Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 191403
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1003 AM EDT TUE AUG 19 2014

.SYNOPSIS...
LOW PRESSURE WILL MOVE AWAY FROM THE AREA TODAY...BUT A BOUNDARY
WILL REMAIN STATIONARY OVER THE REGION. THE BOUNDARY WILL REMAIN
OVERHEAD THROUGH THURSDAY BEFORE SLOWLY DROPPING SOUTH AS A COLD
FRONT FRIDAY INTO THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
LOW PRESSURE IS SLOWLY MOVING TO THE SOUTHEAST AND OFF THE VA
TIDE WATER COAST THIS MORNING. A STATIONARY FRONT STAYS LOCATED
ACROSS THE MID ATLANTIC FROM THE PANHANDLE OF WV TO CENTRAL VA
THIS MORNING. NE-E WINDS CONTINUE TO MOVE INTO THE REGION ON THE
DRIER SIDE OF THE BOUNDARY.

DRIER AIR WILL MOVE INTO THE REGION FROM THE NE AND MOSTLY SUNNY
CONDITIONS ARE EXPECTED FOR NE MD. CLOUDS INCREASE FURTHER SOUTH AS
EASTERLY FLOW PUSHES AGAINST THE BLUE RIDGE MTNS AND INTERACTS
WITH THE STATIONARY BOUNDARY THAT IS IN PLACE. DEWPTS IN THE
UPPER 60S TO LOW 70S ARE LOCATED ON THE WETTER SIDE OF THE
BOUNDARY AND NEAR THE SFC LOW. ISO-SCT SHOWERS WILL BE POSSIBLE
ACROSS SOUTHERN MD THIS MORNING AND INTO THE AFTERNOON AS THE SFC
LOW TRACKS EASTWARD. AS TEMPS RISE NEAR 80...MOISTURE WILL ALLOW
SHOWERS AND ISO THUNDERSTORMS TO FORM NEAR THE STATIONARY FRONT
WHICH WILL BE LOCATED NEAR THE POTOMAC HIGHLANDS/ALLEGHENY FRONT.
LITTLE FORCING ALOFT WILL LIMIT WIDESPREAD AND STRONG STORMS.
SHOWERS THAT DO FORM WILL MOVE SLOWLY SINCE 12Z IAD RAOB HAS A
ZERO SPEED STORM MOTION. SOME PLACES MAY SEE ISOLATED AMTS OF HEAVY
RAIN.

PREVIOUS DISCUSSION...
ANY CONVECTION WILL DISSIPATE ACROSS MOST LOCATIONS THIS EVENING.
THERE MAY BE A FEW SHOWERS THAT HANG AROUND OVERNIGHT ACROSS THE
POTOMAC HIGHLANDS...BUT EVEN ACROSS THESE AREAS MOST OF THE TIME
WILL BE DRY. PATCHY LOW CLOUDS AND FOG ARE EXPECTED...ESPECIALLY
ACROSS THE POTOMAC HIGHLANDS INTO CENTRAL VIRGINIA WHERE THERE
WILL BE A LITTLE MORE MOISTURE. MIN TEMPS WILL RANGE FROM THE
UPPER 50S AND LOWER 60S IN THE POTOMAC HIGHLANDS TO NEAR 70 IN
DOWNTOWN WASHINGTON AND BALTIMORE.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
A STATIONARY BOUNDARY WILL REMAIN OVER THE REGION WEDNESDAY
THROUGH WEDNESDAY NIGHT...BUT THERE WILL BE LITTLE TEMPERATURE OR
DEWPOINT GRADIENT ALONG IT. AN UPPER-LEVEL LOW WILL DROP SOUTH
THROUGH THE GREAT LAKES AND A SHORTWAVE OUT AHEAD OF IT WILL
LIKELY PASS THROUGH THE AREA WEDNESDAY AFTERNOON INTO WEDNESDAY
EVENING. SHOWERS AND THUNDERSTORMS ARE EXPECTED TO DEVELOP
WEDNESDAY AFTERNOON...ESPECIALLY NEAR AND WEST OF THE BLUE RIDGE
MOUNTAINS. THE CONVECTION MAY TRACK FURTHER EAST INTO THE
WASHINGTON AND BALTIMORE METROPOLITAN AREAS WEDNESDAY EVENING AS
THE SHORTWAVE MOVES THROUGH.

WEDNESDAY NIGHT WILL TURN OUT WARM AND HUMID ACROSS MOST
LOCATIONS. CONVECTION SHOULD DISSIPATE ACROSS MOST AREAS OVERNIGHT
DUE TO THE LOSS OF DAYTIME HEATING. AREAS OF LOW CLOUDS AND FOG
ARE EXPECTED OVERNIGHT.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
THE UPPER-LEVEL LOW OVER THE GREAT LAKES WILL SWING THROUGH OUR
AREA LATER THURSDAY INTO THURSDAY NIGHT...BRINGING A CHANCE FOR
MORE SHOWERS AND THUNDERSTORMS.

