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Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
431 FXUS61 KLWX 141346 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 946 AM EDT Wed Aug 14 2024 .SYNOPSIS... Hazy skies today as smoke from Canadian wildfires pushes south around an area of broad high pressure overhead. Quiet weather conditions are expected otherwise through Thursday before precipitation chances return with a slow moving low pressure system Friday into the weekend. A cold front will cross the region late Saturday into Sunday bringing the highest probability for showers and thunderstorms.This system exits off the coast Monday into Tuesday with high pressure set to return to the region by the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... Upper level troughing will continue to exit off the Atlantic coast today while broad high pressure builds eastward from the Great Lakes region. Tranquil weather conditions are expected as a result with less cloud cover and low humidity. Highs today will rise into the low to mid 80s east of the Alleghenies with 70s along the higher ridges. One thing to note will be some Canadian wildfire smoke in the mid to upper troposphere. This smoke is evident on the GOES GeoColor this morning with a subtle band dropping in from central PA and southern NJ. High-resolution smoke guidance also picks up on this with northerly flow carrying this elevated smoke plume through the area mid to late afternoon. Consequently, have opted to put haze in the forecast grids for areas along and east of U.S. 15 starting midday and through at least sunset. While this could impact locations to the west, confidence was not high enough to do so. Smoke is unlikely to affect the surface, although some minor reductions in visibility (5-7SM) are possible throughout the mid to late afternoon period. High pressure will rule the forecast tonight with plenty of subsidence overhead. Looking like a good radiational cooling set up with mainly clear skies and calm winds. This will allow temperatures to fall into the low to mid 60s east of the Blue RIdge with 50s west. Mountain and high valley locations could fall back into the 40s. Patchy river/valley fog is possible heading into daybreak Thursday. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... With longwave ridging across the area on Thursday, expect one more dry day ahead of a wetter period ahead. Additionally, the typical summertime humidity is also held at bay owing to a persistent north to northwesterly wind. High temperatures push into the upper 80s with a few 90 degree readings possible. While skies start off relatively clear, expect increasing clouds late in the day ahead of the next weather maker. As this occurs, winds eventually shift to southerly which yields a gradual moistening of the lower atmosphere. Eventually some showers work their way to the Alleghenies by late Thursday night. Overnight lows will be in the 60s although some low 70s are likely across D.C. and Baltimore. On Friday, the approaching longwave trough is forecast to be located over the Upper Great Lakes with the associated frontal systems nearing the Ohio Valley. Broad ascent ahead of these height falls will continue to spread increasing clouds across the Mid-Atlantic region. The latest timing keeps the bulk of the showers and embedded thunderstorms west of I-95 before dark. Heading into the late evening and night, this activity begins to overspread the entire forecast area. Conditions will also be milder as a warm front pushes through overnight. Low temperatures are to range from the mid 60s to low 70s. && .LONG TERM /SATURDAY THROUGH TUESDAY/... As a trough digs into the Ohio Valley/Mid-Atlantic Saturday, surface high pressure slides off to the east and a low pressure system moves into the Great Lakes. By Saturday, we`ll be in the warm sector of the low passing to our north, with ample moisture from persistent southerly flow. Combined with ascent from the approaching trough, widespread chance to likely PoPs are expected Saturday afternoon/evening. The cold front is currently expected to move through between Saturday evening and Sunday. More widespread showers and thunderstorms can be expected with the frontal passage. Surface high pressure is expected to build in behind the cold front on Monday into Tuesday, but some showers could continue west of the Blue Ridge as a trailing shortwave acts on lingering moisture. Temperatures Saturday are expected to be in the mid-upper 80s for most of the area. Only a few degrees of cooling is anticipated behind the cold front Sunday into early next week. Lows will be in the 60s and 70s outside of the mountains for the duration of the extended. && .AVIATION /14Z WEDNESDAY THROUGH SUNDAY/... VFR conditions are likely across all terminals through Thursday and perhaps the first half of Friday. Some elevated smoke could impact some terminals today, but do not expect any large reductions in the visibility. Winds shift over to northerly today with a few afternoon gusts up to 15 knots. Similar winds are expected on Thursday, but they should be much lighter in nature. By late Thursday evening, southerly warm advection returns. Gusts on Friday could push into the 10 to 15 knot range, accompanied by increasing rain chances from the evening onward. This may come with a few rumbles of thunder as well. Sub-VFR conditions are possible Friday evening and into the night given the threat for showers. While VFR conditions are expected to prevail most of the weekend, showers and thunderstorms could bring brief restrictions to terminals, especially in the afternoon and evening hours. Winds increase out of the south Saturday with gusts to around 15 kts are possible in the afternoon. Behind the cold front on Sunday winds turn W/NW. && .MARINE... A fairly persistent northerly wind continues the next couple of days. Any gusts should top out in the 10 to 15 knot range. A shift to southerlies is expected late Thursday into Friday. This will also lead to a period of southerly channeling, especially Friday evening into the overnight hours. Small Craft Advisories may be needed across portions of the waters. Additionally, showers and few thunderstorms may also impact the waters by late Friday. Winds increase out of the south Saturday and could approach SCA criteria, especially in the open waters of the central and southern Bay. Winds diminish and turn W/NW behind a cold front on Sunday. && .TIDES/COASTAL FLOODING... Tidal anomalies remain low under light N/NW flow. However, a few sensitive sites may approach or reach Action stage during the next few late night/early morning high tide cycles, such as Havre de Grace and Annapolis. Winds turn southerly late this week behind a warm front and increase tidal anomalies. As a result, some sensitive locations may approach Minor flooding. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...EST NEAR TERM...EST SHORT TERM...BRO LONG TERM...CAS AVIATION...BRO/CAS MARINE...BRO/CAS TIDES/COASTAL FLOODING...BRO