Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
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
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 221434 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1034 AM EDT Sun Apr 22 2018 .SYNOPSIS...
-- Changed Discussion --
High pressure over the Great Lakes will slowly move east into the Northeast U.S. by tonight. This high will move offshore Monday. A low pressure system will bring unsettled weather to the region Monday night through the middle of the week.
-- End Changed Discussion --
&& .NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Surface high pressure will continue to dominate the day today with dry conditions, light northeast to southeast winds, and temperatures approaching normal for this time in April. More middle level clouds will move in across the region this afternoon as a weak upper level disturbance slides across us from northwest to southeast. We can`t rule out a sprinkle or a brief shower, but for the most part, dry conditions should prevail. High temperatures today will reach the lower to middle 60s. A couple of degrees cooler over the ridge tops of the Potomac Highlands and the Blue Ridge Mountains. A weak ridge of upper level high pressure will build back into the region tonight after the weak disturbance departs to the southeast. Dry conditions with clouds breaking and low temperatures dropping down into the 40s will be anticipated. Winds will remain light from the southeast.
-- End Changed Discussion --
&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
High pressure will move off of the East Coast Monday as a cut- off low pressure system moves up the East Coast from the Southeast U.S. Winds will persist out of the southeast ahead of the low pressure system. Clouds will thicken through the day Monday. Highs will again be generally in the 60s, with cooler readings in west-central VA where rain may arrive in the afternoon, while warmer readings towards the metro. Rain is likely to spread across the region by late Monday night as the system to the southwest closes in. As the cut-off low and a couple of pieces of upper level energy move into the mid-Atlantic region Tuesday, additional rounds of light to moderate rain will develop and overspread most of the region. This rain should gradually taper to showers Tuesday night and may end from southwest to northeast. However, the ending time may be delayed as the next upper level disturbance will be quick on the heels of the Monday night and Tuesday low pressure system. Temperatures will be about 5 to 10 degrees cooler Tuesday due to cloud cover and rainfall and about 5 to 10 degrees milder Tuesday night due to the same two factors.
-- End Changed Discussion --
&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
-- Changed Discussion --
Lingering shower activity will be ongoing Wednesday morning as low pressure resides on the eastern periphery of our CWA, likely in the vicinity of the Delmarva Peninsula. This area of low pressure will also be receiving lift and support from the mid to upper level troughing overhead, and associated shortwave energy heading toward the New England states. There should be a downward trend in rain coverage during the daytime hours on Wednesday before another shortwave quickly on the heels of the aforementioned features helps enhance additional shower activity Wednesday evening. Highs and lows Wed/Wed night will remain below normal thanks to ample cloud cover and shower activity, reaching the low to middle 60s during the day and upper 40s to near 50 at night. More of a drying trend is looking likely on Thursday as we will see weak surface high pressure build in to the region and along with weak upper level ridging overhead and our area remains in between the exiting system over New England and the next low pressure/shortwave digging across the upper Midwest. Continued slightly below normal temperatures expected Thursday and Thursday night, maybe a touch cooler than Wednesday with a light northwest flow and weak/brief cold air advection aloft early Thursday. Surface low pressure and an associated upper level cut-off low will swing across the Great Lakes region Thursday night. There is a good deal of global model discrepancy at this time on the strength and timing of this feature. Operational GFS trending more progressive and stronger, while the operational ECMWF is slower and weaker. Regardless, ensembles do agree upon a broad mid to upper level trough winning out once again over the Mid Atlantic and Northeast through the first half of the weekend. Will maintain chance POPs the latter half of Friday into Saturday for much of the area with near normal temperatures for late April.
-- End Changed Discussion --
&& .AVIATION /15Z SUNDAY THROUGH THURSDAY/...
-- Changed Discussion --
VFR conditions expected through Monday with light and variable winds, becoming southeast 5 to 10 knots tonight. Winds southeast around 10 knots Monday and Monday night. MVFR conditions are possible at the CHO terminal Monday night with some light rain approaching from the southwest. MVFR conditions possible at all terminals Tuesday and Tuesday night due to light to moderate rain. Winds east 10 to 15 knots Tuesday becoming northeast 5 to 10 knots Tuesday night. Periodic MVFR/IFR conditions expected Wednesday and Wednesday night with an unsettled weather pattern bringing increased rain chances to the terminals. Light northerly winds of 10 knots or less are anticipated. A return to VFR flying conditions forecast Thursday into Thursday night as weak high pressure builds over the area, and winds remain light at less than 10 knots out of the west northwest.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
No marine hazards expected through Monday morning. Winds will be light and variable, becoming southeast around 10 knots this afternoon and tonight. Winds southeast 10 to 15 knots Monday. Small craft advisory starts Monday afternoon through Monday night for the middle bay and lower Potomac, and likely to expand northward Tuesday and Tuesday night. Winds southeast becoming east 10 to 15 knots with gusts 20 knots Monday afternoon through Monday night, with gusts perhaps approaching 30 knots Tuesday. Winds becoming northeast 10 to 15 knots gusts to 20 knots Tuesday night. Sub SCA conditions forecast over the waters Wednesday and Wednesday night as low pressure crosses the Delmarva and exits to the northeast. Marginal SCA gusts possible Thursday morning in the wake of the exiting low pressure system, but weak high pressure is expected to build over the waters the second half of Thursday and into Thursday night, delivering lighter winds.
-- End Changed Discussion --
&& .TIDES/COASTAL FLOODING...
-- Changed Discussion --
As low pressure approaches the waters from the southeastern U.S. late Monday into Tuesday, a persistent onshore flow will develop. This will yield increasing tidal anomalies, and the possibility of coastal flooding toward the middle part of the work week.
-- End Changed Discussion --
&& .LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 1 PM Monday to 6 AM EDT Tuesday for ANZ534-537-543.
-- End Changed Discussion --
&& $$ SYNOPSIS...KLW/RCM NEAR TERM...KLW/RCM SHORT TERM...KLW/RCM LONG TERM...BKF AVIATION...BKF/KLW/RCM MARINE...BKF/KLW/RCM TIDES/COASTAL FLOODING...BKF

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