Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 221912 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 312 PM EDT Fri Jul 22 2016 .SYNOPSIS... A Bermuda high will keep pushing warmer and more humid air into the region throughout the weekend and into the first part of next week. The combination of high air temperatures and humidity will create dangerously high heat index values, especially east of the Blue Ridge, with readings around 105 at times through the weekend. The heat and humidity will also create an unstable airmass, and a series of weak fronts moving through the region will help keep at least a small chance for showers and thunderstorms in parts of our forecast area for the next several days, with increasing chances as we get into next week. && .NEAR TERM /THROUGH SATURDAY/...
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As of 312 PM EDT Friday... The upper level ridge that is providing excessive heat to the central United States will expand eastward over the Tennessee Valley tomorrow. Even though the oppressive heat will remain west of the region, temperatures will still run 4F-7F warmer than normal. Despite the warmer than normal temperatures, record temperatures are not forecasted for the area. Uncomfortable dew points combined with the very warm temperatures will produce heat indices ranging from the upper 80s to lower 90s across the mountains and 98F-103F east into the piedmont. A lee trough laying over the foothills is providing enough convergence along the southern Blue Ridge this afternoon for a few storms to develop. These storms will either fade with loss of heating this evening or move southeast out of the area. This lee trough will drift east over the piedmont Saturday afternoon. A few isolated thunderstorms may develop with this trough as well as a few mountain showers from orographical lift tomorrow afternoon. With the center of the ridge over the central plains, its outer rings are draped over the region. With this setup, we will need to keep an eye on the Ohio Valley for any convection drifting our way. Today`s models fade current convection across West Virginia this evening. The boundary that is left behind today may move into the region tomorrow. This will increase the chances for storm tomorrow.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/...
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As of 309 PM EDT Friday... The upper ridge will control our weather into Sunday. Any diurnal convection Saturday evening will diminish with loss of solar heating. The best chance for a thunderstorm will occur along the southern Blue ridge. Low temperatures Saturday night will be mild with readings from the mid 60s in the mountains to the lower 70s in the Piedmont. As the surface frontal boundary drops south Sunday, its looses its definition stopping near the area. Showers and thunderstorms will be on the increase in advance of this front and in its proximity once it stalls. The best chance of a storm will occur in the west. The region will remain on the hot and humid side of the front. High temperatures on Sunday will range from the mid 80s in the mountains to the mid 90s in the Piedmont. Heat index values are forecast to surpass 100 degrees for one hour or two across the far southeast portion of the region Sunday afternoon. By late Sunday night, a shortwave trough approaching through the upper Mississippi valley will help to buckle the stalled front north as a warm front. This will keep hot and humid conditions across the area, and briefly shift the main focus for additional showers and thunderstorms north of the area. Added the mention of patchy for to the western valleys. Low temperatures Sunday night into Monday morning will range from the mid 60s in the west to the lower 70s in the east. On Monday, the trough axis of a disturbance will be approaching the western portions of the area by Monday afternoon and act as a focus for additional showers and thunderstorms. The greatest concentration will be in the west. High temperatures Monday will the mid 80s in the west to the mid 90s in the east. Monday afternoon some heat index readings may briefly top 105 degrees between roughly South Boston, VA and Charlotte CourtHouse, VA. We will continue to highlight the heat in the Hazardous Weather Outlook. Scattered convection will continue into Monday evening with some decrease by late Monday night as the trough axis moves east of the region. Low temperatures Monday night into Tuesday morning will range from the mid 60s in the mountains to the lower 70s in the Piedmont.
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&& .LONG TERM /TUESDAY THROUGH FRIDAY/...
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As of 309 PM EDT Friday... The large upper ridge will extend from the West coast to the East coast through Wednesday. Towards the end of the week, there is a gradual lowering of H5 heights as ridge splits and develops a Bermuda ridge and desert SW ridge. In the northern stream, a shortwave will drop southeast out of eastern Canada and crosses through New England on Tuesday. A frontal boundary will settle across the Mid-Atlantic and Southeast Wednesday into Thursday. A wave of low pressure along the front will slow the progression of the boundary. The placement of fronts are always a challenge in the summer. Low level moisture will continue to increase into the end of the period. Afternoon and evening showers and thunderstorms are possible Tuesday into Midweek. Temperatures will be above normal early next week and return to normal by end of the week.
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&& .AVIATION /19Z FRIDAY THROUGH WEDNESDAY/... As of 105 PM EDT Friday... High confidence forecast to keep it dry and VFR most of the period at all terminals...with only exception being some brief MVFR to IFR fog at KLWB/KBCB during the early morning hours Saturday. Bands of mid and high clouds this afternoon may lingering into the overnight and will be the key to any fog formation. Will maintain persistent forecast with some high clouds under an upper level ridge limiting mountain valley fog to KLWB. Any fog Saturday morning will burn off quickly. Diurnal convection would be isolated and mainly along the southern Blue Ridge toward GEV/TNB this afternoon. Will still need to keep an eye on upstream convection over the Ohio Valley which may approach KLWB late this evening and perhaps this time could result in thicker cloud deck but confidence in getting any shower or thunderstorm activity through 18Z Sat morning is very low. Extended aviation discussion... Strong high pressure aloft centered across the Midwest will attempt to build eastward into the weekend, then retreat back to the west early next week. Our region will remain on the eastern periphery of the upper high and thus subject to weak disturbances in northwest flow aloft tracking around the Great Lakes and into the Mid-Atlantic. Moisture and instability will be sufficient for isolated pop up thunderstorms, but a slightly better coverage will be possible early next week as weak front moves into the area, stalls, and lingers over the region for several days. Hot and humid conditions east of the Blue Ridge this weekend which may impact density altitude. Late night and early morning fog will still be possible at the usual sites almost every day, and those chances increase if any rain occurs during the afternoon or evening at any of these sites. && .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...None. NC...None. WV...None. Strong high pressure aloft centered across the Midwest will attempt to build eastward into the weekend, then retreat back to the west early next week. Our region will remain on the eastern periphery of the upper high and thus subject to weak disturbances in northwest flow aloft tracking around the Great Lakes and into the Mid-Atlantic. Moisture and instability will be sufficient for isolated pop up thunderstorms, but a slightly better coverage will be possible early next week as weak front moves into the area, stalls, and lingers over the region for several days. Hot and humid conditions east of the Blue Ridge this weekend which may impact density altitude. Late night and early morning fog will still be possible at the usual sites almost every day, and those chances increase if any rain occurs during the afternoon or evening at any of these sites.
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&& $$ SYNOPSIS...RCS NEAR TERM...RCS SHORT TERM...KK LONG TERM...KK AVIATION...RCS/SK

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