Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 131920 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 320 PM EDT Wed Mar 13 2024 .SYNOPSIS...
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Surface high pressure will continue to influence the Mid-Atlantic region through Thursday with well above normal temperatures and mostly dry conditions. A low pressure system will approach the area Friday, bringing a chance of showers and a few thunderstorms. Another low pressure system may impact the region Sunday into Monday.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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The center of surface high pressure extends eastward from Florida this morning. A shortwave trough is overhead producing mid and high level clouds. However there has been enough filtered sunshine for temperatures to rise into the upper 60s to mid 70s. Skies clear out again tonight as the shortwave moves away. Some more high clouds may move back in late tonight though. Overnight lows will be in the 40s for most of the area with light winds continuing. Some sheltered valleys may fall into the 30s.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
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The high remains off the southeast coast Thursday with ridging maximized overhead. Flow will become more southwesterly, which should boost highs into the mid 70s to near 80 despite some patchy high level clouds. The low level airmass will remain fairly dry and should warm quickly. Meanwhile, low pressure will be moving toward the southern Great Lakes by Thursday night. The associated warm front will likely extended across PA, leading to well above average low temperatures for the overnight hours. Most areas will likely only drop down into the mid to upper 50s. A few showers are possible along the Alleghenies and closer to the Pennsylvania border, but deeper moisture and lift is expected to remain north of the area. The low will quickly move toward New England Friday, but with the front nearly parallel to the upper flow, it will be slow to push southeast. With the relatively dry low level airmass remaining in place and a lack of strong upper support as well, there may be some difficulty in getting a whole lot of precipitation. Forecast rain amounts are now in the tenth to quarter inch range, although it`s possible some areas get none. Weak instability and deep layer shear around 40 kt could support a few thunderstorms however. Increased cloud cover will likely knock temperatures down a little, but with enough sun, eastern areas will still likely reach the mid 70s to near 80. The front will push southward through the area Friday night, ending the chance for rain. Lows will be in the 40s to near 50.
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&& .LONG TERM /SATURDAY THROUGH WEDNESDAY/...
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The area will remain dry on Saturday. Highs will still average about ten degrees above Mid-March norms with mid 60s for most. Sunday likely starts dry, but a potent sub-522 dm trough is progged to move through the area Sunday through Tuesday. A cold front will move through Sunday night. This will bring rain showers to the region. On the backside, mountain snow showers are evident across most ensemble guidance Monday into Tuesday. There is a wave of energy that could enhance snow showers late Monday night across the Alleghenies, with rain elsewhere. A more pronounced cooling trend ensues which comes with increasingly gusty northwesterly winds (25-35 mph, higher in the mtns) amidst the CAA. The true extent of the cold blast does not really take shape until Tuesday as temperatures fall back into the mid/upper 40s. Though the growing season has not officially started, any early budding flowers/trees could succumb to the cold temperatures next week with multiple days of sub-freezing nightly lows becoming increasingly likely.
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&& .AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
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VFR conditions will continue through Thursday. Winds will be light and variable but generally between west and south. Only a few periods of mid/high level clouds are expected. By Friday afternoon, scattered showers along with a few thunderstorms will be possible as a cold front approaches the area. Winds shift from southerly to northwesterly and could be briefly gusty. There`s also a chance of sub-VFR ceilings near and behind the front. Behind the front Saturday, conditions will dry out with winds out of the WNW gusting to 15-20 kts. By Saturday afternoon/evening, the winds will lessen and become more south of west. Southerly winds continue ahead of a cold front Sunday. Rain showers are possible along the front. Winds turn back to WNW behind the cold front Sunday night into Monday and could gust to 20-25 kts.
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&& .MARINE...
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No marine hazards are expected through the day on Thursday with light westerly to southerly winds expected. By Thursday night, a low pressure system will move into the Great Lakes. Southerly winds may approach SCA criteria, but warm air over cool waters may produce low level stability. That same theme will continue into Friday. Showers and a few thunderstorms are possible Friday afternoon and evening as a cold front pushes through. Northwesterly winds may be near advisory levels behind the front. SCA may linger out of the NW across the southern waters Saturday morning before diminishing out of the south through the afternoon. Southerly channeling could result in marginal SCA conditions Saturday night. Winds turn back out of the WNW behind the front Sunday night into Monday resulting in renewed SCA conditions.
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&& .FIRE WEATHER...
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Light winds are occurring today, with local terrain and marine influences evident in directions, amidst a continued very warm and dry airmass in place. Min RH in the 20 to 30 percent range is occurring with deep mixing. High and mid-level clouds will provide some shading before exiting this evening. Thursday will be warmer still with only slight increases in Min RH to 25 to 35 percent. Winds will become more southerly with gusts increasing during the evening along the higher elevations. A low pressure system will approach the area Friday and bring the next chance of rain, although forecast amounts have been trending downward.
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&& .TIDES/COASTAL FLOODING...
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Tidal anomalies are on the increase with lighter winds in place, and that upward trend will continue through the end of the week as winds become more southerly Thursday. Some tidal sites may exceed minor flood stage Thursday and (especially) Friday mornings with the increased southerly flow ahead of the next low pressure system. A wind shift Friday evening will end this threat.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...ADS NEAR TERM...ADS SHORT TERM...ADS LONG TERM...CPB AVIATION...ADS/CPB MARINE...ADS/CPB FIRE WEATHER...ADS TIDES/COASTAL FLOODING...ADS

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