Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 161947
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
247 PM EST TUE DEC 16 2014

.SYNOPSIS...

A COLD FRONT OVER WEST VIRGINIA WILL CROSS THE AREA THIS EVENING.
HIGH PRESSURE BUILDS IN TONIGHT AND REMAINS FOR THE SECOND HALF OF
THE WEEK...BRINGING MAINLY DRY CONDITIONS. THE EXCEPTION WILL BE
POSSIBLE RAIN AND SNOW SHOWERS WEST OF THE ALLEGHENY FRONT TONIGHT
THROUGH WEDNESDAY NIGHT. LOW PRESSURE MAY BRING A WINTRY MIX TO
THE AREA THIS WEEKEND.

&&

.NEAR TERM /TONIGHT/...

MAIN AREA OF RA MOVG ONTO THE DELMARVA. IN ITS WAKE THE RMDR OF
THE AFTN WL BE CLDY. ANOTHER AREA OF RW WL BE MOVG INTO THE
HIGHLANDS AFTR 4 PM...REACHING THE BAY ARND 10 PM...BUT AMTS W/
THIS WL BE LGT - PERHAPS A FEW HUNDREDTHS OF AN INCH AT BEST.
THERE IS A THIN BAND OF CLRG SKIES ACROSS THE SHEN VLLY...BUT BLV
THAT WL CLOSE IN FAIRLY QUICKLY. SKIES XPCTD TO BE CLDY TNGT...W/
SOME CLRG PSBL LATE TNGT AS HIGH PRES BEGINS TO BUILD INTO THE
AREA.

UPSLOPE SHRA PSBL IN THE HIGHLANDS...LIQUID VARIETY.

LOWS 35-40.

&&

.SHORT TERM /WEDNESDAY/...

HIGH PRES BUILDS INTO THE AREA WED CREATING M SUNNY SKIES AND BRZY
CONDS. COMFORTABLE TEMPS FOR MID DEC - E OF THE BLUE RDG SHOULD
SEE HIGHS IN THE L50S. UPSLOPE CONDS TO CONT IN THE HIGHLANDS WHICH
COULD BRING SCT SNSH. LTL TO NO ACCUM XPCTD.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...

LOW PRESSURE AT THE SURFACE AND ALOFT WILL CONTINUE TO SLOWLY SPIN
INTO THE CANADIAN MARITIMES WEDNESDAY NIGHT AND THURSDAY...WHILE
HIGH PRESSURE BUILDS SOUTHEAST FROM THE UPPER MIDWEST. A FAST ZONAL
UPPER LEVEL JET WILL STRETCH FROM TEXAS ACROSS THE MID SOUTH.
THEREFORE NO SIGNIFICANT WEATHER MAKERS OR WEATHER CHANGES. FORECAST
SOUNDINGS STILL SHOW A SHALLOW SATURATED LAYER WITHIN THE UPSLOPE
FLOW OVER THE MOUNTAINS THROUGH WEDNESDAY NIGHT. USED SNOW
SHOWER/FLURRIES WORDING IN THE GRIDS...BUT COULD ALSO BE DZ/FZDZ.
LOWS NEAR OR BELOW FREEZING ACROSS THE AREA.

A WEAK MID LEVEL SHORTWAVE WILL APPROACH FROM THE WEST LATE THURSDAY
AFTERNOON AND INTO THE OVERNIGHT HOURS. THIS WILL LIKELY INCREASE
MID AND HIGH LEVEL CLOUDS...WHICH MAY HELP MUTE HIGH TEMPERATURES IN
THE 40S. HOWEVER SOME MIXING WILL OCCUR AND ENOUGH GRADIENT STILL IN
PLACE TO HAVE SOME GUSTS ABOVE 20 KT. HOWEVER OVERALL TRANQUIL
WEATHER WHICH WILL CONTINUE INTO THURSDAY NIGHT...WITH LOWS FALLING
BACK DOWN TO NEAR FREEZING.

THE LONG TERM PERIOD WILL START OUT WITH A FAIRLY SEASONABLE DAY ON
THURSDAY. TEMPS MAY BE JUST A COUPLE OF DEGREES BELOW NORMAL THANKS
TO CANADIAN HIGH PRESSURE RIDGING INTO THE MID-ATLANTIC...BUT WITH
WEAK RIDGING/ZONAL FLOW ALOFT THERE SHOULD BE ENOUGH SUNSHINE TO
KNOCK OFF SOME OF THE CHILL DURING THE DAY.

