Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 231748 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 148 PM EDT Fri Jun 23 2017 .SYNOPSIS... Tropical Depression Cindy was over Arkansas this morning and by Saturday morning will be over Maryland with a cold front trailing into the Southern Plains. High pressure builds in Sunday and Monday from the west behind the front and by Tuesday will cover much of the eastern United States. && .NEAR TERM /THROUGH TONIGHT/...
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As of 148 PM EDT Friday...Overall, no significant changes needed aside from some noise-level tweaks to Sky cover and PoPs. Some greater clearing is becoming apparent, with LAPS-based MUCAPEs on the rise (500-1200 J/kg were the most common). Past couple cycles of the HRRR and the 12z 3-km NAM show isolated to widely scattered cellular convective coverage beginning along the central and southern Blue Ridge. Tried to show slightly higher PoP chances to reflect that potential. If these cells do pan out, they may produce gusty winds based on strong low-level wind fields (ref: MRX VWP showing 50 kts at 5000`). They would be isolated in coverage at best, stemming from stronger differential heating in pockets of cloud breaks. Many areas do stay dry, though cloudy, this afternoon. We are starting to see higher gradient flow gusts develop along the higher elevations, with Bluefield having recently gusted to 31 kts from the southwest. Expect these gusts to continue along the ridges as low- level winds steadily increase. Winds should remain below sub-Advisory, but may cause minor impact to trees especially if dead or shallow-rooted. More to come later... Previous near-term discussion issued at 345 AM Friday follows... It will take 6 to 12 hours for the former tropical system and cold front to cross through southern West Virginia and southwest Virginia. Good diffluence aloft tonight, partially with the tropical feature, but moreso with the strong upper level jet in the northern stream. Some differences in the short range models with how much precipitation there will be following the North Carolina wave and before the tropical/frontal precipitation arrives. Wildcard may be the band of showers in eastern Tennessee to southeast Mississippi and the location of this feature by this afternoon. Will be trimming back probability of precipitation for today but will retain categorical probability tonight. Limited coverage of showers and thunderstorms will also limit severe threat prior to 00Z/8PM, but with surface dew points in the lower 60s to lower 70s, leading to increased CAPE and 0-3KM helicity forecast to be up to 400 m2/s2, the threat for severe thunderstorms is still present. 850mb reach about +19 this afternoon. Should get some sun following the cluster of showers tracking out of North Carolina. Took a blend of MET /MAV guidance. Front does not completely clear the Virginia and North Carolina piedmont before 12Z/8AM. Will keep minimum temperatures mild ahead of the front.
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&& .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 330 AM EDT Saturday... Remnants of TS Cindy will get absorbed into a cold front coming across the Ohio Valley early Saturday morning. This cold front will slide across the mountains during the morning, but may not clear Southside until Saturday evening. Strong ridging off the southeast coast will slow the southern movement of the front, which will stall across the Carolina coast on Sunday. Rain showers will clear the mountains by early afternoon then move south into North Carolina during the evening. Subsidence behind the front will also bring breezy/gusty winds to the mountains through the evening. This front will remove the tropical air mass but humidities will remain slightly elevated until the dew point front moves across the region on Sunday. Dry high pressure will then take control of our weather starting Sunday afternoon. Saturday`s afternoon temperatures will warm to near normal levels. Cooler and drier air will arrive Sunday with temperatures 3F-5F cooler than normal. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 125 PM EDT Thursday... Fairly quiet wx this period with cooler temperatures as 5h trough digs across the eastern U.S. A few shortwaves in the Monday-Tuesday time frame may fuel a few showers, but overall it looks dry. Toward Thursday the upper trough exits to the east with shortwave ridging building across the Appalachians. Highs and lows Monday- Wednesday should run 5 to 10 degrees below normal, then edge close to normal by Thursday. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
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As of 148 PM EDT Friday... Overall active aviation forecast period in the first 12 hrs. VFR to VFR/MVFR conditions should prevail through 00z. May be an isolated to widely scattered thunderstorm but confidence is not high to include in the TAFs at this time. Areas of mechanical turbulence along the spine of the Blue Ridge are likely this afternoon with a southwesterly low- level jet of around 50 kts persists. Surface winds should also be around 6-12 kts, with gusts to 22 kts at BLF. Deterioration to poor flight conditions expected from 00-09z is the overall messsge. A cold front interacting with Cindy`s remnants produces a substantial line of moderate to heavy showers and embedded thunderstorms. See TAF for specific airports on timing; as of now, this was indicated with prevailing VCSH given that we are > 6 hrs out before likely impact. Frequent use of amendments may be likely to narrow down a more specific period of greater risk. While a couple stronger cells are possible and their associated lightning risk they pose, even heavier showers may produce gusty, erratic winds at Roanoke, Bluefield, Lewisburg and Blacksburg. Gusty wind potential is more conditional and more lower- confidence for Danville and Lynchburg. Expect widespread MVFR conditions with temporary IFR/LIFR visibility in heavy rain. Low-level wind shear possible ahead of with the frontal passage. Outside of thunderstorms, winds begin southwest 6-12 kts before veering to west. For Saturday, front should make slow but steady progress southward, with steadily improvement to VFR conditions along with a west/west-northwest wind shift 6-8 kts. Extended Aviation Discussion... VFR conditions to then prevail Saturday night through Sunday night. Potential for radiation fog and related visibility restrictions Sunday night. A cold front passing on Monday may produce VFR/possible MVFR conditions and breezy northwest winds behind it. VFR then lasts through Wednesday.
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&& .HYDROLOGY... As of 735 AM EDT Friday... Rainfall forecast/models/ensemble river forecasts suggests greater threat for flooding will be west and north of our forecast area. Average rainfall amounts of 1 to 2 inches expected from the NC mountains to Mountain empire of SW VA to southeast WV with 2 to 3 inches further west into the KY/TN/OH corridor. Not seeing enough signals to warrant a watch, but given efficient rainfall rates, any convective elements or training will increase the threat. Timing of heavy rain will be this evening into Saturday morning. In summary, based on models looking wet, but still not high enough confidence in a flood/flash flood watch. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AL SHORT TERM...RCS LONG TERM...WP AVIATION...AL/AMS HYDROLOGY...AMS/WP

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