Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 141419 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1019 AM EDT Sat Oct 14 2017 .SYNOPSIS... High pressure over the area will weaken rapidly through Sunday. A cold front will push into the Mid Atlantic Sunday night followed by a return to high pressure early next week. && .NEAR TERM /THROUGH TONIGHT/...
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A solid deck of stratus remains entrenched across much of the forecast area. Clearing is noted on visible satelltite along the spine of the Blue Ridge as well as in the higher peaks of the Potomac Highlands. The forecast challenge today is how quickly these clouds will erode. Some mesoscale guidance suggests that the boundary layer will remain quite saturated throughout the day. While a subsidence inversion is noted from our morning RAOB, the layer is not that thick...and there is hope to mix it out, based on current satellite depiction. Forecast will take that path, especially along and west of the Blue Ridge. Am most pessimistic along/east of I-95. Have made a few temperature adjustments too, trending downward. Considering low-level moisture, any clearing today will quickly cloud and/or fog back up tonight.
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&& .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
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Warm day on Sun under strengthening southwest flow ahead of a cold front especially east of the Blue Ridge where clouds will be less and showers take longer to arrive. Showers appear likely everywhere during the evening Sun as cold front moves through the area. Gusty winds up to 30 mph will accompany the front as models show decent pressure rises. Showers will linger over southern MD into Mon morning before pushing south by midday. Rapid clearing expected Mon as drier air moves in behind fropa and as high pressure builds in. Taste of fall Tue morning with lows dropping into the 40s and even 30s west.
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&& .LONG TERM /TUESDAY THROUGH FRIDAY/... A shortwave trough will be moving off the coast Tuesday morning while surface high pressure builds eastward from the Ohio Valley. That high pressure system will be the story of the extended forecast period as it more or less remains parked over the region. The ensemble suite of guidance is in good agreement with the overall pattern. Aloft, flow will be progressive and wavy through midweek, with east coast ridging becoming amplified by the end of the week as a deep trough moves onto the west coast. Looking at the BUFKIT overview cross-section, there is a stark lack of moisture in the atmosphere for much of the week. It will remain cool through mid-week, but near normal. We`ll have to keep an eye on frost/freeze potential (mostly western valleys at this point) Tuesday and Wednesday mornings. Highs will remain in the 60s again on Tuesday despite sunshine. The airmass will modify as the week progresses with temperatures rising back above normal, although 80s look unlikely at this point. && .AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
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Flight conditions slowly improving to MVFR this morning. There is a better chance at seeing at least some clearing today, so am hopefulthat VFR reachable. However, any clearing today will revert back to low clouds and/or fog tonight given low level moisture. IFR (or lower) likely. Cdfnt will be crossing the area early Sun evening with showers likely. Gusty NW winds behind fropa up to 25 kt Sun night. No significant weather expected Tuesday and Wednesday with high pressure.
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&& .MARINE... Light winds today, but winds strengthen Sun and especially Sun night with fropa. Gusts up to 25 kt expected on the waters. SCA will be raised later this morning. Small Craft Advisory conditions in northwest flow may linger through Tuesday morning on portions of waters. Winds will then subside through mid-week as high pressure builds over the area. && .TIDES/COASTAL FLOODING...
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Water levels running a half-foot to 1 foot above astronomical normals this morning. In most places, that would place today`s tide no worse than action/caution stage. The exception is at St George Island, where an Advisory remains in effect. That Advisory in effect through tonight, as the nighttime tide cycle a pinch higher, and a decrease less likley (or at least less certain). Will also be keeping a close eye on Southwest Washington DC. In the big picture, tides should gradually be decreasing through the weekend into early next week. No additional Advisories anticipated at this time.
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&& .CLIMATE... A surge of warm air is expected Sunday ahead of the cold front. We are not currently forecasting records, but we are expecting temps to be close. Warm Temperature Records for October 15 (Sunday)... High Warm Low DCA 87 (1975) 67 (2008) BWI 86 (1989, 1975) 66 (1941) IAD 88 (1989) 64 (1985) && .EQUIPMENT...
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The NWS 88D Sterling radar (KLWX) will be down through at least 5 PM today. This is for nationally scheduled maintenance on the radome. Surrounding WSR-88D radars as well as FAA Terminal Doppler radars will provide coverage during this downtime.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Coastal Flood Advisory until 1 AM EDT Sunday for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory from 10 AM to 6 PM EDT Sunday for ANZ530>534-539>541-543. Small Craft Advisory from 1 PM to 6 PM EDT Sunday for ANZ536>538-542.
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&& $$ SYNOPSIS...LFR NEAR TERM...HTS SHORT TERM...LFR LONG TERM...ADS AVIATION...HTS/LFR/ADS MARINE...LFR/ADS TIDES/COASTAL FLOODING...HTS CLIMATE... EQUIPMENT...HTS

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