Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 171958 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 258 PM EST Sun Dec 17 2017 .SYNOPSIS...
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A weak boundary overhead will lift to the north as a warm front tonight into Monday. An upper level disturbance will approach the area from the west Monday afternoon and evening. This disturbance could bring some light precipitation to the Appalachian Front later Monday. High pressure will build in briefly before the next storm system scoots by to our south during the middle of the week.
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&& .NEAR TERM /THROUGH TONIGHT/...
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Satellite imagery shows a lot of mid-level and high cloud cover across the region this afternoon. Radar imagery shows a lot of echos across the region, as well. However, due to temperatures being in the upper 40s and dewpoint temperatures being in the lower 30s, there is a lot of dry air in place...especially southern and eastern portions. Therefore, any precipitation that is falling is not reaching the ground. Still, there could be a couple of rain drops or perhaps a sleet pellet or two across the northern tier and nearest the highest terrain later this afternoon into this evening. Chances remain minimal. As for temperatures, we have nudged upwards a little in our forecast due to a persist light southeast wind and lack of low cloud cover. The boundary, providing a safe haven for this cloud cover and limited precipitation, will lift north as a warm front tonight. Any precipitation chances will end from south to north as the front continues its progress. Low temperatures will bottom out near or slightly above freezing.
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&& .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
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As a warm front pushes to the north Monday, so do the milder temperatures will highs about 5 degrees warmer than Sunday. A light persistent southwest wind will aid in this milder trend. By Monday afternoon into Monday evening, clouds and precipitation will return with the bulk of any precipitation remaining light and mainly confined to the Appalachian Front in the form of light rain or drizzle. A leeside trough of low pressure should set up just to the east of the Appalachian spine, thus, allowing for this precipitation to occur with the help from a weak mid- level disturbance. Tuesday should be even milder yet with highs ranging from the middle 50s to the middle 60s widespread across the region. A persistent southwest wind and a little added sunshine during the day should aid in this. Tuesday night will be about the same as Monday night with low temperatures dropping into the middle to upper 30s for the most part.
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&& .LONG TERM /WEDNESDAY THROUGH SUNDAY/...
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Southern stream shortwave energy will be approaching the Mid-Atlantic region on Wednesday into Wednesday night. Guidance suggests that the forcing will stay south of us, but showers associated to this system could reach the southern counties of our CWA. Still to be determined in more detail is timing and p- types. A ridge of high pressure builds over the region on Thursday and into Thursday night bringing a period of dry weather. Sometime on Friday a warm front will push through, followed by a cold front on Saturday. Models suggest that Friday will remain on the drier side while Friday night we might see showers ahead of the front, but it all depends on the timing of it. Saturday`s PoPs are higher with the front moving through the region from the west. Uncertainty exists on Sunday`s weather depending on how close to the area the front stalls.
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&& .AVIATION /20Z SUNDAY THROUGH FRIDAY/...
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VFR conditions at all terminals. We can`t rule out a brief drop to MVFR in any isolated rain or sleet showers near the MRB terminal. Winds generally southeast less than 5 knots through this afternoon, becoming light and variable tonight. VFR conditions Monday through Tuesday night. Winds becoming southwest 5 to 10 knots Monday and Tuesday with light and variable winds Tuesday night. Sub-VFR conditions possible on Wednesday as forcing moves south of the area that could bring some showers to the terminals. VFR conditions expected Thursday and into Friday.
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&& .MARINE...
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No marine hazards through Tuesday night. Winds southeast 5 to 10 knots through this afternoon, becoming light and variable tonight. Winds southwest 10 knots Monday and Tuesday then light and variable each night. Winds are expected to stay below small craft advisory threshold Monday into Tuesday. Winds could increase Tuesday night into Wednesday behind a front, requiring a small craft advisory over the waters.
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&& .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...KLW NEAR TERM...KLW SHORT TERM...KLW LONG TERM...IMR AVIATION...IMR/KLW MARINE...IMR/KLW

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