Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 121405
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1005 AM EDT SAT APR 12 2014

.SYNOPSIS...
HIGH PRESSURE WILL MOVE ACROSS THE REGION TODAY AND PUSH OFFSHORE
THIS EVENING. A WARM FRONT WILL LIFT NORTH ACROSS THE REGION
TONIGHT AND SUNDAY. A COLD FRONT WILL SLOWLY MOVE THROUGH THE
REGION MONDAY NIGHT THROUGH TUESDAY NIGHT. CANADIAN HIGH PRESSURE
BUILDS INTO THE AREA WEDNESDAY AND THURSDAY.

&&

.NEAR TERM /THROUGH SUNDAY/...
SURFACE RIDGE MOVING ACROSS THE CWFA AT THIS HOUR...WITH JUST SOME
HIGH CLOUDS AROUND. 14Z TEMPS RANGE FROM THE LOWER 50S IN WRN MD
AND AT HIGHER ELEVATIONS TO THE MID 60S IN THE I-95 CORRIDOR. AS
WINDS SWITCH AROUND OUT OF THE SOUTH THIS AFTERNOON...ANOTHER WARM
DAY /BUT COOLER THAN YESTERDAY/ IS ANTICIPATED. RAISED MAXES A
COUPLE DEGREES FROM THE OVERNIGHT FORECAST WITH HIGHS EXPECTED TO
REACH THE LOW TO MID 70S IN MOST AREAS. HIGHER ELEVATIONS AND
LOCALIZED AREAS NEAR OPEN WATER WITH AN ONSHORE FLOW SHOULD SEE
HIGHS REMAINING IN THE 60S.

MODELS STILL HINTING AT A SMALL CHANCE FOR SHOWERS THIS AFTERNOON
IN THE SOUTHERN POTOMAC HIGHLANDS...AS WEAK INSTABILITY...DAYTIME
HEATING...AND TERRAIN COMBINE TO PRODUCE ENOUGH LIFT TO PERHAPS
GENERATE SOME WEAK CONVECTION. EXPANDED THE RAIN CHANCE TO INCLUDE
A LITTLE MORE AREA BUT LEFT IT AT LOW CHANCE...AND EXPECT MOST
AREAS WILL REMAIN DRY.

LOW LEVEL MOISTURE MARKEDLY INCREASES TONIGHT IN A WARM ADVECTION
PATTERN. EXTENDED THE HIGHLAND POPS INTO THE EARLY EVENING AND
ALSO INCREASED CLOUD COVER AS THERE ARE SIGNS OF LOW STRATUS
DEVELOPMENT. WINDS STAY UP SO I AM NOT AS CONVINCED ABOUT
FOG...BUT ALSO CANNOT RULE IT OUT. NIGHT SHIFT RAISED LOWS FOR
TONIGHT...BUT IF THAT CLOUD COVER INDEED OCCURS...I MAY HAVE TO
RAISE THEM FURTHER THIS AFTERNOON. WILL REASSESS AFTER 12Z MODELS
ARE IN.

MID-ATLANTIC IS WELL INTO THE WARM SECTOR FOR SUNDAY WITH AND
INCREASING SOUTHWEST FLOW/WIND FAVORING GOOD MIXING. DEWPOINTS
WILL BE A BIT HIGHER...BUT SHOULD STILL SEE TEMPERATURES AROUND OR
INTO THE 80S.

&&

.SHORT TERM /SUNDAY NIGHT THROUGH MONDAY/...
FLOW THRUOUT THE TROPOSPHERE BECOMES INCREASINGLY MERIDIONAL/SLY
OVER THE ERN SEABOARD SUN NGT AND MON AS AN AMPLIFYING UPPER TROUGH
AND SFC COLD FRONT APPROACH FROM THE CENTRAL CONUS AND DOWNSTREAM
RIDGE BUILDS OVER THE WRN ATLANTIC. WARM CONDITIONS WILL CONTINUE AS
A RESULT. FCST LOWS IN THE 50S SUN NGT AND HIGHS IN THE 70S MON ARE
MORE REPRESENTATIVE OF CLIMO FOR LATE MAY THAN FOR MID APRIL.

