Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 131401 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 1001 AM EDT Fri Oct 13 2017 .SYNOPSIS... High pressure over New England will extend into the area through Saturday before moving offshore Sunday. A cold front will push into the Mid Atlantic Sunday night followed by a return to high pressure early next week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... An onshore flow will continue around high pressure over New England. Low-level moisture will remain trapped underneath the subsidence inversion...resulting in more low clouds along with areas of light rain/drizzle. The best chance for any light rain or drizzle will be along and east of the Blue Ridge Mountains. Across the central Shenandoah Valley into the Potomac Highlands...the marine layer will be a bit thinner and with a downsloping flow off the Blue Ridge Mountains there should be a few breaks of sunshine. Max temps will top off on the 60s for most locations with 50s in the mountains and perhaps across northern Maryland...eastern West Virginia and extreme northern Virginia. && .SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/... CAD will persist tonight along with low clouds and easterly winds. Lows in the 50s west of I-95, lower 60s east. Generally it takes a synoptic system to rid the forecast area of the clouds associated with CAD, and that will happen Sunday, but will take a pessimistic approach to Saturday even as the high pressure area moves offshore, keeping the region under extensive cloud cover. Exception may be west of the Blue Ridge. Temperatures are forecast to climb back into the mid 70s, but this may have to be trimmed back depending on cloud cover. But skies should definitely improve Sunday as a cold front approaches from the west. East coast will be on warm southerly flow, and temperatures will likely rise back into the mid 80s - about 15 degrees above normal. See climate section below. There will be chances for showers west of the Blue Ridge during the afternoon. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Cdnft will be crossing the area early Sun evening with scattered showers behind the front. Showers could linger over srn MD into Mon morning. High pressure then builds later Monday and holds through the end of next week. It will feel more like fall during the first half of next week with temperatures trending more normal for the second half as heights rise due to building ridge over the east. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... Overcast skies will continue at the TAF sites today. MVFR will be the predominant ceiling into early this afternoon...but cigs may lower a bit this afternoon and especially tonight with IFR conditions becoming more likely along with areas of drizzle/light rain. Some improvement may occur on Saturday. By Sunday VFR will prevail. Cdfnt will be crossing the area Sun evening with scattered showers expected. Gusty NW winds expected Sun night behind fropa with gusts up to 25 kt. && .MARINE... Winds are expected to become lighter as the day progresses. SCA in effect for bulk of the MD portion of the Bay and lower Potomac through 16Z, then only south of Drum Point and lower Potomac through midnight. There is a chance that SCA-level winds could occur Sunday afternoon ahead of the approaching cold front. Solid small craft advzy conditions expected Sun into Tue. A very small chance (<5%) of gale force winds exists Sun night as a strong pressure surge moves over the waters. && .TIDES/COASTAL FLOODING... A persistent onshore flow has caused tidal anomalies around 1.5 to 2.5 feet above normal. The onshore flow will weaken a bit today into tonight. However...the high anomalies persist across all of the Bay so it will take a bit longer for the anomalies to drop...and when they do it will be slow. Therefore...minor to moderate flooding is anticipated through the high tide cycle Saturday morning. Coastal Flood Advisories and warnings are in effect. Additional minor flooding is possible later Saturday into Sunday. && .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... The NWS 88D Sterling radar (KLWX) will be down during the day from 7 AM through 5 PM through Saturday. This is for nationally scheduled maintenance on the radome. Surrounding 88D radars as well as FAA terminal radars will be operational during this downtime. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...Coastal Flood Advisory until 7 AM EDT Saturday for DCZ001. MD...Coastal Flood Advisory from 2 PM this afternoon to 10 AM EDT Saturday for MDZ508. Coastal Flood Advisory until 2 PM EDT Saturday for MDZ016-018. Coastal Flood Advisory until 8 AM EDT Saturday for MDZ011. Coastal Flood Warning from midnight tonight to 4 AM EDT Saturday for MDZ014. Coastal Flood Advisory until midnight EDT tonight for MDZ014. Coastal Flood Advisory from 4 AM to 5 PM EDT Saturday for MDZ014. Coastal Flood Warning until 1 PM EDT Saturday for MDZ017. VA...Coastal Flood Advisory until 2 PM EDT Saturday for VAZ057. Coastal Flood Advisory until 7 AM EDT Saturday for VAZ054. WV...None. MARINE...Small Craft Advisory until noon EDT today for ANZ531>533- 539>541. Small Craft Advisory until midnight EDT tonight for ANZ534-537- 543. && $$ PRODUCTS...BJL/WOODY!/LFR/DFH

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