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fxus61 klwx 190709 
afdlwx 


Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia 
309 am EDT Friday Mar 19 2010 


Synopsis... 
high pressure dominates...with tranquil and mild weather across 
the region through Saturday night. A strong upper level 
disturbance and its associated cold front are expected to impact 
the region late Sunday through Monday. 
&& 


Near term /through tonight/... 
hipres centered over northern Gulf of Mexico will continue to dominate weather 
today. Surface temperatures starting off this morning a degree or two warmer than 
yesterday...and 800 mb temperatures expected to be slightly higher...so went for maxima a 
degree or two warmer than yesterday...on warm side of guidance. Light northwest 
flow persists...with hi temperatures in u60s/l70s...and sunny skies. 


Low level flow becomes SW overnight as ridge axis shifts toward southeast Continental U.S.. result 
will be temperatures around 5 degrees warmer than previous ngts and 5 to 10 
degrees above average. Took a blend of guidance for minima...generally 
u30s west of Blue Ridge...l40s east. Clear skies and light winds continue. 
&& 


Short term /Saturday through Sunday night/... 
itll still be the hipres ridge in central of eastern Continental U.S. Weather Sat. However...a 
weak cold front enters the Great Lakes and new englnd...and may be responsible 
for a few clouds. That alone shudnt be enough to detract from temperatures... 
which should remain at levels comparable to today. If anything...h8-5 height 
rises/warm air advection ahead of fnt may enhance maxt...especially in central Virginia /mid 70s/. 


Light southerly flow and incrsg clouds could potentially prop min-T up tmrw 
night-- in the 40s. Most of the fnt/S baroclinicity remains displaced 
bhd pressure discontinuity...so dont forsee much more than broken clouds 
N/W...scattered S/E. 


By sun...developing lopres alng this boundary in the lower MS valley becomes the 
primary focal pt. While better than the 12z/18th run...there are 
still some qstns yet to be answered as to the details. Regardless... 
a deep stream of moisture off the Gulf of Mexico and favorable upper jet support favor 
rain showers by lt Sun night. Dont think much /if any/ of this will make it 
during the day Sunday. So the string of mild days will continue...though 
cldcvr will be more xtnsv. The 500 mb cutoff suggests a sloer solution the way 
to go. 
&& 


Long term /Monday through Thursday/... 
the surface low looks to make a trek across the central Appalachians and Potomac 
Highlands during the day on Monday - a bit slower than previous runs 
showed. The minimal convective potential will be south and east of 
the low - but mainly east of the Virginia Blue Ridge and especially closer to 
the coast west/ the more unstable elevated layer and a bit better wind 
sheer values. Still...these elements will be marginal across the middle 
Atlantic - much better down across the southern Atlantic coast. As the still cold 
upper cut-off low moves across the region overnight Monday into early 
Tuesday. Some of this cooler air will be mixed down toward the surface which 
will take temperatures back down into the M/l30s. A mix of rain/snow will 
be possible across the western zones. Another wave of light rain may 
slide through the area on Tuesday afternoon as the upper low finally makes it/S 
exit off the Atlantic. 


Another couple of high pressure days before the next low pressure 
system gears up over roughly the same area. Too early to tell how 
far south this system will develop and then move. 
&& 


Aviation /07z Friday through Tuesday/... 
clear skies and light winds expected through Sat night. Light northwest winds today become light 
SW tonight...with speeds remaining below 10 knots. Flgt restrictions should 
hold off until lt Sun night...closer to the Monday morning push. 
&& 


Marine... 
dry conds and light winds through tonight. Northwest winds near 10 knots today...becoming SW 
with similar velocities tonight. 


Southerly flow will prevail through sun...spds at or below 10 knots Sat...10-15 knots sun. 
Flow backs southeast ahead of cyclone Monday. Small Craft Advisory possible Mon-Tue. 




&& 


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


&& 


$$ 
Synopsis...sbk/bjl 
near term...sbk 
short term...heights 
long term...gms 
aviation...sbk/hts 
marine...sbk/hts