Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 180741 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 341 AM EDT Wed Oct 18 2017 .SYNOPSIS... High pressure will remain across the Mid Atlantic through the rest of the week and this weekend. A low pressure system may affect the region early next week. && .NEAR TERM /THROUGH TONIGHT/... High pressure is located directly over the region this morning. Some patchy fog is possible through sunrise, mainly in the river valleys. Cirrus currently across Kentucky may cross the sky this afternoon, and a light south wind will develop as the high drifts to the southeast. A moderating low level airmass will lead to high temperatures on either side of 70 degrees. An upper level trough will cross the area tonight, although it will have little impact other than some additional cirrus. Dew points will be a little higher, and some locations may be able to hold onto a light south wind since the high will be to the southeast. Thus expect any frost to be much more isolated, with most locations in the upper 30s to mid 40s...and lower 50s in the cities. && .SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/... The center of the high will remain generally to our south and southwest Thursday into Thursday night. The tail end of a decaying cold front/low level trough over New England will clip the area Thursday night, but bring little more than a few clouds and a wind shift to the northwest. The upper level pattern will amplify (west coast trough/east coast ridge) Friday into Friday night, with the surface high expanding back to the north and east. High temperatures will continue to warm through the 70s. Overnight lows will be in the 40s for most, with 50s in the cities. Greater variation is likely Friday night though with a more favorable radiational cooling set up. && .LONG TERM /SATURDAY THROUGH TUESDAY/...
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High pressure will be centered overhead or just to the northeast on Saturday morning, providing light winds and mostly clear skies. After a cool (but not as chilly as this morning) start, it will warm into the 70s with plenty of sun. The high will shift eastward off the coast by Sunday, with more of a southerly flow - however, the gradient will remain weak, so not a whole lot of change in sensible weather. A little warmer, a few more high clouds, that`s likely all the difference between Saturday and Sunday. Overall, ideal weekend weather, particularly for autumn. Guidance still shows a cold front and wave of low pressure moving toward the region early next week, but are a bit less in sync than last night. The GFS is significantly slower than the EC in bringing the upper low and its associated surface wave northeastward into the region, causing Monday to be drier on the GFS than on the EC, with a faster drying trend as we head into the middle of the week on the EC than on the GFS. Overall, will keep chance of showers, and heavy rain remains possible, given strong wave and potential for training along the stalling front. Both models also still show a very deep trough digging over the eastern US behind the system for mid-late week next week. This is something that would likely end the growing season across much of the region, while also perhaps trying to get a few snow flakes flying, especially in our higher terrain. Still, there`s a long time to watch this.
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&& .AVIATION /08Z WEDNESDAY THROUGH SUNDAY/... High pressure will remain in control through the end of the weekend. Given regional observation trends, inserted a short period of MVFR BR this morning at MRB and CHO, although this may ultimately be pessimistic. Can`t rule out a similar scenario any morning this week, but guidance doesn`t look terribly favorable. Otherwise only passing cirrus is expected with winds less than 10 kt. && .MARINE... High pressure will remain nearby through Thursday with light southerly winds developing. A weak front will pass by to the north Thursday night, which will turn winds to the northwest. Potential for Small Craft Advisory conditions will be dependent on mixing, so the greater chance would be over the more open waters. Winds will subside during the day on Friday as high pressure moves back overhead, which will then generally persist through the weekend. && .TIDES/COASTAL FLOODING... Anomalies have risen to around one-half to three quarters of a foot above normal. This should keep water levels below minor flood thresholds but it will be close for the sensitive sites of Straits Point, Annapolis, and Washington DC. Water levels will need to be monitored. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Frost Advisory until 9 AM EDT this morning for DCZ001. MD...Frost Advisory until 9 AM EDT this morning for MDZ003>006-013- 016-017-502>507. VA...Frost Advisory until 9 AM EDT this morning for VAZ028>031- 036>040-050>057-501-502-505-506. Freeze Warning until 9 AM EDT this morning for VAZ025>027. WV...Frost Advisory until 9 AM EDT this morning for WVZ050>053-055. MARINE...None. && $$ SYNOPSIS...RCM NEAR TERM...ADS SHORT TERM...ADS LONG TERM...RCM AVIATION...ADS/RCM MARINE...ADS/RCM TIDES/COASTAL FLOODING...RCM

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