Area Forecast Discussion
Issued by NWS Blacksburg, VA

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233 FXUS61 KRNK 240826 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 426 AM EDT Sat Jun 24 2017 .SYNOPSIS...
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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.
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&& .NEAR TERM /THROUGH TONIGHT/...
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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 Loudoun 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 THROUGH TUESDAY NIGHT/...
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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.
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&& .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 /08Z SATURDAY THROUGH WEDNESDAY/... As of 150 AM EDT Saturday... Following the HRRR as a guideline for events over the next several hours since it matches well with current radar trends, would expect bands of showers and isolated thunderstorms associated with remnants of T.S. Cindy to translate many east of the Blue Ridge through the morning hours, exiting the CWA before daybreak. Generally looking at still VFR cigs with this activity, worst case scenario low end VFR cigs as air mass is very tropical. Visibilities could be briefly reduced into the MVFR category. The exception will be KDAN as activity developing along the Blue Ridge south of U.S. 460 could be somewhat more intense, and may reach KDAN as a TS or VCTS. Will need to watch, otherwise, just looking for VCSH/SHRA at this point. Through the daylight hours, generally looking at improving conditions as the remnants of Cindy track well northeast of the area. Looking at VFR cigs throughout the day with scattered CU and some SCT-BKN CI. Visibility will not be an issue through the daytime or into the evening. The exception will be KBLF where upslope clouds will result in several hours of IFR to LIFR cigs through the mid-morning, then improving to VFR there as well. Will need to watch for thunderstorm development across the NC Piedmont near a lingering frontal boundary and tail of moisture from Cindy. These could translate into the KDAN area before shifting southeast during the evening. Otherwise, not expecting any precipitation at the TAF sites after 12Z. Gusty winds associated with a 850mb core of strong winds traversing the area at the current time and associated with Cindy will move east of the area before daybreak. Looking for SSW-SW winds 15-25kts through the next few hours to generally diminish to 10-20kts overnight and through the daytime hours Saturday, veering more to the northwest with time as well. Medium confidence in ceilings through the TAF valid period. Medium to high confidence in visibilities through the TAF valid period. Medium confidence in wind direction/speed through the TAF valid period. 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. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...RAB NEAR TERM...RAB SHORT TERM...RCS LONG TERM...PH/RCS AVIATION...JH/RAB

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