Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 201358
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
958 AM EDT SUN APR 20 2014

.SYNOPSIS...
HIGH PRESSURE OVER QUEBEC WILL BUILD INTO THE AREA TODAY AND MONDAY.
A COLD FRONT WILL BRING SHOWERS TO THE AREA TUESDAY AND TUESDAY
NIGHT. HIGH PRESSURE BUILDS BACK IN FOR THE SECOND HALF OF THE WORK
WEEK.

&&

.NEAR TERM /TODAY AND TONIGHT/...
DEFORMATION BAND BETWEEN LOW PRESSURE OFF THE CAROLINA COAST AND HIGH
PRESSURE OVER NEW ENGLAND IS THINNING THIS MORNING. SUNSHINE WILL
BE ABUNDANT BY EARLY AFTERNOON AND TEMPERATURES WILL WARM INTO THE
MID 60S METRO AREAS TO 70S WEST AND SOUTH. UNDER HIGH
PRESSURE...SKIES WILL CLEAR AND WIND WILL BE LIGHT. RADIATIONAL
COOLING WILL DROP TEMPERATURES INTO THE 30S EVEN IN THE METRO AREAS
OVERNIGHT. THE MAV GUIDANCE IS THE COOLEST WITH TEMPERATURES BELOW
32 DEGREES OUT IN FREDERICK CO MD AND FAUQUIER CO VA TONIGHT WHILE
OTHER GUIDANCE IS WARMER. WE WILL EVALUATE THE NEED FOR A FROST
ADVISORY IN THE AFTERNOON PACKAGE.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
MONDAY WHILE WE ARE EXPERIENCING ANOTHER QUIET WX DAY ACROSS THE
REGION...A COUPLE OF FAST-MOVING SHORTWAVES WILL BE DRIFTING ACROSS
SRN CANADA. THE WRN SHORTWAVE WILL BE SLIDING TOWARD THE NRN PLAINS
AND WILL PICK UP A DISSIPATING CUT OFF LOW OVER THE CNTRL PLAINS.
COMBINING THE MOISTURE FROM THE TWO AND PHASING THEM INTO ONE MUCH
LONGER SHORTWAVE TROUGH WILL OCCUR DURING THE DAYTIME HRS ON MON.
THIS WAVE WILL BE A SERIES OF SMALLER ZONES OF FORCING/LIFT - SO NOT
A STEADY LINE OF CONVECTION OR STRATIFORM PRECIP BUT INSTEAD MERELY
BATCHES OF THEM ALL ALONG THE TROUGH AXIS. BY LATE MON...THE TROUGH
AXIS WILL BE ON THE DOORSTEP OF THE APLCNS...READY TO THRU OUR
REGION ON TUE. BEFORE THEN...WE`LL TOP OUT AGAIN IN THE U60S/L70S
OVER THE AREA ON MON AFTN FOR DAYTIME HIGHS. TEMPS AHEAD OF THE
UPPER TROUGH WILL ONLY DROP INTO THE L50S MON NIGHT.

AS LOW LEVEL MOISTURE INCREASES AHEAD OF THE TROUGH PASSAGE EARLY
TUE...IT WILL HELP TO ADD SOME INSTABILITY - ALONG W/ ANOTHER
RELATIVELY WARM DAY. CLOUDS WILL STREAM OVER THE REGION IN EARNEST
TUE MRNG...WHICH MAY LIMIT HEATING A FEW DEGREES ULTIMATELY AND HELP
SLIGHTLY INHIBIT A STRONGER CONVECTIVE POTENTIAL FOR THE DAY. ONLY A
COUPLE HUNDRED J/KG OF CAPE APPEARING ON AREA MODELS SOUNDINGS FOR
TUE...FOR MULTIPLE MODELS AND OVER THE BEST POTENTIAL PART OF THE
DAY FOR TSTMS. UNLIKE THE OTHER CONVECTIVE AND A FEW NON-CONVECTIVE
EVENTS SO FAR THIS YEAR...SHEAR WILL BE LACKING - LESS THAN 20KT
BULK AND MEAN LAYER SHEAR AT THE HEIGHT OF THE AFTN HEATING. ADD TO
THAT THE LATEST MODEL TREND OF NEARLY DISINTEGRATING THE PRECIP
ALONG THE SFC BOUNDARY AS IT HAS MOVED ACROSS OUR AREA LATE TUE
AFTN/EVE. STILL SOME RESIDUAL ACTIVITY ACROSS DELMARVA AND THE
TIDEWATER TUE NIGHT....BUT A QUICK DROP OFF IN PRECIP CHANCES TOWARD
AND AFTER SUNSET.

