Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 161952 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 352 PM EDT Wed May 16 2018 .SYNOPSIS... A quasi-stationary front will meander about the Mid-Atlantic region through the end of the week. A subtropical area of low pressure in the northeast Gulf of Mexico will drift north into the south and central Appalachians by Friday. The combination of these two weather systems will result in scattered to numerous showers and thunderstorms across the entire region through the end of the week. A new frontal system will approach by early next week continuing the threat for showers and thunderstorms. Otherwise conditions will remain abnormally warm and humid into the weekend. && .NEAR TERM /THROUGH THURSDAY/...
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As of 330 PM EDT Wednesday... The main focus through Thursday will be quasi-stationary front to our north and subtropical low lifting north into the southern Appalachians from the eastern Gulf of Mexico. Airmass south of the front and covering the entire southeast CONUS is more indicative of August as opposed to May with PWATs 2 standard deviations above normal. As such, showers and thunderstorms which occur within this environment will be very rain efficient. For our forecast area, anticipate numerous to widespread showers. CAPE has been limited to generally 1000 k/gm or less, so nothing severe, but lack of a cap has allowed for showers to bubble up all over the CWA... more of a shotgun pattern but nothing organized. Since the front is well north of the area, not much to focus the heavy rain, so no need for a flood watch attm, but may need to consider possibility of headline pending track of subtropical low as it lifts north into the southern Appalachians Thursday. Until then will entertain occasional showers with embedded thunderstorms with brief heavy downpours. Temperatures/dewpoints will remain summerlike with overnight lows above 60 coinciding with the August-like dewpoints.
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&& .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/...
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As of 340 AM EDT Wednesday... The portion of the forecast is continuing to offer wet conditions across the region. From Thursday night through Saturday, an upper level area of low pressure will make gradual progress from western TN to Wisconsin. Saturday night, the low will open into a wave and start to be transported eastward as it reaches the northern jet. Its associated trough axis will still be extending south into eastern KY. This trough axis will cross our region Saturday night. On the east side of this low/trough, southerly, moisture-rich flow of air will be streaming across our area with its origins off the eastern Gulf of Mexico. It will be this moisture that will allow for a very generous coverage of moderate to heavy rain showers to cross our region during this time period, along with some isolated to scattered thunderstorms, especially during the late afternoon and evening hours. We will be monitoring precipitation patterns and amounts as we progress into this time period. This will help us gauge where and/or if any flood watches may need to be posted. The first time period of increased focus will be Thursday into Thursday night. WPC currently has posted a slight chance for excessive rainfall during this time period. Temperatures during this portion of the forecast are expected to average about five degrees above normal. Low will range from the low to mid 60s across the mountains with mid 60s to near 70 across the Piedmont. High temperatures are forecast in the the mid to upper 70s across the mountains with upper 70s to around 80 across the Piedmont.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/...
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By Sunday, the upper low/trough that has been impacting our weather pattern the past several days, will be far enough north to be caught up by the northern jet, and heading eastward towards New England. This will return our region to a flow that initially will be predominately westerly, all while another baroclinic zone establishes itself along or near the Ohio River Valley by Monday evening. Concurrently, an upper high in the western Atlantic, east of GA/FA will hold fast, and anti-cyclonic flow around this feature will keep a decent fetch of moisture into our region at the lower levels. By Wednesday, the front to our north is expected to have trended farther south to over, or just north of our region. The result of the above scenario will be a weather pattern that will still have daily chances of showers and some thunderstorms. On average, chances will be greatest during the afternoon hours during the peak heating of the day. Chances will also on average increase by mid-week as the frontal boundary gets closer to, or overhead of, the area. Temperatures across the region will begin this portion of the forecast averaging five to ten degrees above normal. While a slight cooling trend is expected, by Wednesday, temperatures will still be averaging five degrees above normal.
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&& .AVIATION /20Z WEDNESDAY THROUGH MONDAY/...
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As of 345 PM EDT Wednesday... Will maintain a mixture of MVFR/IFR ceilings and mostly MVFR visibilities through the 24 hour taf period courtesy of abundant moisture flowing north from a subtropical low over the northeast Gulf of Mexico. Anticipating scattered to numerous showers/thunderstorms through the period, but they are expected to lack organization... more of a shotgun sort of pattern. Winds will be light and variable, except in/near thunderstorms. Medium confidence in ceilings and visibilities through the TAF valid period. Medium to high confidence in wind speed through the TAF valid period. Low confidence in wind direction through the TAF valid period. .Extended Aviation Discussion... Probability for showers/thunderstorms will increase associated with southward sagging front and moisture streaming north from a weak tropical/subtropical disturbance in the northeast Gulf of Mexico Thursday into Friday. As this drifts north over the weekend very slowly, convective activity will become slightly less numerous and more scattered, but a better than normal chance for showers/thunderstorms and associated aviation issues will continue through the weekend. Winds will be mostly light through the period.
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&& .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RAB NEAR TERM...PM SHORT TERM...DS LONG TERM...DS AVIATION...PM

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