Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 141423 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1023 AM EDT Thu Mar 14 2024 .SYNOPSIS...
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High pressure will slide offshore today with a low pressure system approaching from the Ohio Valley. Well above normal temperatures and dry conditions will persist through today before showers and a few thunderstorms impact the area on Friday. A secondary weaker system may impact the region Sunday into Monday. A cooler airmass is expected through much of next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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A very warm day is on tap for today as SSW flow draws warmer air into the region. Yesterday had considerable high clouds which held temps down a bit, but despite that, we still managed to hit the mid 70s. Ample sunshine with less high clouds and higher heights aloft today should support highs approaching 80F. Continued dry today for one more day. Previous afd... The high pressure situated across the southeast will continue to nudge further offshore throughout the day today. Flow becomes more southwesterly today, which should allow highs to rise into the mid 70s to near 80. Mostly dry conditions are expected for the daytime hours today. The approaching center of low pressure will be nearing the Great Lakes tonight with an associated warm front draped across portions of PA. This will likely lead to well above average overnight lows tonight with widespread 50s expected. Light rain may begin to approach the Alleghenies and along the MD/PA border late tonight, mainly after midnight. Most of the rain is expected to hold off until daybreak on Friday.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... By Friday, the low pressure system will continue to track further east across New England. The associated cold front will drop southeast into the area during the day on Friday, with areal coverage of rain increasing across the region. This system continues to not impress in terms of QPF across the area, with less than a quarter of an inch expected across most locations. Having said that, with some minor instability around coupled with 40 knots of bulk shear, cannot rule out the chance for a few isolated thunderstorms ahead of the cold front. Any thunderstorms that do develop may produce a quick 0.10-0.25" of rain during a shorter period of time. Flooding concerns remain low with this system. Highs on Friday may be a degree or two lower than today given the increased cloud coverage and flow direction but it will still be well above normal for this time of year. The cold front likely pushes through the area by Friday night, bringing a cooler airmass with lows in the mid 30s for the mountains to 40s for the lower elevations. Some brief ridging will influence the area on Saturday with highs about 10 to 15 degrees cooler than Thursday and Friday. This is still 5 to 10 degrees warmer than average for this time of year. Northwest winds early in the day will soon turn more west/southwesterly for the afternoon and evening hours. Overnight lows on Saturday will drop down into the 40s across most of the area. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... A rex block persists across western North America while the northern stream amplifies across the central/eastern U.S. This particular configuration largely holds on through the early portions of next week. Within the longwave trough extending up into much of central to eastern Canada, a series of embedded disturbances will track from the Upper Midwest toward the northeastern states. One of these more formidable shortwaves is primed to push toward the local area late Sunday into Monday. This carries a reinforcing cold front through the area resulting in a pronounced drop in temperatures. While Sunday yields high temperatures in the upper 50s to mid 60s, the new work week will bring near to below normal temperatures. For Monday and Tuesday, forecast highs range from the mid 40s to low 50s, with low temperatures in the mid 20s to low 30s. For mountain locales, expect these readings to be around 10 to 15 degrees colder, especially during the daytime. Ensembles do show some gradual moderation by mid-week as heights slowly rise. Looking at the precipitation and wind forecasts, some uptick in wind fields are likely on Sunday in response to a frontal passage. The more notable cool down ensues with a trailing system which quickly lowers 1000-500 mb thicknesses on Monday. The cold advection will lead to a brisk northwesterly wind with gusts up to 25 to 35 mph, locally up to 40 to 45 mph in the mountains. Expect such winds to persist into Tuesday as well given the tight cyclonic gradients overhead. Besides the wind, upslope snow showers are possible along the Allegheny Front. It is difficult to say how much snow will fall as this will depend on moisture availability, the 0-3 km wind speed and direction, and strength of the upper forcing. What appears to be less of an issue are the temperatures given the cold air mass settling in. Any precipitation is likely relegated to the higher terrain with drier conditions downstream. && .AVIATION /14Z THURSDAY THROUGH MONDAY/...
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VFR conditions are expected through the day today with light, variable winds in place. Sub-VFR conditions return during the day on Friday as a cold front approaches the area. Cannot rule out a brief thunderstorm for the terminals during the afternoon hours but confidence is low at this time. VFR conditions return on Saturday but winds will be elevated out of the WNW 15 to 20 knots before turning more westerly/southwesterly later in the day. VFR conditions are expected on Sunday and Monday across the area terminals. Some snow showers enter the picture on Monday, but these remain along the Allegheny mountain chain. The big story will be the increasing winds as a series of cold fronts push through the area. Wind start to back to northwesterly on Sunday as the first boundary moves through. Gusts up to 20 to perhaps 25 knots are possible, especially during the afternoon. A stronger cold front arrives on Monday with northwesterly gusts increasing to around 25 to 30 knots.
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&& .MARINE... Light, variable winds are expected today with high pressure off to the south moving further offshore. Low pressure system approaches the Great Lakes tonight, with winds increasing late tonight into Friday. SCAs may be needed starting late tonight and into Friday but confidence is low given the warmer air over cooler waters producing low level stability. Showers and isolated thunderstorms may impact the waters during the day on Friday before pushing further offshore by Friday night. SCA winds are possible just behind the front for a 6 to 8 hour period. These winds will likely diminish heading into early Saturday as upper ridging builds in across the area. Initial southwesterlies give way to west-northwesterlies the second half of Sunday. This is in response to the initial cold frontal passage. This could bring near-advisory caliber winds to portions of the waterways. A better chance for Small Craft Advisories loom on Monday into Monday night as the stronger frontal system presses through. Northwesterly gusts range from 20 to 30 knots, with these higher bounds over the southern waters. && .FIRE WEATHER... Today will be warmer, 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. && .TIDES/COASTAL FLOODING... Anomalies will continue to increase through the end of the week as winds begin to increase out of the south. Some tidal sites may reach minor flood stage later today and again on Friday ahead of the next low pressure system expected to impact the area. The wind shift behind the cold front Friday evening will alleviate temporary tidal flooding concerns. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...ADM LONG TERM...BRO AVIATION...LFR/BRO MARINE...LFR/BRO FIRE WEATHER...ADS TIDES/COASTAL FLOODING...ADM

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