Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 250747
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
347 AM EDT FRI APR 25 2014

.SYNOPSIS...
HIGH PRESSURE WILL MOVE OFF THE COAST TODAY AND A COLD FRONT WILL
PASS THROUGH THIS EVENING. ANOTHER COLD FRONT WILL PASS THROUGH THE
AREA LATE SATURDAY INTO SATURDAY NIGHT BEFORE HIGH PRESSURE RETURN
FOR SUNDAY. CUTOFF LOW PRESSURE WILL DEVELOP OVER THE CENTRAL CONUS
EARLY NEXT WEEK AND IT WILL LIKELY CAUSE UNSETTLED CONDITIONS ACROSS
THE MID-ATLANTIC DURING THIS TIME.
&&

.NEAR TERM /THROUGH TONIGHT/...
A POTENT SHORTWAVE AND ITS ASSOCIATED SURFACE LOW ARE MOVING INTO
THE MIDWEST THIS MORNING WHILE HIGH PRESSURE REMAINS ALONG THE
MID-ATLANTIC COAST. THE SHORTWAVE AND ITS ASSOCIATED LOW WILL MOVE
THROUGH THE OHIO VALLEY THIS MORNING BEFORE MOVING INTO UPSTATE NEW
YORK THIS EVENING. THE COLD FRONT ASSOCIATED WITH THE SURFACE LOW
WILL MOVE INTO OUR AREA DURING THIS TIME.

A SOUTHERLY FLOW WILL INCREASE AHEAD OF THE COLD FRONT...ALLOWING
FOR WARM AND MOIST AIR TO MOVE INTO THE REGION. GUIDANCE CONTINUES
TO TREND A BIT SLOWER AND STRONGER WITH THIS SYSTEM...WHICH WILL
ALLOW FOR DEEPER MOISTURE TO ADVECT INTO THE AREA AHEAD OF IT.
THEREFORE...WIDESPREAD SHOWERS ARE EXPECTED ACROSS THE ENTIRE AREA.
THE BEST CHANCE FOR PRECIPITATION WILL BE FROM MID-MORNING THROUGH
THROUGH THIS AFTERNOON WEST OF THE BLUE RIDGE MOUNTAINS...AND FROM
THIS AFTERNOON INTO THIS EVENING EAST OF THE BLUE RIDGE MOUNTAINS.

THERE WILL BE ENOUGH WARM AND MOIST AIR FOR SOME INSTABILITY TO
DEVELOP AS WELL. THEREFORE...A FEW THUNDERSTORMS CANNOT BE RULED
OUT. THE AMOUNT OF INSTABILITY THAT DEVELOPS IS STILL UNCERTAIN AT
THIS TIME...BUT GUIDANCE CONTINUES TO BRING HIGHER AMOUNTS OF
INSTABILITY FARTHER NORTH INTO SOUTHERN PORTIONS OF OUR CWA. LATEST
NAM/GFS BUFKIT SHOW AROUND 300-600 J/KG OF MLCAPE DEVELOPING ACROSS
CENTRAL VIRGINIA WITH LITTLE TO NO INHIBITION. GIVEN THE POTENT
DYNAMICS FROM THE SHORTWAVE...SHEAR PROFILES SUPPORT THE POTENTIAL
FOR SEVERE WEATHER...INCLUDING AN ISOLATED THREAT FOR TORNADOES
SHOULD STORMS BE ROOTED WITHIN THE BOUNDARY LAYER. THE BEST CHANCE
FOR SEVERE/ISOLATED TORNADOES WILL BE FROM MID-AFTERNOON INTO EARLY
THIS EVENING ACROSS CENTRAL VIRGINIA INCLUDING THE VIRGINIA
PIEDMONT.

MAX TEMP FORECAST REMAINS TRICKY GIVEN EXPECTED CLOUD COVER AND
PRECIPITATION. MAX TEMPS WILL MOST LIKELY RANGE FROM THE UPPER 50S
IN THE MOUNTAINS TO THE MID AND UPPER 60S ACROSS MOST OTHER
LOCATIONS. SOME WARMER AIR MAY WORK ITS WAY INTO CENTRAL
VIRGINIA...CAUSING MAX TEMPS TO REACH INTO THE 70S.

