Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 150800 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 400 AM EDT Fri Mar 15 2024 .SYNOPSIS...
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A cold front will cross the area this afternoon and evening bringing showers and thunderstorms to the area. Cool high pressure briefly returns to the area Saturday before a secondary cold front crosses Sunday into early next week. This brings a return to below normal temperatures next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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The latest radar trends across the area have shown a decrease in convective coverage. What is currently pushing through is what remains from severe weather which impacted the Ohio Valley the previous evening. Any lightning activity has ceased within the last couple of hours. Currently light showers extend from north-central Maryland back to the eastern West Virginia panhandle. A rather pronounced outflow boundary is surging southward to southern Maryland with peak wind gusts up to around 20 to 30 mph. Overall, expect shower activity to dissipate in the next hour or two as instability has become exhausted per the RAP objective analysis. Early morning observations are very mild for mid-March standards. Most areas sit in the upper 50s to mid 60s accompanied by winds mainly out of the south to southwest. The current exceptions are places which have seen the mentioned outflow move through which led to a shift to north to northwesterlies. A warm advection pattern will maintain well above average temperatures yet another day. Today`s highs are expected to range from upper 60s to mid 70s, locally down into the 50s to low 60s across the higher terrain. An upstream cold front currently extending from northeastern Ohio back toward southern Illinois will play a key role in today`s weather. This boundary is forecast to cross through the local area during the afternoon to early evening before sagging south into the night. Expect scattered to numerous showers to cross through as this system approaches. The air mass is fairly dry so it may take some saturation of the lower atmosphere to see appreciable rainfall. Although convective chances are not terribly high, isolated thunderstorms are in the forecast mainly from I-66/U.S. 50 southward. This spans the afternoon into early evening hours before any remaining instability wanes. MUCAPE values largely top out in the 200-400 J/kg range. Rain chances diminish into the night with low temperatures in the mid 30s over the mountains to the 40s elsewhere.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
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Behind the exiting frontal system, high pressure briefly returns for the first half of the weekend. This will promote a dry forecast over the region with cooler temperatures owing to a period of northwesterly winds. While still above average for this time of year, it will feel cooler as highs are expected to be in the 60s with 50s across mountain locales. As the anticylone exits the Atlantic coast, winds shift back to southerly for the second half of the day. Skies should be filled with plenty of sunshine despite some passing clouds. Nighttime temperatures remain mild given the return flow. The next frontal system of interest currently resides over northern Alberta. Over the next couple of days, this feature will race southeastward, bringing it to the Appalachian chain by early Sunday. This system will bring another round of northwesterly winds, albeit more gusty than the previous day. Afternoon gusts could reach 20 to 25 mph, while being closer to 35 to 45 mph over the Allegheny Front. This could bring a few of the higher peaks to near Wind Advisory criteria. While this cold front may bring a few showers to western Maryland early Sunday, the day will largely be dry. Forecast highs are mild which generally sit in the upper 50s to 60s, with 40s to low 50s in the mountains. Winds may stay up a bit into the night with low temperatures in the 30s to low 40s, with 20s along the Alleghenies.
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&& .LONG TERM /MONDAY THROUGH THURSDAY/...
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The first half of next week looks colder than normal as large scale troughing pivots across the eastern CONUS. Embedded shortwaves may bring periods of mountain snow showers Monday and Tuesday, and a flurry, sprinkle, or shower or two are possible east of the mountains depending on the strength of each of the waves (though most if not all of the time/area east of the Alleghenies should stay dry). This period early in the week will also feature blustery conditions in a tight gradient between low pressure to the northeast and high pressure building in from the west. Moderating temperatures are likely heading into the second half of next week. As the pattern shifts a bit, another storm system may develop which would bring more widespread (likely liquid) precipitation chances to the region later next week, but uncertainty surrounds the specifics given the extended time range and shifting pattern locally.
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&& .AVIATION /07Z FRIDAY THROUGH TUESDAY/...
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An outflow boundary from earlier convection continues to drop southward toward southern Maryland. Any impacts to the terminals have already occurred at this point. The shift to north to northwesterlies at the D.C. and Baltimore terminals should be somewhat brief with winds returning to south-southwesterly. Otherwise, a strong low-level jet overhead will promote enhanced low-level wind shear through late this morning. For the rest of the day, an approaching cold front will bring a shift in the pattern this afternoon and evening. Although VCTS is shown for a 4-hour period (roughly 2 PM-6 PM) at all terminals, the better threat extends from the D.C. terminals and points southward. However, there is enough uncertainty to keep VCTS at the northern terminals. While not explicitly shown, brief restrictions and gusty winds are possible during the period of convection. This cold front brings a shift to northwesterly winds which persist into the first half of Saturday. For the remainder of the weekend, expect VFR conditions at the area terminals. With high pressure shifting offshore, winds turn over to southerly on Saturday afternoon while continuing into the night. The next cold front takes aim at the area early Sunday leading to gustier northwesterly flow. Gusts up to 20 to 25 knots are possible behind this front. Mainly VFR Mon-Tue with blustery NW winds; gusts to 30 kts possible.
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&& .MARINE...
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Southward sinking outflow boundaries continue to bring 25 to 35 knot winds to portions of the waterways. As such, Marine Weather Statements and Special Marine Warnings have been hoisted over the past couple of hours. This threat should gradually wane as these outflows exit the waters by 5 to 6 AM. Otherwise, Small Craft Advisories remain in effect over the lower tidal Potomac and southern third of the Chesapeake Bay until 2 PM this afternoon. For the remainder of the day, some convection may impact the waters this afternoon and evening which would bring some gale- force winds to the waters. As the cold front pushes through early this evening, northerlies ensue in the wake. This may bring Small Craft Advisory criteria to the southern waters late this evening into early Saturday. With a shift back to southerlies, some channeling effects may yield additional advisories along the Chesapeake Bay for Saturday evening into portions of the night. A quick moving cold front leads to a return to northwesterlies on Sunday. Winds near advisory levels at times. Blustery northwest winds and mainly dry conditions are expected Monday into Tuesday. Gusts of 20 to 30 knots are most likely.
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&& .TIDES/COASTAL FLOODING...
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Elevated tide levels in southerly flow are forecast through tonight. The higher of the two tides astronomically is the morning, and this is the most likely tide to experience minor flooding, especially for the typically more vulnerable shoreline locales. Depending on the timing of a wind shift to offshore heading into Saturday, flooding chances may linger into the morning. Overall, though, tide levels will decrease through the weekend. Persistent offshore flow could lead to some lower then normal levels early next week, as well.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 2 PM EDT this afternoon for ANZ533- 534-537-543.
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&& $$ SYNOPSIS...BRO NEAR TERM...BRO SHORT TERM...BRO LONG TERM...DHOF AVIATION...BRO/DHOF MARINE...BRO/DHOF TIDES/COASTAL FLOODING...DHOF

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