Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 101047 AAB
AFDLWX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
647 AM EDT WED SEP 10 2014

.SYNOPSIS...
LOW PRESSURE WILL MOVE OUT TO SEA TODAY AND A COLD FRONT WILL
APPROACH THE AREA FROM THE WEST TONIGHT THROUGH THURSDAY. THE
BOUNDARY WILL MOVE THROUGH THURSDAY NIGHT BEFORE STALLING OUT TO
THE SOUTH FRIDAY NIGHT THROUGH SATURDAY. A REINFORCING COLD FRONT
WILL PASS THROUGH THE AREA SATURDAY NIGHT AND HIGH PRESSURE WILL
RETURN FOR SUNDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
UPDATE...NEW COASTAL FLOOD ADVISORY FOR DC/ALEXANDRIA WATERFRONT
FOR THIS MORNING`S HIDE TIDE CYCLE. CANCELLED PORTIONS OF THE
ADVISORY FOR THE MD CHES BAY AND ANNAPOLIS CURRENTLY AT THEIR H.T.
CYCLE. LEVELS WILL BE ABOUT A TENTH OF A FOOT BELOW THAT OF THE
PREV H.T. CYCLE BUT STILL JUST ABOVE MINOR CF LEVELS.

PREV DISC...
THE WEAK COASTAL LOW IS NOW E OF THE MID ATLC COASTLINE NEAR THE
VA TIDEWATER REGION...AFTER TAKING A SOLID TWO DAYS TO MAKE IT
THERE FROM ITS ORIGINS ALONG THE SC COAST. THE LINGERING EFFECTS
OF THIS FEATURE FOR THE AREA IS THE STILL DENSE CLOUD COVER AND
ONSHORE FLOW. THE PRECIP HAS ALL BUT DISSIPATED AND MOVED AWAY
FROM THE AREA...AS HIGH PRESSURE BUILDS DOWN INTO ACROSS THE ERN
SEABOARD FROM THE NE. LEFTOVER DEWPOINTS IN THE L-M60S FROM THE
PRESENCE OF THE COASTAL LOW HAS GIVEN THE AREA ANOTHER COOL BUT
RELATIVELY MODERATED OVERNIGHT PERIOD.

AS SKIES BEGIN TO SLOWLY LOSE SOME OF THE CURRENT THICK LOW CLOUDS
LATER THIS MRNG...TEMPS WILL RISE SLIGHTLY HIGHER THAN IN PAST DAYS
W/ THE LOW JUST SOUTH AND EAST OF THE AREA. DEWPOINTS WILL STAY IN
THE L-M60S THROUGHOUT THE DAY...NOT MUCH MIXING OF THE AIRMASS AS
HIGH PRESSURE ESSENTIALLY CONTROLS THE WX TODAY. WHILE WE HAVE OUR
ONE-DAY WX REPRIEVE...A POTENT LOW PRESSURE SYSTEMS CONTINUES TO
SPEED EWD ACROSS THE NRN PLAINS INTO THE GREAT LAKES/UPPER MIDWEST.
THE SFC LOW WILL TAKE A DUE NE JOG FROM SRN WI TO NRN MI AND OFF
INTO THE SRN REACHES OF QUEBEC LATER TODAY. WITH DEWPOINTS STAYING
WHERE THEY ARE CURRENTLY AT EVEN LATE TONIGHT...OUR OVERNIGHT LOWS
WILL RESPOND AND STICK AROUND W/IN THE RANGE OF THE M60S.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
OUTSIDE OF THE FRONTAL PASSAGE LATER IN THE DAY...THE HEAT OF THE
DAY WILL ALSO BE A NOTABLE STORY - AND LIKELY ONE THE WARMEST DAY WE
WILL HAVE IN THE FORESEEABLE FUTURE. DESPITE INCREASING CLOUD COVER
OVER THE COURSE OF THE DAY...THE STRONG AND COLD UPPER TROUGH
APPROACHING FROM THE WEST WILL CAUSE AN EQUALLY INTENSE WARMING
EFFECT FROM THE UPPER RIDGE CENTERED ALONG THE ATLC/ERN SEABOARD.
SLY SFC WINDS WILL INCREASE AND BRING RELATIVELY WARMER AND MORE
MOIST AIR FROM THE SOUTH AS THE DAY PROGRESSES. LEANED ON THE NAM
FOR DEWPOINTS...WHICH WILL LEVEL-OUT IN THE L70S - AMPLE FOR
ENHANCED INSTABILITY AS WELL AS A MUGGY/HUMID DAY REMINISCENT OF THE
LAST WEEK OF AUG/FIRST WEEK OF SEP.

