326 
fxus61 klwx 200026 
afdlwx 


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


Synopsis... 
high pressure will continue to bring dry and mild conditions through 
Saturday night. A strong upper level disturbance and its associated 
cold front are expected to impact the region late Sunday through 
Monday. High pressure will then build in for middle week. 


&& 


Near term /through Saturday/... 
00z iad sndg tells it all - high pressure over area...dry throughout the 
entire atmospheric column. Temperatures should drop off quickly in the 
coming hours. 


Min temperatures will range from the middle 30s in the colder valleys to 
the upper 40s and lower 50s in downtown Washington and Baltimore. 


A southwest flow around the surface high Saturday will bring even 
warmer conditions along with more sunshine. Maximum temperatures will range 
from near 60 along the ridge tops of the Potomac Highlands to the 
lower and middle 70s across most other locations. 


&& 


Short term /Saturday night through Monday night/... 
our next weather-maker may be dropping several inches of snow over the 
Colorado rockies...but by the time it reaches the middle Atlantic - liquid 
precipitation will be result. This feature will prove to be an anomalously 
cold and strong system as it moves through the Southern Plains and lower 
Mississippi Valley over the weekend. The sharp upper trough axis that is 
currently digging down into the Front-Range of The Rockies will 
produce a potent cut-off low over the Texas/OK Red River valley Sat into 
sun. 


By late Sunday...clouds and low level moisture will be on the 
increase up the eastern Seaboard - ahead of the approaching system. 
Between late Sunday and midday Monday...mainly a widely scattered/ 
low rain chances for the region. Weak along and near a weak 
pseudo-stationary front will create only isolated shower activity - 
stretching across the Ohio Valley back into the NE. As the cut-off low 
approaches the southern Appalachians Sunday evening...more widespread showers 
will move toward the middle Atlantic up the southern aplcn chain. The heaviest 
precipitation bands /mainly a mix of light-moderate rain showers/ will push 
up the Piedmont from the Carolinas into northern Virginia/southern Maryland. Placed a low 
chance of thunder in the grids /mainly east of the Blue Ridge/ for the 
afternoon/evening hours. Very low instability values so this would mainly 
be isolated and very weak convection. The dry-slot will push into 
central Virginia into the evening hours - west/ a bulk of this heavier precipitation 
racing off to the NE overnight. 


Earlier guidance brought the upper low directly over the County Warning Area...but 
since then a consensus has taken the feature much further south - 
now trekking across the NC/SC border and off the Atlantic coast by 
midday Tuesday. With the proximity of this feature to the middle 
Atlantic...just a scattering of low chance rain showers across the County Warning Area 
overnight Monday through late morning Tuesday...possibly a few bands lingering 
across the I-95 corridor into the afternoon hours. 


&& 


Long term /Tuesday through Friday/... 
after a cloudy-cool Tuesday - since the upper low will take all-day to 
completely exit off the coast...high pressure will again build 
across the southeast and up the eastern Seaboard. Another complex 
scenario will then take shape back to the west. A fairly similar 
upper low feature will cross the same areas of The Rockies/Southern 
Plains Wednesday/Thursday of next week...but not west/ the same upper support at 
the beginning - which would likely mean not as far of a trek to the 
south as the current system. 


Rain chances will begin to increase toward the end of the work 
week...though a more accurate depiction for next weekend still 
uncertain and will depend of the effects a strong upper wave that 
will swinging around the southern Hudson Bay/northern Great Lakes region at 
the time. 


&& 


Aviation /tngt through Wednesday/... 


VFR conditions are expected through Saturday. 


VFR conditions continue into Sunday. Middle and upper cloud decks 
will begin to move into the region west/ a few isolated light rain 
showers possible across the area by late sun. Another low 
pressure system moving through on Monday - exiting on Tuesday. Breezy surface 
winds...sub-VFR clouds and occasional showers west/ this system on 
Monday. High pressure for the middle part of next week. 


&& 


Marine... 
no flags are expected through Saturday. 


A low pressure system will approach late sun into early Monday. Southerly 
winds will increase...which may create intermittent Small Craft Advisory conditions 
- lasting through the exit of the low on Tuesday. Then...high pressure 
will build into the region. 


&& 


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


&& 


$$ 
Update...Woody! 
Prvs...bjl/gms