Area Forecast Discussion
Issued by NWS Sterling, VA

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000 FXUS61 KLWX 160053 AFDLWX Area Forecast Discussion National Weather Service Baltimore MD/Washington DC 853 PM EDT Thu Jun 15 2017 .SYNOPSIS... A nearly stationary front will meander across the region through Friday before lifting back northeast of the area as a warm front over the weekend. A cold front is forecast to cross the area Monday into early Tuesday. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
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Frontal boundary remains stalled across the region this evening, as noted by east/southeasterly winds and dew points in the mid 60s east of a line from roughly CJR to MRB, and more southwesterly flow and dew points near 70F west of the line. This had also led to quite the CAPE gradient as well earlier today, which dictated much of today`s shower/thunderstorm development. Following earlier rounds of convection and the loss of daytime heating, instability is lessening, and much of the activity has weakened. Exception currently is across portions of Albemarle and Nelson counties where strong thunderstorms with heavy rain (and localized flash flooding threat) will continue for the next couple of hours. Elsewhere, scattered showers and isolated embedded thunderstorms remain possible, mainly west of the previously mentioned boundary, although a few may make it east. Overnight, low stratus, fog, and drizzle development is likely, especially in areas that saw rain this afternoon/evening and dew points remain elevated. Lows tonight from the mid 60s to low 70s.
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&& .SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/... The stationary boundary Friday morning will gradually shift north and east as a warm front Friday afternoon. More popup showers and thunderstorms are expected...but coverage will be more widespread across central and eastern portions of the CWA compared to Thursday. Limited shear profiles suggest that the severe threat will be low. Locally heavy rain is expected with thunderstorms due to high amounts of atmospheric moisture and the fact that storm motion will be slow. Coverage of convection should dissipate Friday night due to the loss of daytime heating. Patchy low clouds and fog are expected overnight into early Saturday morning. Bermuda high will develop for Saturday and a south to southwest flow around this system will continue to usher in warm and humid conditions across our area. The warm and humid airmass will lead to more showers and thunderstorms...especially during the afternoon and evening hours. Warm and humid conditions are expected Saturday night with patchy low clouds and fog. && .LONG TERM /SUNDAY THROUGH THURSDAY/... Hot and humid conditions continue into Sunday with heat indexes reaching the mid to upper 90s. Scattered showers and thunderstorms possible, mainly diurnally driven. PoPs increase Monday and into early Tuesday ahead of a cold front that could bring additional showers and thunderstorms, with the potential for strong storms. Heavy rain is also possible with PW near the 2 inches. Weather conditions will improve behind the cold front on Tuesday and into Thursday. Some showers may linger into Tuesday night, while another weaker system may allow for some other showers on Wednesday. && .AVIATION /01Z FRIDAY THROUGH TUESDAY/...
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Scattered showers and thunderstorms will gradually lessen in intensity and coverage this evening, with MRB/CHO having the greatest risk of seeing activity. Mainly VFR although some brief reductions in the showers/storms possible. Low clouds will develop late tonight along with areas of fog and drizzle. IFR conditions are expected late tonight through mid- morning Friday before CIGS gradually improve. More popup showers and thunderstorms are expected Friday afternoon and evening. Coverage will be farther north and east compared to Thursday. Warm and humid air will remain in place through Saturday night. Popup showers and thunderstorms are likely...especially during the afternoon and evening hours Saturday. Areas of low clouds and fog are possible during the overnight and early morning hours Friday and Saturday. Showers and thunderstorms possible Sunday into early Tuesday due to diurnal heating and an approaching cold front. Sub-vfr conditions possible at times during this period. Conditions improve/vfr Tuesday into Tuesday night.
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&& .MARINE...
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Small Craft Advisory continues for portions of the middle and lower tidal Potomac as well as portions of the central Chesapeake Bay through 10 PM this evening. Easterly wind gusts near 20 knots expected across these areas through the evening hours. Elsewhere winds should largely stay below SCA criteria, however gusts may still approach 20 knots for a brief window until 10 PM this evening. Winds should remain below SCA criteria overnight through Friday night. The gradient will strengthen as Bermuda high sets up late Saturday and Saturday night. An SCA may be needed for portions of the waters during this time. Popup showers and thunderstorms are likely Friday and Saturday...especially during the afternoon and evening hours. Showers and thunderstorms possible Sunday into early Tuesday due to diurnal heating and an approaching cold front. Wind gusts will be near or above the small craft advisory threshold Sunday into Monday night, and improving into Tuesday behind the front.
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&& .TIDES/COASTAL FLOODING...
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Tidal anomalies have increased to around 1 to 1.5 feet above normal due to an onshore flow. The onshore flow will continue through tonight and into Friday. With the high tide this evening and tonight being the lower of the next two high tides, minor flooding is not expected at most locations...however have issued a Coastal Flood Advisory for St. Mary`s County where water levels are likely to just reach minor flood stage. Minor flooding is then possible during the next high tide early Friday morning which will be the higher of the two. Have extended the Coastal Flood Advisory for St. Mary`s County to cover this, and will Anne Arundel may need to be added as well. Elevated water levels are expected through the weekend. Minor tidal flooding will be possible for sensitive areas near high tide.
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&& .LWX WATCHES/WARNINGS/ADVISORIES...
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DC...None. MD...Coastal Flood Advisory until 10 AM EDT Friday for MDZ017. VA...None. WV...None. MARINE...Small Craft Advisory until 10 PM EDT this evening for ANZ532>534-536-537-542-543.
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&& $$ SYNOPSIS...BJL NEAR TERM...BJL/MM SHORT TERM...BJL LONG TERM...IMR AVIATION...BJL/MM/IMR MARINE...BJL/MM/IMR TIDES/COASTAL FLOODING...BJL/MM

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