Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 291912 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 312 PM EDT Wed Mar 29 2017 .SYNOPSIS...
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High pressure will build overhead tonight before moving off the coast Thursday. Low pressure will pass through the area Friday. High pressure will gradually return Saturday and Sunday before another low pressure possibly impacts the area Monday and Tuesday next week.
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&& .NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
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Cold front has pushed well south of the region with high pressure building in from the north. For this evening, winds will gradually subside over land with mostly clear skies. Later tonight, next system approaching from the west will cause clouds to start increasing. In addition, low level flow will become easterly and this will result in upslope clouds in and just east of the mountains. Some spotty rain and drizzle is possible over the southern Shenandoah Valley. Lows tonight will be cooler than the last few nights, with readings in the 30s and 40s.
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&& .SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
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CAD will more or less remain in place in the low levels Thursday with the high pressure sliding eastward to our north. At the same time, low pressure system will be ejecting out of the plains with warm/moist air advection. In addition, the upslope flow will result in lower clouds and perhaps some light rain or drizzle in the mountains. Highs will be cooler than today due to the lack of sun and onshore flow, with 50s widespread and the cooler spots in the 40s. Warm and moist air advection continues Thursday night and with that we`ll see increasing chances for rain. Lows mainly in the 40s. Model guidance in good agreement that the low pressure system will track east-northeastward from near St. Louis Thursday evening to Ohio by Friday afternoon, before redeveloping near the DelMarVa late Friday and Friday night. Thus, most widespread coverage of rain expected late Thursday night and Friday. We`ll also have to monitor how far north the warm sector can make it Friday afternoon. Latest guidance indicates it may approach portions of central VA and southern MD, so have maintained a slight chance of tstorms there Friday afternoon. Highs on Friday uncertain, with locations that get south of the warm front possibly heading towards 70, while northern locales near the Mason-Dixon line may struggle to reach 50. Showers will begin to slowly wind down Friday night as the low pulls away and winds turn northwesterly. Low pressure slides northeast of the region Saturday, but lingering instability and weak vort max could produce a few stray showers still. Highs will be in the 50s to lower 60s.
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&& .LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
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High pressure will settle into the region Sunday through early Monday. Dry and seasonable temperatures expected throughout the period. The next storm system will move into the region midday Monday through Tuesday, bringing the chance for rain showers to the region once again. Brief high pressure will build into the region Wednesday before the next storm system approaches Wednesday night.
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&& .AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
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VFR will continue through at least the first half of Thursday all terminals. Winds mainly light, less than 10 knots tonight and Thursday. They will turn northeasterly later tonight, and east-southeasterly on Thursday. This will help usher in additional clouds, although ceilings still expected to remain VFR. Highest chances for some MVFR ceilings will be at CHO and MRB. Greater chances for sub-VFR conditions will occur Thursday night through Friday night with widespread rainfall. IFR conditions likely. A northwest flow will allow for cigs/vsbys to improve Saturday behind departing low pressure...but a few showers cannot be ruled out. Vfr conditions evolving Saturday night. Winds northwest 5 knots Saturday night. Vfr conditions expected Sunday into Sunday night. Winds becoming light and variable Sunday and Sunday night.
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&& .MARINE...
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Small Craft Advisory remains in effect for all of the waters. Gusts will taper off late this afternoon and SCA expires at 6 PM for some of the waters. A second surge of northeasterly winds is expected later tonight, and a SCA will continue for the Chesapeake Bay and lower Tidal Potomac until 6 AM Thursday. Sub-SCA winds then expected Thursday, with next potential for increasing winds on Thursday night/Friday ahead of our next system, especially across our southern waters. Low pressure will move away from the waters Saturday and northwest flow will develop. A Small Craft Advisory may be needed for portions of the waters during this time. No marine hazards expected Saturday night through Sunday night. Winds northwest 5 to 10 knots Saturday night through Sunday night.
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&& .TIDES/COASTAL FLOODING... Low pressure will pass through the area Friday night. An onshore flow will develop ahead of the low and this will cause elevated water levels Friday into Friday night. Minor tidal flooding near high tide is possible during this time. && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...Small Craft Advisory until 6 AM EDT Thursday for ANZ530>534- 537-539>541-543. Small Craft Advisory until 6 PM EDT this evening for ANZ535- 536-538-542. && $$ SYNOPSIS...RCM NEAR TERM...RCM SHORT TERM...RCM LONG TERM...KLW AVIATION...RCM/KLW MARINE...RCM/KLW TIDES/COASTAL FLOODING...LWX

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