Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 271937
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
337 PM EDT WED MAY 27 2015

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN OFFSHORE THIS WEEK. A SOUTHERLY FLOW
WILL BRING WARM HUMID CONDITIONS TO THE MID ATLANTIC THROUGH
SATURDAY. SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE EACH
AFTERNOON AND EVENING. A WEAK COLD FRONT WILL APPROACH THE REGION
THURSDAY BUT WEAKEN AND STALL OVER THE REGION. A STRONGER COLD
FRONT WILL ARRIVE SUNDAY.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
A SEVERE THUNDERSTORM WATCH IS IN EFFECT FOR PARTS OF
NORTH-CENTRAL MARYLAND...NORTHERN VIRGINIA AND WASHINGTON DC.

SHOWERS AND THUNDERSTORMS HAVE FORMED ON THE LEADING EDGE OF A WAVE
OF LOW PRESSURE THAT MOVED OVER THE HIGHLANDS THIS MORNING. SURFACE
HEATING AND MARGINAL SHEAR HAVE LED TO STRONG THUNDERSTORMS
PRODUCING GUSTY WINDS...HAIL...HEAVY RAIN AND LIGHTNING. A BROKEN
LINE OF SHOWERS AND THUNDERSTORMS LOCATED ON THE WESTERN METRO
SUBURBS WILL CONTINUE TO MOVE EASTWARD INTO A UNSTABLE ENVIRONMENT.
THIS REGION INCLUDING THE I-95 CORRIDOR IS AN AREA OF CONCERN DUE TO
THE HIGHER DEWPTS AND MAXIMUM OF DOWNWARD CAPE AS EVIDENT ON THE
MESOANALYSIS. THIS POSES THE THREAT FOR DAMAGING WINDS. REPORTS OF
HEAVY RAIN OCCURRED IN NRN MD. PLEASE USE CAUTION WHILE TRAVELING
OR IF OUTSIDE LATE THIS AFTERNOON AND EVENING. A SECOND AREA OF
CONVECTION IS EXPECTED TO FORM ACROSS CENTRAL-SOUTHERN VA AND MOVE
NORTHWARD LATE THIS AFTERNOON AND EVENING IN VICINITY OF A LEE
TROUGH. THIS ACTIVITY WILL MOVE N-NE AND MAY IMPACT THE
PIEDMONT...SOUTHERN MARYLAND AND SURROUNDING WATERS. AT THIS
TIME...NO WATCH HAS BEEN ISSUED.

SHOWERS AND THUNDERSTORMS WILL MOVE OFF TO THE EAST THIS EVENING.
SOUTHERLY WINDS WILL CONTINUE OVER NIGHT RESULTING IN HUMID
CONDITIONS. PATCHY FOG IS POSSIBLE INTO THURSDAY MORNING.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
SHORTWAVE TROUGH WILL BE MOVING INTO NEW ENGLAND ON THURSDAY AS A
SFC COLD FRONT APPROACHES FROM THE NW. HOWEVER...THE FRONT WILL NOT
MAKE A LOT OF SOUTHERN PROGRESS THROUGH THE REGION. WHILE THESE
FEATURES WILL ONCE AGAIN ALLOW SCATTERED SHOWERS AND THUNDERSTORMS
TO ONCE AGAIN FORM...BULK SHEAR IS ON THE WEAK SIDE...SO SEVERE WX
THREAT IS MINIMAL. HUMIDITY WILL STILL BE HIGH THOUGH SO LOCALLY
HEAVY DOWNPOURS POSSIBLE. HIGHS TEMPS WELL INTO THE 80S. FRONT
BEGINS TO LOSE DEFINITION OVERNIGHT AS PRECIP CHANCES DIMINISH. SOME
SLIGHTLY DRIER AIR MAY WORK INTO THE NORTHERN PART OF THE CWA. LOWS
WILL DROP INTO THE 60S...EXCEPT 50S IN HIGHER ELEVATIONS AND AROUND
70 URBAN CENTERS.

BY FRIDAY...THE MID AND UPPER LEVEL RIDGES BUILD BACK TO THE
NORTH...AS WHAT/S LEFT OF THE SFC FRONT LIFTS BACK TO THE NORTH.
WITHOUT A DEFINED FORCING MECHANISM...CONVECTIVE DEVELOPMENT WILL BE
BE MORE DIURNALLY AND TERRAIN DRIVEN. THUS COVERAGE SHOULD BE LOWER
THAN WED/THU...ESPECIALLY EAST OF THE BLUE RIDGE. DAYTIME HIGHS A
TOUCH LOWER ON FRIDAY...BUT THE OVERALL LOOK AND FEEL OF THE
FORECAST REMAINS THE SAME...WARM AND MUGGY.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
A COLD FRONT WILL APPROACH THE REGION SATURDAY...BRINGING A CHANCE
OF SHOWERS AND THUNDERSTORMS TO THE REGION INTO SATURDAY NIGHT.
TEMPERATURES SATURDAY WILL REACH THE MIDDLE TO UPPER 80S WITH LOWS
SATURDAY NIGHT GETTING INTO THE MIDDLE 60S.

