Area Forecast Discussion
Issued by NWS Sterling, VA

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775 FXUS61 KLWX 191016 AAA AFDLWX Area Forecast Discussion...UPDATED National Weather Service Baltimore MD/Washington DC 516 AM EST Mon Feb 19 2018 .SYNOPSIS... A warm front will approach the area from the south today before passing through later tonight through Tuesday morning. Record warmth is possible behind this system for Tuesday and Wednesday. A cold front pass through the area Thursday before stalling out nearby during the end of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A warm frontal zone will move into the region today, bringing with it overcast skies and increased chances of rain showers. Main area of rain early this morning is progressing across eastern WV and central VA as of 5 AM on the leading surge of warm air advection. Additional showers have also developed across Kentucky, Indiana, and Ohio, and will push northeastward as well. Model guidance is in relatively good agreement that the initial surge of rain will continue its progress eastward across the region this morning, with the most concentrated and longest lasting across central VA and into southern MD, while the second area moves into OH/PA this afternoon. Thus, the highest probabilities of rain are this morning and by later in the day, rain showers will have pushed northward/eastward out of the entire region. Temperatures have been able to drop to near or below freezing in some locations, but are expected to rise before precip moves in. High temperatures will occur late today under low clouds and as southerly flow kicks in, reaching the upper 40s across NE MD to mid/upper 50s across parts of WV and central/western VA.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/... Southerly flow and increasing low level moisture will continue tonight. This will keep temperatures considerably milder with lows from the mid 40s to low 50s. Low clouds and some fog are also possible. An anomalously strong upper level ridge (heights 2-3 SD above climatology for February) will become positioned near the southeastern US coastline from Tuesday and through the end of the week. This will set the stage for near-record or record warmth for Tuesday and Wednesday across the region. Some lower clouds and patchy fog are possible Tuesday morning, especially from the I-95 corridor eastward, but as southwesterly flow increases throughout the day, breaks of sun become likely, especially across western areas. As 850 mb temperatures reach 12C and 925 mb temperatures surge to 14-15C, high temperatures are likely to soar through the 70s area-wide, with some locations possibly nearing 80F in central VA and west of the Blue Ridge. Dry weather is expected. Southwesterly flow continues Tuesday night, and temperatures will only drop into the 50s. Wednesday will likely end up being the warmest day for many locations as a cold front approaches the region from the west. Some shower activity is possible in the afternoon as well west of the Blue Ridge. With 850 mb temperatures warming to 12-14C and 925 mb possibly reaching 17C or higher, widespread upper 70s to near 80F are forecast. This, in addition to the daily lows, will be approaching 30 degrees above climatological normals for the date (49/32F at DCA). Daily record high maxes and minimums are all likely in jeopardy, with all-time February highest minimums also possible. The cold front will cross the region Wednesday night, with increasing chances of rain showers. Temperatures by Thursday morning drop back into the 40s/50s. && .LONG TERM /THURSDAY THROUGH SUNDAY/... A cold front will continue to drop to our south Thursday before stalling out Thursday night. High pressure will build to our north this time and a north to northeast flow will usher in a return of seasonably chillier conditions. A wave of low pressure may develop along the front as well...likely bringing some rain to the area during this time. The boundary will return north as a warm front Friday but it may stall out near our area for Saturday before a stronger cold front from the west passes through later Sunday/Sunday night. Unsettled weather is likely during this time. Temperature forecasts are with low confidence since there is uncertainty as to exactly where the front will set up. The boundary will separate much cooler marine air from unseasonably warm conditions. Will continue with the Superblend which keeps cooler conditions for most areas Friday thinking that the boundary remains to our south but is warmer for Saturday and Sunday when there is a better chance for the front to move a bit farther north. && .AVIATION /10Z MONDAY THROUGH FRIDAY/... VFR conditions early this morning will see a deterioration into MVFR/IFR through the day as low clouds and some showers move northeastward into the region along a warm frontal zone. BWI/MTN/DCA/CHO are the sites with the highest risk of seeing IFR. Tonight into Tuesday morning, potential for additional low clouds and fog exists, with IFR conditions possible. BWI/MTN/CHO/DCA once again most at risk to be impacted by sub- VFR conditions. As southwesterly flow increases aloft, low level wind shear also becomes more likely overnight. Any low clouds and fog should lift by Tuesday afternoon, and VFR is then expected through Wednesday. Additional sub-VFR conditions become possible as a cold front crosses the region Wednesday night bringing chances of rain showers. Gusty southwest winds will develop both Tuesday and Wednesday afternoons. A cold front will stall out to the south later Thursday through Thursday night. Low pressure will develop along the boundary during this time...likely bringing rain to the area along with subvfr cigs/vsbys. The boundary will return north as a warm front Friday. At this time...it appears that the terminals will still be on the cool side of the boundary...resulting low clouds along with a chance for rain/drizzle and IFR conditions. && .MARINE... Winds will remain below SCA criteria today and through Tuesday morning. As southerly flow increases Tuesday afternoon, Small Craft Advisories become possible. With warm air temperatures expected over considerably cooler waters, the strongest gusts will likely be observed along the shorelines. The same situation will occur Wednesday. A cold front will drop to our south Thursday before stalling out Thursday night. A Small Craft Advisory may be needed for portions of the waters Thursday. The boundary will return north as a warm front Friday but it should remain to our south during this time. This means that an onshore flow is likely. && .CLIMATE... Some all-time February highest minimum temp records could be in jeopardy, but it depends on how quickly a cold front moves through Wednesday night. If the Wednesday calendar day low does not drop below 60 degrees, it would be the first time not dropping below 60 at DCA in February since 1891, and only the sixth time on record in the entire meteorological winter season. Even a low 56 or higher at DCA would be the warmest low in the month of February since 1976. The all-time February highest minimums are: 61 at DCA/Washington (2/17/1891) 58 at BWI/Baltimore (2/17/1891) 55 at IAD/Dulles (2/17/1976) - records only go back to 1960 at IAD It almost goes without saying that daily records are in jeopardy. A table of those records follows: Record warm daily maximum temperatures Tue 2/20 Wed 2/21 DCA 76 (1930) 75 (1953) BWI 76 (1930) 74 (1930) IAD 70 (1971) 70 (1997) Record warm daily minimum temperatures Tue 2/20 Wed 2/21 DCA 59 (1939) 51 (1954) BWI 57 (1939) 49 (1981) IAD 46 (1981) 45 (1981) && .LWX WATCHES/WARNINGS/ADVISORIES... DC...None. MD...None. VA...None. WV...None. MARINE...None. && $$ SYNOPSIS...BJL NEAR TERM...MM SHORT TERM...MM LONG TERM...BJL AVIATION...BJL/MM MARINE...BJL/MM CLIMATE...JE

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