HIGH PRESSURE WILL BEGIN TO RETREAT TO THE NORTH ON FRIDAY AS A
STRONG SHORTWAVE MOVING ACROSS THE MIDDLE OF THE COUNTRY DEVELOPS
SURFACE LOW PRESSURE NEAR THE TEXAS GULF COAST. MODELS REALLY BEGIN
TO DIVERGE IN SOLUTIONS AT THIS POINT. THE PRIMARY VARIANCE INVOLVES
THE STRENGTH OF THE SHORTWAVE TROUGH AS IT CONTINUES ITS MARCH
ACROSS THE EASTERN CONUS. DETERMINISTICALLY...THE EURO HAS A MUCH
MORE AMPLIFIED SHORTWAVE...WHILE THE GFS NEARLY ELIMINATES THE
SHORTWAVE ALTOGETHER...AND THE STRENGTH OF THE SURFACE LOW REFLECTS
THIS WITH THE EUROS SURFACE LOW BEING NEARLY 20 MB DEEPER AT 06Z
SUNDAY OVER SOUTHEAST VIRGINIA. WITHIN THE ENSEMBLE MEMBERS OF BOTH
MODELS THERE ARE RUNS THAT RESEMBLE THE DETERMINISTIC RUNS OF THE
OPPOSITE MODEL...SO BOTH SOLUTIONS REMAIN POSSIBLE...WITH SOME
SOLUTION IN BETWEEN BEING MOST LIKELY.

DESPITE THE LARGE SPREAD AMONGST GLOBAL MODELS...THERE ARE SOME
ASPECTS THAT WE CAN BE PRETTY CONFIDENT ABOUT. CLOUD COVER WILL
BEGIN TO INCREASE FRIDAY NIGHT AS MOISTURE ADVECTS IN AHEAD OF THE
APPROACHING LOW FRIDAY NIGHT. MOST OF THE AREA WILL LIKELY SEE SOME
FORM OF PRECIP SATURDAY AND SATURDAY NIGHT AS THE LOW CENTER PASSES
NEAR THE AREA. AS EXPECTED...THERE IS UNCERTAINTY IN P-TYPE AT THIS
POINT...BUT HIGHER ELEVATIONS WILL HAVE A BETTER CHANCE AT SNOW THAN
LOW ELEVATIONS...SO GENERALLY STUCK WITH MOSTLY SNOW ACROSS THE
WESTERN PORTION OF THE CWA WITH MORE OF A MIX BAG OF WINTRY PRECIP
FOR THE EASTERN PORTION.

HIGH PRESSURE WILL BUILD BACK INTO THE AREA SUNDAY AND TEMPS WILL BE
SLIGHTLY BELOW NORMAL WITH DRY CONDITIONS TO BEGIN NEXT WEEK.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...

LOW CLDS/VSBYS WL BE SLOW TO IMPROVE FOR THE RMDR OF THE AFTN. CD
FNT WL CROSS THE RGN THIS EVE. SCT RW WL BE PSBL THIS EVE THEN
IMPRVG CIGS/VSBY OVRNGT.

BRZY W WINDS XPCTD WED. VFR CONDS.

VFR CONDITIONS WEDNESDAY NIGHT-THURSDAY NIGHT. WNW WIND GUSTS ABOVE
20 KT POSSIBLE DURING THE DAYLIGHT HOURS OF THURSDAY.

MVFR AND IFR CONDITIONS ARE POSSIBLE IN SHOWERS AND LOW CEILINGS A
LOW PRESSURE PASSES NEAR THE AREA SATURDAY.

&&

.MARINE...

NO PROBS FORESEEN ON THE WATERS TNGT. HIGH PRES WL BLD INTO THE
WATERS WED. AS A RESULT WIND ARE XPCTD TO GUST 20-25 KT. SCA HAS
ALREADY BEEN ISSUED FOR THIS.

WINDS WILL DIMINISH WEDNESDAY EVENING WITH CONFIDENCE NOT HIGH
ENOUGH AT THIS TIME TO EXTEND THE SCA. A SCA IS LIKELY DURING
DIURNAL MIXING OF GUSTY WNW FLOW ON THURSDAY OVER PORTIONS IF NOT
ALL OF THE WATERS. WINDS DIMINISH AGAIN THURSDAY EVENING.

A SMALL CRAFT MAY BE NEEDED INTO THE DAY THURSDAY IN BREEZY
NORTHWEST WINDS. A SMALL CRAFT ADVISORY WILL LIKELY BE NEEDED
SATURDAY AS LOW PRESSURE PASSES NEAR THE AREA.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...NONE.
VA...NONE.
WV...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 11 AM TO 6 PM EST WEDNESDAY FOR
     ANZ530>534-538>543.

&&

$$
PRODUCTS...WOODY!/ADS/CEB





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