Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 031021
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
621 AM EDT SUN MAY 3 2015

.SYNOPSIS...
HIGH PRESSURE WILL SHIFT TO OUR SOUTH TODAY BEFORE BUILDING TOWARD
BERMUDA MONDAY. A COLD FRONT WILL APPROACH FROM THE NORTH TUESDAY
AND BECOME STATIONARY DURING MIDWEEK. HIGH PRESSURE IS THEN
EXPECTED LATE IN THE WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
...UPDATE TO CANCEL THE COASTAL FLOOD ADVISORY. PREVIOUS
DISCUSSION FOLLOWS...

HIGH PRESSURE WILL CONTINUE TO BUILD SOUTH TOWARD THE CAROLINAS
TODAY. A RETURN FLOW AROUND THE HIGH ALONG WITH UPPER-LEVEL
RIDGING AND PLENTY OF SUNSHINE WILL RESULT IN WARM CONDITIONS.
LEANED TOWARD THE WARMER GUIDANCE DUE TO THE SUNSHINE AND A DEEP
MIXING LAYER ANTICIPATED. MAX TEMPS WILL RANGE FROM THE 60S IN THE
MOUNTAINS TO THE UPPER 70S AND LOWER 80S NEAR WASHINGTON AND
BALTIMORE. A SCT CU DECK WILL DEVELOP LATE THIS MORNING AND
AFTERNOON DUE DAYTIME HEATING...BUT NO PRECIPITATION IS EXPECTED
THANKS TO A STRONG SUBSIDENCE INVERSION.

A LIGHT SOUTHWEST FLOW WILL CONTINUE AROUND HIGH PRESSURE TO OUR
SOUTH TONIGHT. MILD CONDITIONS ARE EXPECTED...BUT RADIATIONAL
COOLING MAY RESULT IN CHILLIER CONDITIONS FOR SHELTERED VALLEYS
AND RURAL AREAS. MIN TEMPS ARE FORECAST TO RANGE FROM THE UPPER
40S IN SHELTERED VALLEYS AND RURAL AREAS TO THE LOWER AND MIDDLE
60S IN DOWNTOWN WASHINGTON AND BALTIMORE.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
HIGH PRESSURE WILL REMAIN WELL TO OUR SOUTH AND EAST...EXTENDING
FROM THE CAROLINAS TOWARD BERMUDA MONDAY THROUGH TUESDAY NIGHT.
A SOUTHWEST FLOW AROUND THIS SYSTEM WILL USHER IN EVEN WARMER
CONDITIONS FOR MONDAY AND TUESDAY. MAX TEMPS WILL REACH THE LOWER
TO MIDDLE 80S ACROSS MANY LOCATIONS.

THE SOUTHWEST FLOW WILL ALSO USHER IN MORE MOISTURE DURING THIS
TIME. THE INCREASED MOISTURE WILL LEAD TO INCREASED INSTABILITY.
FOR MONDAY...STILL EXPECT MOST AREAS TO BE DRY DUE TO A STRONGER
CAPPING INVERSION. HOWEVER...AN ISOLATED SHOWER/T-STORM CANNOT BE
RULED OUT LATE IN THE AFTERNOON/EVENING ACROSS THE BLUE RIDGE
MOUNTAINS INTO CENTRAL VIRGINIA AND THE POTOMAC HIGHLANDS. TERRAIN
CIRCULATION WOULD BE THE PRIMARY LIFTING MECHANISM WITH AN UPPER-
LEVEL DISTURBANCE LIKELY REMAINING OFF TO OUR SOUTH. CONFIDENCE IS
TOO LOW AT THIS TIME TO ADD POPS IN THE FORECAST.

FOR TUESDAY...A COLD FRONT IS EXPECTED TO APPROACH FROM THE NORTH.
MOISTURE MAY BE A BIT DEEPER DURING THIS TIME AS WELL. TERRAIN
CIRCULATION AND THE COLD FRONT WILL ACT AS THE PRIMARY LIFTING
MECHANISMS...AND WITH A LITTLE MORE INSTABILITY TO WORK WITH
THERE IS A BETTER CHANCE FOR A SHOWER/THUNDERSTORM...MAINLY ACROSS
NORTHERN MARYLAND...NORTHERN VIRGINIA AND FOR LOCATIONS NEAR AND
WEST OF THE BLUE RIDGE MOUNTAINS. HAVE CHANCE POPS IN THE FORECAST
FOR THESE AREAS TUESDAY AFTERNOON/EVENING.

