Area Forecast Discussion
Issued by NWS Sterling, VA

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221 FXUS61 KLWX 171528 AAA AFDLWX Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 1028 AM EST Tue Jan 17 2017 .SYNOPSIS... A stationary front over the Carolinas will move north as a warm front today. A weak cold front will push through the area early Wednesday. High pressure returns Thursday followed by an approaching warm front Friday. High pressure returns again for Saturday. Low pressure will affect the area to start the new week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Main batch of steady light warm air advection showers continues to progress quickly eastward across the area...with radar imagery showing the back edge nearly east of our office (Sterling, VA) as of 1020 AM. Generally a tenth of an inch or less...though perhaps up to a quarter of an inch along the Allegheny Front. Some locally dense fog developed across portions of N MD and eastern WV this morning...though, most places have risen above a quarter mile as rain has moved through. Expect that trend to continue in areas that remain AOB a quarter mile (mainly KFDK). Visible satellite imagery also showing an area of clearing across the Shenandoah valley...any clearing should be short-lived as clouds fill back in across these areas. Another area of rainfall across eastern WV will cross the area through early afternoon. By mid-afternoon, forcing will weaken, although areas of showers will still be around. Temperatures likely to be stuck in the 40s for a good chunk of the day with low clouds and scattered rain showers, but likely to make a run into the 50s late in the day for most with some drying. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... We`ll be briefly warm sectored this evening and into tonight out ahead of an approaching cold front that will be crossing the region during the overnight/early morning hours. With increased low level wind field, not expecting widespread fog coverage, but some areas of patchy fog are possible given moist low level conditions. Some scattered showers also possible until frontal passage. Lows will be generally in the 40s. Upper level trough will move across Wednesday morning, keeping slight to low chances for a few showers across the northern half of the area, as well as chances for rain and possibly a few snow showers along the Allegheny Front in upslope flow. Otherwise, will see developing northwest flow with drying by the afternoon. Highs Wednesday from 50-60F, except 40s along the Allegheny Front. High pressure and calm weather then takes hold Wednesday night through much of Thursday night. Lows in the 30s, highs in the low/mid 50s. Chances for rain showers then increase late Thursday night in southwestern areas ahead of the next approaching system. && .LONG TERM /FRIDAY THROUGH MONDAY/... Confidence is increasing regarding the possibility of rain Friday. Both GFS and Euro show an open short wave moving into the forecast area around 18Z. This will probably be pushing north of the region by Friday evening but the afternoon hours are looking wet. But it is mid January...and temperatures could be far colder than the mid to upper 40s expected. A ridge of high pressure will move over the east coast Saturday. Highs should be in the low to mid 50s. Lows Saturday night 35-40. The ridge will be short lived as the upper atmosphere remains in fast flow over the CONUS. Long range models are showing deepening low pressure over TX Sunday...tracking NE and centered over KY Monday night. This means on southerly flow the Mid Atlantic will be fairly mild - this in contrast to one year ago when the blizzard of 2016 wracked the region Jan 22-24. Instead of blizzard conditions this year there`ll be a chance of rain on the 22nd...rain likely the 23rd. && .AVIATION /15Z TUESDAY THROUGH SATURDAY/... Widespread reductions expected today with low clouds and rain showers. A mix of LIFR/IFR/MVFR is expected as low stratus and patchy fog and rain showers move across the TAF sites. Highest risk of LIFR at MRB this morning and BWI later this afternoon. Lowest risk of IFR at DCA. Most widespread rain will occur this morning into the early afternoon hours. Later tonight, rain showers will taper off, but additional low ceilings and patchy fog possible, along with another round of IFR. VFR will return on Wednesday and persist through Thursday night. Winds light and variable this morning will become southerly this afternoon up to about 10 knots, before turning southwest this evening. A cold front will then cross the region late tonight/early Wednesday with a turn to northwest winds. Winds will gust up to around 20 knots Wednesday afternoon. For Friday an approaching warm front will likely bring rain to the airports. Ceilings could drop into MVFR range...improving late in the day. Saturday`s weather is expected to be VFR. && .MARINE... Primarily southerly sub-SCA winds expected through today and tonight. That being said, with strong low level wind field, may see some gusts approach SCA-criteria late this afternoon and tonight. However confidence is too low for issuance at this time. Winds will then turn to the northwest on Wednesday following cold frontal passage. Gusts up to about 20 knots expected, and a SCA has been issued. Winds will then subside for Wednesday night through Thursday night. No problems expected on the waters Friday or Saturday. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory from 7 AM to 6 PM EST Wednesday for ANZ530>543. && $$ UPDATE...MSE PRODUCTS...MJM/WOODY!

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