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fxus61 klwx 240758 
afdlwx 


Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia 
358 am EDT Thursday Jul 24 2008 


Synopsis... 


A cold front will move east of the Chesapeake Bay this morning. 
High pressure will move into the region today and tonight. Another 
cold front will cross the area on Sunday. High pressure will build 
over the region next week. 


&& 


Near term /today/... 


After a fairly active period of weather it's nice to see the cold fnt moving 
out of the County Warning Area. Problem over the next few hours is going to be fog 
formation. Cho/mrb have gone "poof" in dcrsd visibilities in past hour as 
skies have clrd...and in front of the office it looks lake it may as 
well on the iad runway. We'll keep an eye on this...will put patchy fog west 
of the cities in the zones for the Erly morning hours. As dawn approaches 
we'll see if fog is dense/widespread enough to warrant an advisory. 
Eta model BUFKIT seems to have a good handle on this...and predicts it will 
burn off b4 9 am. 


Aftr that a rather comfortable day looks to be on tap for the region. 
M sun skies..temps reaching the m80s east of the mountains...u70s at the 
higher elevs. 


&& 


Short term /tonight/... 


High pressure over region tonight. "Late jul" and "good sleeping wx" are 
gnrly mutually exclusive terms...but west/ overnight lows expeceted to be 
5-10 degrees below normal the upcoming night loks to be a plsnt one. 


&& 


Long term /Friday through Wednesday/... 


A more difficult long term west/ the immense uncertainty west/ the upper 
low through the end of the week...into early next week. Then...followed 
closely by another active upper level system which may or may not 
dip further south /into the middle atlnc region/ by this time next 
week. 


Tackling the more immediate feature...00z GFS has backed off 
from the intense upper trough axis for Saturday. The focus now on a 
slowly developing long wave trough the digs S/wrd across the Great 
Lakes region and into the cntl aplchns into early next week. 
Embedded in the flow are several weak axis regions that push 
across the region about every other day. There/S Little Point in 
trying to pin down exact timing/strength of any individual upper 
lifting mechanism. Future runs may develop an even further deepening 
trough /like the one that is currently exiting off the atlnc coast/. 
One certainty is that even west/ the timing and progression differences 
in the long range models...the eastern half of the country /and espc the 
NE quadrant/ is still in a fairly active pattern for late July. This 
is evidenced by the middle-late week /next week/ system that models are 
fairly progressive in painting across the region. 


Long range high temperatures will be near persistence /and near normal/ west/ 
only a degree or two difference through the weekend into early next 
week. Kept chance probability of precipitation in for Sat as decent warm air advection and moist S/rly flow 
will enter the region. A weak in-situ cap may limit widespread convn 
though at least isolated to possibly scattered/d storms may develop along surface 
boundaries from the stronger than normal surface S/rly flow...along west/ 
the aprch of a slightly deepening upper shortwave trough from the west. 


By Sun afternoon...the weakly negatively tilted trough axis exptd to be 
overhead. In subsequent updates...sun may have the better chance 
for widespread activity across the middle atlnc region...though the NAM 
has nearly zonal flow settled over the NE quadrant. Psble surface cold front 
may drift slowly across the area late sun and off the atlnc coast by 
early Monday. Summertime diurnal instability may in fact end up being 
the main Mode for development drng this period...and into the middle 
part of next week. 


&& 


Aviation /today through Monday/... 


Poor visibilities at iad/mrb/cho through 13z in fog. Afterwards VFR conds at 
all taf sites for rmdr of today. High pressure builds in tonight. Qustn 
exists of whether air will be dry enough to suppress fog formation 
overnight. Later shifts can evaluate. 


Little concern going into the weekend...though Sat afternoon may see some 
scattered/d storms and a repeat for sun. A cold front exptd to move through 
the region on sun west/ brief influence of high pressure for early next 
week. 


&& 


Marine... 


Rain shower exiting the Bay West/ the departing cold fnt. High pressure to build 
into the waters this afternoon. For now will cap the winds at 15 knots. Light 
winds tonight. 


High pressure for the rest of the week...W/ S/rly wind increase on Sat afternoon 
west/ psble Small Craft Advisory conditions/S and scattered/d storms also psble for the afternoon/evening 
hours. A fairly similar scenario for Sunday as a cold front then 
slides across the area by late sun. High pressure into the middle of 
next week. 


&& 


Lwx watches/warnings/advisories... 
District of Columbia...none. 
Maryland...none. 
Virginia...none. 
WV...none. 
Marine...none. 


&& 


$$ 
Products...Woody!/Gms