THE COLD FRONT WILL PROGRESS EWD TOWARD THE WRN SIDE OF THE
APPALACHIANS ON MON. CLOUDS WILL INCREASE THRUOUT THE DAY AS A
40-50KT SLY LLVL JET AHEAD OF THE FRONT TRANSPORTS DEEPER MOISTURE
UP THE ERN SEABOARD. THE GREATEST LIFT WILL STILL REMAIN UPSTREAM OF
THE AREA ON MON SO COVERAGE OF SHOWERS WILL BE LOW DURING THE AFTN.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
MODELS INDICATE A WEAK REX BLOCK FORMING OVER THE ATLANTIC NEAR 60W
NEXT WEEK...WHICH WOULD WILL CAUSE THE COLD FRONT TO SLOW DOWN AS IT
MOVES EWD TOWARD THE ERN SEABOARD. AN EXTENDED PERIOD OF CLOUDY AND
WET CONDITIONS ARE IN THE FCST MON NGT THRU TUE NGT WITH THE FRONT
LOCATED OVER THE AREA. COVERAGE OF PRECIP SHOULD BE WIDESPREAD WITH
FAVORABLE JET DYNAMICS IN RIGHT ENTRANCE REGION OF ULVL JET STREAK
AND A PERSISTENT FEED OF MOISTURE FROM THE GULF OF MEXICO AND
ATLANTIC ALONG THE FRONTAL BOUNDARY. 00Z GUIDANCE HAS GENERALLY
BACKED OFF ON HIGHER QPF AMOUNTS A BIT COMPARED TO YDA/S RUNS BUT
THE POSSIBILITY FOR A HEAVY RAINFALL EVENT STILL CANNOT BE DISMISSED
GIVEN THE AFOREMENTIONED SYNOPTIC SETUP.

THE COLD FRONT MOVES OFF THE EAST COAST WED. CANADIAN HIPRES
EVENTUALLY BUILDS INTO THE AREA DURING THE SECOND HALF OF THE WEEK.
WELL-BELOW NORMAL TEMPS ARE FCST FOR WED WITH HIGHS ONLY IN THE 40S
AND LOW WED NGT NEAR FREEZING. FROST/FREEZE HEADLINES MAY BE NEEDED
EAST OF THE BLUE RIDGE WHERE THE GROWING SEASON HAS STARTED.

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
VFR TODAY AS WINDS VEER TO THE SOUTHEAST. WINDS WILL INCREASE
TONIGHT INTO SUNDAY AS A WARM FRONT PUSHES NORTH. AREAS OF MVFR
STRATUS MAY DEVELOP LATE TONIGHT. CONFIDENCE ON DEVELOPMENT AND
COVERAGE OF STRATUS IS STILL LOW...BUT INCREASING ENOUGH THAT IT
PROBABLY WILL BE INCLUDED IN 18Z TAF PACKAGE.

PATCHY FOG OR LOW STRATUS MAY DEVELOP SUN NGT UNDER MOIST SLY
FLOW. SLY WINDS WILL BE BREEZY ON MON WITH GUSTS 25-30 KT
POSSIBLE DURING THE AFTN BUT VFR CONDITIONS. COLD FRONT SLOWS
DOWN AS IT MOVE THRU THE TERMINALS MIDWEEK...RESULTING IN A
PROLONGED RISK OF FLGT RESTRICTIONS AND SHOWERS LATE MON THRU ERY
WED.

&&

.MARINE...
HIGH PRESSURE WILL MOVE ACROSS THE WATERS TODAY AS LIGHT WINDS
VEER FROM NORTH TO SOUTHEAST. WINDS WILL INCREASE OVERNIGHT AND
SCA CONDITIONS ARE EXPECTED SUNDAY BEHIND A WARM FRONT.

SCA MAY NEED TO BE EXTENDED INTO SUN NGT FOR THE MAIN STEM OF THE
CHSPK BAY WHERE SLY WINDS WILL CHANNEL. SCA CONDITIONS LIKELY ACROSS
ALL MARINE ZONES ON MON INTO TUE AS SLY WINDS INCREASE AHEAD OF A
COLD FRONT. A STRONG PRESSURE GRADIENT LOOKS TO DEVELOP BEHIND THE
FRONT DURING MIDWEEK AS THE FRONT MOVES OFFSHORE AND HIPRES BUILDS
IN FROM THE GREAT LAKES. NW WINDS DURING THIS TIME SHOULD CONTINUE
TO PRODUCE SCA CONDITIONS WITH GALES POSSIBLE BRIEFLY BEHIND THE
FRONT SOMETIME EITHER LATE TUE OR ERY WED.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TO 6 PM EDT SUNDAY FOR
     ANZ530>543.

&&

$$
SYNOPSIS...AEB
NEAR TERM...JE/AEB
SHORT TERM...JRK
LONG TERM...JRK
AVIATION...JE/AEB/JRK
MARINE...AEB/JRK





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