THE POTENT DYNAMICS DEVELOPING AND CARRYING THE GREAT LAKES LOW PRES
SYSTEM ACROSS THE UPPER MIDWEST WILL ALSO LARGELY SPEED OFF W/ THE
FEATURE AS IT MOVES NORTH OF NEW ENGLAND. THE INITIALLY POTENT COLD
FRONT QUICKLY PUSHING DOWN FROM THE UPPER MIDWEST WILL BEGIN TO
DECELERATE AND LOSE SOME OF ITS INITIAL PUNCH W/ THE DYNAMICS OF THE
UPPER TROUGH LEAVING IT BEHIND TO THE NE. A REINFORCING UPPER TROUGH
WILL BE DIVING BACK DOWN ACROSS THE NRN PLAINS TO AT LEAST MAINTAIN
SOME OF THE LONGWAVE TROUGH`S CHARACTERISTICS THROUGHOUT THE DAY.
BUT THIS FEATURE WILL STILL BE A DAY-AWAY FROM THE FRONTAL
BOUNDARY...SO THE LEADING EDGE CONVERGENCE POTENTIAL WILL DECREASE
AS IT MOVES FURTHER SOUTH AND EAST.

BY THE TIME THE FRONT REACHES THE MID ATLC REGION DURING THE
MID-LATE AFTN HRS THOUGH...PLENTY OF HEAT/HUMIDITY WILL BE THERE TO
MEET IT AND AT LEAST GIVE THE AREA THE POTENTIAL FOR ISOLATED SVR
TSTMS. EVEN A WEAK FRONTAL PASSAGE W/ THE TYPES OF MODEST
INSTABILITY VALUES WILL CREATE THE ELEVATED RISK OF SVR WX FOR THE
AREA...ESP NRN SECTIONS OF THE CWA AND TOWARD THE METRO AREAS - AT
LEAST FOR MORE LINEAR/WIDESPREAD CONVECTION. MORE INSTABILITY WILL
RESIDE FURTHER SOUTH WHERE TEMPS/DEWPOINTS WILL BE AT THEIR HIGHEST
ACROSS THE AREA.

A COLD FRONT WILL PASS THROUGH THE REGION THURSDAY NIGHT. SHOWERS
AND THUNDERSTORMS ARE POSSIBLE AHEAD OF THE FRONT...ESPECIALLY
THURSDAY EVENING. A WARM AND HUMID AIRMASS AHEAD OF THE COLD FRONT
MAY CAUSE SOME THUNDERSTORMS TO BE SEVERE EARLY THURSDAY
EVENING...WITH LOCALLY DAMAGING WIND GUSTS BEING THE PRIMARY
THREAT.

COOLER AND DRIER AIR WILL BEGIN TO WORK ITS WAY INTO THE AREA
BEHIND THE COLD FRONT OVERNIGHT. MIN TEMPS WILL RANGE FROM THE 50S
IN THE POTOMAC HIGHLANDS TO THE MID AND UPPER 60S IN DOWNTOWN
WASHINGTON AND BALTIMORE.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
THE COLD FRONT WILL STALL OUT NEAR THE VIRGINIA/NORTH CAROLINA
BORDER FRIDAY AND A NORTHERLY FLOW ON THE COOL SIDE OF THE BOUNDARY
WILL ALLOW FOR COOLER AND NOTICEABLY LESS HUMID CONDITIONS. A
STRAY SHOWER OR TWO CANNOT BE RULED OUT CLOSER TO THE COLD FRONT
ACROSS CENTRAL VIRGINIA AND SOUTHERN MARYLAND...BUT EVEN ACROSS
THESE AREAS MOST OF THE TIME WILL BE DRY.

LOW PRESSURE AND ITS ASSOCIATED COLD FRONT WILL TRACK THROUGH THE
OHIO VALLEY FRIDAY NIGHT AND THIS WILL ALLOW THE STALLED BOUNDARY
NEAR THE VIRGINIA/NORTH CAROLINA BORDER TO RETREAT NORTHWARD INTO
OUR CWA AS A WARM FRONT. OVERRUNNING AHEAD OF THE WARM FRONT WILL
ALLOW FOR MORE CLOUDS ALONG WITH THE CHANCE FOR SHOWERS...MAINLY
AFTER MIDNIGHT.

THE WARM FRONT WILL STALL OUT OVER THE REGION SATURDAY WHILE THE
COLD FRONT APPROACHES FROM THE OHIO VALLEY. MORE CLOUDS ALONG
WITH POSSIBLE SHOWERS ARE EXPECTED DURING THIS TIME. THE COLD
FRONT WILL PASS THROUGH THE REGION SATURDAY NIGHT AND HIGH
PRESSURE SHOULD RETURN FOR SUNDAY...BRINGING DRIER CONDITIONS.

ANOTHER COLD FRONT MAY PASS THROUGH THE REGION LATER MONDAY INTO
TUESDAY...BRINGING THE CHANCE FOR SHOWERS.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
A COASTAL LOW ALONG THE SC/NC LOWLANDS WILL DRIFT OFF THE COAST
TODAY. STILL SOME POCKETS AND STRANDS OF MVFR CIGS POSSIBLE ACROSS
THE CHES BAY AREA BUT TAPERING OFF FURTHER WEST. BREAKS IN THESE
LOW CLOUD BANDS WILL BEGIN LATER THIS MRNG...BUT FILL BACK IN W/
HIGH CLOUDS AS A STRONG COLD FRONT APPROACHES FROM THE WEST. THE
FRONT WILL MOVE ACROSS THE AREA LATE IN THE DAY ON
THU...DEVELOPING SCATTERED SHOWERS AND TSTMS LOCALIZED NEAR THE
FRONT ITSELF.

