AFD from Thursday afternoon (don't think it's been posted)
000
FXUS61 KLWX 042006
AFDLWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
306 PM EST THU FEB 4 2010
.SYNOPSIS...
-- Changed Discussion --HIGH PRESSURE WILL MOVE AWAY FROM THE AREA TONIGHT. A STRONG WINTER
STORM IS EXPECTED TO IMPACT THE REGION FRIDAY INTO SATURDAY. HIGH
PRESSURE MAY RETURN BY MONDAY...BUT ANOTHER STORM WILL AFFECT THE
REGION TUESDAY.-- End Changed Discussion --
&&
.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
-- Changed Discussion --DENSE OVERHEAD CIRRUS IS A SIGN OF THE INCOMING LOW PRESSURE
SYSTEM AND PRECURSOR TO WINTRY END TO THE WEEK ACROSS THE MID-
ATLANTIC. TEMPS THIS AFTN HAVE RISEN INTO THE U30S AND L40S...
ALLOWING FOR SOME MELTING OF THE SNOW ACROSS THE REGION.
DEWPOINTS HAVE NOT DROPPED VERY MUCH AND WILL REMAIN FAIRLY STEADY
OVERNIGHT INTO EARLY FRIDAY. THIS WILL MODIFY TEMPS OVERNIGHT A
BIT...KEEPING LOWS IN THE M-U20S BUT ALSO KEEPING SFC TEMPS STEADY
INTO THE MORNING HRS JUST AHEAD OF THE STORM SYSTEM.-- End Changed Discussion --
&&
.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
-- Changed Discussion --MID-LVL CONFLUENCE ACRS NEW ENGLAND SHUD SUSTAIN LOW-LVL HIPRES
AND ASSOCIATED COLD AIR IN PLACE FOR MID-ATLC RGN. COMPACT BUT
STRONG SHRTWV TROF WILL MOVE ACRS MS RVR VLY FRI...WITH DEEP MSTR
SPREADING NEWD ON SWLY FLOW.
SFC LOPRES ASSOCIATED WITH THE SHRTWV TROF WILL MOVE ACRS AL AND
GA BFR EMERGING INTO THE ATLC NEAR THE NC/SC BORDER. COASTAL
LOPRES XPCD TO BOMB FRI NGT OVER COASTAL NC BFR DVLPG NNEWD TWD
HAMPTON ROADS AREA OF VA.
RESULT OF THIS MVMT WILL BE A VERY TIGHT PRESSURE GRADIENT AND
ENSUING STRONG NELY WINDS. HIGHEST WINDS XPCD FRI NGT THRU SAT
WITH GUSTS APRCHG 30KT IN COASTAL ZONES.
CONCERNING PCPN...SNOW XPCD TO FORM ACRS CNTRL FOOTHILLS...CNTRL
SHENANDOAH VLY AND SRN PORTIONS OF POTOMAC HIGHLANDS BY DAWN FRI.
SNOW WILL SPREAD NEWD ACRS RMNDR OF FCST AREA THRU FRI MRNG. EARLY
ONSET OF PCPN WILL LIMIT HEATING...AND MAXIMA FRI SHUD BE IN UPR
20S AND LWR 30S MOST AREAS.
AS UPR WAVE AND COASTAL SYSTEM APRCH...PCPN WILL BCM MDT TO HEAVY
BY LATE AFTN. SNOW TOTALS BY LATE FRI AFTN ARE XPCD TO BE IN 4-6
INCH RNG IN DC METRO AREA...UP TO ONE FOOT IN CNTRL SHENANDOAH VLY
AND CNTRL FOOTHILLS.
HEAVY SNOW XPCD AREAWIDE FRI NGT AS UPR SYSTEM MOVES ACRS. SFC LOW
MOVES NEWD ON SAT...AND SNOW BANDS XPCD TO DVLP ACRS DC/BALTIMORE
METRO AREAS IN DEFORMATION ZONE. ADDITIONAL MDT/HEAVY SNOW PSBL
SAT MRNG BFR ENTIRE SYSTEM MOVES AWAY AND SNOW INTENSITY WANES.
WINTER STORM WRNG FOR HEAVY SNOW CONTS THRU SAT EVE. HAVE ADJUSTED
SNOW TOTALS SLGTLY FROM PREV ISSUANCE...BUT SYNOPTIC EVOLUTION IS
SIMILAR TO PREV FCST. SOME VARIABILITY IN SNOW TOTALS FCST FOR SRN
MD AND ADJACENT PORTIONS OF VA WOULD BE PSBL IF SLEET DVLPS LATE
FRI NGT AS WARM AIR BRIEFLY WRAPS INTO SYSTEM. ATTM HAVE RETAINED
PRIMARILY SNOW FCST /WITH SNOW AND SLEET MIX INCLUDED IN GRIDS/...