H5 PATTERN IS ENERGETIC THROUGH THE PERIOD AS THE MID ATLANTIC IS
CAUGHT BETWEEN A RETROGRADING UPPER LOW EAST OF THE CANADIAN
MARITIMES AND LARGE ANTI-CYCLONE OVER THE LOWER MISSISSIPPI VALLEY.
THE H5 CLOSED HIGH PRESSURE WINS OUT THROUGH THE PERIOD WITH HEIGHT
RISES FOR OUR AREA...BUT WITH A SERIES OF VORT MAXES MOVING
SOUTHEAST FROM THE GREAT LAKES.  THE SFC REFLECTION IS AN INVERTED
ANTICYCLONIC RIDGE EMANATING FROM THE SFC HIGH OVER THE CANADIAN
MARITIMES.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
LOW CLOUDS WILL CONTINUE AT IAD-DCA-BWI-CHO THIS MORNING AND CIGS
SHOULD HOLD AT MVFR LEVELS. CONDITIONS WILL IMPROVE LATER THIS
MORNING AND VFR CONDITIONS ARE EXPECTED ACROSS MOST AREAS THIS
AFTERNOON. ANY SHOWER OR THUNDERSTORM WILL BE CONFINED TO KCHO
THIS AFTERNOON AND EVENING.

MORE LOW CLOUDS AND FOG ARE POSSIBLE TONIGHT...AGAIN MAINLY ACROSS
KCHO AND KMRB WHERE THERE WILL BE MORE MOISTURE. THERE IS A BETTER
CHANCE FOR THUNDERSTORMS ACROSS THE TERMINALS LATER WEDNESDAY AND
WEDNESDAY EVENING. LOW CLOUDS AND FOG MAY BE MORE WIDESPREAD
OVERNIGHT WEDNESDAY INTO THURSDAY. MORE SHOWERS AND THUNDERSTORMS
ARE POSSIBLE THURSDAY AFTERNOON AND EVENING.

PERIODS OF MVFR/IFR CIGS ARE EXPECTED FROM LOW CLOUDS ASSOCIATED
MARINE AIR.

&&

.MARINE...
A WAVE OF LOW PRESSURE WILL MOVE OFF TO THE EAST TODAY. AN
EASTERLY FLOW WILL CONTINUE DURING THIS TIME AND GUSTS OF 15-20KTS
HAVE BEEN REPORTED ON THE LOWER TIDAL POTOMAC AND MD CHESAPEAKE
BAY SOUTH OF NORTH BEACH THIS MORNING. A SCA IS IN EFFECT TODAY AS
THE SFC LOW SLOWLY MOVES AWAY FROM THE WATERS.

A STATIONARY BOUNDARY WILL REMAIN NEAR THE WATERS FOR WEDNESDAY
AND THURSDAY. EAST TO SOUTHEAST WINDS ARE EXPECTED DURING THIS
TIME...BUT WIND SPEEDS SHOULD REMAIN BELOW SCA CRITERIA. A FEW
SHOWERS AND THUNDERSTORMS ARE POSSIBLE...MAINLY DURING THE
AFTERNOON AND EVENING HOURS FOR WEDNESDAY AND THURSDAY.

A BACKDOOR COLD FRONT WILL PASS THROUGH THE WATERS FRIDAY AND A
NORTHEASTERLY FLOW IS EXPECTED DURING THE WEEKEND. NO MARINE
HEADLINES ARE EXPECTED DURING THIS TIME.

&&

.TIDES/COASTAL FLOODING...
AN ONSHORE FLOW WILL CONTINUE THROUGH TONIGHT...BUT IT WILL REMAIN
WEAK. TIDAL ANOMALIES AROUND ONE-HALF FOOT ABOVE NORMAL WILL
LIKELY PERSIST THROUGH TONIGHT. MINOR TIDAL FLOODING IS NOT
EXPECTED WITH THE LOWER OF THE TWO HIGH TIDES THIS AFTERNOON.
WATER LEVELS WILL BE CLOSE TO MINOR FLOODING THRESHOLDS DURING THE
HIGH TIDE CYCLE LATE TONIGHT...BUT CURRENT THINKING IS THAT WATER
LEVELS WILL REMAIN BELOW MINOR FLOODING THRESHOLDS SINCE THE
ONSHORE FLOW IS WEAK.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 PM EDT THIS EVENING FOR ANZ533-
     534-537-541-543.

&&

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






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