Area Forecast Discussion
Issued by NWS Sterling, VA

Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
-- Remove Highlighting --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS61 KLWX 231901 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 201 PM EST Mon Jan 23 2017 .SYNOPSIS... Low pressure over southern Virginia will track northeast off the Delmarva tonight. A cold front will pass through the area Wednesday night. An upper-level trough will build overhead for the end of the week into the weekend. && .NEAR TERM /THROUGH TONIGHT/... This has been an extremely challenging forecast given the variety of problems presented by the low...and its interaction with the high pressure over northern Maine. The pressure gradient has caused strong easterly winds which led to the wind advisory over the eastern part of the forecast area...and this easterly fetch led to a strong moisture flow off the Atlantic and areas of moderate/heavy rainfall. Temperatures have turned cold enough at higher elevations to cause the rain to change to snow in the Highlands...and freezing rain in Shenandoah National Park. These same wids are responsible for waters of the Potomac and Ches Bay to rise...and we`ve even seen a few lightning strikes. In good news the low is tracking to the northeast - slowly, but it is happening. The heaviest precipitation should be coming to an end this evening. Wind advisory and winter weather advisories are in effect until 7 pm. Flood watch for the I-81 corridor until 11 pm. && .SHORT TERM /TUESDAY THROUGH THURSDAY/... Tuesday remains a transition day...as center of surface low continues its eastward progression off the Jersey coast and high pressure across the Gulf states gradually builds northward toward the area. A few lingering light showers remain possible through midday mainly from DC and to the N/NE. Upslope snow/rain showers could continue into mid-afternoon before moisture becomes too shallow and winds turn southerly as high pressure moves into the area. Breezy W/NW winds gusting up to 25 kts...with relatively warm conditions on the drying flow. Upper level ridge across the region Wednesday...with unseasonably warm temperatures (highs 55-60). Cold front crosses the region late Wednesday into Thursday...and, with limited moisture east of the mountains, expect most areas to remain dry. Upslope flow will allow for some rain/snow showers to develop by late Wednesday night. && .LONG TERM /THURSDAY NIGHT THROUGH SUNDAY/... Some precipitation possible early on Thursday over the southeast of our CWA as a cold front moves away from our region. Deep upper trough extends through half of the CONUS Thursday into Monday as multiple waves of energy move overhead, before the trough axis move across on Monday. Snow showers expected west of the Appalachians through this period, and with westerly flow over our area, some snow showers could be seen east of the mountains... nothing significant if any. This prolonged period of snow showers on the Allegheny Front could bring significant snow to this region, but it looks like it will be a couple of inches of snow each day/night. Low pressure moves overhead on Monday bringing more widespread precipitation. && .AVIATION /18Z MONDAY THROUGH SATURDAY/... IFR conditions will continue through tonight. Showers become more scattered tonight. Gusty 30-40 knot winds will begin to weaken this evening. MVFR may linger at MD airports for a few hours Tuesday morning... before showers move out of the area and all sites become VFR. However, breezy conditions will continue with NW wind gusts 20-25 kts...before subsiding Tuesday night. High pressure nudges into the area late Tuesday into Wednesday with dry weather and VFR prevailing. Weak front moves through late Wednesday. Cold front moves away early on Thursday, so some showers possible early that day. Then an upper level disturbance and breezy westerly winds will bring cooler and dry conditions Thursday through Saturday. Sub-VFR maybe early on Thursday, then VFR conditions expected. && .MARINE... Gale Warning in effect until 6 PM. Expect solid SCA conditions to continue into Tuesday behind departing low pressure system...with an SCA in effect from 6 PM tonight to 6 PM Tuesday. Winds slacken late Tuesday as influence from low wanes. Mostly dry cold front crosses the waters late Wednesday into Thursday...with gusty winds possibly to SCA criteria behind it Thursday afternoon. Cold front moves away early on Thursday, so some showers possible early that day. Then an upper level disturbance and breezy westerly winds will bring cooler and dry conditions Thursday through Saturday. Small craft advisory may be needed during this period. && .HYDROLOGY... Flood watch in effect along the I-81 corridor from Rockingham to Berkeley. Only water to show much response is Wardensville...but is is still only half way to flood stage. Area of moderate rainfall continue to fall in that area. We will continue to monitor. The heavy rain move north of the watch area by midnight. && .TIDES/COASTAL FLOODING... Persistent easterly flow has lead to elevated water levels. Coastal Flood Advisory was issued for Straits Point through the evening high tide cycle. Elsewhere...action stage is expected at Annapolis and Solomons...though further increase in anomalies could lead to tidal levels near minor stage. DC/Alexandria also forecast to reach minor stage late this afternoon. Developing westerly flow should allow for some decrease in anamolies by later Tuesday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Wind Advisory until 7 PM EST this evening for DCZ001. Coastal Flood Advisory until 9 PM EST this evening for DCZ001. MD...Winter Weather Advisory until midnight EST tonight for MDZ501. Wind Advisory until 7 PM EST this evening for MDZ004>006-011- 013-014-016>018-503>508. Coastal Flood Advisory until 3 AM EST Tuesday for MDZ016-018. Coastal Flood Warning until 3 AM EST Tuesday for MDZ017. VA...Winter Weather Advisory until midnight EST tonight for VAZ503- 507-508. Flood Watch until 11 PM EST this evening for VAZ026>031- 038>040-507. Wind Advisory until 7 PM EST this evening for VAZ052>055-057- 506. Coastal Flood Advisory until 3 AM EST Tuesday for VAZ057. Coastal Flood Advisory until 9 PM EST this evening for VAZ054. WV...Winter Weather Advisory until midnight EST tonight for WVZ501- 503-505. Flood Watch until 11 PM EST this evening for WVZ052-053. MARINE...Small Craft Advisory from 6 PM this evening to 6 PM EST Tuesday for ANZ530>543. Gale Warning until 6 PM EST this evening for ANZ530>543. && $$ PRODUCTS...WOODY!/IMR/ADS/BJL

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.