BUT A PROLONGED PD OF SLEET COULD REDUCE TOTALS IN THIS AREA.-- End Changed Discussion --
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --MAIN FOCUS OF EXTENDED PDS IS A STRONG CLOSED UPR LOW THAT MOVES
ACRS NRN CONUS TUE-WED AND DISLODGES ARCTIC ORIGIN AIR INTO OH
VLY. THIS SYSTEM MAY PROMOTE A ROUND OF LIGHT SNOW ACRS MUCH OF
FCST AREA TUE...WITH UPSLP FLOW AND A SEQUENCE OF SHRTWV TROFS IN
WAKE OF CLIPPER SYSTEM XPCD TO SUSTAIN SHSN FOR WRN SLOPES IN VERY
COLD AIR.-- End Changed Discussion --
&&
.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
-- Changed Discussion --VFR CONDITIONS THROUGH THE OVERNIGHT HRS. A RAPID CHANGE IN
CONDITIONS WILL SPREAD NORTHEAST FRI MRNG. AREAS IN N-CNTRL VA
SUCH AS KCHO WILL SEE LIGHT-MOD SNOW MOVE IN CLOSER TO SUNRISE...
AND ONLY A COUPLE OF HRS LATER IN THE DC AND BALT METRO AREAS.
CONDITIONS WILL DETERIORATE QUICKLY BY EARLY AFTN...AS HEAVIER
SNOW BANDS AND A HEAVY...WET SNOW DROP CIGS/VSBYS ACROSS THE
REGION.
SUB-VFR CONDITIONS XPCD TO PERSIST THRU SAT EVE AS LOPRES MOVES
NEWD AND DEFORMATION ZONE DVLPS. PCPN ENDS QUICKLY SAT EVE...WITH
IMPROVED AVIATION CONDITIONS THRU MON.-- End Changed Discussion --
&&
.MARINE...
-- Changed Discussion --WINDS WILL BE MAINLY IN THE 10-15 KT RANGE THIS AFTN...SUB-SCA
CRITERIA. A GRADUAL DECREASE WILL OCCUR INTO THIS EVENING. SPEEDS
WILL STAY LIGHT OVERNIGHT INTO EARLY FRI.
PRESSURE GRADIENT TIGHTENS ACRS WATERS BY LATE FRI AFTN AS LOPRES
DEEPENS RAPIDLY OFF CAROLINA COAST. SMALL CRAFT ADZY THRESHOLD
WINDS XPCD FOR SRN PORTIONS OF CHSPK BAY AND TIDAL POTOMAC FRI
AFTN. GALE WRNG HAS BEEN ISSUED FOR MUCH OF MD CHSPK BAY AND LWR
TIDAL POTOMAC FRI NGT THRU SAT...WITH SMALL CRAFT ADZY POSTED FOR
RMNDR OF WATERS DURG THIS TIME.
SMALL CRAFT ADZYS MAY BE NEEDED LATE NEXT WEEK AS A CDFNT WITH
ARCTIC ORIGINS MOVES THRU MID-ATLC.-- End Changed Discussion --
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --DC...WINTER STORM WARNING FROM 10 AM FRIDAY TO 10 PM EST SATURDAY
FOR DCZ001.
MD...WINTER STORM WARNING FROM 10 AM FRIDAY TO 10 PM EST SATURDAY
FOR MDZ003>007-009>011-013-014-016>018-501-502.
VA...WINTER STORM WARNING FROM 10 AM FRIDAY TO 10 PM EST SATURDAY
FOR VAZ028-031-042-052>057-501-502.
WINTER STORM WARNING FROM 6 AM FRIDAY TO 10 PM EST SATURDAY
FOR VAZ021-025>027-029-030-036>040-050-051.
WV...WINTER STORM WARNING FROM 10 AM FRIDAY TO 10 PM EST SATURDAY
FOR WVZ050>053-503-504.
WINTER STORM WARNING FROM 6 AM FRIDAY TO 10 PM EST SATURDAY
FOR WVZ054-055-501-502.
MARINE...GALE WARNING FROM 6 PM FRIDAY TO 6 PM EST SATURDAY FOR
ANZ531>534-537>543.
SMALL CRAFT ADVISORY FROM 2 PM TO 6 PM EST FRIDAY FOR ANZ533-
534-537-541>543.
SMALL CRAFT ADVISORY FROM 6 PM FRIDAY TO 6 PM EST SATURDAY FOR
ANZ530-535-536.-- End Changed Discussion --
