Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 010856
AFDLWX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
356 AM EST SUN FEB 1 2015

.SYNOPSIS...
LOW PRESSURE MOVES THROUGH THE REGION THROUGH MONDAY. HIGH PRESSURE
WILL RETURN FOR THE FIRST HALF OF THE WEEK. A COLD FRONT IS
EXPECTED TO MOVE INTO THE REGION WEDNESDAY NIGHT.
&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SFC HIGH PUSHING EAST THIS MORNING AS THE NEXT LOW PRESSURE SYSTEM
APPROACHES FROM THE WEST. LIGHT RETURNS CURRENTLY APPEARING ON RADAR
JUST TO THE WEST...ASSOCIATED WITH THE INITIAL SURGE OF ISENTROPIC
LIFT AND A PASSING SHORTWAVE. HOWEVER...HIGH DEW PT DEPRESSIONS
RIGHT NOW SHOULD KEEP ANYTHING FROM REACHING THE GROUND. HAVE SLIGHT
CHC POPS FOR LIGHT SNOW OVER THE WESTERN ALLEGHENY FRONT...BUT NO
ACCUMULATION REALLY EXPECTED.

HEADING INTO TODAY...SOME DISCREPANCIES IN THE MODELS ON THE
HANDLING OF THE PCPN. THERE CONTINUES TO BE SOME SUGGESTION OF PCPN
DEVELOPMENT LATER THIS MORNING/EARLY AFTN...WHICH IF IT DOES
OCCUR...WOULD BE IN THE FORM OF LIGHT SNOW. HOWEVER...AGAIN A VERY
DRY AIRMASS NEEDS TO BE OVERCOME. SOUTHERLY FLOW SETS UP...BUT IS
WEAK...AND WITH THE LLJ NOT IN PLACE TILL TONIGHT...IT COULD VERY
WELL END UP BEING DRY ACROSS MUCH OF THE AREA DURING THE DAY. BEST
CHC FOR ANY PCPN WOULD BE ALONG THE MASON-DIXON LINE AND WEST OF THE
BLUE RIDGE.

HIGHER CONFIDENCE OF PCPN MOVING IN BY LATE THIS AFTN...AND HAVE
SPREAD POPS EAST AND SOUTH TO ACCOUNT FOR THIS. AS FOR P-TYPE...A
GOOD SURGE OF WAA FINALLY ARRIVES WITH THE SOUTHERLY FLOW...WHICH
WILL WORK TO PUSH BACK THE SNOW/RAIN LINE TO THE NORTH. INITIALLY
SHOULD SEE SLEET MIXING IN...THINKING MAINLY 20-00Z TIME PERIOD...AS
850MB TEMPS WARM UP QUICKER THAN SFC TEMPS. AREAS ALONG THE
MASON-DIXON LINE EXPECTED TO REMAIN SNOW...WITH UP TO AN INCH OF
SNOW PSBL.
&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
LOW PRESSURE MOVES INTO THE OHIO RIVER VALLEY BY 06Z THIS
EVENING...WITH THE BIGGEST SURGE OF WAA AND MOISTURE RIDING THE
SOUTHERLY FLOW OUT AHEAD OF THE LOW. THIS EVENING WILL BE THE
BIGGEST TRANSITION PERIOD FOR PCPN...AND ALSO THE LOWEST CONFIDENCE
OF P-TYPE AS THERE REMAINS SOME QUESTION AS TO HOW QUICKLY THE
WARMER AIR CAN ERODE THE PERSISTING COLD AIR...ESPECIALLY ALONG THE
MASON-DIXON LINE. USING A COMBINATION OF THE 00Z GFS AND NAM BUFKIT
SOUNDINGS...CONTINUED WITH THE MENTION OF FZRA CENTRAL AND WESTERN
MD...AND SOUTH INTO PORTIONS OF NORTHERN VA AND NORTHERN PARTS OF DC
METRO...WHERE TEMPS ARE HOVERING RIGHT NEAR FREEZING. CONFIDENCE
WOULD LEAN THAT IF ANYTHING THE TEMPS WARM UP QUICKER...AND THUS A
SHORTER TIME PERIOD OF FZRA. BUT WITH THE POTENTIAL FOR AT LEAST A
PERIOD OF FZRA RESULTING IN A TRACE TO A COUPLE HUNDREDTHS OF AN INCH
OF ICE...HAVE GONE AHEAD AND EXTENDED THE WINTER WEATHER ADVISORY TO
INCORPORATE NW HOWARD...NW MONTGOMERY...WESTERN LOUDOUN...AND THE
REMAINDER OF THE EASTERN WV PANHANDLE...AS WELL AS
HAMPSHIRE...FREDERICK VA...AND CLARKE. WHILE THE TIMING OF THE
ADVISORY CURRENTLY EXISTS FROM THIS AFTN THROUGH TONIGHT...THE MAIN
POTENTIAL FOR ICE ACCUM WILL BE BETWEEN 23-09Z TONIGHT.
ELSEWHERE...PCPN CHANGES OVER TO ALL RAIN AS 850MB TEMPS WARM WELL
INTO THE SINGLE DIGITS ABV ZERO...AND BUFKIT SOUNDINGS INDICATING
WET BULBING FINALLY BEING ACHIEVED BY 06Z. WITH MULTIPLE SHORTWAVES
WORKING THROUGH TONIGHT AS THE SFC LOW PASSES OVER THE
MID-ATLANTIC...CAN EXPECT PERIODS OF MODERATE TO HEAVY PCPN.

