Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 220424 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 1124 PM EST Sun Jan 21 2018 .SYNOPSIS... High pressure offshore will maintain a warmer southwest flow across the region tonight into Monday. A strong cold front will approach from the west later Monday, before crossing the region Monday night into early Tuesday. Cool high pressure follows the front with drier weather on gusty northwest winds into midweek. && .NEAR TERM /THROUGH MONDAY/... As of 845 PM EST Sunday... Evening soundings show lower level moisture slowly increasing with a shallow layer of moisture trapped beneath the mid level inversion this evening. This supportive for added mid clouds or high level strato-cu overnight within the axis of better warm advection that continues to head in from the west. Could see a few added sprinkles or light showers far west but not enough to include mention at this point. Otherwise will continue with varying intervals of clouds overnight with more west and less south. Also some patchy fog possible, espcly in some of the northwest valleys around LWB where already seeing ribbons of dense fog along the rivers where the warmer/moist air is riding over leftover ice. Low temps again to have quite a range pending clouds and valleys vs ridges overnight. Despite higher dewpoints, winds remain light and given cold ground can see some low spots dip into the low/mid 30s while struggling to drop below 50 at elevation. Thus opened up the ranges a bit more given potential for clearing and better radiational cooling in spots at times through dawn. Previous discussion as of 336 PM EST Sunday... High pressure centered across the Southeast will slide east tonight and Monday into the Atlantic ocean. The warm front in the Ohio Valley this afternoon will lift northeast tonight into Monday as the low pressure center moves northeast. The clockwise flow around the high pressure center is pushing warm and moist air northward into our region. The warm advection stratus is spreading east across the Appalachians. With the WSR-88d tracking some light moisture this afternoon mainly in the west, increased pops to allow for a slight chance of light rain and added the mention of spotty drizzle in the western portions tonight. Low temperatures tonight will range from around 30 degrees in the colder locations with less clouds and snow pack to the mid 40s across the higher ridges. The warmest readings will be across the ridgetops where winds will be stronger with better mixing. As the low pressure center moves to near Chicago by 00z Tuesday, a cold front will approach us from the west. The chance of showers will increase Monday afternoon into Monday evening. Rich moisture will spread north along the southern Blue ridge mountains. It is going to be mild Monday with Highs from the upper 40s in the mountains to around 60 degrees in the piedmont. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... As of 336 PM EST Sunday... Warm front lifts north Sunday night into Monday with warm advection and southwest flow increasing. Will see some sun in the east Monday though cloudiness will move in aloft quickly ahead of the front. Models overall still advertising a line of showers, low topped with limited instability. Shear is high and shallow convection seems likely where winds aloft gust to the surface along the line of showers. At the moment SPC has not threat of severe, but cannot rule out some strong winds Monday evening/overnight, mainly southwest over the NC mountains/foothills. Will see area of showers lift out by midday Tuesday with lingering rain showers in the west. Colder air arrives Tuesday afternoon in the mountains with a few snow showers possible but moisture appears to dry out fast. Expect post-front winds Tuesday to possibly reach advisory levels along the Blue Ridge with 8h jet of 40-50kts and 4-6mb 6 hr pressure rises. Cloudiness may inhibit some of the stronger gusts. These winds along with potential gusty winds with showers will be mentioned in the HWO. Temperatures in the 50s to around 60 Monday cool to the 40s Tuesday in the mountains with falling temps over the higher terrain. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 155 PM EST Sunday... Dry weather expect into Friday as high pressure moves across the area then sets up along the northeast, while upper trough digs across the central and northern plains. Will start to see moisture work northeast on southwest flow late Friday into Friday night. Better threat of rain showers moves in late Saturday into Sunday ahead of slow moving front, as the front becomes parallel to the upper flow. These looks like a good threat for seeing an inch or more of rain. Colder air will be delayed until Sunday night but we could see some accumulating snow showers in the mountains per strong forcing aloft with trough. Temperatures will average above normal this period, falling back toward normal or below beyond Sunday. && .AVIATION /04Z MONDAY THROUGH FRIDAY/...
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As of 1115 PM EST Sunday... Overall VFR to ocnl MVFR cloud bases to persist overnight as passing bands of strato-cu work across the region into early Monday. While VFR ceilings are likely in the east, the best chance at seeing MVFR will continue to reside over the western mountains. Visibilities are expected to remain VFR into tonight, then patchy MVFR fog is possible overnight into Monday morning. Only exception around the KLWB vicinity where warm/moist air over the colder river will make for locally dense fog/stratus with IFR/LIFR cigs/vsbys likely through daybreak on Monday. Appears VFR to hold for much of the day on Monday with a gradual increase in MVFR cigs from the south and west ahead of an upstream cold front by later in the afternoon. Looks like a few showers well ahead of the front could arrive in the west by later in the day but for now leaving out any vsby restrictions due to showers until after 00z/7PM Monday evening. South to southeast winds will also increase with speeds of 10-20 kts possible Monday afternoon, including gusts to perhaps 25 kts or higher along the western ridges near KBLF. NOTAM...The ASOS at KDAN remains INOP tonight due to a power supply failure and likely wont return to service until sometime later Monday. Therefore the observation remains missing at this time. Also since lower ceilings and/or patchy fog may impact the site, TAF amendments will not occur until data is once again available from the ASOS unit. This includes an addition of AMD NOT SKED in the terminal forecast at KDAN at this point. Extended Discussion... Sub-VFR conditions are expected to overspread the area from west to east ahead of a strong cold front Monday night as a swath of showers passes across overnight into early Tuesday. In addition an embedded QLCS with isolated thunderstorms, may accompany the front overnight including a 50-60kt low level jet. Consequently, the greatest concern with these showers will be strong wind gusts, potentially of 45-50 mph or possibly even greater for a short duration in the Monday night/early Tuesday morning time frame. Strong gusty northwest winds are expected behind the front Tuesday into Wednesday. VFR ceilings should return to the Piedmont by Tuesday afternoon, but MVFR ceilings with low clouds and potentially -SHSN can be expected across the westernmost sites, and possibly as far east at times as KBCB. High pressure and VFR conditions along with diminishing winds should return to the entire area by Wednesday. Dry weather including good flying conditions can be expected Thursday and Friday.
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&& .EQUIPMENT... As of 325 PM EST Friday... NOAA Weather Radio, WXL60 (Roanoke Transmitter) which broadcasts at 162.475 MHz remains off the air. The phone company reported that the circuit line had been cut and will take until Monday January 22nd to fix it. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...JH NEAR TERM...JH/KK SHORT TERM...WP LONG TERM...WP AVIATION...JH/KK/RAB EQUIPMENT...WP

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