Area Forecast Discussion
Issued by NWS Sterling, VA

Home | 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
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 091930 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 330 PM EDT Sun May 9 2021 .SYNOPSIS... Low pressure will track just to our north and west today into tonight, eventually dragging a cold front through the area on Monday. High pressure will build back in toward the middle of the week. && .NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
Breaks of sun have developed early this afternoon as a warm front lifts northward through the area. However, high clouds are starting to filter back in from the west in advance of a mid- level shortwave and associated surface low situated over the Ohio Valley. Winds have picked up out of the south in advance of the area of low pressure and will become quite gusty later this afternoon into this evening. Showers have moved back into far northwestern portions of the forecast area. As low pressure tracks along the Mason-Dixon Line tonight, a few showers can`t be ruled out anywhere, but it won`t be a washout by any means. As low pressure lifts off to our northeast later tonight, it will drag a cold front through the area, bringing an end to any shower activity. Winds will abruptly shift to northwesterly behind the front, allowing cooler and drier air to filter into the area once again.
-- End Changed Discussion --
&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
-- Changed Discussion --
A fairly stagnant pattern will persist across the area through Monday and Tuesday, with mid-upper level troughing to our north over the Great Lakes, and persistent northwesterly flow at the surface locally. Northwesterly flow will maintain a supply of cool and dry air, with temperatures both days running well below normal for mid-May. Highs both days will be in the 60s for most, with overnight lows primarily in the 40s. Some 30s may even be possible across the higher elevations Monday Night, and across most spots to the west of the Blue Ridge Tuesday night. Frost and Freeze headlines may eventually be needed Tuesday night. In terms of sensible weather, tomorrow should feature increasing sunshine through the day, with a mix of sun and clouds on Tuesday. A stray shower or two can`t be ruled out Tuesday afternoon as the upper level trough to our north nudges southward toward our area, but confidence was too low to incorporate into the forecast at this point.
-- End Changed Discussion --
&& .LONG TERM /WEDNESDAY THROUGH SATURDAY/...
-- Changed Discussion --
By mid-week, a broad negative height anomaly lingers over the Canadian Maritimes with an attendant positively-tilted trough crossing through the Mid-Atlantic. This will reinforce the cool air mass in place as northwesterly winds ensue. A seasonably strong dome of high pressure approaches from the west, with this ridge extending from the Missouri Valley to the interior northeastern U.S. by Thursday. This will provide continued chances for frost from the Blue Ridge and Catoctins westward on Wednesday morning, with perhaps another chance the following night. Winds need to remain relatively light which would be one inhibiting factor here. Additionally, some higher elevations of the Allegheny Front could deal with freeze concerns. Daytime temperatures through Thursday are forecast to stay around 5 to 10 degrees below average. This equates to mid/upper 60s across the lower elevations with 50s in the mountains. Late Thursday, an upper trough begins to approach from the Ohio Valley. The 12Z CMC/GFS and 00Z ECMWF all depict its presence as it slides toward the southeast into Friday. The GFS/GEFS solutions in past days had advertised a coastal cyclone of sorts. However, the last few model cycles favor weaker cyclogenesis that is displaced well offshore. Depending on the strength of this upper low, some showers may occur as it crosses through the Mid-Atlantic. In the wake, high pressure further re-establishes its presence across the eastern U.S. into next weekend. This continues the period of near to below average temperatures. By next Sunday, ensembles show some potential warmth ahead, albeit with quite a bit of model spread. Another round of precipitation is possible, but is also very model dependent.
-- End Changed Discussion --
&& .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
-- Changed Discussion --
Winds have turned southerly and showers have moved out of the area early this afternoon. The southerly winds will become quite gusty this afternoon, with gusts of 25-30 knots possible just prior to dark. Breaks of sun have developed, but clouds will move in again later this afternoon. Chances for showers will return again tonight, but activity will be intermittent in nature. Ceilings may briefly become MVFR for a time tonight at MRB, but elsewhere VFR conditions are expected. A sharp wind shift is expected overnight as a cold front passes through, with winds turning from southerly to northwesterly. Winds may briefly gust to around 25-30 knots for an hour or two immediately behind the front. Northwesterly winds and VFR conditions are expected tomorrow through Tuesday, with gusts generally between 15 and 20 knots both afternoons. With Wednesday and Thursday looking dry given the presence of high pressure, VFR conditions are quite likely. Winds will initially be northwesterly with gusts possibly reaching 15 to 20 knots before turning northeasterly by Thursday as the surface high closes in to the west. Weaker gradients will favor a decrease in winds.
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Southerly winds will pick up as we move through the remainder of the afternoon. They may briefly approach gale force this evening just before dark, but warmer air moving over cooler waters may be an inhibiting factor for those stronger gusts moving over the waters. Solid SCA conditions are expected overnight, with an eventual shift to northwesterly winds as a cold front passes over the waters between roughly 3 and 6 AM. Winds may be close to gale force again for an hour or two immediately in the wake of the front, but current thinking is that it should remain just below. Winds will remain northwesterly tomorrow through Tuesday, and could reach SCA levels at times. On Wednesday, northwesterly breezes across the area waterways may approach small craft levels before diminishing in strength into the night. Thereafter, gradients will decrease with high pressure approaching the region. Thus, sub SCA conditions are likely with somewhat variable winds at times.
-- End Changed Discussion --
&& .TIDES/COASTAL FLOODING... Minor coastal flooding will be possible late tonight into Monday morning as water levels rise on srly flow ahead of a cold front Monday morning. Blowout tides expected Monday afternoon through mid week on NW flow. && .LWX WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 PM EDT Monday for ANZ530>543.
-- End Changed Discussion --
&& $$ SYNOPSIS...LFR/KJP NEAR TERM...KJP SHORT TERM...KJP LONG TERM...BRO AVIATION...BRO/KJP MARINE...BRO/KJP TIDES/COASTAL FLOODING...LFR

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