


Area Forecast Discussion
Issued by NWS Blacksburg, VA
Issued by NWS Blacksburg, VA
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326 FXUS61 KRNK 142321 CCA AFDRNK Area Forecast Discussion...CORRECTED National Weather Service Blacksburg VA 621 PM EST Fri Feb 14 2025 .SYNOPSIS... A large storm system in the central United States Saturday will spread rain and freezing rain into the area on Saturday. Rain and possibly thunderstorms will continue into Saturday night and Sunday increasing the threat of flooding. Blustery and much colder conditions arrive Sunday night and Monday as the low tracks across New England. && .NEAR TERM /THROUGH SATURDAY/... As of 610 PM EST Friday Key message: - Winter Weather Advisories Issued - Flood Watch Expanded Forecast on track with high clouds increasing. Models still showing any precip holding off til around 6-8am Saturday. Previous discussion... High clouds were already spreading into Virginia and North Carolina ahead of the next storm system. At the surface winds will be light this evening and dew points were in the teens. There is the potential for temperatures to drop sharply in locations that do not have cloud cover this evening. The arrival time of precipitation has been slowed down until after 6AM Saturday morning. An in-situ wedge will develop as the precipitation saturates and cools near surface layers along the Blue Ridge. Have gone with the cooler MAV guidance for temperatures on Saturday, which keeps the New River Valley, the Roanoke Valley and the southern Shenandoah Valley in the 30s for much of the day. Warm air advection increases throughout the day and will scour out the wedge from southwest to northeast. This is aided by a 40 to 60 knot 850 jet. These stronger winds over the wedge will create a layer of warm air that will be enough to melt any frozen hydrometeors. Freezing rain remains in the forecast for Saturday morning but will gradually end as temperatures rise above freezing. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... As of 1245 PM EST Friday... Key Points: 1. Flood Watch Continues for parts of the area into Sunday. 2. Very gusty and colder Sunday night into Monday. 3. Cold weather concerns late Monday night for western Greenbrier County for wind chills at or below -5F. A look at the 14 Feb 00Z NCEP Ensemble Mean 500mb Geopotential Heights show a closed low centered over the western sections of Hudson Bay. A longwave trough is expected to extend south of the low over central CONUS. Flow over our region will be southwest. On Sunday, the axis of the trough shifts east over our region by the evening hours and trends negatively tilted. The center of the parent low heads south to near western Ontario. On Monday into Monday night, the center of the low and its associated trough will be over the Canadian Maritimes. Nearly zonal flow is expected for our region. At the surface, low pressure early Saturday night is expected to located over the Mid-Mississippi and Lower Ohio Valleys. An associated warm front is expected to be extending eastward into the Tennessee Valley. A cold front will extend southwest of the low into South Texas. By Sunday evening, the low is expected to have moved northeast, and be situated over New England with its associated cold front trailing southwest along the East Coast. Concurrently, high pressure will be building south into central CONUS. By Monday evening, an associated ridge axis of the high building into the central US will be nosing into our region. A look at the 14 Feb 00Z NAEFS Ensemble Situational Awareness data shows 850mb temperatures within the +8C to +10C range, n-s, across the area Saturday night. These values for the overnight hours fall within the 90 to 99 percentile of the 30-year CFSR climatology. On Sunday, values will fall rapid in the wake of a cold front. By the evening hours, anticipate values of -6C to 0C, nw-se. Values continue to fall Sunday night, reaching -13C to -10C, nw-se, by daybreak Monday. On Monday, values only moderate slightly with values of -10C to -5C, n-s, by the evening hours. Monday night expect only a minor upward change to -9C to -3C, n-s, by daybreak Tuesday. The above weather patterns offers a generous coverage of rainfall Saturday night, especially in the area along and immediately north of the warm front which will cross our region. A secondary maximum is expected to be along and immediately east of the crest of the Blue Ridge. Strong southerly very moist flow advecting into the higher terrain will allow for enhanced upslope flow precipitation within this corridor. As we progress into Sunday, the warm front will continue its trek north of the region, with the best potential for precipitation during the early morning hours again along and immediately east of the crest of the Blue Ridge. By the late morning into the afternoon hours, a cold front is expected to progress into, across, and exit our region. This feature will help yield a strong convective line of heavy rain showers which will cross our region. Some of the