THE COLD FRONT WILL MOVE INTO NORTHERN MARYLAND OVERNIGHT TUESDAY. THE
BOUNDARY WILL BE WEAK WITH LITTLE TEMPERATURE GRADIENT ASSOCIATED
WITH IT. THEREFORE...MILD CONDITIONS WILL CONTINUE BUT THERE MAY
BE A COUPLE SHOWERS ACROSS NORTHERN PORTIONS OF THE CWA DURING
THIS TIME.

&&

.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
PERIOD OF UNSETTLED WX CONTINUING INTO THE SECOND HALF OF THE
WEEK WITH THE COLD FRONT DROPPING SOUTH TUES NIGHT STALLING ACROSS
THE MID ATLANTIC. ANY PCPN INITIALLY WED MORNING CONFINED NEAR THE
MASON DIXON LINE...CLOSER TO THE FRONTAL BOUNDARY. PCPN INCREASES
IN COVERAGE TO THE SOUTH DURING THE DAY AS THE FRONT SLIDES
SLIGHTLY TO THE SOUTH AS SFC HIGH PRESSURE TO THE NORTH BUILDS
SOUTH. THE COMBINATION OF RIDGING BUILDING IN ALOFT AND A
DEVELOPING LOW OFF THE SOUTHEAST US WILL KEEP THE MOVEMENT OF THE
FRONT MINIMAL THRU THE END OF THE WEEK. TSTMS MENTIONED ON WED
WITH DECENT INSTABILITY...THOUGH LAPSE RATES ARE THE WEAKER SIDE.
ELY FLOW COULD KEEP ANY THUNDER MORE CONFINED TO SOUTHWESTER
PORTIONS OF THE CWA. ANY PCPN MENTION ENDS WED EVENING.

SLIGHT CHC FOR PCPN AGAIN ON THURS...MAINLY WEST OF THE BLUE RIDGE
AS THE FRONT ALIGNS ALONG THE VA/MD BORDER. WITH THE REGION UNDER
RIDGING ALOFT...FEEL BEST PCPN CHC COMES FROM THE UPSLOPING FACTOR
FROM THE ELY FLOW. HAVE MENTION YET AGAIN OF THUNDER ON THURS.

RIDGE AXIS NUDGES EAST FRIDAY HEADING INTO THE WEEKEND...ALLOWING
FOR THE SFC LOW IN SOUTHERN CANADA IN WHICH THE FRONTAL BOUNDARY IS
ASSOCIATED WITH TO PROGRESS TO THE EAST. THIS WILL LIFT THE FRONT TO
THE NORTHEAST AS A WARM FRONT SOMETIME FRIDAY...CLEARING THE AREA BY
SAT MORNING. PCPN ASSOCIATED WITH THE FRONT PSBL DURING THIS TIME
MAINLY OVER WESTERN AND NORTHERN AREAS. ANOTHER THING TO KEEP WATCH
ON IS THE DEVELOPING LOW WELL TO THE SOUTH OFF THE SOUTHEASTERN US
COAST. MODELS HAVE DIVERGING SOLUTIONS ON THE PATH AND STRENGTH OF
THIS SYSTEM...BUT IF IT PUSHES FAR ENOUGH NORTH...COULD RESULT IN
PCPN TO THE SOUTH AND EASTERN AREAS OF THE CWA TO END THE WEEK AS
WELL.

THE BUILDING RIDGE AND RISING HEIGHTS WILL BRING WELL ABV NORMAL
TEMPS FOR THE SECOND HALF OF THE WEEK...WITH MANY AREAS HAVING
MULTIPLE DAYS OF 80+ HIGHS. FOR WED AND THURS...DID KEEP THE EASTERN
AREAS A BIT ON THE COOLER SIDE TO ACCOUNT FOR ELY FLOW...BUT STILL
REACHING INTO THE MID TO UPPER 70S. LOWS THRU THE PERIOD IN THE 50S
AND 60S.

