Area Forecast Discussion
Issued by NWS Sterling, VA

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165 FXUS61 KLWX 162030 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 330 PM EST Fri Feb 16 2018 .SYNOPSIS...
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Cold front will push south of the area this evening. High pressure will briefly build north of the region tonight, then a wave of low pressure will pass to the south Saturday. High pressure will return briefly again on Sunday before another storm system approaches from the west early next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Cdfnt has cleared much of the area except across southern MD with any showers expected to move out of the area by 6PM. Clearing and turning colder tonight as high pressure builds to the north over PA with lows dropping into the 20s and 30s.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/...
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High clouds associated with next wx system will be on the increase around daybreak Sat with a high dense overcast developing by midday. Model trends have remained fairly consistent with low pres developing along the NC coast Sat evening and moving quickly out to sea late Sat night. Precip onset looks to be late morning across the southwest with precip spreading quickly northeast during the afternoon. Precip totals are expected to be generally around half inch for a 6-hr duration precip event. P-type fcst continues to remain challenging due to mixed precip potential with models showing temps at the warm nose of +1C or +2C south of the I-70 corridor in central MD and south of I-66 and U.S.50 in western VA. Snow at onset will likely change to sleet south of those locations with all snow across north central MD and rain across southern MD. Given warm nose of only +1C or +2C, strong omega and wet- bulb cooling could overcome that shallow warm layer and make the layer isothermal potentially resulting in more snow than what is currently forecast. So, if the fcst were to go wrong it would probably be for more snow than what is fcst, but latest thinking is that warm sfc temperatures and high likelihood of sleet mixing in will cut down on snow totals significantly. The chance of freezing rain has decreased significantly due to warm antecedent conditions and shallow warm layer aloft. So, fzra was removed from the fcst. Precip will end around 10PM as a brief period of light rain south of I-70 and remaining all snow north of there. Please see snow maps in our website for specific snow/sleet amounts. High pressure builds for Sun with any snow melting rather quickly as temps rise into the upper 40s and low 50s.
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&& .LONG TERM /MONDAY THROUGH FRIDAY/...
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High pressure will be moving away from the coast as return flow settles in. Isentropic lift will allow showers over our area through the day and possibly into the night. Temperatures will remain well above freezing, with highs reaching the 50s. A cold front will stall to our west Tuesday into Wednesday. We will remain in the warm sector and high temperatures both days will reach the 70s. Showers associated to this front are more likely towards the western counties of our CWA Tuesday and part of the day Wednesday. The front will then moves across slowly Wednesday night or Thursday. The front will then stall to our south as waves of low pressure tracks along it and maintain the unsettled weather over our area Thursday and into Friday. Temperatures will decrease behind the front, but not enough to bring p-type concerns. High temperatures will be in the 50s.
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&& .AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
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Gusty winds ending late this evening. Wintry precip expected Sat afternoon with IFR conditions likely in the evening. Precip ends by midnight Sat night but low cigs will likely persist until daybreak Sun. Periods of sub-VFR conditions possible Monday into Monday night as a front moves through our area. VFR conditions expected Tuesday and Wednesday. Some sub-VFR periods possible late on Wednesday as showers move through.
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&& .MARINE...
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SCA conditions expected through tonight. Winds 10kt or less Sat through Mon. Winds are expected to remain below SCA criteria on Monday, then they will increase on Tuesday but are not expected to reach SCA criteria. Similar conditions expected on Wednesday, therefore no small craft advisory expected these days.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 10 PM EST this evening for ANZ530- 531-535-536-538>540. Small Craft Advisory until 3 AM EST Saturday for ANZ532-533- 537-541-542. Small Craft Advisory until 6 AM EST Saturday for ANZ534-543. && $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...IMR AVIATION...IMR MARINE...IMR/LFR

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