Area Forecast Discussion
Issued by NWS Blacksburg, VA

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279 FXUS61 KRNK 241901 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 301 PM EDT Sat Jun 24 2017 .SYNOPSIS... The remnants of former T.S. Cindy, located over northern Virginia this morning will accelerate northeast of the Mid- Atlantic coast by evening as upper troughing deepens across the Great Lakes. A weak cold front will push slowly southeast through the day, then southeast of the area by Sunday morning. Upper troughing will remain in place through much of the upcoming week, but at the surface weak high pressure will hold until late week, leaving the area with mostly dry conditions until late week with slightly below normal temperatures. && .NEAR TERM /THROUGH SUNDAY/...
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As of 255 PM EDT Saturday... Mid-afternoon update to reflect a greater concentration that just scattered showers and storms for the next couple hours over parts of the North Carolina Foothills. Good coverage of showers and storms currently over Yadkin county will progress northeast into parts of Surry and Stokes over the next couple of hours. This activity than will progress eastward along the NC/VA border through 600 PM. As of 1255 PM EDT Saturday... The biggest adjustments to the forecast for this afternoon is an increase in forecast high temperatures by roughly two to four degrees across the eastern parts of the area. A bit more sunshine was received than earlier anticipated across the region which allowed the increase. Clouds are now advancing into that area, so the rate of increase should start to decrease, but there will still be enough sunshine to warrant the forecast high increase. Adjusted precipitation forecast from this morning is on track with isolated showers now located across North Carolina generally along and west of I-77. As of 955 AM EDT Saturday... The biggest forecast adjustment for today is a increase in arrival time of clouds and isolated to scattered showers over and east of the Foothills and neighboring sections of southwest Virginia. Latest radar trends and the most recent meso-scale models suggest arrival about three to four hours later than those earlier advertised. Have adjusted the forecast accordingly. The only other adjustment is a reflection of the current observations of temperature, dew point, and wind with expected trends into the early afternoon. As of 415 AM EDT Saturday... Surface pressure analysis shows that the remnants of T.S. Cindy tracked through the heart of the CWA overnight and early this morning were located over Loudon county VA, just west of D.C. Any area of showers and gusty winds moved quickly through the CWA just after midnight blowing a few trees down in the Henry County VA/Rockingham County NC area, but other than that it was just a breezy and muggy night, albeit about 10 degrees cooler with the passage of the showers and Cindy. So, we are done with problems associated with Cindy now as it is progged to continue racing off quickly to the east-northeast amidst strengthening 500mb flow thanks to a trough deepening over the Great Lakes. A trailing cold front, will be much slower to push south of the area, as the flow aloft is largely parallel to the front. With the trough deepening, the front will eventually sag south of the CWA later tonight and early Sunday. Convective allowing models in addition to most of the synoptic scale models, indicate good potential for showers and thunderstorms to develop across eastern TN/western NC and perhaps even into far southwest VA, such as the Grayson/Carroll county area, this afternoon, before drifting east-southeast through the evening. Brooks-Craven parameters suggest that there is even some potential for a few severe storms, but mainly closer to the I-40 corridor just south of the CWA. SPC has indicated a marginal risk for severe this afternoon/evening, but has kept it just south of our CWA with general thunder indicated to the northwest into most of the areas previously mentioned. With the wind fields much weaker than was the case earlier with the passage of the remnants of T.S. Cindy, main threat would be locally heavy downpours, CG lightning, and perhaps small hail/localized wind gusts. Any threat of convection will end very quickly after sunset with the boundary shifting southeast of the area under the deepening upper trough. Cooler/drier air will start to filter further southeast overnight and Sunday morning will start off quite a bit cooler than we have seen in the past few days with lows ranging from the 50s in the northwest to the 60s in the southeast with dewpoints dropping into the 50s northwest to the 60s southeast. This will end the daily thunderstorm threat for the next few days. The passing remnants of T.S. Cindy and the deepening upper trough/lower heights will lead to fairly breezy conditions today, so some wind gusts into the 20-25 mph range not out of the question at all. But for most of us, especially north and west of the Blue Ridge, it will be a very pleasant Saturday.
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&& .SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY NIGHT/... As of 330 AM EDT Sunday... A broad upper level trough will reside over the eastern half of the US through early next week. Northwest winds will usher in cooler drier air both Sunday and Monday. Besides some fair weather cumulus clouds forming in the afternoon, both days look very comfortable. Afternoon temperatures will average 3F-5F cooler than normal. Dew points will range from the upper 40s across the mountains to upper 50s in the piedmont. No rain is expected until Tuesday afternoon. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 339 PM EDT Friday... The long range models are in good agreement with the overall upper air pattern during this period with an anomalously deep upper trof over the eastern U.S. early in this period, with 500mb heights 2-3 standard deviations below normal,transitioning to a zonal flow by mid week, with ridging building by the end of the week. The 12Z GFS is still fastest with the eastward progression of the upper trof Tuesday night into Wednesday, but this has little impact on the tranquil weather expected during this time. A weak frontal boundary moving through early Tuesday morning may generate some spotty showers in the mountains, but forecast RAOBS indicate there will be very little moisture available. Otherwise, PWAT values will remain below average until Thursday night/Friday so expect a prolonged period of dry weather. By late in the week...a deep southwest flow developing on the west side of an upper ridge and ahead of an approaching upper trof in the upper mid west will increase moisture and provide the opportunity for weak upper level disturbances to pass over our area. This will result in increase chances for scattered thunderstorms during this period. As for temperatures, forecast 850mb temps from the GEFS are 2-3 standard deviations below average, which will lead to some cool mornings Tuesday and Wednesday. Adjusted low temperatures down a couple of degrees below guidance during this period. Temperatures will moderate late in the week. && .AVIATION /19Z SATURDAY THROUGH THURSDAY/... As of 130 PM EDT Saturday... Isolated to scattered showers are expected the remainder of the afternoon and into the early evening between roughly KTNB-KDAN. MVFR to low end VFR ceiling are expected within this region with mainly VFR ceilings north of this area. Visibilities will be primarily VFR with brief IFR/MVFR visibilities associated with the heavier showers or stray thunderstorm that develops. The activity should wane around sunset as we lose the heating of the day and the cold front partially responsible for the activity moves southeast. Overnight, most of the area will experience VFR conditions. Areas between roughly KLWB-KBLF will encounter a brief period of MVFR/IFR ceilings late tonight as low level moisture, and weak upslope flow, combined to yield some stratus. Any sub-VFR conditions should improve quickly to VFR a little after sunrise Sunday. Winds will gradually increase Sunday morning from the northwest with gusts around 15 to 20 mph possible across the mountains. Confidence is moderate to high regarding this portion of the aviation discussion. Extended Aviation Discussion... Other than the potential for some brief late night/early morning mountain and river valley fog, VFR conditions are expected to prevail through Thursday. On Friday, the potential will increase for some brief, localized sub-VFR conditions as showers and thunderstorm chances increase. Confidence is high regarding this portion of the aviation discussion. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RAB NEAR TERM...DS/RAB SHORT TERM...RCS LONG TERM...PH/RCS AVIATION...DS

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