Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 020142
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
942 PM EDT MON JUN 1 2015

.SYNOPSIS...
A COLD FRONT WILL SLOWLY PASS THROUGH THE AREA TONIGHT THROUGH
TUESDAY. THE BOUNDARY WILL STALL TO THE SOUTH DURING THE MIDDLE
PORTION OF THE WEEK BEFORE DIMINISHING LATE IN THE WEEK.

&&

.NEAR TERM /UNTIL 6 AM TUESDAY MORNING/...
BROAD SFC LOW PRESSURE IS LOCATED OVER THE MID-ATLANTIC THIS
EVENING...WITH A STALLED FRONT WHICH EXTENDS ALONG THE MASON-DIXON
LINE THEN SOUTHWARD ALONG THE APPALACHIANS. DEW POINTS HAVE
DROPPED INTO THE 50S NEAR CUMBERLAND. A MESOLOW CAN BE SEEN IN
RADAR OVER N-CENTRAL MD. A CLOSED UPPER LOW IS LOCATED OVER TN
WITH DEEP SW FLOW AHEAD OF IT...PARALLEL TO THE FRONT.

SEVERAL CLUSTERS OF SHOWERS AND THUNDERSTORMS EXIST AROUND THE
REGION. THE NORTHERN ONE NEAR BALTIMORE HAS UNDERGONE
STRATIFICATION...BUT THE ONES TOWARD CENTRAL VA STILL CONTAIN
NOTABLE CONVECTIVE CHARACTERISTICS WHERE SOME INSTBY STILL EXISTS.
EXCEPT FOR AN ISOLATED STRONGER CORE...THE BIGGEST CONCERN WILL BE
HEAVY RAIN AND FLOODING FOR THE REMAINDER OF THE NIGHT. AFTER
THE CLUSTER FROM CENTRAL VA MOVES ACROSS THE AREA...THERE MAY BE A
BIT OF A DOWNTURN IN ACTIVITY. HOWEVER WITH THE STALLED FRONT AND
BROAD OVERRUNNING EXPECT THERE TO BE THE POTENTIAL FOR SHOWERS
THROUGHOUT THE NIGHT. WE MAY BE ABLE TO EVENTUALLY TRIM OUT SOME
OF THE WESTERN COUNTIES IN THE FLASH FLOOD WATCH AS THE HEAVIEST
RAIN IS ALIGNING TO THE EAST. SOME FOG WILL LIKELY DEVELOP
OVERNIGHT AS WELL IN THE MOIST LOW LEVEL AIRMASS. THE SLIGHTLY
COOLER/DRIER AIR IS EXPECTED TO MAKE SOME INROADS TONIGHT...BUT A
LITTLE UNCERTAIN HOW FAR.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH WEDNESDAY NIGHT/...
THE COLD FRONT WILL CONTINUE TO DROP SOUTH TUESDAY EVENTUALLY
PASSING THROUGH THE CENTRAL SHENANDOAH VALLEY DURING THE AFTERNOON
HOURS OF TUESDAY. A POTENT UPPER-LEVEL LOW WILL CONTINUE TO SPIN
OVER THE TENNESSEE VALLEY. THE SOUTHWEST FLOW ALOFT WILL OVERRUN
COOLER AIR FROM THE NORTHERLY FLOW BEHIND THE FRONT...RESULTING IN
PLENTY OF CLOUDS ALONG WITH SHOWERS. THE BEST CHANCE FOR SHOWERS
WILL BE ACROSS CENTRAL AND SOUTHERN AREAS...CLOSER TO THE
BOUNDARY. LOCALLY HEAVY RAIN AND THUNDERSTORMS ARE POSSIBLE ACROSS
THE CENTRAL SHENANDOAH VALLEY PERHAPS INTO EXTREME SOUTHERN
MARYLAND WHERE THERE MAY BE MORE INSTABILITY.

MAX TEMPERATURES TUESDAY WILL BE MUCH COOLER AND WELL BELOW CLIMO
DUE TO THE NORTHERLY FLOW BEHIND THE FRONT ALONG WITH PLENTY OF
CLOUDS. MAX TEMPS ARE FORECAST TO RANGE FROM THE MIDDLE 60S NEAR
THE MASON-DIXON LINE TO THE UPPER 60S/LOWER 70S NEAR WASHINGTON
AND BALTIMORE TO THE MID AND UPPER 70S IN THE CENTRAL SHENANDOAH
VALLEY.