A COLD FRONT WILL PASS THROUGH THE TERMINALS THURSDAY NIGHT.
SHOWERS AND THUNDERSTORMS ARE POSSIBLE THURSDAY EVENING. A FEW
THUNDERSTORMS MAY PRODUCE LOCALLY DAMAGING WIND GUSTS EARLY
THURSDAY EVENING. NORTHERLY WINDS WILL BRING DRIER CONDITIONS
OVERNIGHT THURSDAY THROUGH FRIDAY EVENING. HOWEVER...THE COLD
FRONT WILL RETREAT BACK NORTH TOWARD OUR AREA OVERNIGHT FRIDAY
INTO SATURDAY. OVERRUNNING AHEAD OF THE BOUNDARY WILL BRING THE
CHANCE FOR SHOWERS ALONG WITH MVFR/IFR CIGS.

ANOTHER COLD FRONT WILL PASS THROUGH SATURDAY NIGHT AND DRIER AIR
WILL RETURN FOR SUNDAY.

&&

.MARINE...
SCA GUSTS HAVE SUBSIDED AS A COASTAL LOW MOVES AWAY FROM THE AREA.
HIGH PRES WILL BUILD IN TODAY...QUIETING WINDS DOWN FURTHER BUT THEN
BRINGING A SLY FLOW IN FROM THU. A COLD FRONT WILL SLIDE DOWN FROM
THE UPPER MIDWEST LATE IN THE DAY...W/ TSTMS POSSIBLE AND GUSTY
WINDS FROM THE STRONGEST ACTIVITY.

A COLD FRONT WILL PASS THROUGH THE WATERS THURSDAY NIGHT. SHOWERS
AND THUNDERSTORMS ARE POSSIBLE AHEAD OF THE FRONT. A FEW
THUNDERSTORMS WILL BE CAPABLE OF PRODUCING GUSTY WINDS THURSDAY
EVENING.

A SMALL CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE
WATERS BEHIND THE FRONT LATE THURSDAY NIGHT THROUGH FRIDAY
MORNING. THE BOUNDARY WILL RETREAT NORTHWARD AS A WARM FRONT
FRIDAY NIGHT INTO SATURDAY...BRINGING UNSETTLED CONDITIONS.
ANOTHER COLD FRONT WILL PASS THROUGH THE WATERS SATURDAY NIGHT. A
SMALL CRAFT ADVISORY MAY BE NEEDED FOR PORTIONS OF THE WATERS
BEHIND THIS BOUNDARY LATE SATURDAY NIGHT INTO SUNDAY.

&&

.TIDES/COASTAL FLOODING...
A COASTAL FLOOD ADVISORY REMAINS IN EFFECT UNTIL 8 AM THIS MORNING
FOR LOCATIONS ALONG THE WESTERN SHORE OF THE MARYLAND CHESAPEAKE
BAY FROM ANNE ARUNDEL CO. WATER LEVELS WILL BE NEAR THRESHOLDS
FOR MINOR FLOODING IN SENSITIVE AREAS EARLY THIS MORNING NEAR HIGH
TIDE. NEWLY ISSUED CF ADZY FOR DC/ALEX THRU 11 AM.

ONSHORE FLOW EXPECTED TO TURN MORE TOWARD THE NORTH LATER THIS
MORNING AND THIS MAY ALLOW FOR ANOMALIES TO DROP JUST A
BIT...KEEPING WATER LEVELS BELOW MINOR FLOODING THRESHOLDS.

POSITIVE TIDAL ANOMALIES WILL CONTINUE FOR THE HIGH TIDE CYCLES
THIS AFTERNOON THROUGH THURSDAY MORNING...BUT THE FLOW WILL BE LIGHT.
THEREFORE...THE CURRENT FEELING IS THAT WATER LEVELS WILL REMAIN
JUST BELOW MINOR FLOODING THRESHOLDS. HOWEVER...CERTAINTY IS LOW
SO THIS WILL HAVE TO BE MONITORED.

SOUTHERLY WINDS WILL INCREASE AHEAD OF AN APPROACHING COLD FRONT
THURSDAY AFTERNOON INTO THURSDAY EVENING. TIDAL ANOMALIES WILL
LIKELY INCREASE AS WELL...INCREASING THE CHANCES FOR MINOR TIDAL
FLOODING NEAR HIGH TIDE. 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 11 AM EDT THIS MORNING FOR DCZ001.
MD...COASTAL FLOOD ADVISORY UNTIL 8 AM EDT THIS MORNING FOR MDZ014.
VA...COASTAL FLOOD ADVISORY UNTIL 11 AM EDT THIS MORNING FOR VAZ054.
WV...NONE.
MARINE...NONE.

&&

$$
UPDATE...GMS
PREV DISCUSSION...GMS/BJL







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