FXUS61 KLWX 260303 AAB
AFDLWX
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
1003 PM EST WED NOV 25 2009
.SYNOPSIS...
A WEAK COLD FRONT WILL MOVE ACROSS THE MID ATLANTIC OVERNIGHT. LOW
PRESSURE WILL FORM OFF THE FLORIDA COAST TONIGHT...AND MOVE UP THE
EASTERN SEABOARD THANKSGIVING DAY. ANOTHER COLD FRONT WILL MOVE
ACROSS THE MID ATLANTIC THURSDAY NIGHT. HIGH PRESSURE RETURNS FOR
THE WEEKEND.
&&
.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
OBS AT 10PM INDICATED NUMEROUS LOCATIONS AOB 1/4 MILE VSBY IN FOG. AREAS
OF DENSE FOG E OF BLUE RIDGE WILL CONT OVNGT...AND SHUD DEVELOP
ACRS SHENANDOAH VALLEY AFTER MIDNIGHT. CIRRUS OVR SE HALF OF CWA
XPCD TO DO LITTLE TO INHIBIT FOG WITHIN SATURATED BOUNDARY LAYER.
GENERALLY CALM WINDS TNGT...GRADUALLY BCMG LGT NW TOWARD SUNRISE.
DENSE FOG ADZY RMNS IN EFFECT THRU 14Z. UPDTD HOURLY GRIDS TO
REFLECT PRESENT CONDITIONS...OTHERWISE NO CHANGES TO OVERALL FCST.
PREVIOUS DISCUSSION FOLLOWS...
SKIES HAVE PARTIALLY CLEARED BEHIND SHRTWV PUSHING INTO NEW
ENGLAND...ALLOWING FOR ENUF RADIATIONAL COOLING TO PRODUCE PATCHY
FOG EAST OF BLUE RIDGE ERY THIS EVE. WITH MOIST BOUNDARY
LAYER...WIDESPREAD FOG XPCD AFTER 02Z AREAS E OF BLUE RIDGE ALONG
WITH SHENANDOAH VLY. AREAS OF LESS THAN 1/4 MILE VSBY XPCD...THUS DENSE
FOG ADZY POSTED FOR THESE AREAS THRU 14Z THU. ADJUSTED WX GRIDS TO
REFLECT EARLIER ONSET AND FURTHER VSBY REDUCTIONS.
ADDITIONALLY...WINDS SHUD RMN NEARLY CALM OVNGT E OF BLUE
RIDGE...WITH A SLOWER INFILTRATION OF DRIER AIR THAN PREVIOUSLY
FCST...AS CDFNT RMNS W OF CWA THRU MUCH OF OVNGT. EDITED HOURLY
GRIDS ACCORDINGLY. PREVIOUS DISCUSSION FOLLOWS...
SOME CHANGES WERE OCCURRING IN THE ATMOSPHERE THIS AFTERNOON. WEAK
COLD FRONT WAS APPROACHING FROM THE WEST...AND LOW LEVEL WINDS WHICH
HAVE FAVORED AN EASTERLY COMPONENT FOR THE LAST COUPLE OF DAYS WERE
TURNING TO THE SOUTH/SOUTHWEST AHEAD OF THE FRONT.
LAST VESTIGES OF DRIZZLE WERE MOVING NORTHEAST ACROSS NORTH/CENTRAL
MARYLAND THIS AFTERNOON. THIS WILL LIFT NORTHEAST OF THE BAY IN THE
21Z-22Z TIME FRAME.
CEILINGS WERE ALSO RISING THIS AFTERNOON...AND SATELLITE IMAGERY
EVEN INDICATED SOME BREAKS IN THE CLOUDS WORKING INTO THE
HIGHLANDS/SHENANDOAH VALLEY AREA. CLOUDS MAY EVEN SCATTER FOR A TIME
LATER ON THIS EVENING...BEFORE FILLING BACK IN OVERNIGHT.
WHILE ADDITIONAL DRIZZLE IS NOT EXPECTED OVERNIGHT...THERE IS THE
POTENTIAL FOR FOG FORMATION WITH LOW LEVEL MOISTURE LINGERING
UNDERNEATH THE INVERSION AND A WEAK GRADIENT/CALM WINDS BEHIND THE
FRONTAL PASSAGE. SOME GUIDANCE FORECASTS VISIBILITIES LOWERING TO
1/4 MILE. THIS MAY BE PLAUSIBLE IF WE ARE ABLE TO DEVELOP SOME
BREAKS/SCATTERINGS IN THE CLOUD COVER LATER THIS EVENING. WOULD
THINK THE MOST LIKELY AREA FOR THIS WOULD OCCUR ACROSS THE WASH/BALT
CORRIDOR...BUT DO NOT HAVE ENOUGH CONFIDENCE AT THIS TIME TO ISSUE A
DENSE FOG ADVISORY. FOG WILL BE INCLUDED IN HWO.
&&
.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
MORNING FOG WILL LINGER INTO EARLY THANKSGIVING MORNING...BUT WILL
BREAK UP BY MID MORNING. NEXT FRONT WILL APPROACH FROM THE
WEST...BRINGING SHOWER CHANCES ACROSS THE HIGHLANDS DURING THE
AFTERNOON. 12Z GFS/NAM AND 09Z SREFS AGREE WITH KEEPING POPS OUT OF
THE FORECAST EAST OF THE MTNS THROUGH THE AFTERNOON HOURS.
