Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 180759 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 359 AM EDT Sun Jun 18 2017 .SYNOPSIS...
-- Changed Discussion --
A very warm and humid air mass will remain in place through Monday until a cold front clears the area Monday night. Weak high pressure will build over the area for the middle of the week.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
A stratus layer has developed east of the Blue Ridge mountains early this morning as seen on nighttime microphysics RGB with some patchy fog over some of the valleys in eastern WV. After morning clouds scatter out, it will be a sultry Father`s day with temperatures getting into the mid 90s and dewpoints around 70F resulting in heat indices around 100F. Afternoon convection will likely remain scattered at best given lack of sfc and upper level forcing and no appreciable height falls. The first part of the night is likely to be quiet with showers or t-storms beginning to move into the Potomac highlands after midnight. Model guidance now shows faster progression of showers overnight tonight into Mon morning, so have increased PoPs somewhat.
-- End Changed Discussion --
&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
An upper level trough will be moving across the eastern Great Lks Mon pushing a cdfnt into the area. As cdfnt intercepts a plume of very high PWATs aoa 2.0 inches, expect widespread showers and t-storms to develop and last into the evening except in southern MD where they will likely last through much of the night. While shear will be on the increase through the day (0-6km values of 30-35kt) which would support organized convection, amount of instability available still remains questionable given thick clouds are likely to arrive early and there might be showers already by 12Z. 00Z EPS indicate probabilities of CAPE greater than 1000 J/kg well below 50%. While individual storm cell motion is progged at 30-35 kt, unidirectional wind profiles suggest some training/repeated convective activity is likely causing some concerns for flash flooding especially given the very high PWATs. Still believe the primary threat will be flash flooding and a flash flood watch may be required for the I-95 urban corridor of DC and Baltimore. Cdfnt clears the area late Mon night with showers ending in most areas except perhaps southern MD. Drier and more seasonable Tue-Tue night.
-- End Changed Discussion --
&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
-- Changed Discussion --
Low humidity but seasonable temperatures for Wednesday. A departing broad upper trough will allow for some potential for instability convection. By Thursday and Friday zonal flow will replace the trough. Surface features will be fairly benign...but given the low level flow, some amount of tropical moisture could make it up here from the Southeast during the late week. Next weekend looks to be our next cold front, although the timing of which day is uncertain given the model spread. Dewpoint temps and humidity are expected to increase day by day Wednesday thru Saturday.
-- End Changed Discussion --
&& .AVIATION /08Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
Low clouds have developed this morning with IFR conditions expected. This could repeat itself again tonight, but no fog is anticipated due to strengthening winds. Other than possible showers and thunderstorms at times, no significant aviation concerns Wed through Fri.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Solid SCA winds today through Mon under strengthening srly winds. T-storms on Monday may require special marine warnings. Winds begin to diminish late Mon night. Other than thunderstorms, no significant marine concerns Wed through Fri.
-- End Changed Discussion --
&& .LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 AM EDT Monday for ANZ530>534- 536>543. Small Craft Advisory from noon today to 6 AM EDT Monday for ANZ535.
-- End Changed Discussion --
&& $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...CAS AVIATION...CAS/LFR MARINE...CAS/LFR

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.