Weather

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fxus61 klwx 060307 
afdlwx 


Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia 
1007 PM EST Monday Jan 5 2009 


Synopsis... 
a strengthening storm system will track across the region Tuesday 
and Wednesday. That storm will bring another round of mixed 
precipitation...mainly from Tuesday morning through Wednesday morning. 


As the storm exits...cold air will be pulled in behind it for Thursday 
and Friday. A warm front will lift north of the region Friday 
night...followed quickly by another strong cold front Saturday. Cold 
air will last into next week. 


&& 


Near term /through Tuesday/... 
high pressure ridge axis has settled across the northern County warning forecast area. A 
warm front remains along the Virginia/Maryland border. Temperatures are 
approaching freezing along the Maryland/PA border and along the higher 
elevations along the Blue Ridge. One thing to note...actual 
dewpoints are several degrees lower than what the models were 
progging. The cold air will continue to settle southward overnight. 


A wintry mix is still expected across much of the County warning forecast area. Earlier this 
evening...went ahead and expanded the advisory further south into 
the Shenandoah Valley and into Nelson and Albemarle counties. Even 
though temperatures were rather warm in this region today...the cold 
air should make it into the elevations above 1 kft. The lower 
elevations may stay right above freezing...and may only get some 
rain mixed with some sleet. 


In the far northwest...upgraded the advisory to a Winter Storm Warning for 
Allegany and Mineral counties. Models have been continually showing 
good qfp in this region. In addition...the coldest air tends to be 
hardest to scour out in this area. A quarter inch of ice is not out 
of the question. 


Elsewhere...the Winter Weather Advisory looks good. Onset of 
precipitation still looks good. 




&& 


Short term /Tuesday night through 6 PM Tuesday/... 
I wrote in my morning dscn about concern regarding the posn of the surface 
high at this time if one is looking for a prolongued period of cold dry air 
to filter into the middle Atlantic for a freezing rain event. High is currently 
over Indiana and prognosticated to track across New Jersey - not a normal 
source region for subfreezing air. 


Models are in reasonable agreement that if anywhere in the County Warning Area is 
under the gun it's the northwestern corner...where sub 1300 dm thckns is 
expeceted to last throughout the day. I don't feel comfortable enough about 
ice accretion amts to go west/ a freezing rain warning...but have impemented an 
advisory west of the major cities extending to the PA/WV borders. If later 
models come in colder there is still time to up this to a warning. 


&& 


Long term /Tuesday night through Monday/... 
mixed precipitation will continue to phase over to a cold rain from southeast to northwest 
Tuesday night. As usual areas around hgr and cbe should be the last to 
phase over to regular rain...probability not until Wednesday morning. Those areas 
will have the worst potential for an icing threat. At the moment 
will have a Winter Weather Advisory for those areas... but may need 
to be upgraded to a Winter Storm Warning if conditions proceed 
towards the more worst case scenario. Right now...expect less than a 
quarter inch of ice...even in the northwest counties. 


As the low passes through and wraps up to our NE...winds will pick up 
and the cold air will surge in with 850mb temperatures falling into the 
negative teens by late Thursday. 


Next up is a cold front Saturday with the chance for rain or snow 
showers...but not that much total precipitation with the front. Another 
surge of cold air follows with 850mb temperatures dropping even lower to 
around minus 20c by Sunday. 


&& 


Aviation /03z Tuesday through Saturday/... 
ceilings most areas are currently VFR. Expect ceilings/visibilities to drop to 
MVFR/IFR early tomorrow morning as wintry precipitation overspreads 
the area. 


IFR conditions are expected Tuesday night into Wednesday before breaking up 
after the cold front moves through. Gusty surface winds g30kt possible 
Wednesday afternoon through Friday morning...and again late Sat into sun. 


&& 


Marine... 
winds below Small Craft Advisory values tonight and Tuesday. 


Small craft winds are expected to develop late Wednesday and persist 
into Thursday night. Small craft will return Friday night through Sunday. 


&& 


Lwx watches/warnings/advisories... 
District of Columbia...none. 
Maryland...Winter Weather Advisory from 6 am Tuesday to 9 am EST 
Wednesday for mdz003>007-009-010. 
Winter Storm Warning from 6 am Tuesday to 9 am EST Wednesday 
for mdz501-502. 
Virginia...Winter Weather Advisory until 11 PM EST Tuesday for vaz021-025- 
026-036>038. 
Winter Weather Advisory from 6 am Tuesday to 9 am EST 
Wednesday for vaz027>031-039>042-051>053. 
WV...Winter Weather Advisory until 11 PM EST Tuesday for wvz054. 
Winter Weather Advisory from 6 am Tuesday to 9 am EST 
Wednesday for wvz050>053-055-501-502. 
Winter Storm Warning from 6 am Tuesday to 9 am EST Wednesday 
for wvz503-504. 
Marine...none. 


&& 


$$ 
Update...listemaa