best dynamics and convection are expected to develop along this line south of our region. This activity will have the potential to mitigate, but not completely remove the heavy rain impact for this line of showers across our region. While chances are low, but not non-zero, parts of the area on Sunday could also experience a few thunderstorms. The greatest potential looks to be the far southeastern sections during the early afternoon. In the wake of the cold front, winds shift northwest and become gusty. Gusts of 25 to 40 mph will be common across the mountains with 20 to 30 mph across the Piedmont. Locally higher values are possible for both geographical area. The northwest flow across the mountains will help generate upslope snow showers, especially over the preferred locations of southeast West Virginia, south into the Northern Mountains of North Carolina. Coverage will gradually decrease through the night, ending last over parts of Southeast West Virginia perhaps as late as Monday morning. High pressure will gradually work its way into the region on Monday. This feature will provide for colder temperatures and drier conditions. Our pressure gradient will be relaxing, but enough will remain so that winds will still be gusting to around 15 to 25 mph across the mountains in the late afternoon. Dry and colder and less gusty conditions are expected Monday night. Western parts of Greenbrier County could be a candidate for Cold Weather Advisory conditions with wind chills dipping to under -5F for parts of this region. Confidence in the above weather scenario is moderate to high. && .LONG TERM /TUESDAY THROUGH FRIDAY/... As of 100 PM EST Friday... Key Point: 1. Potential winter storm Wednesday into Thursday, confidence on the details are still not high, but confidence is trending upward. A look at the 14 Feb 00Z NCEP Ensemble Mean 500mb Geopotential Heights shows the axis of a longwave trough developing over central CONUS on Tuesday. In response, flow over our region backs southwest. On Wednesday, the trough axis is expected to make progress eastward, reaching the Mississippi Valley by the evening hours. There are hints that a closed low may try to form on the northern end of the trough over the Great Lakes. Flow over our region remains southwest but likely increases in speed. Heights drop slightly. For Thursday, the through axis crosses our region, reaching the area of Maine southwest to the VA/NC coast. A secondary shortwave trough may trail over the Great Lakes. Concurrently, a shortwave trough is expected to develop over the Rockies. By Friday, the shortwave trough in the west ejects into central CONUS. The east coast trough is expected to be centered over Newfoundland-Labrador by the evening hours. At the surface, by Tuesday evening, a ridge axis is expected to remain over our region. Low pressure in the form of an inverted trough is expected to develop over the Lower Mississippi Valley. By Wednesday evening, the ridge over central CONUS holds fast. The inverted trough to the south is expected to head eastward, reaching the area of northern Florida to just off the Southeast US coast. By Thursday evening, the central US high pressure expands even further in scope. The trough off the US East Coast heads northeast over the Canadian Maritimes. On Friday, the center of the surface high shifts east to over the Lower Ohio Valley. A look at the 14 Feb 00Z NAEFS Ensemble Situational Awareness data shows 850mb temperatures on Tuesday inching upward during the day reaching a range of -7C to -2C, n-s, by the evening hours. Values change little Tuesday night. On Wednesday, values by the early evening are expected to range from -8C to -3C, nw-se. Values trend lower Wednesday night, reaching -13C to -7C, nw-se, by daybreak Thursday. These values correspond to the 2.5 to 10 percentile of the 30-year CFSR climatology. On Thursday, values continue their downward trend, reaching -16C to -11C, nw-se, by the early evening. These values correspond to the 1 to 10 percentile of the 30-year climatology. For far southwestern sections of the region, the range would be the 0.5 to 2.5 percentile. For Thursday night, expect values of -14C to -10C, nw-se, or within the 2.5 to 10 percentile of climatology. For Friday, values moderate slightly, reaching -10C to -6C, nw-se, by the early evening. The above weather patterns offer dry and below normal temperatures on Tuesday thanks to the influence of high pressure over the region. Tuesday night into Wednesday, moisture will begin to stream into the region on the east side of the eastward moving inverted trough. The bulk of the energy and associated moisture is expected to remain south of the region. However, the moisture that does arrive will be intersecting the cold high will be situated over or just north of the region. There are still uncertainties regarding the values of the low level thermal profile across the region during this precipitation event. However, the latest trends point toward northern and western sections of the area more like