Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 142135 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 535 PM EDT Fri Oct 14 2016 .SYNOPSIS... High pressure will move into the region through Saturday before moving south of the area Sunday. A cold front is expected to remain north of the region during the first half of next week leading to above average temperatures. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Update: Frost advisory was extended further east and south. As mentioned below...good set-up for radiational cooling tonight. Looking at guidance it does look like cirrus should move south late tonight and into Saturday morning allowing temperatures to rapidly drop into the morning hours. Previous discussion... High pressure is centered across New York State and Pennsylvania this afternoon. With dry air (dewpoints near 40F) and very little wind, the atmosphere is set for good radiational cooling. The only thing that could get in the way is cirrus streaming east from the lower Ohio Valley. Don`t believe that will be a big influence across the northern portion of the Potomac Highlands and the Martinsburg/Hagerstown area. Have posted a Frost Advisory for these areas. Will let the evening forecaster adjust as needed. Lows near 40 elsewhere...mid- upper 40s in the heart of DC/Baltimore City.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... Quiet weather conditions should continue through the weekend as high pressure slowly drifts overhead. As shortwave energy approaches Saturday afternoon, there could be a few more clouds/maybe a sprinkle in the mountains. The same can be said across northern Maryland Sunday night as a weak cold front drops across New England/New York. Think the ridge will be dominant, and therefore won`t be mentioning any tangible weather. Warm advection will be minimal Saturday, but it does increase Saturday night and Sunday. Therefore, high temperatures tomorrow will be comparable to today. 850 mb temperatures rises of a degree or two Celsius would support high temperatures 70-75 by Sunday afternoon. Similar increases would be seen each night; frost won`t be a concern. && .LONG TERM /MONDAY THROUGH FRIDAY/... A decaying cold front will drop into the area from the north Monday. This front is expected to be moisture-starved so little if any precipitation is expected with it. The boundary will weaken to a surface pressure trough that will linger near or just north of the area through the first half of next week. A very strong ridge of high pressure both at the surface and aloft will build south of the area during the middle of next week. A ridge of this caliber would be more common in late August and temperatures may resemble warmth more normal for that time of the year as well. A deepening trough/possible cutoff upper low may begin approaching the region from the mid-Mississippi River Valley later next week, but details are highly uncertain in the speed and evolution of the trough this far out. && .AVIATION /22Z FRIDAY THROUGH WEDNESDAY/... VFR conditions can be expected through the valid TAF period, and beyond. Light north flow today will be replaced by a light south flow Saturday. South flow will continue through the weekend, but speeds should generally be less than 10 kt. No flight restrictions anticipated. Mainly VFR expected Monday-Tuesday. Westerly winds around 10 knots Monday become southerly Tuesday. && .MARINE... Winds have diminished on the waters, and the Small Craft Advisories have been dropped. Flow through the weekend will mostly be 10 kt or less. Saturday will be the transition from north to south flow (via the east). A weak front stalled near or over the waters will result in winds likely staying below Small Craft Advisory criteria early next week. && .TIDES/COASTAL FLOODING... Water levels near astro normals at this time. South flow will arrive by Saturday. We could see some caution stages being reached by Sunday. River guidance suggests minor flooding possible on the upper Potomac. Am somewhat skeptical of that at this time. We will need to see future HEC-RAS runs. && .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Frost Advisory from 1 AM to 9 AM EDT Saturday for MDZ003>006- 501-502-507. VA...Frost Advisory from 1 AM to 9 AM EDT Saturday for VAZ027>031- 505. WV...Frost Advisory from 1 AM to 9 AM EDT Saturday for WVZ050>053- 055-501>504. MARINE...None.
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&& $$ SYNOPSIS...HTS NEAR TERM...HSK/HTS SHORT TERM...HTS LONG TERM...DFH AVIATION...HTS/DFH MARINE...HTS/DFH TIDES/COASTAL FLOODING...HTS is the U.S. government's official web portal to all federal, state and local government web resources and services.