3 FT ABOVE NORMAL ON THE
WESTERN SHORE OF THE BAY/TIDAL POTOMAC RIVER THIS EVENING. WATER
LEVEL AT APAM2 WAS AROUND 2.8 FT MLLW AT HIGH TIDE...BLTM2 NEAR
3.1 FT MLLW. HAVRE DE GRACE SHOULD BE JUST UNDER. HIGH TIDE HAS
YET TO OCCUR ON THE UPPER TIDAL POTOMAC BUT LOOKS TO BE IN SOLID
MINOR CATEGORY.

WITH SOUTHERLY FLOW INCREASING...ANOMALIES MAY INCREASE A LITTLE
MORE OVERNIGHT INTO THURSDAY MORNING. COASTAL FLOOD ADVISORIES
CONTINUE FOR THE NEXT HIGH TIDE CYCLE. WILL HAVE TO KEEP A CLOSE
EYE ON ANNAPOLIS AREA AS CBOFS BRINGS WATER LEVEL CLOSE TO
MODERATE. WOULD HAVE TO HAVE THE ANOMALY BE GREATER THAN 1.5 FT.
RIGHT NOW HIGH END ADVISORY APPEARS MOST LIKELY.

THURSDAY EVENING HIGH TIDE COULD EXPERIENCE MINOR TIDAL FLOODING
AS WELL...THEN AN OFFSHORE FLOW BEHIND THE COLD FRONT WILL CAUSE
ANOMALIES TO SHARPLY DROP LATE THURSDAY NIGHT AND FRIDAY.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...COASTAL FLOOD ADVISORY UNTIL 2 PM EDT THURSDAY FOR DCZ001.
MD...COASTAL FLOOD ADVISORY UNTIL 11 AM EDT THURSDAY FOR MDZ011-014-
     017-018.
     COASTAL FLOOD ADVISORY UNTIL 2 PM EDT THURSDAY FOR MDZ013.
VA...COASTAL FLOOD ADVISORY UNTIL 2 PM EDT THURSDAY FOR VAZ054.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 11 AM EDT
     THURSDAY FOR ANZ531>534-537>541-543.

&&

$$
SYNOPSIS...BPP/HAS
NEAR TERM...BPP/HAS
SHORT TERM...HAS
LONG TERM...CEM
AVIATION...BPP/HAS
MARINE...BPP/HAS
TIDES/COASTAL FLOODING...BPP/HAS







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