Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 141912
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
312 PM EDT TUE APR 14 2015

.SYNOPSIS...
A WAVE OF LOW PRESSURE WILL PASS BY TO OUR SOUTH THIS EVENING.
HIGH PRESSURE WILL BUILD IN BEHIND THIS SYSTEM FOR WEDNESDAY INTO
THURSDAY BEFORE MOVING OFF THE COAST LATE IN THE WEEK. A COLD
FRONT WILL PASS THROUGH LATE SATURDAY INTO SUNDAY.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
AS OF 230 PM...SFC FRONT IS PUSHING INTO CENTRAL VA. A SFC LOW
CENTER IS LOCATED NEAR THE TRI-CITIES OF TN. AHEAD OF THIS LOW...A
SOLID SHIELD OF OVERRUNNING RAIN HAS DEVELOPED AND ENCOMPASSES MUCH
OF THE CWA. THE HEAVIEST RAIN CONTINUES TO BE SLATED FOR CENTRAL VA.
AUTOMATED GAUGES INDICATE SOME LOCATIONS TOPPING 1 INCH. AS THE LOW
PASSES TO THE SOUTH...SOME BREAKS IN THE RAIN WILL BEGIN DEVELOPING
TOWARD LATE AFTERNOON/EARLY EVENING. DRIER AIR IS IMPINGING FROM THE
NORTH (32F DEWPT AT CBE)...SO EXPECT THE ORIENTATION OF THE RAIN
SHIELD TO TRANSLATE AS IT IS...POSSIBLY PIVOTING SLIGHTLY NEAR THE
BAY. DESPITE NEARLY UNIFORM RAIN TOTALS IN CENTRAL VA...EXPECT THE
PACE OF THE RAIN AND HIGHER FLOOD GUIDANCE TO PREVENT THE NEED FOR
EXTENDING THE FLOOD WATCH FARTHER EAST.

THE RAIN WILL TAPER OFF FROM NW TO SE THIS EVENING. WHILE THERE MAY
BE A FEW LINGERING SHOWERS...IT APPEARS SUBSIDENCE BEHIND THE
DEPARTING WAVE MAY SPELL A DRIER LATE NIGHT PERIOD THAN WAS
PREVIOUSLY ADVERTISED. EXPECTING TEMPS TO GRADUALLY FALL INTO THE
40S...WITH A FEW LOW 50S.

FOR WED...HIGH PRESSURE WILL BUILD TOWARD THE LOWER GREAT
LAKES...WEDGING DOWN THE EASTERN SIDE OF THE APPALACHIANS. A SHORT
WAVE RIDGE ALOFT WILL ALSO TRAVERSE THE AREA. ADJUSTED POPS DOWNWARD
AS THE AIRMASS IS LOOKING FAIRLY DRY. THE ONLY EXCEPTION MAY BE IF
THE LOW LEVEL EASTERLY FLOW IS ABLE TO FORCE SOME LIGHT UPSLOPE
PRECIP IN THE SOUTHERN MOUNTAINS. AMOUNT OF CLEARING IS
QUESTIONABLE...AND THERE MAY ALSO BE A GOOD DEAL OF MID/HIGH CLOUDS.
COMBINED WITH THE CAD SIGNATURE...UNDERCUT TEMP GUIDANCE BY SEVERAL
DEGREES. FORECAST HIGHS RANGE FROM THE UPPER 50S TO MID 60S.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
HIGH PRESSURE BOTH AT THE SURFACE AND ALOFT WILL BUILD OVERHEAD
WEDNESDAY NIGHT. A NORTHERLY FLOW WILL ALLOW FOR SEASONABLY CHILLY
CONDITIONS. MIN TEMPS WILL RANGE FROM THE UPPER 30S AND LOWER 40S
IN NORTHERN MARYLAND TO THE UPPER 40S/NEAR 50 IN DOWNTOWN
WASHINGTON AND BALTIMORE.

THE HIGH ALOFT AND AT THE SURFACE WILL MOVE OFF THE COAST
THURSDAY. AN UPPER-LEVEL DISTURBANCE WILL MOVE IN FROM THE
SOUTHWEST THURSDAY AFTERNOON. HIGH AND MID-LEVEL CLOUDS WILL
INCREASE...BUT MOST AREAS SHOULD BE DRY. THE ONE EXCEPTION WILL BE
ACROSS CENTRAL VIRGINIA INTO THE POTOMAC HIGHLANDS...WHERE A FEW
SHOWERS ARE POSSIBLE ESPECIALLY LATER IN THE AFTERNOON. EVEN
ACROSS THESE AREAS MOST OF THE TIME WILL BE DRY AND PRECIPITATION
WILL BE LIGHT.

