Area Forecast Discussion
Issued by NWS Sterling, VA

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239 FXUS61 KLWX 180802 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 402 AM EDT Thu Oct 18 2018 .SYNOPSIS...
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High pressure will build overhead through tonight before moving offshore Friday. A cold front will pass through Saturday and high pressure will return for early next week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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High pressure will build over the area today with diminishing winds. Highs will be about 10-12 degs cooler than yday in the mid 50s. Model guidance overall has trended much warmer for overnight lows tonight and it appears most locations will stay abv freezing except in the valleys west of the Blue Ridge mtns, higher elevs should stay abv freezing due to warm air advection aloft. However, do expect areas of frost with clear skies, light winds and temperatures in the mid 30s. Given large swing in temperature trends in the past 24 hrs and to maintain consistency, kept the freeze watch in effect for most areas, but removed it for Baltimore and Harford counties where no guidance show temps getting below freezing. Anticipating that the freeze watch will get canceled for many areas later today and be replaced with a frost advisory as far east as Leesburg and northwestern Baltimore county.
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&& .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/...
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Warmer Fri as high pressure moves offshore and winds turn southerly. Clouds increase through the day with showers developing in the evening as moisture gets drawn northward ahead of an approaching cdfnt. Showers should linger through Sat until frontal passage Sat evening. Rain showers could turn into snow showers over the Appalachians Sat night with trof passage.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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Cool and dry autumnal weather will be featured for the second half of the weekend and into next week. Cool and blustery conditions are expected for Sunday with strong northwest flow behind the departing low pressure system. Some upslope snow showers are possible in the morning across the higher terrain of the Allegheny Front. High pressure will then build into the region for Sunday night and Monday bringing calmer conditions. For both Sunday and Monday temperatures will average about 10-12 degrees below normals, with highs in the 50s and lows in the 30s. Warm air advection will begin later Monday and Monday night as a clipper system moves well north of the area Tuesday. This will promote moderating temperatures with highs on Tuesday/Wednesday rebounding back into the 50s/60s with dry conditions continuing. A dry cold front may move through Tuesday night/Wednesday followed by additional high pressure.
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&& .AVIATION /08Z THURSDAY THROUGH MONDAY/...
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Gusts up to 20 kt today becoming light and variable tonight. Showers expected Fri night and Sat with frontal passage late Sat or Sat evening. Gusts up to 20 kt expected Sat. VFR is expected Sunday and Monday under building high pressure. Gusty northwest winds are expected Sunday.
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&& .MARINE...
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SCA conditions expected through today, then again late Fri or Fri night through Sun night. Gale conditions are possible late Sat into Sunday. SCA conditions are probable Sunday and into Sunday night in gusty northwest flow behind a departing low pressure system. Sub-SCA conditions return by Monday.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Freeze Watch from late tonight through Friday morning for MDZ003>005-501-502. Freeze Warning until 11 AM EDT this morning for MDZ501. VA...Freeze Watch from late tonight through Friday morning for VAZ025>031-503-504. Freeze Warning until 11 AM EDT this morning for VAZ503-504. WV...Freeze Watch from late tonight through Friday morning for WVZ050>053-055-501>506. Freeze Warning until 11 AM EDT this morning for WVZ501-503-505- 506. MARINE...Small Craft Advisory until 6 PM EDT this evening for ANZ530>534-537>543. Small Craft Advisory until 6 AM EDT early this morning for ANZ535-536. Small Craft Advisory from 10 AM this morning to 6 PM EDT this evening for ANZ535-536.
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&& $$ SYNOPSIS...LFR NEAR TERM...LFR SHORT TERM...LFR LONG TERM...MM AVIATION...MM/LFR MARINE...MM/LFR

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