274 
fxus61 klwx 071557 
afdlwx 


Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia 
1057 am EST Sat Nov 7 2009 


Synopsis... 
high pressure dominates through early next week. A weak cold front 
will bring a wind shift to the area early Sunday...with little 
effect on temperature. High pressure then dominates through early 
next week...before a cold front approaches the area late Tuesday. 


&& 


Near term /until 6 PM this evening/... 
hipres centered along the Carolina coast will slowly sag southeastward off 
the coast this afternoon but control the middle Atlantic weather pattern. Temperatures 
should quickly rebound from a cold start this morning as southerly winds 
and abundant sunshine moderate the airmass ovrhd. Weighted more 
towards met guidance for maximum temperatures which have verified the best 
recently. 


&& 


Short term /6 PM this evening through 6 PM Sunday/... 
ripple in upper flow sends weak cold front through late Sat night. Increased 
clouds...especially northern zones...and wdshft to west-northwest only effects of frontal passage 
on middle Atlantic. With mixing and cloud cover...minima expected to be 10-15 
degrees warmer than Sat morning. 


Hipres at the surface and upper levels builds on sun...with mostly sunny 
skies and light winds. Temperatures rise above average. Used a mav/met blend 
to obtain maxima in M/u60s. 


&& 


Long term /Sunday night through Friday/... 
high pressure to dominate most of the period...with a cold front passage 
sandwiched in Tuesday night. From sun 12z to Tuesday 12z...a positive 850 mb 
temperature anomaly of +1sd which translates this time of year to +12c at 
850 mb will give our region a couple of pleasant Indian Summer days on 
Monday and Tuesday with highs in the upper 60s and maybe lower 70s at 
higher elevations. 


Cold front will push through on late Tuesday after or Erly evening...with 
a digging 500 mb trough. The gefs washes out the precipitation...with only a 
couple ensemble members giving any precipitation on Tuesday night...but will 
leave in the 20 pop but anticipate at this time little if any precipitation. Winds 
should be gusty late Tuesday night into Wednesday...and with any appreciable 
dryness in fuel moisture may have fire weather issues on Wednesday. 


High pressure from the Great Lakes will move in behind the front and 
continue dry and seasonably warm weather for Thursday and Friday. 


Gefs has a precipitation system moving into region for next weekend. 


&& 


Aviation /16z Saturday through Wednesday/... 
aside from scattered hi cirrus today...mostly clear skies and VFR conditions 
through the weekend. 


Southerly winds 5-10 knots with gusts to 15 knots today become westerly after 
midnight tonight as cold front passes through. Light westerly winds expected sun. 


Long term not of concern with VFR conditions thoughout period. Potl 
for turb Tuesday night across regn with upper level jet associated with 
digging trough as it moves through the NE US. 


&& 


Marine... 
winds have increased late this morning with southerly channeling across the 
chesepeake Bay. Small Craft Advisory conditions with gusts around 20 knots expected across 
the Maryland Chesapeake Bay and lower tidal Potomac through sunset. 


By sunset mixing subsides...and winds should return below Small Craft Advisory 
speeds. Winds become westerly early sun as cold front passes over waters...but 
wind speeds will be light. 


Have increased winds to Small Craft Advisory levels for Tuesday night and Wednesday as models 
show strong low level jet and tight surface pressure gradient behind cold front. 


&& 


Lwx watches/warnings/advisories... 
District of Columbia...none. 
Maryland...none. 
Virginia...none. 
WV...none. 
Marine...Small Craft Advisory until 6 PM EST this evening for 
anz530>534-537>543. 


&& 


$$ 
Update...Klein 
previous disc...sbk/jel