THE COLD FRONT SHOULD SLOWLY PUSH THROUGH THE REGION SUNDAY. THE
EUROPEAN MODEL STILL REMAINS THE SLOWER MODEL OVER THE GFS.
SHOWERS AND THUNDERSTORMS WILL FORM AHEAD OF AND ALONG THE FRONT.
TEMPERATURES WILL BE ABOVE NORMAL SUNDAY.

A WEDGE OF HIGH PRESSURE WILL BUILD SOUTHWARD ALONG THE EAST
COAST SUNDAY NIGHT AND MONDAY...HELPING TO COOL CONDITIONS DOWN A
LITTLE. HOWEVER...OVERRUNNING MOISTURE AND MID-LEVEL
DISTURBANCES APPROACHING FROM THE WEST WILL BRING YET ANOTHER
THREAT FOR RAIN SHOWERS AND PERHAPS A THUNDERSTORM. TEMPERATURES
MAY BE A FEW DEGREES ABOVE NORMAL EACH PERIOD BUT COOLER THAN RECENT
DAYS.

AS THE RIDGE OF HIGH PRESSURE BREAKS DOWN TUESDAY...UPPER LEVEL
DISTURBANCES ARE EXPECTED TO MOVE ACROSS THE OHIO VALLEY INTO THE
LOWER GREAT LAKES. THESE DISTURBANCES COULD POSE A SHOWER THREAT
TUESDAY WITH HIGH TEMPERATURES ONLY IN THE LOWER 80S.

A SHOWER OR THUNDERSTORM IS POSSIBLE WEDNESDAY...BUT THE STRENGTH
OF THE HIGH PRESSURE ALONG THE EASTERN SEABOARD MAY REDUCE THAT
THREAT EVEN FURTHER. IT WILL BE A FEW DEGREES WARMER WEDNESDAY.

&&

.AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
TSRA AND SHRA EXPECTED THIS AFTERNOON AND SUB-VFR
CONDITIONS EXPECTED WITHIN ACTIVITY. SOME TSRA MAY PRODUCE GUSTY
WINDS AND HAIL AS WELL AS HEAVY RAIN THAT WILL REDUCE VSBYS. TEMPO
ADDED FOR IAD BUT WILL LIKELY BE ADDED FOR BWI/MTN/DCA SHORTLY.
HUMID CONDITIONS PERSIST TONIGHT AND PATCHY FOG MAY IMPACT THE
TERMINALS INTO EARLY THURSDAY. SUB-VFR CONDITIONS POSSIBLE.

SCATTERED THUNDERSTORMS POSSIBLE FRIDAY AFTERNOON...WITH SLIGHTLY
HIGHER CHANCES NEAR/WEST OF BLUE RIDGE. OVERALL LOWER COVERAGE THAN
PREVIOUS DAYS. THERE IS A CHANCE OF SUB-VFR VSBYS IN BR EARLY FRIDAY
AND SATURDAY MORNINGS...MAINLY IN THE TYPICAL LOCATIONS...BUT
OVERALL CONFIDENCE IS NOT GREAT.

LOCALIZED SUB-VFR CONDITIONS POSSIBLE SATURDAY THROUGH SUNDAY
WITH SHOWERS AND THUNDERSTORMS IN PARTS OF THE AREA.

&&

.MARINE...
SHOWERS AND THUNDERSTORMS WILL MOVE ACROSS THE WATERS THIS
AFTERNOON AND EVENING. GUSTY WINDS...HEAVY RAIN ARE EXPECTED. SMW`S
WILL LIKELY BE ISSUED INTO THE EARLY EVENING. S WINDS CONTINUE ON
THE WATERS THROUGH THURSDAY...WITH SCATTERED SHOWERS AND
THUNDERSTORMS AGAIN POSSIBLE DURING THE AFTERNOON AND EVENING. THEY
SHOULD DIMINISH TONIGHT AND SCA WILL END OVERNIGHT.

LIGHT/VRB WINDS THURSDAY NIGHT WILL BECOME SOUTHERLY AGAIN FRIDAY AS
HIGH PRESSURE RE-ESTABLISHES OFFSHORE. GUSTS MAY COME CLOSE TO SCA
CRITERIA BY LATE FRIDAY AFTERNOON OVER THE BAY DUE TO
CHANNELING...BUT CONFIDENCE IS TOO LOW TO ISSUE AT THIS TIME.
WHILE THUNDERSTORMS WILL BE POSSIBLE FRIDAY AFTERNOON...OVERALL
COVERAGE APPEARS FAIRLY ISOLATED.

WIDESPREAD MARINE HAZARDS ARE UNLIKELY SATURDAY THROUGH
SUNDAY...ALTHOUGH SCATTERED AFTERNOON/EVENING THUNDERSTORMS WILL
POSE LOCALIZED THREATS.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ531>533-
     537>542.
     SMALL CRAFT ADVISORY UNTIL 6 AM EDT THURSDAY FOR ANZ534-543.
     SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR ANZ530.

&&

$$
SYNOPSIS...ADS
NEAR TERM...HAS
SHORT TERM...ADS
LONG TERM...KLW
AVIATION...ADS/HAS/KLW
MARINE...ADS/HAS/KLW



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