Area Forecast Discussion
Issued by NWS Sterling, VA
Issued by NWS Sterling, VA
147 FXUS61 KLWX 250151 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 851 PM EST Sun Nov 24 2024 .SYNOPSIS... High pressure will dominate into Monday. A quick moving cold front will cross the area Monday night into early Tuesday with brief high pressure returning midweek. An area of low pressure will track north and east from the Tennessee River Valley and bring widespread precipitation and colder temperatures toward the Thanksgiving holiday. && .NEAR TERM /UNTIL 7 AM MONDAY MORNING/... The latest surface analysis shows broad cyclonic flow across New England into the Canadian Maritimes. To the west of the Mid- Atlantic, a stalled boundary arcs from west to east across the Ohio River Valley. With the local area in between these two features, a surface ridge stretches southward from Ontario into the Mid-Atlantic states. Weak gradients around this anticyclone center will favor light and variable winds overnight. The usual cooler rural locations have already seen temperatures plummet over the last couple of hours. Expect nighttime temperatures to fall fairly close to the dew point which currently runs in the upper 20s to mid 30s. Lows could be locally a bit lower in locations with a snowpack (i.e., along and west of the Alleghenies). && .SHORT TERM /7 AM MONDAY MORNING THROUGH TUESDAY NIGHT/... Dry conditions will persist through much of Monday as high pressure exists off to the east and low pressure approaches from the west. The low and it`s associated cold front will move through late Monday night into Tuesday morning. Cloud cover will increase through the day, but precipitation/rain chances do not increase from west to east until Monday evening along the Allegheny Front and later Monday night along the I-95 corridor. Rainfall amounts will remain fairly light with this system with most of the area outside the Alleghenies receiving less than a tenth of inch. Highs Monday will be above average, reaching into the right around 60 for most (mid 60s central VA, 50s in mtns). High pressure briefly builds back in behind the front Tuesday. Not much of a cold front given the airmass behind the front and rather zonal H5 pattern. Highs Tuesday are contingent upon how quickly cloudcover exits associated with the front, however there is the potential for some downsloping winds/compressional warming resulting in highs a couple degrees higher than currently forecast. Currently have 40s in the mountains with near 60 most other places. Post-frontal winds will turn to the west and northwest with gusts 20 to 30 mph Tuesday morning into Tuesday afternoon. Winds will decrease fairly quickly Tuesday night as high pressure builds overhead. Lows Tuesday night will fall into the upper 20s and low to mid 30s. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... High pressure will be overhead Wednesday morning but quickly progress eastward in a fast zonal flow aloft. Clouds will increase through the day with seasonable temperatures in the upper 40s to mid 50s. Low pressure will advance toward the area from the southern Plains Wednesday night. It now looks like precipitation will begin overnight and continue into Thursday morning. With the preceding airmass being relatively mild and a lack of diurnal cooling, most areas will just see rain. The mountainous areas to the west will need to be monitored however since dew points may start out in the upper 20s to lower 30s. As another shortwave quickly follows, a second area of low pressure will develop to the south Thursday. If this moisture stays to the south, many areas will be drying out Thursday afternoon. Otherwise, there is potential for more rain Thursday night into Friday. The tracks of these lows will also have some impact on Thursday`s temperatures (40s vs. 50s). Rainfall amounts should be beneficial in nature. Friday is forecast to dry out east of the mountains with a gusty northwest wind and temperatures trending below normal. Meanwhile, accumulating upslope snow will commence west of the Allegheny Front. Confidence remains low on amounts this far out. There is some trend in recent guidance that the best moisture advection off the lakes will remain north of the area. Saturday has trended dry with brief high pressure, but temperatures will run well below normal with some lingering wind. A shortwave will approach on Sunday as temperatures remain well below normal. Most precipitation (snow) should remain focused on the upslope side of the Appalachians, but there is some potential for light rain or snow to the east as well. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... VFR conditions are expected at most terminals through Wednesday. A brief period of sub-VFR conditions remain possible Monday night into Tuesday as a quick moving cold front crosses the region. The front will bring light to moderate showers to the terminals leading to some cig/vsby restrictions at times. The highest confidence for sub-VFR will be at terminals west of the corridor (i.e KMRB, KHGR, and KFDK). Winds will turn to the south Monday at 5 to 15 kts. Winds increase late Monday night into Tuesday as the front passes. The front quickly exits Tuesday morning into Tuesday midday allowing conditions to improve. Post-frontal west to northwest winds will be the biggest issue to aviation through sunset Tuesday with gusts of 20 to 30 kts expected. These values decrease Tuesday night into Wednesday as high pressure builds overhead. No significant weather is expected during this time. No significant weather is forecast Wednesday with high pressure. The next low pressure system will arrive Wednesday night with rain and sub-VFR conditions. Depending on the track of a second area of low pressure, there is some risk of rain and low ceilings through Friday morning. Northwest winds may gust 20-30 kt behind the system on Friday. && .MARINE... As advertised, north-northwesterly winds across the marine waters have dropped off after dark. The highest wind gusts generally are topping out in the 5 to 10 knot range. Expect similar conditions into the night. Winds turn to the south on Monday as high pressure pushes offshore. Some southerly channeling may be noted of the middle and open waters of the Chesapeake Bay ahead of an approaching cold front. Currently favoring wind gusts around 15 kts over the open waters, but will continue to monitor trends. The front may bring a line of gusty showers across the waters late Monday night into early Tuesday morning resulting in the potential for SMWs. Winds increase out of the west/northwest Tuesday morning into Tuesday afternoon behind the front. SCA conditions are likely with gusts upwards of 20 to 30 kts through at least sunset. SCAs could continue into Tuesday night before dropping off Wednesday as high pressure returns to the waters. No significant weather is forecast Wednesday with high pressure. The next low pressure system will arrive Wednesday night with rain and sub-VFR conditions. Depending on the track of a second area of low pressure, there is some risk of rain and low ceilings through Friday morning. Northwest winds may gust 20-30 kt behind the system on Friday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...EST NEAR TERM...BRO/CPB SHORT TERM...CPB LONG TERM...ADS AVIATION...ADS/BRO/CPB MARINE...ADS/CPB