Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | 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
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 221910 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 310 PM EDT Wed Jun 22 2016 .SYNOPSIS...
-- Changed Discussion --
Low pressure will approach from the Ohio Valley tonight and then move across the region Thursday. High pressure will build into the area Thursday night and remain through the weekend. A cold front will approach the mid-Atlantic early next week.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH THURSDAY/...
-- Changed Discussion --
At present...slow-moving cold front has sunk south of most of the CWA but remains draped across central Virginia. Much drier and more stable air mass in place across most of the region at present. Tonight, the front will try to back northward in advance of low pressure moving eastward from the midwest. This low will pass near the area during the day Thursday. There is a lot of uncertainty regarding severe weather and flooding...mainly due to the presence of the aforementioned front. Some guidance (GFS in particular) shoves the front back north late tonight and early Thursday...resulting in an extremely unstable atmosphere on Thursday afternoon (4000+ j/kg cape) from which strong to severe storms would be likely. However...this would not seem particularly likely if the idea of an MCS moving across the region is correct...in which case the rain cooled air would likely be stuck in a wedge east of the mountains and the front would be unable to push back north. The other question revolves around said MCS...which may or may not bring a round of severe weather later tonight. With the front sagging southward still and a stable air mass in place...any MCS moving in from the west could just ride right over the stable air mass and start weakening...which would reduce the severe threat. However...should the front manage to slide back northward late tonight ahead of the MCS...it could tap the more unstable air to the south directly and bring another round of severe thunderstorms and heavy rain. Right now...it is all very uncertain and hinges as mentioned on any MCS development and the movement of the front. We have banked more on MCS potential with the front perhaps pushing back north overnight...and then stabilizing behind it with the front going back south again during the day Thursday. This would mean a severe/flood threat later tonight/early Thursday across the region. However...given high uncertainty...have not expanded flash flood watch any further east despite large amount of guidance suggesting we should. This will be reviewed again during the evening. Lows tonight will be mostly in the 60s. Highs on Thursday are uncertain but are forecast mainly in the upper 70s and 80s. Depending on where the front ends up...this forecast could be off by some degree.
-- End Changed Discussion --
&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY/...
-- Changed Discussion --
Front drops south of the area Thursday night and remains south through Saturday. High to the north will provide northeast to east flow across the region in its wake. Upslope flow combined with trough aloft may allow isolated to scattered showers and perhaps even a stray thunderstorm mainly near the mountains...and especially further south. Otherwise it will be rather pleasant. The threat of showers will diminish Saturday.
-- End Changed Discussion --
&& .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
-- Changed Discussion --
500 MB height rises through Sunday night before zonal flow sets up through the Monday night. H5 trough and associated surface cold front approaches late Monday with frontal passage in the Tuesday/Tuesday night time frame. Best chances of shower/thunderstorms will be from Monday afternoon through Tuesday evening. Maximum/minimum temperatures and POPs are close to normals for early summer. No outstanding heat or humidity issues in the forecast at this moment.
-- End Changed Discussion --
&& .AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
-- Changed Discussion --
Big uncertainty overnight into Thursday regarding severe weather threat...but at least through midnight we should generally stay VFR at all terminals. Thunderstorms late tonight into Thursday can bring reductions in vis and cigs briefly to IFR...along with damaging winds. Improving conditions generally Thursday night and VFR Friday - Sunday. MVFR conditions possible early next week for all terminals with cold frontal passage.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
SCA conditions waning late this afternoon. Winds light overnight but system moving in from the west will bring rain...thunderstorms and another round of SCA winds on Thursday. Conditions improve Friday-Saturday. In the extended time frame, best chances of small craft conditions will be on Monday pre-frontal, and then again on Tuesday post- frontal.
-- End Changed Discussion --
&& .LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...None. MD...Flash Flood Watch from 2 AM EDT Thursday through Thursday afternoon for MDZ003-501-502. VA...Flash Flood Watch from 2 AM EDT Thursday through Thursday afternoon for VAZ027-028-030-031-503-504. WV...Flash Flood Watch from 2 AM EDT Thursday through Thursday afternoon for WVZ050>053-055-501>506. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ530>543. Small Craft Advisory from 6 AM to 6 PM EDT Thursday for ANZ530>543.
-- End Changed Discussion --
&& $$ SYNOPSIS...Lee NEAR TERM...RCM SHORT TERM...RCM LONG TERM...Lee AVIATION...Lee/RCM MARINE...Lee/RCM

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