FXUS61 KLWX 290803 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 403 AM EDT Fri Mar 29 2024 .SYNOPSIS... High pressure will build across the southeastern states today while low pressure moves toward the Canadian Maritimes. A front will become stalled over the Mid Atlantic this weekend, with multiple waves of low pressure tracking along it through the middle of next week. && .NEAR TERM /THROUGH TONIGHT/... Strengthening low pressure is tracking northeastward toward the Canadian Maritimes today while strong high pressure builds across the southeastern states. Meanwhile, a couple of shortwaves in northwest flow aloft are moving through the Great Lakes and central Appalachians. Most of the moisture associated with these features is mid level in nature (relatively high ceilings across the Ohio Valley), so it's not having difficulty crossing the mountains, both in the form of cloud cover as well as precipitation. Given dry subcloud layers, areas east of the Allegheny Front should only see some sprinkles. Along the higher elevations of the Alleghenies, snow is occurring, but the light/brief nature of precipitation and marginal temperatures will keep any accumulations to less than an inch. The chance of precipitation should wind down by midday, with lingering cloud cover quickly departing the area. Attention then turns to gusty winds as boundary layer mixing increases into stronger winds aloft amongst the tight pressure gradient. Models generally agree the strongest core of winds aloft will stretch across southwestern portions of the CWA. A dry airmass with deep mixing and downsloping will result in gusts of 40-50 mph in this area, so expanded the Wind Advisory eastward to the Blue Ridge. While the advisory has some potential to expand a tier of counties or so, most of the remainder of the area should see slightly lesser winds. See the fire weather section below for more details on that topic. The deep mixing will also result in warmer high temperatures, ranging from the mid 50s north to mid 60s south. Winds should decrease quickly this evening with sunset, although higher winds may linger for a time on the higher ridges with the core of winds persisting aloft. Clouds will start to increase the second half of the night with some upglide ahead of the next shortwave. This, combined with a more southwesterly wind, will keep temperatures in the 40s across the southwestern CWA, while it drops into the 30s to the northeast. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... A warm front will lift into the Mid Atlantic Saturday ahead of an area of low pressure tracking through the southern Great Lakes. Uncertainty increases at this point in the forecast and beyond, as the front will stall parallel to the upper flow and waver near the area into next week. The position of the front will affect both rain chances as well as temperatures. As the area of low pressure tracks across the area Saturday, the highest chances of rain remain north of I-66/US-50. There should be a break Saturday night, except for upslope showers, that perhaps continues through at least part of Sunday. There is some potential for a round of heavier rain Sunday night as low pressure tracks along the tightening baroclinic zone. A few rumbles of thunder are possible at times if enough instability can creep eastward, but the higher thunderstorm chances will remain west of the Appalachians. Will also have to keep an eye on gusty winds on the ridges Saturday into Saturday night, but the scope of this looks limited at this time. Highs on Saturday could exhibit a range from mid 50s north to mid 70s south. Sunday should be warmer areawide, but there could still be a range from lower 60s north to near 80 south. Overnights will be mild in the 40s and 50s. && .LONG TERM /MONDAY THROUGH THURSDAY/... Low pressure approaches from the west Monday into Tuesday, bringing greater chances of rain for the start of the week. As the shortwave attendant to the low moves east and energy makes a sharp descent from Canada into the Ohio Valley, the surface low is expected to intensify. Where the low tracks will determine which areas receive the most rainfall, but for now the area can expect widespread rain Monday through Wednesday. We'll also continue to monitor the flood threat given the prolonged period of rain. Guidance has trended colder after the system exits Wed/Thurs, bringing possible upslope snow along the Alleghenies to finish off the extended. Temperatures will be generally near normal for the duration of the extended, but will be dependent on the track of the low and where fronts track through the area. For now Tuesday looks the warmest, cooling down to below normal behind the cold front Wednesday and Thursday. && .AVIATION /08Z FRIDAY THROUGH TUESDAY/... A batch of mid level clouds and perhaps a few sprinkles will cross the area this morning with an upper level disturbance. Winds increase quickly by late morning through the afternoon, with WNW gusts of 25-35 kt. Winds diminish quickly with sunset, with clear skies until Saturday morning. A warm front will move into the area Saturday. Showers are possible, especially in the afternoon. Ceilings are more uncertain, but MVFR bases are possible at MRB to BWI/MTN if the front is on the southern side of the envelope. There should be a gap in notable weather Saturday night and Sunday morning, but another round of rain and sub-VFR ceilings are possible late Sunday into Sunday night. Restrictions are possible early next week with shower activity as a low pressure system moves into the region. ESE winds Monday with gusts up to around 15 kts possible during the afternoon. Winds turn south Tuesday and pick up by Tuesday night. As the frontal system moves passes through, the latter half of the week looks to maintain gusty conditions. && .MARINE... Marginal gale conditions on the main channel of the bay should decrease by sunrise as low pressure departs to the northeast. However, stronger WNW flow will develop later this morning, with the highest gusts in the upper Potomac and northern Bay zones. A Gale Warning is in effect for these areas, although gusts may be somewhat sporadic. It's possible SCAs may linger for a time into this evening, but overall winds will diminish tonight. A front will stall across the area Saturday and Sunday. Depending on the front and track of low pressure centers, a period of SCA conditions can't be ruled out, but the probability is low at this time. Onshore flow over the waters Monday may approach SCA criteria during the evening, but SCAs appear more likely beginning Tuesday night and possibly continuing through the end of the work week as a frontal system moves through the area. && .FIRE WEATHER... Today, winds will increase (WNW 15-25 mph with gusts 30-50 mph, highest on the ridges and central Shenandoah Valley). These winds will be coupled with RHs in the low to mid 20s in the eastern WV panhandle, north-central and western MD as well as portions of northern and central VA. An SPS for elevated fire danger is in effect through early evening in the aforementioned area. While 10-hr fuel moistures may not necessarily be near threshold, local observations from fire behavior analysts in the Shenandoah Valley indicated the 1-hr fuels were sufficient enough to burn this afternoon. Lingering cloud cover may inhibit the RHs a bit for a period in the morning but should diminish late in the morning into the early afternoon. Gusty southwest winds and min RH approaching 30 percent are possible in the central Shenandoah Valley and central Virginia on Saturday, but the overall conditions will be less favorable compared to today. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...Wind Advisory from 10 AM this morning to 8 PM EDT this evening for VAZ025>027-029-507-508. Wind Advisory until 8 PM EDT this evening for VAZ503-504. WV...Wind Advisory from 10 AM this morning to 8 PM EDT this evening for WVZ055. Wind Advisory until 8 PM EDT this evening for WVZ501-502-505- 506. MARINE...Small Craft Advisory until 6 AM EDT early this morning for ANZ530-531-535-536-538>542. Gale Warning until 6 PM EDT this evening for ANZ530-531-535- 536-538>542. Gale Warning until 6 PM EDT this evening for ANZ532-533. Gale Warning until 6 AM EDT early this morning for ANZ534-537- 543. Small Craft Advisory until 6 PM EDT this evening for ANZ534- 537-543. && $$ SYNOPSIS...ADS NEAR TERM...ADS SHORT TERM...ADS LONG TERM...CAS AVIATION...ADS/CAS MARINE...ADS/CAS FIRE WEATHER...ADS