Area Forecast Discussion
Issued by NWS Blacksburg, VA

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093 FXUS61 KRNK 230925 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 425 AM EST Sat Feb 23 2019 .SYNOPSIS... Canadian high pressure to our northeast will combine with upper low pressure anchored in the south central U.S. to keep widespread clouds and rain along with cold temperatures in place across the entire forecast area today. A cold front will move through the region from the west by Sunday afternoon, finally bringing an end to the rain, but accompanied by strong and gusty west winds. High pressure building into the region behind the front Monday will bring diminishing winds and also provide mostly sunny conditions along with milder temperatures for the first part of next week. && .NEAR TERM /THROUGH TONIGHT/... As of 400 AM EST Saturday... Another soggy wet day on tap for the area with the continued threat of mostly minor flooding from non-stop light to occasionally moderate rain. The pattern remains the same as it has pretty much for the last several days. A wedge of cool air east of the Appalachians supported by Canadian high pressure to our northeast, a mid-level baroclinic zone draped from the TN Valley across NC/VA, and a deep upper low pressure area in the southwest blocked by a strong subtropical ridge off the southeast U.S. coast. A series of upper-level disturbances continue to track northeast from the parent southwest U.S. upper low. These factors combine to keep the clouds and rain in place, and will continue to do so for the next 24-36 hours. Finally on Sunday, as low pressure develops in the Midwest and moves toward the Great Lakes, a cold front will move into and through the CWA bringing an end to the rain. Again, the main concern for the near term remains that of flooding. One area of light to moderate rain moved from south to north through much of the CWA around midnight. Another area is now moving into the far western part of the CWA and this is expected to spread east and northeast through the morning and into the afternoon, keeping steady rain over nearly all of the forecast area again today, with periods of moderate rain for sure. In fact, with some enhancement expected of the upper-level dynamics today as the upper low in the southwest takes on a negative tilt, the likelihood of periods of heavier rain than what we have seen during the past 24 hours is likely. We are already seeing this take place in far eastern TN and western NC where rainfall rates are approaching 0.50/hour. Thus, WPC has expanded the moderate risk of excessive rainfall into far western VA and the slight risk extends eastward now almost to the eastern border of the CWA, with a marginal risk in all other areas not covered by the slight. Additional rainfall during the next 24 hours should be mostly in the 1-2 inch range, but some amounts between 2-3 inches will be possible in the west, where the threat of flooding is the greatest. Concerns are particularly high in the Clinch, Holston, Watauga, and Greenbrier basins. FFG values are incredibly low, in many parts of the CWA less than 1.0 inch/3 hours. Rainfall rates during the night have been mostly in the 0.10 to 0.25 inch/hour range and there has not been any flooding or river flooding yet of note. That could well change today. Thus, the Flood Watch will continue and has been extended slightly in time to accommodate neighbors and highlight the threat of longer term river flooding into the day Sunday across the east. With the wedge locked in across the area today, do not look for the temperatures to warm much if any at all and will likely hold steady overnight as well, at least until the cold front arrives. Temperatures will remain in the 30s to lower 40s at best around the edge of the wedge today and tonight. Have removed the mention of ice, however, as temperatures have only fallen into the upper 30s and at this point mid 30s should be the lowest point, so feel all areas should remain safely above freezing averting the threat of any ice this go around. /Confidence in Forecast Parameters/ Temperatures - High, Probabilities of Precipitation - High, Winds - Moderate to High. && .