Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 031549 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1049 AM EST Sat Dec 3 2016 .SYNOPSIS... High pressure will gradually move into the region through Sunday. An upper-level disturbance will pass through the area Sunday night and high pressure will briefly return for Monday. Coastal low pressure will impact the area Tuesday before high pressure briefly returns for Wednesday. A potent cold front will move through late next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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High pressure will slowly progress eastward from the Midwest and into the mid-atlantic states by tonight. However we are still feeling the effects of the system departing southeastern Canada with another day of persistent northwest flow. Snow and freezing drizzle along the Allegany Front has generally ended, so have allowed Winter Weather Advisory to expire. Otherwise, cloud cover will be similar to yesterday with more clouds north and west, and more sun south and east, as is typical in northwest flow. Temperatures will be near seasonal normals with highs from the 40s to low 50s. A breeze is expected again as well with some gusts 20-25 mph.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/... Surface high pressure will move across the region tonight, leading to slackening winds and dry weather. However, high cirrus clouds will already be increasing aloft ahead of the next system coming out of the plains. Lows will be in the 20s/30s. Northern stream energy will eject out of the plains on Sunday with southwest flow/warm air advection developing ahead of it. This will continue to lead to thickening and gradually lowering clouds on Sunday. The weakening system will then traverse the area late Sunday and Sunday night. Most of the southern stream energy/moisture located over the deep south will remain untapped, so while a period of light precipitation is likely, amounts will be on the low side. Thermal profiles favor predominantly rain for the metros and the I- 95 corridor south and east. However some light snow is likely for areas to the north and west and a light accumulation is possible in the higher elevations. Highs Sunday will be in the 40s area-wide, with lows in the 30s Sunday night. High pressure and dry weather will then move in behind the system for Monday with highs in the 40s to low 50s. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
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Low pressure will track through the Gulf Coast States into the Tennessee Valley Monday night. The surface ridge from high pressure over New England will continue to extend southwest into our area. Clouds will lower and thicken as the low approaches from the southwest...and precipitation may begin to overspread the area overnight from southwest to northeast. The low will slowly move northeast into the Ohio Valley Tuesday while it transfers its energy to a coastal low along the North Carolina Coast. Warm and moist air from the Gulf of Mexico and Atlantic Ocean will overrun the surface cooler air in place...likely resulting in a soaking rain for most areas. However...there still remains some concern with precipitation type. There will be plenty of dry air ahead of the system and as precipitation into the dry air...it may lead to insitu cold air damming from evaporative cooling. The cooling effect may be enough for snow or, perhaps more likely, sleet to fall late Monday night through Tuesday...especially for the the ridge tops. This will have to be monitored since uncertainty remains high this far out. Any snow or sleet should change over to rain Tuesday afternoon as warmer air takes over with the primary low moving off to our north. Coastal low pressure may hang around for Tuesday night before finally moving off to the east on Wednesday. Have increased pops for Tuesday night with rain likely across most areas. Any leftover rain should end Wednesday morning and high pressure will briefly bring drier conditions for Wednesday afternoon. A strong cold front will pass through the area late in the week. Blustery and much colder conditions are expected by Friday.
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&& .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/...
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Predominantly VFR conditions expected through at least Sunday. Scattered-broken stratocumulus deck at 4000-6000 feet will continue with varying coverage through today. This will be replaced by an increasing high cirrus deck tonight and on Sunday. Clouds will lower and thicken Sunday night as a weakening system moves through, along with the chance for some light rain, and possibly some light snow at MRB. Thus a period of sub-VFR conditions are possible. Monday will see an improvement back to VFR at all TAF sites. Winds will be out of the west/northwest through today, with gusts up to 20-25 knots. Winds will decrease tonight and turn light southerly Sunday afternoon and Sunday night, before turning back to the north Monday. VFR conditions will persist for most of Monday night. Rain and subvfr conditions are expected either late Monday night or Tuesday morning. IFR conditions are possible later Tuesday through Tuesday night along with more rain. Conditions will improve Wednesday.
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&& .MARINE... Small Craft Advisory remains in effect for all waters through today for persistent gusty northwest flow with gusts in excess of 20 knots. Winds begin to decrease tonight, but SCA will continue through tonight for portions of the central Chesapeake and lower Tidal Potomac. Winds finally drop below SCA criteria Sunday and remain below through Monday. Coastal low pressure will develop Tuesday before slowly moving out to sea later Tuesday night into Wednesday. A Small Craft Advisory may be needed for portions of the waters Tuesday into Wednesday. High pressure will briefly build overhead later Wednesday before a potent cold front approaches Thursday. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until midnight EST tonight for ANZ531-532- 538>540. Small Craft Advisory until 6 PM EST this evening for ANZ530- 535-536-542. Small Craft Advisory until 6 AM EST Sunday for ANZ533-534-537- 541-543.
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&& $$ SYNOPSIS...BJL NEAR TERM...MM/RCM SHORT TERM...MM/RCM LONG TERM...BJL/RCM AVIATION...BJL/MM/RCM MARINE...BJL/MM/RCM

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