THE BOUNDARY WILL STALL OUT TO THE SOUTH FOR TUESDAY NIGHT THROUGH
WEDNESDAY NIGHT WHILE THE UPPER-LEVEL LOW CONTINUES TO SPIN OVER
THE TENNESSEE VALLEY. PLENTY OF CLOUDS ALONG WITH UNUSUALLY COOL
CONDITIONS ARE EXPECTED FOR THIS TIME OF YEAR. RAIN IS LIKELY
DURING THIS TIME. THE HIGHEST CONFIDENCE FOR RAIN WILL BE ACROSS
CENTRAL AND SOUTHERN AREAS...BUT THE LATEST GUIDANCE HAS TRENDED
FARTHER NORTH INTO NORTHERN AREAS AS WELL. TRENDED THE FORECAST
THIS WAY...BUT THAT TREND MAY HAVE TO CONTINUE.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
A CUT-OFF MIDDLE AND UPPER LEVEL LOW PRESSURE SYSTEM WILL SLOWLY
WORK EASTWARD ACROSS THE TENNESSEE VALLEY AND MID ATLANTIC REGION
THURSDAY THROUGH FRIDAY. EXPECT THE CHANCE FOR SHOWERS AND AN
ISOLATED THUNDERSTORM IN SPOTS WITH RESPECT TO THE MID AND UPPER
LEVEL LOW WITH THE BETTER CHANCE ON THURSDAY. RAIN COVERAGE AND
INTENSITY SHOULD DIMINISH THURSDAY NIGHT THROUGH FRIDAY NIGHT AS A
WEAK SURFACE AREA OF HIGH PRESSURE BUILDS IN FROM THE WEST.

THE NEXT UPPER LEVEL LOW PRESSURE SYSTEM WILL ARRIVE LATE SATURDAY
INTO SUNDAY...POSSIBLY SLOWING DOWN IN ITS EASTWARD PROGRESSION LATE
SUNDAY INTO SUNDAY NIGHT. THERE IS A CHANCE OF SHOWERS AND
THUNDERSTORMS AHEAD OF THE SYSTEM EACH PERIOD. AN ASSOCIATED COLD
FRONT WILL STALL MONDAY...ALLOWING FOR ADDITIONAL SHOWERS TO DEVELOP
IN THE REGION.

&&

.AVIATION /01Z TUESDAY THROUGH SATURDAY/...
WAVES OF SHOWERS AND THUNDERSTORMS WILL CONTINUE TO MOVE ACROSS
THE AREA THROUGH TONIGHT. THE GREATEST IMPACTS WILL BE THROUGH 06Z
GIVE OR TAKE A COUPLE HOURS...WITH LESS INTENSE SHOWERS EXPECTED
THEREAFTER. HOWEVER...LOCAL REDUCTIONS TO IFR WILL BE POSSIBLE AND
WILL HAVE TO BE HANDLED WITH AMENDMENTS IN THIS DYNAMIC SITUATION.
THE STRONG WIND THREAT HAD GREATLY DIMINISHED. CLOUDS WILL LOWER
INTO THE MVFR AND POSSIBLY IFR CATEGORY LATER TONIGHT INTO TUESDAY
MORNING. VSBYS MAY BE REDUCED TO THE SAME CATEGORIES IN FOG.
OUTSIDE OF THUNDERSTORM-INFLUENCED WINDS...THE PREVAILING
DIRECTION WILL BECOME NORTHERLY AFTER THE FRONT SLIPS
THROUGH...TIMING UNCERTAIN BUT SPEED WILL REMAIN LIGHT.

SHOWERS ARE LIKELY TUESDAY MORNING...BUT THERE MAY BE SOME DRIER
AIR THAT WORKS ITS WAY IN FOR A LULL IN ACTIVITY TUESDAY
AFTERNOON. THE BEST CHANCE FOR THE LULL WILL BE ACROSS THE
NORTHERN TERMINALS.

