Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 241533 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1033 AM EST Tue Jan 24 2017 .SYNOPSIS...
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Low pressure off the New Jersey coast will continue to track to the northeast. High pressure will build into the area this afternoon through Wednesday. A cold front will pass through the area Wednesday night. An upper level trough will move over the eastern Canada for the end of the week and into the weekend. Another cold front crosses the area late in the weekend.
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&& .NEAR TERM /THIS AFTERNOON/...
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In NW flow we are still seeing snow showers at Dolly Sods but elsehwere snow has come to an end. Drying NW flow will allow most areas to begin to dry out through the day today. Gusty winds also continue...with gusts up to 25 kts along and north of I-66. Highs should be in the 40s over most of the area...lower 50s in the central Shen Valley.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
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Chance of upslope rain/snow showers remains till around midnight...before column dries sufficiently to limit ice crystal formation and wind direction becomes less favorable for upslope. As this occurs...and before column dries completely, could see some drizzle (perhaps freezing at the highest elevations) along the Allegheny Front as low levels remain moist through Wednesday morning. Confidence in this is low. Remaining dry across the rest of the area...with lows in the L/M30s. Unseasonably warm and dry Wednesday...with highs in the M50s/M60s across the north/south (~15F above normal) and relatively light southerly flow. Cold front crosses the region late Wednesday into early Thursday. Limited moisture coupled with weak forcing for ascent will restrict precipitation potential...with only slight chances of measurable precipitation (mainly across the southern 1/4 of the area)...some areas may remain completely dry. Upslope snow machine kicks in by Thursday morning...as broad upper troughing becomes entrenched across the eastern CONUS. This will set the stage for a prolonged upslope event along the Allegheny Front. First stab at 24-hr accumulations from Thursday morning through Friday morning during the period generally 1-2 inches.
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&& .LONG TERM /FRIDAY THROUGH MONDAY/... The area will remain in northwest flow/cold advection through the weekend, with several impulses rotating around a closed upper low centered in Quebec. Most of the moisture will be squeezed out by the Appalachians, in the form of snow showers. While its looking snowy, am still skeptical whether forcing or background conditions will support anything other than periodic light snow. Do believe that the airmass will be cold enough for high snow-liquid ratios. East of the mountains, there should be at least some sunshine. Temperatures won`t be that cold (near normal), but 20-25 kt gusts within the mean mixed layer suggests that there will be breezy conditions, hence a wind chill factor. A final shortwave will steepen the trough axis Sunday night into Monday. This wave could bring enough energy east of the mountains for a greater amount of clouds and at least some flurries if not snow showers to the entire area. Its still early, so PoPs at 20 percent will keep wording out of text forecasts at this time. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/...
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Lower clouds will erode by the afternoon bringing a return to VFR over the entire area. High pressure builds into the area late Tuesday into Wednesday with dry weather and VFR continuing. Weak front moves through Wednesday night...though VFR should prevail as any showers should be light and isolated in nature. Gusty westerly winds develop behind the front Thursday. Mainly VFR conditions should prevail Friday into Saturday. Northwest flow pattern could support 20-25 kt gusts. Believe snow showers should be caught up in the mountains.
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&& .MARINE...
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High pressure building into the region while low pressure east of the Jersey coast heads to the NE. This will keep the Bay/Potomac in NW winds with winds gusting into the mid/upper 20s through the day. Cold front crosses the waters Wednesday night into early Thursday...with gusty solid SCA criteria wind gusts in its wake continuing into Friday. Gale force winds are possible across portions of the waters during this time. Northwest flow pattern and several upper air disturbances will keep atmosphere mixed Friday into Saturday. Gusts of 20-25 kt available in mean mixed layer. Hence, Small Craft Advisory potential will continue.
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&& .TIDES/COASTAL FLOODING...
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Tidal departures of 2 ft of more continue, but am starting to see a decrease in the hydrograph trace as the coastal low pulls away from the area. As northwest winds increase today in a tight pressure gradient water levels should drop. Straits Point still in minor flood. This should be the final high tide cycle in coastal flood there. Water level departures will continue to decrease through the middle of the week. Although there will be a brief window of return flow Wednesday, speeds will be light and the current excess should be able to evacuate from the estuary first. Otherwise, nothing but northwest flow through the week.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Coastal Flood Advisory until 1 PM EST this afternoon for MDZ017-018. VA...None. WV...None. MARINE...Small Craft Advisory until 2 AM EST Wednesday for ANZ531>534- 537-539>541-543. Small Craft Advisory until 10 PM EST this evening for ANZ530- 535-536-538-542.
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&& $$ UPDATE...WOODY! PREVIOUS...MSE/HTS

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