THE UPPER-LEVEL DISTURBANCE WILL SWING THROUGH THE AREA THURSDAY
NIGHT AND SOUTHEAST WINDS WILL CONTINUE TO USHER IN MORE MOISTURE
OFF THE ATLANTIC. RAIN IS POSSIBLE AS A RESULT...ESPECIALLY ACROSS
THE SOUTHWESTERN PORTION OF THE CWA WHERE GUIDANCE IS MOST
CONFIDENT AND MOISTURE WILL BE DEEPER. HOWEVER...RAIN MAY
OVERSPREAD THE WASHINGTON AND BALTIMORE METROPOLITAN AREAS AS WELL
AS EASTERN MARYLAND. PRECIPITATION AMOUNTS WILL BE LIGHT. WILL
HAVE TO WATCH FOR LOW PRESSURE THAT WILL DEVELOP OFF THE SOUTHEAST
COAST...BUT AS OF NOW IT APPEARS THAT IT WILL BE TOO FAR TO OUR
SOUTH TO IMPACT OUR WEATHER. IF IT DOES DEVELOP FURTHER
NORTH...THEN A STEADIER RAIN WOULD DEVELOP OVER OUR AREA.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
HIGH PRESSURE WILL REMAIN OFF THE COAST FRIDAY THROUGH SATURDAY. A
COLD FRONT WILL APPROACH THE AREA SATURDAY BEFORE PASSING THROUGH
SATURDAY NIGHT INTO SUNDAY. SHOWERS ARE POSSIBLE DURING THIS TIME.
THE FRONT WILL STALL OUT JUST TO OUR SOUTH EARLY NEXT WEEK AND LOW
PRESSURE MAY DEVELOP ALONG THE FRONT...BRINGING UNSETTLED
CONDITIONS DURING THIS TIME.

&&

.AVIATION /17Z TUESDAY THROUGH SATURDAY/...
COLD FRONT HAS PUSHED THROUGH ALL TERMINALS...WITH WINDS FROM EITHER
THE N OR NE. A STEADY LIGHT TO MODERATE RAIN WILL CONTINUE THROUGH
LATE AFTERNOON...WITH MRB DRYING OUT THE FASTEST. EXPECT GENERALLY
MVFR CIGS AND VSBYS...ALTHOUGH THERE WILL BE TRANSIENT IFR CIGS AS
WELL. EXPECT THE RAIN TO TAPER OFF AND CONDITIONS TO IMPROVE TO VFR
THIS EVENING. MVFR CONDITIONS WILL LINGER LONGER IN CHO. CANNOT RULE
OUT A LINGERING SHOWER OVERNIGHT...ESPECIALLY AT CHO.

VFR CONDITIONS ARE PROBABLE WED...ALTHOUGH SKY COVER IS LOWER
CONFIDENCE. WINDS WILL BE N TO NE AT LESS THAN 10 KT.

HIGH PRESSURE OVERHEAD WEDNESDAY NIGHT WILL ALLOW FOR LIGHT WINDS.
THE HIGH WILL MOVE OFF THE COAST THURSDAY AND THURSDAY NIGHT.
SOUTHEAST WINDS ARE EXPECTED. SOUTHERLY WINDS MAY GUST AROUND 20
KNOTS THURSDAY. RAIN MAY OVERSPREAD THE TERMINALS LATE THURSDAY OR
THURSDAY NIGHT. CONFIDENCE IN TIMING IS LOW...BUT IT DOES APPEAR
THAT PRECIPITATION AMOUNTS WILL BE LIGHT. HOWEVER...SUBVFR CIGS
AND VSBYS ARE POSSIBLE...ESPECIALLY THURSDAY NIGHT.

SUBVFR CONDITIONS MAY CONTINUE FRIDAY INTO SATURDAY AS SOUTHERLY
WINDS USHER IN MORE MOISTURE ACROSS THE AREA

&&

.MARINE...
THE COLD FRONT HAS NOW PASSED THROUGH THE WATERS WITH WINDS FROM A N
OR NE DIRECTION. A SURGE OF STRONGER WIND GUSTS HAS FOLLOWED THE
FRONT...WITH SOME ISOLATED GUSTS TO 20 KT. THINK THESE WILL BE
TRANSITORY FOR MOST OF THE WATERS...ALTHOUGH THE WINDS MAY CHANNEL A
BIT LONGER DOWN THE MAIN PORTION OF THE BAY WHERE A SCA IS IN
EFFECT. LOW PRESSURE WILL PASS SOUTH OF THE WATERS THIS
EVENING...AND THE INCREASING GRADIENT MAY ALLOW SOME STRONGER GUSTS
TO CONTINUE...ALTHOUGH THE LEVEL OF GUSTS IS UNCERTAIN DUE TO POOR
MIXING. WILL KEEP THE SCA IN EFFECT. MODERATE RAIN WILL ALSO REDUCE
VSBYS ON THE WATERS THROUGH THIS EVENING. BY WED...EXPECT NORTHERLY
WINDS GENERALLY LESS THAN 15 KT.

HIGH PRESSURE OVERHEAD WEDNESDAY NIGHT WILL MOVE OFF THE COAST
THURSDAY THROUGH THURSDAY NIGHT. SOUTHEAST WINDS ARE EXPECTED
DURING THIS TIME. A SMALL CRAFT ADVISORY MAY BE NEEDED FOR
PORTIONS OF THE WATERS THURSDAY. HIGH PRESSURE WILL REMAIN OFF THE
COAST FRIDAY AND A COLD FRONT WILL PASS THROUGH LATE SATURDAY INTO
SUNDAY. UNSETTLED CONDITIONS ARE POSSIBLE DURING THIS TIME.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR VAZ025-026-503-504-
     508.
WV...FLOOD WATCH UNTIL 8 PM EDT THIS EVENING FOR WVZ505-506.
MARINE...SMALL CRAFT ADVISORY UNTIL 6 AM EDT WEDNESDAY FOR ANZ532>534-
     537-540>543.

&&

$$
SYNOPSIS...BJL
NEAR TERM...ADS
SHORT TERM...BJL
LONG TERM...DFH
AVIATION...BJL/ADS/DFH
MARINE...BJL/ADS/DFH


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