Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 281805 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 205 PM EDT Thu Jul 28 2016 .SYNOPSIS... Low pressure will move along a stalled front from the mid Mississippi Valley to the Ohio Valley today and tonight. This wavy frontal system will remain across the region through Monday. The front is expected to drift south and dissipate next Tuesday and Wednesday. && .NEAR TERM /THROUGH TONIGHT/... As of 1255 PM EDT Thursday... Expect no significant changes to the forecast through the remainder of the afternoon. Isolated to scattered convection is expected to start to develop within the hour across primarily the mountains. After roughly 400 PM or 500 PM a more organized band of showers and storms is expected to progress into the area from the west and make progress eastward through the evening. Forecast highs are on track for most areas. Added a degree or two to the forecast highs around the Roanoke region based upon the latest observations. As of 1215 PM EDT Thursday... Have decided to hoist a Flash Flood Watch for our southeast West Virginia counties and Tazewell County Virginia. Latest one hour flash flood guidance values for parts of these counties is in the one to one and one-half inch range. These values will be obtainable from late this afternoon into tonight with the potential of multiple thunderstorms training across the same location. As of 1020 AM EDT Thursday... Adjustments to the forecast for this afternoon will reflect a slightly slower arrival time of the main band of showers and storms that will enter the region from the west. While isolated to scattered coverage of showers and storms are expected across the mountains starting around noon, the main swath of potentially strong storms is more likely going to arrive in the west closer to 400-500 PM EDT and spread eastward into the evening hours. The storm prediction center has expanded the Slight Risk for today farther west into southeast West Virginia. If severe weather is to occur, the greatest potential will be damaging winds rather than large hail. Will continue to monitor and assess any potential for flash flood watches for any portion of the forecast area. The latest guidance suggests portions of southeast West Virginia may have the best potential. As of 430 AM EDT Thursday Cluster of showers and thunderstorms was tracking northeast through western part of the county warning area at 400AM. High resolution guidance has a majority of this precipitation north of the forecast area at 13Z/9AM. There will be some residual cloud cover this morning which will cut back on the potential heating and instability. Temperatures will still climb into the 80s today in the mountains and into the 90s in the piedmont. Starting with muggy conditions this morning in part due to surface dew points in the upper 60s to lower 70s. Heat index will top out around 100 in the east of the Blue Ridge this afternoon but will fall short of advisory level values. Short waves over the mid Mississippi valley early this morning are forecast to track into the Ohio Valley by Friday morning. This will provide better synoptic scale lift plus forecast area will be in the right entrance region of the upper jet this afternoon and evening. low and mid level winds increase from the southwest to west by late this afternoon which will increase the helicity. Bufkit forecast soundings were showing some decent speed shear. Directional shear becomes stronger this afternoon too as the surface low that was over southeast Missouri this morning moves east and backs the surface winds to the southeast. Once the short wave moves east...surface through mid level winds turn to the northwest and best lift will be confined to the western county warning area. No change in air mass overnight so minimum temperatures will be similar to past few mornings. && .SHORT TERM /FRIDAY NIGHT THROUGH SATURDAY NIGHT/...
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As of 145 PM EDT Thursday... Frontal boundary will stay just north of us Friday night with spoke of upper energy moving east Friday evening. Timing of impulses is problematic but seems next best wave works toward the PA/OH border Saturday afternoon which may slowly nudge front southward. Appears best threat of showers and storms will be focused from far Southwest Virginia into SE WV and north of Highway 460 across Roanoke and Lynchburg north Saturday afternoon with widely scattered further south. Nonetheless kept pops no higher than 50. Temperatures stay elevated at night thanks to high pwats with lows from the mid to upper 60s west to lower 70s east. Saturday should be at or just above typical late July values of lower to mid 80s west to around 90 east.
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&& .LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 1150 AM EDT Thursday... Belt of westerlies will be laying across the area Sunday night into Monday, with front situated across the mid-Atlantic. Afterward the upper flow takes on a more NW to SE orientation across our area as ridge builds over the Central Plains. The front weakens but convergence along it to remain through midweek. In addition, the upper pattern favors potential ridge runners, where convective clusters form over the upper midwest and shift southeast over our area. Overall, will keep threat of showers and storms in the forecast all periods but looks like Sunday-Monday have the better chance for measurable rainfall. May see slight nudge downward in temps early but overall humidity levels should stay the same, so no appreciable dry air expected thru Thursday. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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As of 145 PM EDT Thursday... VFR conditions prevail across most of the region. Isolated showers were beginning to develop across the mountains, with some locations bordering on scattered coverage. Thunderstorms have yet to develop, but anticipate no more than an hour or two until the first lightning strike. Coverage will increase from west to east across the region beginning around 20Z/4PM as a more organized band of showers and storms moves into the region. Conditions will trend to MVFR for ceilings and visibilities under the stronger cells. Overnight, look for cloud cover to increase across the area with most locations in the MVFR range with areas of IFR in across the mountains. Showers and storms will continue, especially in western and northern parts of the area. Visibilities will be a mix of MVFR and low end VFR with pockets of IFR under the heavier cells. Much of the activity will wane by sunrise Friday, with lingering showers in the west. MVFR ceiling and visibilities will last a few hours after sunrise. Extended aviation discussion... The area will remain in a relatively active period for showers and storms through Tuesday thanks to a persistent, nearly stationary frontal boundary across or near our region. Outside of the precipitation and during the daylight hours, VFR conditions are expected to prevail. Within the heavier showers and storms, and during the overnight hours sub-VFR conditions are more likely.
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&& .CLIMATE... Record warm minimum temperatures for July 28 Bluefield WV.....69 in 2010 Danville VA......76 in 1997 Lynchburg VA.....77 in 1930 Roanoke VA.......80 in 1930 Blacksburg VA....68 in 1987 && .RNK WATCHES/WARNINGS/ADVISORIES...
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VA...Flash Flood Watch through Friday morning for VAZ007. NC...None. WV...Flash Flood Watch through Friday morning for WVZ042>044-507- 508.
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&& $$ SYNOPSIS...AMS NEAR TERM...AMS/DS/WP SHORT TERM...WP LONG TERM...WP AVIATION...DS CLIMATE...PM

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