&&
.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
COLD FRONT WILL MOVE THROUGH THE CWFA LATER IN THE DAY ON
THANKSGIVING. WINDS ARE EXPECTED TO SHIFT TO THE NW BEHIND THE
BOUNDARY...BECOMING FAVORABLE FOR UPSLOPE SNOW SHOWERS ALONG THE
WESTERN RIDGES OF THE ALLEGHENIES. THE UPSLOPE SNOW SHOWERS ARE
EXPECTED TO LINGER THROUGH EARLY SATURDAY AS CONDITIONS REMAIN
FAVORABLE...PRODUCING SEVERAL INCHES OF SNOW. HAVE ISSUED A WINTER
STORM WATCH FOR EXTREME WESTERN ALLEGANY...GRANT AND MINERAL
COUNTIES...AS SNOWFALL TOTALS COULD APPROACH WINTER STORM CRITERIA.
HIGH PRESSURE BEGINS TO BUILD IN FROM THE SW LATER ON SATURDAY...AND
REMAINS IN CONTROL OF THE SENSIBLE WEATHER THROUGH THE REMAINDER OF
THE WEEKEND. THE HIGH CENTER MOVES OFFSHORE ON MONDAY...AHEAD OF THE
NEXT FRONTAL SYSTEM. THE FRONT MOVES THROUGH DURING THE MIDDLE OF
NEXT WEEK.
&&
.AVIATION /03Z THURSDAY THROUGH MONDAY/...
LIFR CONDS IN FOG ONGOING AT MRB AND BALTIMORE TAFS AT 3Z. IFR OR
BELOW VSBY XPCD ACRS BALTIMORE/WASHINGTON AREA TAFS THRU THE
NIGHT...WITH DCA BEING LAST TO HAVE FOG DEVELOPMENT...BY 6Z. XPCT
CHO TO BEING EXPERIENCING IFR CONDS BY 6Z AS WELL. AFTER
SUNRISE...IMPROVING CONDS TO MVFR DURING THE MRNG...WITH VFR BY
AFTN.
SCATTERED TO ISOLATED SHOWERS WILL BE POSSIBLE THURSDAY NIGHT AND
FRIDAY AS AN UPPER LEVEL DISTURBANCE MOVES THROUGH THE
AREA...IMPACTING LOCAL VSBYS. ANY CIGS SHOULD REMAIN ABOVE 3 KFT.
BREEZY CONDITIONS ARE EXPECTED ON FRIDAY...WITH GUSTS TO AROUND 25
KT AT THE TERMINAL SITES. CIGS/VSBYS ARE EXPECTED FOR THE REMAINDER
OF THE WEEKEND INTO EARLY NEXT WEEK.
&&
.MARINE...
WINDS HAVE SHIFTED TO A SOUTH-SOUTHWEST DIRECTION ACROSS THE WATERS
THIS AFTERNOON AND MAY BECOME NORTH LATE TONIGHT BEHIND A WEAK FRONT
BEFORE TURNING TO THE NORTHEAST ON THANKSGIVING DAY. DURING THIS
TIME...SPEEDS ARE FORECAST TO BE AOB 10 KT.
NW WINDS WILL INCREASE BEHIND A COLD FRONT LATE THURSDAY INTO
SATURDAY. SMALL CRAFT CONDITIONS ARE LIKELY FRIDAY INTO SATURDAY.
WINDS MAY GUST TO NEAR 20 KT RIGHT ALONG AND JUST BEHIND THE FROPA
LATE THURSDAY NIGHT...BUT NOT CONFIDENT THE DURATION OF GUSTS WILL
BE MORE THAN A FEW HOURS.
&&
.TIDES/COASTAL FLOODING...
WATER LEVELS WERE CONTINUING TO RUN A FOOT TO FOOT AND A HALF
ABOVE NORMAL THIS AFTERNOON. HOWEVER...GIVEN THE LOWER
ASTRONOMICAL TIDES...MINOR TIDAL FLOODING HAS NOT OCCURRED DURING
THE LAST COUPLE OF HIGH TIDE CYCLES NOR IS IT EXPECTED OVER THE
NEXT COUPLE.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...DENSE FOG ADVISORY UNTIL 9 AM EST THURSDAY FOR DCZ001.
MD...DENSE FOG ADVISORY UNTIL 9 AM EST THURSDAY FOR MDZ003>007-
009>011-013-014-016>018.
WINTER STORM WATCH FROM THURSDAY EVENING THROUGH FRIDAY
EVENING FOR MDZ501.
VA...DENSE FOG ADVISORY UNTIL 9 AM EST THURSDAY FOR VAZ025>031-
036>042-050>057.
WV...DENSE FOG ADVISORY UNTIL 9 AM EST THURSDAY FOR WVZ051>053.
WINTER STORM WATCH FROM THURSDAY EVENING THROUGH FRIDAY
EVENING FOR WVZ501-503.
MARINE...NONE.
&&
$$
UPDATE...SBK
PREVIOUS DISCUSSION...SBK/PELOQUIN/LISTEMAA