THE SFC LOW PUSHES OFF THE NJ COAST BY MIDDAY MONDAY...WHILE THE
STRONG UPPER LEVEL TROUGH FINALLY SWINGS THROUGH THE REGION MONDAY
AFTN. CONTINUED POPS EVERYWHERE FOR MONDAY MORNING...THEN TAPERED
OFF FROM WEST TO EAST...WITH THE THINKING ALL PCPN SHOULD CLEAR THE
AREA BY MONDAY EVENING EXCEPT WITH THE CHC FOR UPSLOPE SNOW SHOWERS.
STRONG SURGE OF CAA WITH THE NW FLOW ON THE BACKSIDE OF THE LOW WILL
INCREASE WINDS BY MONDAY AFTN...WITH GUSTS INTO THE 20S. THIS WILL
ALSO RESULT IN A NON-DIURNAL TEMP TREND...MAINLY FOR WESTERN AREAS
AS THEY WILL SEE THEIR DAYTIME HIGHS IN THE MORNING. OVER THE
EASTERN AREAS...BEFORE THE CAA MOVES IN...COULD SEE HIGHS IN THE
UPPER 40S.
&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
STRONG NW FLOW KICKS IN MON EVENING AS CSTL LOW BOMBS OUT OFF CAPE
COD. THE COMBO OF A TIGHTENING P-GRAD AND GOOD MIXING FM CAA WL
EASILY PROVIDE MEAN MIXED LYR WINDS GREATER THAN 30 KT. THIS
GRADIENT WL BE SUBSIDING/DCPLG SLIGHTLY THRU THE EVNG...BUT IT WL
STILL BE A BRZY /AND CHILLY/ NGT. SCT LINGERING UPSLP SHSN AT START
OF PD WL DIMINISH AS HIPRES BLDS. WL HV PT-MOCLDY INTHE MTNS BUT CLR
ELSW. TEMP GDNC NOT QUITE AS COLD AS PRVS RUNS. WL LEAN ON THE
COOLER SIDE OF LTST DATA. WIND CHILLS NOT TO ADVY LVL...BUT SINGLE
DIGITS SHUD BE COMMON.

HIPRES WL BE NEARBY TUE...W/ RETURN FLOW BGNG TUE NGT. H8 THERMAL
TROF STILL AN INFLUENCE TUE /-10 TO -12C/. MAXT ADJUSTMENTS
MINIMAL...MAYBE A DEGF OR TWO HIER ACRS MD/NRN VA. CENTRL VA THE
ONLY PLACE THAT SAFELY WL GET ABV FRZG. MIN-T TUE NGT WONT BE QUITE
AS HARSH...DUE PARTLY TO A BLDG MID CLD DECK.

LOPRES IN THE NRN STREAM DROPS FM S-CENTRAL CNDA ACRS NEW ENGLAND
WED-WED NGT. ITS NOT EXACTLY CLEAR HOW MUCH MSTR WL BE ASSOCD W/
IT...BUT FOR THE MID ATLC ITS OUTPACING ANY UPA SUPPORT. THEREFORE
WL BE BANKING ON A SYSTEM THAT WL BE STRUGGLING TO PRODUCE PCPN ON
ITS OWN. AFTER A RELATIVELY MILD DAY WED...WL BE KEEPING SCHC SNW
CONFINED TO THE MTNS WED NGT.