&&

.AVIATION /10Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS ARE EXPECTED THROUGH TONIGHT. LIGHT AND VARIABLE
WINDS WILL TURN NORTHWEST AFTER SUNRISE BEFORE SHIFTING TOWARD THE
SOUTHWEST BY SUNSET. WIND SPEEDS AROUND 5 TO 10 KNOTS ARE
EXPECTED. WINDS WILL BECOME LIGHT AND VARIABLE TONIGHT.

VFR CONDITIONS WILL PERIST FOR MOST OF THE TIME MONDAY THROUGH
TUESDAY NIGHT. HOWEVER...AN AFTERNOON/EVENING THUNDERSTORM IS
POSSIBLE TUESDAY. COVERAGE IS EXPECTED TO BE SCATTERED AT THIS
TIME.

GENERALLY EXPECTING VFR CONDITIONS TUES-SAT. PSBL SUB-VFR
CONDITIONS WITH ANY SHOWERS/TSTMS THRU THE PERIOD.

&&

.MARINE...
HIGH PRESSURE WILL BUILD TO OUR SOUTH TODAY THROUGH TUESDAY. A
COLD FRONT WILL MOVE INTO THE NORTHERN PORTIONS OF THE WATERS
TUESDAY NIGHT. A SOUTH TO SOUTHWEST FLOW IS EXPECTED DURING THIS
TIME. HOWEVER...THERE MAY BE A BRIEF PERIOD OF WESTERLY WINDS
LATER THIS MORNING INTO THE MIDDAY HOURS. WIND SPEEDS WILL REMAIN
BELOW SCA CRITERIA THROUGH MONDAY. THE PRESSURE GRADIENT MAY
STRENGTHEN A BIT MONDAY NIGHT AND WIND GUSTS MAY APPROACH SCA
CRITERIA FOR PORTIONS OF THE WATERS.

A SHOWER OR THUNDERSTORM CANNOT BE RULED OUT TUESDAY AFTERNOON
INTO TUESDAY EVENING...ESPECIALLY FOR NORTHERN PORTIONS OF THE
WATERS. CONFIDENCE IS LOW AT THIS TIME. SOUTH TO SOUTHWEST WINDS
MAY COME CLOSE TO SCA CRITERIA TUESDAY...BUT GUSTS HAVE BEEN
CAPPED AROUND 15 KNOTS FOR NOW DUE TO THE RELATIVELY COOLER
WATERS.

SUB-SCA CONDITIONS EXPECTED TUES-THURS WITH PERSISTENT ELY FLOW
GENERALLY 10 KTS OR LESS. PSBL SCA GUSTS FRI...DEPENDING ON THE
TRACK OF THE LOW.

&&

.TIDES/COASTAL FLOODING...
THE MINOR TIDAL FLOODING HAS ENDED AT ANNAPOLIS WITH WATER LEVELS
FALLING DUE TO THE APPROACHING LOW TIDE THIS AFTERNOON. TIDAL
ANOMALIES SHOULD BE LOW ENOUGH TO PREVENT MINOR TIDAL FLOODING FOR
THE NORTHERN CHESAPEAKE BAY AND UPPER TIDAL POTOMAC RIVER LATER
THIS MORNING.

THE NEXT HIGH TIDE WILL BE THE LOWER OF THE TWO ASTRONOICAL NORMS
THIS AFTERNOON AND EVENING. ALSO...A LIGHT OFFSHORE WILL LIKELY
CAUSE ANOMALIES TO DECREASE A BIT. THEREFORE...NO MINOR TIDAL IS
FLOODING. ALSO WITH THE DECREASED ANOMALIES...MINOR TIDAL FLOODING
IS UNLIKELY WITH THE HIGHER OF THE TWO HIGH TIDES LATE TONIGHT
INTO MONDAY MORNING.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...NONE.

&&

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



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