Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 202322 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 722 PM EDT FRI MAY 20 2016 .SYNOPSIS...
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A complex area of low pressure will approach from the southwest tonight and cross the region Saturday through Sunday. High pressure will slowly build into the area on Monday, and remain in place for much of the week, resulting in warmer and drier weather for most of the workweek.
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&& .NEAR TERM /THROUGH SATURDAY NIGHT/... As of 350 pm EDT Friday... An upper ridge of low pressure will approach the region overnight. Plenty of moisture will ride north along the eastern side of this trough and across a lee side wedge of high pressure. A surface low pressure will start to develop over the region tonight, and then strengthen off the coast Saturday afternoon. Patchy light rain will spread northeast through the area this evening. A larger swath of moderate to heavy rain will reach the area during the late evening, and begin to exit the area late tonight. A generous amount of rain is still expected in the one to two inch range. See the HYDROLOGY section of this discussion for more details. On Saturday the area will start to experience northwest flow on the backside of the developing surface low pressure. This flow will help to gradually erode the wedge. Instability will increase through the day with showers still expected in the west with isolated to scattered thunderstorms in the west and south by the afternoon. Saturday night the main upper low will continue approach and then cross the region. Anticipate additional scattered showers under the increased lapse rate of its associated cold pool. Temperatures during this portion of the forecast will be slightly below normal. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 320 pm Friday... A broad upper level trough, sitting over New England and the Mid Atlantic region, is expected to become a closed low Sunday. This closed low is forecasted to track south across the coastal piedmont of Virginia and North Carolina Sunday night, then off Cape Hatteras Monday. This low is then forecasted to track north to New England on Tuesday. Since this low will remain inland, there is a good chance for showers Sunday, especially east of the Blue Ridge. Also with a cold pool pivoting over the piedmont during the afternoon, isolated strong to severe storms are possible with hail being the primary threat. Bulk of the stronger storms and heavy rain will remain with the low and points east. With this in mind, the actual track of this upper low will dictate our weather for Sunday. Stay tune. The chance for showers will remain in the area Sunday night, however, strong storm threat will decrease as the low jogs to the east. As this low continues to move east, showers will taper off from west to east with rain leaving the piedmont sometime Monday evening. It is obvious with the change in this low`s track, PoPs have been increased and durations has been stretched into Monday, mainly across the piedmont. While this low is in the vicinity, temperatures will remain cooler than normal Sunday and Monday. Sunday afternoon temperatures will range from the mid 60s to lower 70s. Slight warmer Monday with the chance to see more sun. Highs Monday will be in the upper 60s to mid 70s. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 330 pm Friday... Finally, the upper level low is out of our hair and ridging begins to build along the east coast Tuesday. Temperatures will warm above normal Tuesday, then well above normal Wednesday through Friday. With the warmer weather comes a better chance for showers and thunderstorms each afternoon and evening. Storms do not look organized but pulse-like, tracking slowly from the southwest to the northeast. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/...
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As of 700 pm EDT Friday... Flying conditions will continue to deteriorate this evening with spotty light rain and drizzle resulting in cigs falling to MVFR levels or worse over the next few hours. A more widespread area of light to moderate rain will overspread the southern/western sections by midnight, and the remainder of the region overnight. Visibilities will trend to MVFR including ocnl IFR in heavier rainfall with ceilings lowering to IFR at most locations. Conditions will start to improve toward daybreak Saturday as the heaviest rain moves northeast, out of the region. Expecting widespread rainfall to exit the region early Saturday morning with residual areas of fog/stratus keeping sub-VFR conditions in place. Appears some improvement to MVFR or perhaps brief VFR possible around midday Saturday as the region slides in between exiting surface low pressure to the east and the upper low to the nw. This may create enough low level west/nw flow to help scour out low cigs along/east of the Blue Ridge pending how deep the leftover wedge gets. Cigs will again lower over the west later Saturday as the upper cold pool drops in from the north resulting in scattered showers along with isolated thunderstorms. However given uncertainty with the degree of instability will only keep prevailing showers in from KBCB westward and VCSH at KROA without any thunder mention for now. Otherwise mainly MVFR cigs and vsbys west and possible VFR at KDAN/KLYH by late in the day. Extended discussion... Saturday night into Sunday night, cigs look to remain quite variable under the passing upper low with periods of mainly MVFR cloud bases during the daylight hours and VFR cigs at night. Isolated to scattered showers will also occur, espcly over the mountains Saturday evening and across the east Sunday into Sunday evening making for MVFR vsbys or worse at times. Isolated thunder will also be possible along with patchy sub-VFR vsbys overnight in fog where earlier rainfall occurred. Northwest upslope flow may maintain some IFR ceilings at times in the west espcly around KBLF. Surface gusts of 20 to 25 kts will be possible across the mountains during this time frame. 850 mb winds are progged to increase to 25 to 35 kts, and gradually veer northwest to north. On Monday, winds will start to decrease as the center of the upper low continues to exit the region. Isolated showers will still be possible, especially in the east, related to this feature. Monday night through Wednesday, expect mainly VFR conditions as high pressure settles offshore with southwest flow in place.
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&& .HYDROLOGY... As of 400 pm EDT Friday... Consistent forecast from the models and the Weather Prediction Center with one to two inches of rain expected across the forecast area from this evening through late in the day Saturday. The bulk of this precipitation will fall this evening into early Saturday morning. There is still a potential that this longer duration rainfall will lead to localized minor flooding along streams and creeks. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...DS/JH NEAR TERM...DS SHORT TERM...RCS LONG TERM...RCS AVIATION...DS/JH HYDROLOGY...DS

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