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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Thursday
• 
• High: 82 °
• Low: 66 °
• T-Storms

• Friday
• 
• High: 88 °
• Low: 68 °
• Chance of T-Storms

• Saturday
• 
• High: 95 °
• Low: 64 °
• Chance of T-Storms

• Sunday
• 
• High: 88 °
• Low: 66 °
• Chance of T-Storms

• Monday
• 
• High: 95 °
• Low: 66 °
• Chance of T-Storms

Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia 
925 PM EDT Wednesday may 23 2012 


Synopsis... 
low pressure will persist over the middle Atlantic through Thursday. 
High pressure will build into the region Friday through the 
Memorial Day weekend...bringing well above normal temperatures. 


&& 


Near term /through Thursday/... 
still have some showers and thunderstorms across the County Warning Area this 
evening...but the overall coverage seems to be on the decrease 
from earlier. Unfortunately...area of mesoscale convergence/weak 
steering flow has supported slow-moving storms over Prince William 
County which has received very heavy rainfall over the past couple 
of days. Flash Flood Warning remains in effect. 


With the atmosphere stabilizing overnight...coverage of 
convection will continue to decrease but with a surface trough 
still in place along with plenty of low-level moisture...will keep 
isolated showers in the forecast after midnight. Rich moisture may 
also contribute to patchy fog and stratus overnight. 


Atmosphere remains similar on Thursday...and expect another round 
of showers and thunderstorms especially in the afternoon and 
evening. 


&& 


Short term /Thursday night through Friday night/... 
shower and thunderstorm coverage will become less Thursday night 
as the weakening upper low/trough shifts north of the forecast 
area. The GFS holds additional energy back to the west overnight 
into Friday which may aid in additional isolated to scattered 
development mainly over the east into Friday evening. A strong 
upper level high pressure system will nose into the forecast area 
from the southwest. This feature will bring rising heights and 
moderating temperatures into the middle 80s Friday afternoon and 
slightly milder overnight lows Friday night. 


&& 


Long term /Saturday through Wednesday/... 
high pressure will build further north over the weekend. 
Temperatures will continue to moderate through the upper 80s and 
possibly into the lower 90s Saturday through Monday. The 
heat...when combined with added moisture may cause heat indices to 
rise into the 95-100 degree range for the Holiday weekend. 
Scattered showers and thunderstorms will be possible as the region 
will remain on the northern periphery of the ridge axis. 
Additional afternoon and evening showers and thunderstorms will be 
possible Sunday and Memorial Day. A cold front will approach from 
the west Tuesday into Wednesday. 


&& 


Aviation /01z Thursday through Monday/... 
thunderstorms should continue to decrease in coverage through 
03z...still potentially affecting cho/iad/dca through then. 
Concern then turns to fog and stratus development overnight. 
Plenty of low level moisture remains in place...and expect IFR at 
mrb/cho/iad overnight. Held BWI/dca in MVFR category with lower 
confidence...but with a low level easterly flow a stratus deck 
could attempt to advect west to these sites later at night as well 
/per hrrr/. 


Scattered afternoon and evening showers and thunderstorms 
expected Thursday with less coverage on Friday and Saturday. Any 
storm that does develop will be capable of producing locally heavy 
rainfall and gusty outflow winds. High pressure builds in over the 
Holiday weekend with mostly VFR expected although isolated to 
scattered storms could still develop. 


&& 


Marine... 
thunderstorms over southeast Virginia are expected to weaken as they 
move northeast toward the waters overnight. East-southeast flow 
will continue through Thursday...but is expected to remain 10 knots 
or less. Thunderstorms Thursday may bring locally stronger wind 
gusts. 


Scattered showers and thunderstorms will be possible over the 
waters each afternoon from Friday through the Memorial Day 
weekend. Any storm that does develop could produce gusty outflow 
winds and locally heavy rainfall. 


&& 


Tides/coastal flooding... 
anomalies remain around 0.5 feet above normal...a magnitude that should not 
be sufficient to induce tidal inundation tonight or Thursday. 


&& 


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


&& 


$$ 
Synopsis...sdg 
near term...bpp/sdg 
short term...krw 
long term...krw 
aviation...bpp/sdg/krw 
marine...bpp/sdg/krw 
tides/coastal flooding...sdg