to experience snow with this evening. The farther southeast within the forecast area a person is located, the better the chance of other wintry weather types such as freezing rain or sleet. However, for the sake of simplicity and recognition of the uncertainties, our forecast will continue to reflect a rain versus snow forecast with surface temperature being the determining factor. Uncertainties continue Wednesday night into Thursday. Guidance varies regarding how much influence the trough/low moving over the Great Lakes region will have on our area. Some solutions offer a better pairing of this northern stream system with the exiting southern stream system. Other solutions allow enough time to pass so that there is not a pairing of systems. If there is a pairing, precipitation on Wednesday would like continue into Wednesday night and Thursday. As colder air arrives with the northern system, the greater the probability the precipitation would fall as snow. If the pairing does not occur, then we would more like see a clear ending of precipitation from the southern stream system. This would be followed by primarily northwest flow upslope snow showers across the mountains, with limited to no precipitation for eastern sections Thursday into Thursday night. For consistency, our forecast will continue to favor a solution that has a least some pairing of the two system. All guidance is pretty good agreement of high pressure arriving for Friday. Confidence in the above weather scenario is moderate for Tuesday and Friday, but still low, but inching upward for Wed/Thurs. && .AVIATION /23Z FRIDAY THROUGH WEDNESDAY/... As of 610 PM EST Friday... High clouds will increase this evening, then lower through the night to a mid deck. The arrival time of precipitation has been slowed down until after 6AM Saturday morning. An in-situ wedge will develop as the precipitation saturates and cools near surface layers along the Blue Ridge. Ceilings drop to MVFR as the rain begins, mainly after 14Z/9AM at local TAF sites. KLWB, KBCB, and KROA may begin as freezing rain, lasting only 1-3 hours. Warm air increases throughout the day and will scour out the colder low levels changing freezing rain to liquid rain. Poor flying weather expected though from about 13z-end of this taf period with cigs/vsbys lowering areawide to IFR, possibly some LIFR vsbys at times. A strong low level jet may bring some low level wind shear Saturday afternoon into the mountains. Above average confidence for ceiling, wind, and visibility. Average confidence in type of precipitation on Saturday. .EXTENDED AVIATION OUTLOOK... Ceilings will continue to stay in the IFR range into Sunday, maybe rising to MVFR with the front Sunday afternoon. Rain showers could be heavy at times Sunday. Isolated thunderstorms are also possible across southern Virginia and northern North Carolina late Saturday night through Sunday. Behind the front ceilings/vsbys improve east of the mountains but upslope may keep sub-VFR with snow showers across BLF/LWB into early Monday. Also west to northwest winds behind the front Sunday could gust over 40 mph along/west of the Blue Ridge. Should be VFR into late Tuesday maybe even Tuesday night but another winter storm could bring poor aviation conditions across the mid-Atlantic/NC midweek. && .HYDROLOGY... As of 330 PM EST Friday... Key Message: -Flood Watch in effect until Sunday evening along and west of the Blue Ridge A prolonged period of rain will move into the area Saturday. The precipitation will start as freezing rain, mainly at the higher elevations, but then change to rain from southwest to northeast Saturday as temperatures rise above freezing. Rain continues through Sunday. Rainfall amounts will be from 1 to 2 inches. Snow remains on the ground north of US 460. Rain that falls in this area will melt the snow adding to the efficient runoff due to frozen ground. Rapid rises are possible along streams and creeks. Saturday night and Sunday rainfall rates higher than 1 inch/hour are possible. This would produce excessive runoff on the saturated ground. Thunderstorms are possible south of US 460 late Saturday night and Sunday morning. As these smaller streams and tributaries drain into the main stem rivers, flooding is also possible. The Greenbrier, Upper James, and upper Clinch river valleys are especially susceptible to river flooding. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Flood Watch from Saturday morning through Sunday evening for VAZ007-009>020-022>024-035. Winter Weather Advisory from 7 AM to 7 PM EST Saturday for VAZ011-013>020-022>024-032>035. NC...Flood Watch from Saturday morning through Sunday evening for NCZ001-002-018. Winter Weather Advisory from 7 AM to 7 PM EST Saturday for NCZ001>003-018-019. WV...Flood Watch from Saturday morning through Sunday evening for WVZ042>044-507-508. Winter Weather Advisory from 7 AM to 7 PM EST Saturday for WVZ043-044-507-508. && $$ SYNOPSIS...AMS NEAR TERM...AMS/WP SHORT TERM...DS LONG TERM...DS AVIATION...AMS/PM/WP HYDROLOGY...AMS