THE COLD FRONT WILL MOVE OFF TO OUR EAST BY MIDNIGHT...BUT LOW
PRESSURE WILL INTENSIFY ALONG THE FRONT...CAUSING A PERIOD OF WINDY
CONDITIONS BEHIND THE FRONT. MIN TEMPS WILL RANGE FROM THE 40S IN
THE MOUNTAINS TO THE LOWER AND MIDDLE 50S IN DOWNTOWN WASHINGTON AND
BALTIMORE.
&&

.SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
ANOTHER COLD FRONT WILL APPROACH THE REGION FROM THE NORTH SATURDAY.
A DOWNSLOPING WESTERLY FLOW IS EXPECTED AHEAD OF THE FRONT...SO IT
WILL LIKELY TURN OUT TO BE A WARM AFTERNOON. A DEEP MIXING LAYER
ALONG WITH SOME SUNSHINE AND THE DOWNSLOPING FLOW SHOULD ALLOW FOR
MAX TEMPS TO REACH THE 70S ACROSS MOST LOCATIONS...WITH SOME AREAS
IN CENTRAL VIRGINIA TOPPING OFF AROUND 80 DEGREES.

MOISTURE WILL BE LIMITED AHEAD OF THE FRONT...BUT THERE WILL BE SOME
INSTABILITY DUE TO THE WARMER CONDITIONS. THEREFORE...A CU DECK WILL
DEVELOP WITH SKIES TURNING OUT PARTLY TO MOSTLY CLOUDY BY THE
AFTERNOON. THERE WILL BE ENOUGH INSTABILITY AHEAD OF THE FRONT FOR
SOME SHOWERS TO DEVELOP ACROSS THE NORTHERN AND CENTRAL PORTIONS OF
THE CWA...BUT RAINFALL AMOUNTS WILL BE LIGHT DUE TO LOW-LEVEL DRY
AIR.

AS THE LOW SPIRALS ACRS THE NERN CONUS SAT EVE...THE CDFNT WL SWING
ACRS THE CWFA. BAROCLINICITY/INSTABILITY STILL SEEMS TO BE FVRBL TO
SQUEEZE OUT A LTL QPF ALONG/AHD OF THE BNDRY. A FEW SPRINKLES...
MAYBE? MDL FIELDS PICKING UP ON THIS MORE THAN MOS. WL CONT
THOUGHT PROCESS FM THE AFTN...CARRYING 30 POPS ACRS SRN MD/NRN VA
PIEDMONT ELY EVNG. AFTER THAT...SAT NGT WL BE ALL ABT THE CAA.
SKIES SHUD BE CLRG QUITE EFFICIENTLY IN NW FLOW AS DEWPTS DROP
INTO THE 30S. DIURNALLY...ITS NOT TIMED APPROPRIATELY FOR MIXING
THRU THE NGT. HV A GUSTY EVNG /MDL SNDGS SUGGEST G20KT/ BEFORE
DCPLG STARTS TO TAKE HOLD.

RDGG WL BUILD INTO CWFA SUN-SUN NGT. H8 TEMPS WL BE COOLER THAN
SAT...BY AS MUCH AS 6C. HV MAXT ARND 10 DEGF LWR...IN LINE W/ A MDL
BLEND. CLR SKIES DURING THE DAY WL FADE BY NGT AS MID-LVL MSTR
ADVECTS THIS WAY.
&&

.LONG TERM /MONDAY THROUGH THURSDAY/...
GFS HAS 500 MB RIDGE AXIS BLDG OVR AREA ERY NEXT WEEK BEFORE MVG
OFSHR TUESDAY NIGHT. MANY CHCS OF WETNESS DURG THE MIDWEEK
TIMEFRAME - AREAS OF SUPPORTING VORT ENTERING RGN TUESDAY
AFTN...WEDNESDAY MRNG THROUGH THURSDAY MRNG AND AGAIN FRIDAY MRNG.
SEEMS HPC ENSEMBLE IS MVS SYS E ARND 12 HRS FASTER THAN GFS/ECMWF.
CLOSED 500 MB LOW WL REMAIN CENTERED OVR NRN PLAINS/GT LAKES AREA
THROUGH THE PD. EURO IS IMPLYING A CAD WEDGE WL DVLP WED. THIS
WOULD HELP IN KEEPING TEMPS BLO NRML...PSBLY HIGHS ONLY IN THE
50S!

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
CIGS/VSBYS WILL DETERIORATE TO MVFR/IFR LEVELS LATE THIS MORNING
INTO THIS AFTERNOON AHEAD OF A COLD FRONT. SHOWERS ARE EXPECTED
ALONG WITH THE CHANCE FOR THUNDERSTORMS. THERE IS A THREAT FOR
SEVERE THUNDERSTORMS THIS AFTERNOON INTO EARLY THIS
EVENING...ESPECIALLY ACROSS KCHO.