TEMPS WL BE DROPPING THU /15 DEGF COOLER THAN MAXT WED/...WHICH CUD
PROVIDE AN ENVIRONMENT FOR DIURNAL SHSN. TOO FAR OUT TO PINPOINT
CVRG...BUT IT WUD BE A SITUATION FOR BRIEF...MINIMAL ACCUM /IF
ANY/...BUT SUDDEN ONSET SHSN. WL HV MID-RANGE CLDS AND LOW END POPS.

HIPRES SHUD CLOSE OUT THE WEEK. NO OTHER HAZARDS ANTICIPATED ATTM.
TEMPS GRADUALLY MODERATING TWD CLIMO...BUT NOT SURE IF WE WL GET
THERE.
&&

.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS THIS MORNING. CONDITIONS DIMINISH AS THE PCPN MOVES
IN...WITH IFR BCMG LIKELY BY SUN NIGHT WITH THE HEAVIEST PCPN.
INITIAL PCPN -SN/PL/RA MIX...BCMG ALL RAIN TONIGHT EVERYWHERE.
TRANSITION TIMING IN TAFS COULD BE +/- 2 HOURS. ANY SNOW ACCUMS AT
THE TERMINALS TODAY WOULD BE LESS THAN ONE INCH.

S WINDS LESS THAN 10 KTS TODAY/TONIGHT WILL SHIFT TO THE NW MONDAY
AND INCREASE...WITH GUSTS MIXING IN BY MONDAY AFTN. VFR CONDITIONS
AS WELL BY MONDAY AFTN AS THE PCPN EXITS THE REGION.

VFR SHUD PREVAIL MON NGT THRU AT LEAST WED. BIGGEST IMPACT WL BE THE
WINDS MON NGT...WHICH WL BE FM THE NW AND MAY GUST UP TO 35-40 KT
DURING THE EVNG PUSH.

ANOTHER CDFNT WL CROSS LT WED. MAY HV WIDELY SCT SHSN REDUCING VSBY
ON THU...ALONG W/ MORE GUSTY WINDS.
&&

.MARINE...
SUB-SCA CONDITIONS ON ALL THE WATERS THROUGH 06Z TONIGHT. HAVE
ISSUED A SCA OVER THE CENTRAL CHESAPEAKE BAY AND THE LOWER UPPER
TIDAL POTOMAC TO ACCOUNT FOR INCREASING SOUTHERLY FLOW LATE
TONIGHT...AND THEN NW FLOW BY TOMORROW AFTN. PSBL LULL IN THE SCA
GUSTS AS THE WINDS SHIFT...BUT THIS WILL BE SHORT LIVED.

AS CSTL LOPRES STRENGTHENS LT MON...IT WL INCREASE THE P-GRAD.
COMBINED W/ DEEPENING FVRBL MIXING IN CAA...WINDS SHUD EXHIBIT A
MARKED INCREASE LATE MON AFTN INTO MON NGT. WL HV MEAN 35-40 KT W/IN
THE MIXED LYR. HV RAISED GLW FOR THE 2ND HALF OF THE AFTN INTO THE
EVNG. SCA CONDS WL CONT THEREAFTER...AND MAY LEAK INTO TUE. BLDG
HIPRES WL GRDLY RESULT IN DIMINISHING WINDS.
&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...NONE.
MD...WINTER WEATHER ADVISORY FROM NOON TODAY TO 8 AM EST MONDAY FOR
     MDZ003-501-502.
     WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 8 AM EST
     MONDAY FOR MDZ004>006-503-505-507-508.
VA...WINTER WEATHER ADVISORY FROM NOON TODAY TO 8 AM EST MONDAY FOR
     VAZ028-031.
     WINTER WEATHER ADVISORY FROM 3 PM THIS AFTERNOON TO 8 AM EST
     MONDAY FOR VAZ505.
WV...WINTER WEATHER ADVISORY FROM NOON TODAY TO 8 AM EST MONDAY FOR
     WVZ050>053-503-504.
MARINE...GALE WARNING FROM 3 PM MONDAY TO 1 AM EST TUESDAY FOR
     ANZ530>543.
     SMALL CRAFT ADVISORY FROM 1 AM TO 3 PM EST MONDAY FOR ANZ533-
     534-537-542-543.

&&

$$
SYNOPSIS...SEARS/HTS
NEAR TERM...SEARS
SHORT TERM...SEARS
LONG TERM...HTS
AVIATION...SEARS/HTS
MARINE...SEARS/HTS







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