WARM AIR WILL CONTINUE TO OVERRUN COOL AIR BEHIND A COLD FRONT
TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. MORE LOW CLOUDS ARE
EXPECTED WITH IFR/MVFR CONDITIONS. RAIN IS LIKELY DURING THIS
TIME.

MVFR OR IFR CONDITIONS POSSIBLE THURSDAY THROUGH FRIDAY WITH
SHOWERS AND THUNDERSTORMS DEVELOPING IN THE REGION.

&&

.MARINE...
THE MOST IMMEDIATE THREAT OVER THE WATERS IS THE POTENTIAL FOR
STRONG THUNDERSTORMS AND GUSTY WINDS. THE STRONGEST STORMS WILL BE
AFFECTING THE SOUTHERN WATERS LATE THIS EVENING INTO THE
OVERNIGHT. GRADIENT WINDS APPEAR LIKE THEY WILL SUPPORT THE SCA TO
EITHER EXPIRE AT MIDNIGHT ON SCHEDULE OR BE CANCELLED EARLY. WINDS
WILL BE VRB DUE TO THE INFLUENCE OF STORMS...BUT THE PREVAILING
DIRECTION WILL BECOME NORTHERLY AS A FRONT SLIPS SOUTHWARD
TONIGHT.

THE GRADIENT WILL WEAKEN TONIGHT INTO TUESDAY AS A COLD FRONT
DROPS THROUGH. HOWEVER...NORTH TO NORTHEAST WINDS ARE EXPECTED TO
INCREASE BEHIND THE FRONT TUESDAY AFTERNOON THROUGH TUESDAY NIGHT.
A SMALL CRAFT ADVISORY IS IN EFFECT FOR THE MARYLAND CHESAPEAKE
BAY AND LOWER TIDAL POTOMAC DURING THIS TIME.

A NORTHEAST FLOW WILL CONTINUE WEDNESDAY AND WEDNESDAY NIGHT AS
THE BOUNDARY STALLS OUT TO OUR SOUTH. A SMALL CRAFT ADVISORY MAY
BE NEEDED FOR PORTIONS OF THE WATERS DURING THIS TIME.

NO MARINE HAZARDS THURSDAY THROUGH FRIDAY.

&&

.CLIMATE...
UNUSUALLY COOL CONDITIONS ARE EXPECTED BEHIND A COLD FRONT FOR
TUESDAY AND WEDNESDAY DUE TO NORTHERLY WINDS AND PLENTY OF CLOUDS.
BELOW ARE THE RECORD LOW MAX TEMPS FOR THOSE DATES.

TUESDAY JUNE 2ND...
IAD: 64 DEGREES IN 1975
DCA: 53 DEGREES IN 1907
BWI: 53 DEGREES IN 1907

WEDNESDAY JUNE 3RD...
IAD: 56 DEGREES IN 1997
DCA: 58 DEGREES IN 1997
BWI: 57 DEGREES IN 1997

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...FLASH FLOOD WATCH UNTIL 6 AM EDT TUESDAY FOR DCZ001.
MD...FLASH FLOOD WATCH UNTIL 6 AM EDT TUESDAY FOR MDZ004>006-011-
     013-014-016-503>508.
VA...FLASH FLOOD WATCH UNTIL 6 AM EDT TUESDAY FOR VAZ026>031-
     038>040-050>056-501-502-505>507.
WV...FLASH FLOOD WATCH UNTIL 6 AM EDT TUESDAY FOR WVZ050-053-055.
MARINE...SMALL CRAFT ADVISORY UNTIL MIDNIGHT EDT TONIGHT FOR ANZ532>534-
     537-540>543.
     SMALL CRAFT ADVISORY FROM NOON TUESDAY TO 6 AM EDT WEDNESDAY
     FOR ANZ530>534-537>543.
     FLASH FLOOD WATCH UNTIL 6 AM EDT TUESDAY FOR ANZ535-538.
     SMALL CRAFT ADVISORY FROM 6 PM TUESDAY TO 6 AM EDT WEDNESDAY
     FOR ANZ536.

&&

$$
SYNOPSIS...BJL
NEAR TERM...ADS
SHORT TERM...BJL
LONG TERM...KLW
AVIATION...BJL/ADS/KLW
MARINE...BJL/ADS/KLW
CLIMATE...LWX



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