CIGS/VSBYS WILL IMPROVE BY MIDNIGHT AS THE COLD FRONT MOVES OFF TO
OUR EAST LATER THIS EVENING. HOWEVER...THERE WILL BE A PERIOD OF
GUSTY WEST-NORTHWEST WINDS. GUSTS AROUND 30 TO 35 KNOTS ARE POSSIBLE
FOR A FEW HOURS BEHIND THE FRONT LATE TONIGHT.

ANOTHER COLD FRONT WILL APPROACH FROM THE NORTH SATURDAY. A DEEP
MIXING LAYER WILL ALLOW FOR GUSTY WESTERLY WINDS AROUND 20 TO 30
KNOTS DURING THE AFTERNOON. A FEW SHOWERS CANNOT BE RULED OUT
SATURDAY AFTERNOON.

VFR ANTICIPATED REST OF THE WKND. HWVR...THE PTNL EXISTS FOR LOW
CIGS/VSBYS DURG THE FIRST HALF OF NEXT WK DUE TO RA.
&&

.MARINE...
A SOUTHERLY FLOW WILL INCREASE AHEAD OF A COLD FRONT TODAY. A SMALL
CRAFT ADVISORY IS IN EFFECT FOR THE WATERS THIS AFTERNOON. THE COLD
FRONT WILL PASS THROUGH THE WATERS THIS EVENING AND GUSTY NORTHWEST
WINDS ARE EXPECTED FOR A FEW HOURS BEHIND THE FRONT LATE TONIGHT. A
GALE WARNING IS IN EFFECT FOR THE WATERS LATE TONIGHT.

SHOWERS ARE EXPECTED THIS AFTERNOON INTO THIS EVENING AHEAD OF THE
COLD FRONT. A FEW THUNDERSTORMS CANNOT BE RULED OUT...ESPECIALLY
ACROSS THE LOWER TIDAL POTOMAC RIVER AND MIDDLE PORTION OF THE
MARYLAND CHESAPEAKE BAY.

ANOTHER COLD FRONT WILL APPROACH THE WATERS SATURDAY FROM THE NORTH.
A DEEP MIXING LAYER WILL ALLOW FOR GUSTY WESTERLY WINDS. A SMALL
CRAFT ADVISORY WILL LIKELY BE NEEDED FOR THE WATERS AND A GALE
WARNING MAY BE POSSIBLE AS WELL.

CDFNT CLRS WATERS SAT NGT. WNDS SVRL THSND FT OFF DECK WUD SUPPORT
GLW...BUT NOT SURE THE MIXING WL BE PRESENT. ITLL DEPEND UPON HOW
QUICKLY COLD AIR MOVES ACRS WATERS...TO IMPROVE LAPSE RATES. AM
CARRYING A SOLID SCA INSTEAD. GLW PSBL CAN REMAIN IN THE HWO.

SHUD HV A CPL QUIET DAYS AFTER THAT /SUN-MON/. CONDS LOOKING UNSTLD
THEREAFTER.
&&

.TIDES/COASTAL FLOODING...
SOUTHERLY FLOW WILL STRENGTHEN AHEAD OF A COLD FRONT THROUGH THIS
EVENING. THIS WILL CAUSE TIDAL ANOMALIES TO SHARPLY INCREASE DURING
THIS TIME. SINCE THE HIGH TIDE WILL BE THE LOWER OF THE TWO
ASTRONOMICAL NORMS...MINOR FLOODING IS NOT EXPECTED TODAY.
HOWEVER...MINOR COASTAL FLOODING IS POSSIBLE LATE THIS EVENING INTO
THE OVERNIGHT HOURS DURING THE HIGHER OF THE TWO ASTRONOMICAL NORMS.

THE FLOW WILL TURN OFFSHORE LATE TONIGHT BEHIND THE FRONT AND IT
WILL BE STRONG. THEREFORE...ANY ELEVATED WATER LEVELS WILL QUICKLY
DROP BY SATURDAY MORNING.
&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO MIDNIGHT EDT TONIGHT
     FOR ANZ531>534-537-539>543.
     GALE WARNING FROM MIDNIGHT TONIGHT TO 6 AM EDT SATURDAY FOR
     ANZ530>543.
     SMALL CRAFT ADVISORY FROM NOON TODAY TO 8 PM EDT THIS EVENING
     FOR ANZ530-535-536-538.

&&

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







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