A MODEST REGION OF SUBSIDENCE WILL THEN SPREAD ACROSS THE AREA ON
WED...BRINGING GUSTY NW WINDS AND DRIER/COOLER AIR. NOT NEARLY AS
POTENT AS THE STORM SYSTEM A WEEK AGO AT THE SAME TIME...BUT STILL
ONLY ALLOWING TEMPS TO RISE BARELY INTO THE L60S ACROSS MUCH OF THE
AREA W/ A BRISK 15-25MPH NW WIND. A POTENT CUT-OFF UPPER LOW OVER
THE NRN ROCKIES WILL LOSE SOME OF ITS PUNCH AS IT SLIDES EAST OF THE
MISS RVR LATE THIS WEEK...AS HIGH PRESSURE AGAIN GIVES THE MID ATLC
ANOTHER QUIET WX DAY ON THU. ANOTHER COLD AND CLOSED UPPER LOW WILL
BARREL ACROSS THE NRN PLAINS AND THE GREAT LAKES THU INTO FRI. BY
THE TIME THE TAIL END OF THE ASSOCIATED COLD FRONT SWINGS ACROSS THE
REGION...IT SHOULD BE LOSING MUCH OF ITS PRECIP W/ ONLY SCATTERED
BATCHES MOVING ACROSS THE AREA FRI INTO SAT.

&&

.AVIATION /14Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS XPCD TDA THRU MON MRNG. HIGH PRESSURE WILL BRING
CLEAR SKIES BEFORE HIGH CLOUDS INCREASE OVER THE AREA LATER
TONIGHT - JUST AHEAD OF ANOTHER STORM SYSTEM. THE FRONTAL SYSTEM
LOOKS RELATIVELY WEAK FOR TUE AFTN/EVE...THOUGH A FEW TSTMS ACROSS
STILL POSSIBLE FOR SCATTERED AREAS OF THE MID ATLC REGION. THE
FRONTAL SYSTEM WILL THEN WORK ITS WAY OFF THE COAST INTO THE LATE
NIGHT HRS. HIGH PRESSURE AND SOME GUSTY NW WINDS ON WED - QUIETING
DOWN OUR WX FOR THU BRIEFLY BEFORE A FRONTAL BOUNDARY SWEEPS THRU
THE AREA ON FRI.

&&

.MARINE...
SCA CONDITIONS IN PLACE AS THE PRES GRAD BTWN THE SERN CSTL LOW AND
THE NERN HIGH PRES GROWS STRONGER. SCA IS IN EFFECT FOR THE DAYLIGHT
HRS THEN WINDS WKN TNGT.

WINDS WILL SLACK OFF OVER THE WATERS BY EARLY TUE...AS THE CENTER OF
SFC HIGH MOVES OFF THE COAST AND WINDS TURN SLY. A COLD FRONT WILL
PUSH THRU THE REGION LATE TUE...BRINGING SOME SCATTERED SHOWERS AND
POSSIBLY SOME ISOLATED TSTMS JUST SOUTH OF THE METRO DC AREA. BREEZY
NW WINDS OF WED AFTN...THOUGH HIGH PRESSURE WILL AGAIN OVERTAKE THE
REGION FOR THE SECOND HALF OF THE WEEK.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR ANZ530-
     535-536-538>540.
     SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR
     ANZ531>534-537-541>543.

&&

$$
SDG/WOODY







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