Area Forecast Discussion
Issued by NWS Sterling, VA

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531 FXUS61 KLWX 011847 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 247 PM EDT Wed May 1 2024 .SYNOPSIS...
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Brief high pressure settles over the region today through Thursday leading to a warm and dry conditions. A weak cold front will cross the area late Thursday into Friday before sinking south this weekend. An additional cold front and area of low pressure will pass through the area Sunday into early next week. This will result in increased chances for showers and thunderstorms along with cooler conditions.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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The cold front from yesterday continues to push south and east of the region this afternoon while brief shortwave ridging/surface high pressure takes over the lower Ohio River Valley. Outside of a few mid and high level clouds mainly along and east of the Blue Ridge mostly sunny skies prevail. High temperatures today will push into the low to mid 80s with mountain locations remaining in the 60s and 70s. Humidity values will come down as well with dewpoints hovering in the upper 40s and lower 50s this afternoon. Winds will remain light out of the northwest at 5-10 mph with a few sporadic gusts up to 15 mph (given terrain and bay breeze circulations). High pressure slides over the southern Appalachians and southern Blue Ridge this evening into Thursday leading to a continuation of quiet weather conditions. Lows tonight will fall into the mid to upper 50s with low 60s over the Baltimore/Washington DC metro areas. Some patchy river and bay fog are possible although confidence is lower for fog development given dry air advection moving in.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
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Upper level ridging firmly builds over the area Thursday leading to a continuation of warm and dry conditions. 850 mb temperatures will be back up around +14 to +18 degrees C with PWAT values around 1". Meanwhile, a moisture starved cold front will sit across far western portions of the forecast area acting as a catalyst for perhaps an isolated mountain shower or thunderstorm (chances less than 15 percent). Elsewhere across the region expect dry conditions with passing fair weather strato-cumulus during the peak heating of the day. High temperatures will remain above average in the upper 80s and low 90s with upper 70s and low 80s over the mountains. Lows Thursday night will fall back into the upper 50s and low to mid 60s. By Friday, the weak cold front looks to cross the region. Once again most areas will remain dry with high pressure slowly pushing offshore and increased heights across the region. Some showers and thunderstorms are likely over the mountains given added orographic lift and increasing moisture from southeasterly flow. Temperatures will remain above average with highs in the upper 70s and low to mid 80s despite increasing clouds. The front will continue south of the region late Friday into Saturday as strong high pressure over eastern Canada wedges south. This will allow for onshore east to southeast flow to increase across the area especially east of the Blue Ridge. As a result, expect increased cloud cover, cooler temperatures, and rain at times for the start of the weekend. Shower activity will be fairly scattered throughout the day with even a few rumbles of thunder west of the Blue Ridge and Allegheny Front where better heating can take place. Overall we should remain stable limiting any severe weather concerns. Locally heavy rainfall will remain possible especially late Saturday into Sunday as an area of low pressure and cold front move into the region. With that said, no washouts are expected, but the increasing need for wet weather gear will come in handy this weekend. PWATS will run 1.25 to 1.75 inches Saturday which is within the 90 to 97.5 percentile of 30 year climatology for this time of year. Rainfall amounts of a quarter to three quarters of an inch are expected Saturday with an additional quarter to a half an inch Sunday as the front passes through. High temperatures Saturday will push into the upper 50s and low to mid 60s. Overnight lows Saturday night will into the low to mid 50s. East to southeast winds will remain sustained at 5 to 15 mph with gusts up to 25 mph at times especially along the ridges/waters.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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Unsettled weather returns for the weekend along and and ahead of a surface low pressure and associated cold fronts that will impact the region. Rain chances increase by late Friday night from west to east. Saturday does not look like a total washout, with the better forcing remaining off to the west. Nonetheless, off and on showers will continue through the day on Saturday. Thunderstorm chances will likely remain fairly low with the limited instability across the Mid- Atlantic during that time. Highs will mostly be in the 60s for most of the area Saturday afternoon. By late Saturday night into Sunday, precipitation rates and thunderstorm chances will likely increase. The front will slowly cross the area and bring rainfall totals potentially beyond one inch in localized areas. Given the drier antecedent conditions, isolated instances of flooding will be possible on Sunday. Afternoon showers and isolated thunderstorms will be possible Monday and Tuesday as a result of a warm front lifting north of the area and lingering moisture sticking around Tuesday with highs continuing to climb across the area from 70s on Monday to low 80s by Tuesday.
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&& .AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
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VFR conditions are expected through Friday. Outside of mid and high level clouds at terminals east of KMRB and KSHD clear skies prevail. Winds remain light out of the northwest at 5-10 kts with a few sporadic gusts up to 15 kts at times. SKC conditions are expected tonight into Thursday as strong high pressure builds in from the lower Ohio River Valley. Winds will turn to the west and southwest Thursday at 5-10 kts. River valley fog may develop late tonight. Confidence on this happening is low. Mid and high level clouds will move back into the area Friday as a weak cold front drops in the region. Sub-VFR conditions are possible at terminals west of the Blue Ridge where a few showers and thunderstorms are possible Friday afternoon. Areas further east will likely stay dry with increasing cloud cover. Winds will switch to the east and northeast late Friday into Saturday. Multiple cold fronts will bring showers and perhaps an isolated thunderstorm to the terminals both Saturday and Sunday. Sub-VFR conditions are expected at times on both days. In addition to reduced CIGs and VSBYs, southeasterly winds will gusts up to 20 knots on Saturday and 10-15 knots on Sunday. Additional chances for sub-VFR conditions are possible early next week as the chances for showers and thunderstorms remain with multiple fronts passing through.
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&& .MARINE...
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No marine hazards are expected through Friday morning. SCA level winds return Friday afternoon and into the weekend as a series of fronts drop into the region. Winds will remain light out the northwest today before switching to the west and southwest Thursday. Onshore SCA level winds develop Friday into Saturday. Gusty southeasterly winds will gust between 15-25 knots on Saturday as multiple cold fronts bring showers and isolated thunderstorms to the waters. Small Craft Advisories are likely both Saturday and Sunday. While winds diminish slightly on Sunday, gusts 15-20 knots are possible in the afternoon.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...EST NEAR TERM...EST SHORT TERM...EST LONG TERM...ADM/EST AVIATION...ADM/EST MARINE...ADM/EST