Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 030101 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 901 PM EDT Mon Oct 2 2023 .SYNOPSIS... High pressure will extend across the Mid Atlantic to New England through Wednesday before slowly pushing east Thursday. A cold front will push through the area late Friday or Saturday. High pressure approaches from the west to conclude the weekend. && .NEAR TERM /THROUGH TUESDAY/...
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Scattered clouds have redeveloped this evening, though coverage is sparse enough to maintain skies partly cloudy. These clouds should be transient, with most dissipating overnight. Winds are already calm at most locations, with just a bit of light wind right along the Tidal Potomac. The mostly clear skies and light wind will allow patchy fog to develop in favored locations overnight. This includes river/stream valleys, particularly those which are more sheltered in nature. Locally dense fog is possible in some areas. Temps tonight settle in the 50s, with low 60s near the D.C. and Baltimore city centers.
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&& .SHORT TERM /TUESDAY NIGHT THROUGH WEDNESDAY NIGHT/... Above average temperatures continue given the presence of ridging aloft. By mid-week the extent of this 588-mb mid-level ridge extends from the western Gulf Coast up through the Tennessee Valley and into the northeastern U.S. At some point, a cyclonic circulation spins off the South Carolina coast. However, any influence from this feature would be far removed from the Mid-Atlantic region. Expect at least a couple more days of high temperatures rising into the low 80s, locally approaching 85 degrees. Even the cooler mountain locales should rise into the 70s. Relative to typical early October climatology, highs are forecast to be around 8 to 13 degrees above average. Tuesday may bring a few additional clouds to the sky given some weak vorticity centers meandering about the central Appalachians. Weak pressure gradients makes daily wind fields light and somewhat variable in nature. Additional chances for patchy fog are in the forecast each night. There should be a bit more marine influence to the pattern by late Wednesday as winds shift to southeasterly. Depending on the strength of the onshore/moist advection, low clouds may enter the picture for areas east of the Blue Ridge mountains. Forecast lows stay in the 50s for all, locally a bit milder toward the metro areas. && .LONG TERM /THURSDAY THROUGH MONDAY/... Upper ridging coupled with an area of high pressure nearby will keep conditions mostly dry on Thursday, with highs remaining at or just above normal with 70s for most of the area. By Thursday night, lows will drop down into the mid to upper 50s along and west of the Blue Ridge with 60s closer to the I-95 corridor. By Friday, precipitation chances begin to creep into the area with a digging trough centered over some of the Canadian provinces progressing eastward. An associated cold front is expected to cross through the Mid-Atlantic somewhere between Friday and Saturday. Model agreement is rather sparse at this juncture with respect to timing but generally later in the afternoon and evening on Friday looks to be when the cold front approaches our far western areas and continues to move further east. Showers and maybe and maybe an isolated thunderstorm will be possible with the system. It looks to be fairly progressive so most rainfall will likely be beneficial in nature. Behind the front Saturday and Sunday will be much cooler temperatures with highs starting out in the upper 60s to low 70s further east for the start of the weekend before most areas struggle to reach 65 on Sunday. Some of the higher elevations may only top out in the mid 40s. Overnight lows will be in the 40s across the lower elevations both days with even some 30s mixing in for the highest elevations Sunday night. Frost and freeze headlines may be needed but confidence is low at this time. && .AVIATION /01Z TUESDAY THROUGH SATURDAY/...
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Patchy ground fog is possible tonight, especially at MRB and CHO where the fog could be locally dense. Onset of any fog looks to be around 07Z-08Z Tuesday, with fog quickly dissipating after sunrise Tuesday morning. The IAD/BWI TAFs mention 6SM BR, though confidence in any lower restrictions from fog remains low. Otherwise, VFR conditions are expected. Light winds eventually become southeasterly by Wednesday. VFR conditions will persist into Thursday with high pressure nearby. Some sub-VFR conditions may begin to creep in on Friday as a cold front tracks from the west towards the terminals for the afternoon and evening hours. Winds will be out of the southeast most of the period, gusting 10 to 15 knots for the afternoon hours to end the work week.
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&& .MARINE...
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Favorable marine conditions are expected through Wednesday. Sub-SCA winds are expected Thursday and Friday as a result of a departing high pressure. Precipitation returns later in the day on Friday but no other marine hazards are possible through the work week. As the front departs late Friday and into early Saturday, gale-force winds may be possible but confidence is low in this outcome at this time.
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&& .TIDES/COASTAL FLOODING...
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Elevated tides and coastal flooding are likely to be a persistent issue for much of the upcoming week. High pressure over the Northeast slides offshore, causing winds to veer east to southeast for the remainder of the week. Tidal anomalies are forecast to rise through Tuesday. Minor tidal flooding will be possible again at Annapolis, Straits Point, and DC SW Waterfront for the Tuesday afternoon/evening high tide cycle. Guidance hints at a slight decline in tide levels Wednesday, perhaps in part due to lower astronomical tides. However, an increase may occur in SE flow Thursday into Friday.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...Coastal Flood Advisory until 2 AM EDT Tuesday for DCZ001. MD...Coastal Flood Advisory until 11 PM EDT this evening for MDZ014. VA...None. WV...None. MARINE...None.
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&& $$ SYNOPSIS...BRO NEAR TERM...KRR SHORT TERM...BRO LONG TERM...ADM AVIATION...KRR/ADM MARINE...KRR/BRO/ADM TIDES/COASTAL FLOODING...LWX

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