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... As of 300 AM EST Saturday... Prefrontal showers will be across the Appalachians and central mid Atlantic region early Sunday before being swept out by the actual frontal boundary. The front will move west to east across the area Sunday morning, then push through Southside and move into the piedmont early Sunday afternoon. Expect a good burst of strong winds to accompany the front, with strong gusty winds then persisting across the entire region through the afternoon as low pressure moving into the Great Lakes deepens rapidly and enhances the low level wind field. Winds will taper off east of the Blue Ridge during the evening, but expect the winds to continue howling west of the Ridge, especially at the higher elevations, through sunday night as the inversion lowers and accelerates winds by squeezing the flow. The strong gusty winds will be problematic since the ground is waterlogged from rainfall and trees may topple more readily. Expect this will result in downed trees and power outages being more widespread than is typical during wind events to include locations east of the Blue Ridge as well. One more surge of gusty winds is expected Monday morning after diurnal heating breaks the inversion and mixes winds down to the lower elevations. High pressure then continues to build over the eastern part of the country with quiet weather expected into the middle of next week. The arrival of colder air will lag a bit behind the front on Sunday and this will allow for temperatures to warm considerably. Expect highs Sunday to reach the mid 60s to near 70 east of the Blue Ridge with middle/upper 50s to the west. Highs will be cooler for Monday and Tuesday though still a bit above normal. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 300 AM EST Saturday... A northern stream cold front will try to join forces with a southern stream disturbance late Wednesday and bring a chance for rain showers. At this time, the two do not phase until both systems move off the Mid Atlantic Coast Wednesday evening. Dry high pressure will briefly keep the area dry before the next front brings rain to the region Thursday night into Friday night. Temperatures will be above normal Wednesday. Clouds and rain will bring temperatures back to normal Thursday and Friday. && .AVIATION /09Z SATURDAY THROUGH WEDNESDAY/... As of 1135 PM EST Friday... Little change in the weather pattern through the TAF forecast period across southwest Virginia, northwest North Carolina and southeast West Virginia, with widespread IFR to LIFR ceilings and MVFR visibilities. Light to moderate rain along with areas of fog are expected. Winds will generally trend toward the east and northeast as weak lower pressure remains west of the central and southern Appalachians and a strong wedge covers the mountains and foothills. Extended Aviation Discussion... Cold front is expected to sweep east through the Mid Atlantic area on Sunday, gradually diminishing/ending the threat for precipitation with subsequent return to VFR conditions east of the Blue Ridge during the afternoon. However, colder upslope winds from the west or northwest following the front will likely maintain the threat for sub-VFR weather west of the Blue Ridge through Sunday night, but dry air will allow VFR conditions to return to all areas Monday, which should continue into Tuesday before the next frontal system arrives in the Wed-Thu time frame. Winds are expected to become strong and gusty behind the front Sunday afternoon into Monday morning, especially over the mountains, until high pressure can sufficiently build into the region later Monday into Tuesday, thereby relaxing the pressure gradient. && .HYDROLOGY... As of 1130 PM EST Friday... Currently have a river flood warning out for Danville through South Boston along the Dan River and at Randolph on the Roanoke River. Guidance is suggestion potential minor flooding at Buckingham on the James. With where the axis of heaviest QPF is expected, have concerns that some parts of the Roanoke, New, Greenbrier, Clinch and Holston Rivers. Smaller creeks and streams, especially along and west of the Blue Ridge will likely stay elevated with flooding a good possibility by Saturday. Stay tuned for any flood advisories or warnings. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Flood Watch through Sunday morning for VAZ007-009>020. High Wind Watch from Sunday morning through Monday morning for VAZ007-009>020-022>024. Flood Watch through Sunday afternoon for VAZ022>024-032>035- 043>047-058-059. High Wind Watch from Sunday afternoon through Sunday evening for VAZ032>035. NC...Flood Watch through Sunday morning for NCZ001-002-018. High Wind Watch from Sunday morning through Monday morning for NCZ001-002-018. Flood Watch through Sunday afternoon for NCZ003>006-019-020. High Wind Watch from Sunday afternoon through Sunday evening for NCZ003-019. WV...Flood Watch through Sunday morning for WVZ042>044-507-508. High Wind Watch from Sunday morning through Monday morning for WVZ042>044-507-508. && $$ SYNOPSIS...RAB NEAR TERM...RAB SHORT TERM...MBS LONG TERM...MBS/RCS AVIATION...AMS/WP HYDROLOGY...RAB

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