Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 181443 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 943 AM EST Sat Nov 18 2017 .SYNOPSIS...
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A warm front will lift north across the area today, followed by a strong cold front tonight. Colder temperatures follow this front for Sunday along with windy conditions, starting tonight. High pressure builds in from the southwest late Sunday into Monday.
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As of 940 AM EST Saturday... Made a few changes to the hourly grids to reflect rapidly increasing temperatures where increased mixing has removed low level inversion, and also to delay onset of any precipitation until around or after sunset. After making adjustment for the next three to four hours to boost rate of thermal climb where needed, overall thermal trend should merge back into previous forecast curve by noon. No ground-based precipitation is evident upstream in central or southern WV, with only virga noted. Therefore, sprinkles or light showers no longer expected in Greenbrier County this morning or in the early-mid afternoon. Further west, precipitation moving into western KY scant at best, and latest higher resolution short-range guidance consistent in not allowing lower troposphere in Blacksburg forecast area to saturate sufficiently to support ground-based precipitation until around/after sunset, even across the western portion of the area - with the better threat of precipitation delayed until at least mid- late evening. As of 322 AM EST Saturday... Noticable temperature differences this morning between the mountains and piedmont where clouds and mixing winds have kept readings in upper 40s to lower 50s across southwest VA near Richlands/Abingdon into southern WV, while clearer skies and light winds allow temps to fall into the mid 30s in the piedmont. For today, should see increasing clouds as southwest flow increases ahead of a digging upper trough moving into the mid-MS valley. A warm front works northward across the Ohio Valley, central Appalachians with a few showers scattered along it, which may scrape our Southeast WV counties this morning. Otherwise looking at prefrontal showers arriving in the mountains by late afternoon/evening and shifting east to the piedmont by midnight. A narrow very wind driven line of showers with embedded thunder should impact WV by early evening. Some of these showers could mix down the stronger winds with the showers, especially in higher ridges. The main line exits to the east by late tonight with dry slot working toward the NC foothills. Strong post-frontal winds along with 6 hr pressure rises of 5 to 9 mb will amplify the winds in the mountains overnight into early Sunday before subsiding. Running local study on winds with model guidance puts most of the western CWA in wind advisory level winds, which is gusts 46-57 mph, though most will be in the 45-50 mph range. After collaboration with neighboring weather offices, agreed to post wind advisory from late this afternoon through noon Sunday, first for the potential strong prefrontal winds and mainly for the post frontal winds. Stronger winds look to occur midnight to 8am tonight-Sunday. As the front passes cold air advection will switch rain showers to snow showers in the mountains of WV down to the high country of NC. Again deeper moisture appears to push out as cold air rushes in, then you get upslope snow showers. Through 12z Sunday around an inch could fall in the western slopes of Greenbrier county with a dusting elsewhere in the higher ridges of SW VA into NW NC. Expect mild temps today with upper 50s to mid 60s area wide. Temperatures tonight will drop to the upper 20s to lower 30s higher elevations after midnight, to mid to upper 30s rest of the mountains, while cold air battles downsloping winds with a warming effect in the east, where lows should be in the mid to upper 40s.
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&& .SHORT TERM /SUNDAY THROUGH TUESDAY NIGHT/... As of 215 AM EST Saturday... Gusty northwest winds, with the higher ridge tops in the Advisory level category, still look promising through mid-day Sunday. By the afternoon there will be a lull in the stronger winds, only to reinforce again Sunday night with the passage of yet another jet max. At this time, there is no plan to have a second Wind Advisory in place to account for this feature. Would prefer to have the first come and go prior to any second one. Plus there still is time to assess the trends future model runs of this feature. However, it is prudent to have this second surge referenced in the Hazardous Weather Outlook. Upslope isolated/scattered rain/snow showers are still expected across parts of southeast West Virginia, south into the Northern Mountains of North Carolina during the Sunday and Sunday night time frame, with decreasing coverage from south to north Sunday night. Where snow accumulates will be limited to the highest elevations with totals generally around or less than one inch. Temperatures on Sunday will struggle to rise much at all in the west, with only limited increase in the east from the overnight lows Saturday night. Low temperatures Sunday night will range from the low to mid 20s across the mountains with upper 20s to near 30 across the Piedmont. Monday into Tuesday, look for high pressure to enter the region from the west and exit to the east. The result will be a gradual trend towards the prevailing winds becoming southwest, with milder temperatures. By Tuesday high temperatures will range from the low to mid 50s across the mountains with mid to upper 50s across the Piedmont. A shortwave trough will push through the Great Lakes region Tuesday night. Moisture and lift will be limited across the area with precipitation unlikely. More promising will be an increase in cloud cover, especially across western sections of the area. && .LONG TERM /WEDNESDAY THROUGH FRIDAY/... As of 300 PM EST Friday... A more upper level split flow regime looks to develop for the rest of the week. High pressure builds in Wednesday afternoon through Friday. This should result in overall quiet weather with slightly below normal temperatures through Day7. && .AVIATION /15Z SATURDAY THROUGH WEDNESDAY/... As of 630 AM EST Saturday... Not much change to the previous thinking, as will see southwest winds increase ahead of a cold front today, with increasing mid/high clouds. Should be VFR through the day with showers and MVFR cigs at BLF/LWB arriving after 23z. Look for ceilings to fall into the MVFR range late Saturday into Saturday night as a narrow line of showers/convection accompany the frontal boundary through the region, reaching BCB/ROA in the 00-02z time frame and LYH/DAN in the 03z-05z time frame. With strong mixing of winds most of the time will be MVFR to VFR both cigs/vsbys at all sites. May see IFR cigs at times late tonight at BLF. Winds shift from the south to southwest by midday, then west this evening and overnight. Gusts as high as 30 to 50 mph may occur at the mountain taf sites, including Roanoke, with 20 to 35 mph. Medium confidence in ceilings through the TAF valid period. Medium to high confidence in visibilities through the TAF valid period. High confidence in wind direction and speed through the TAF valid period. Extended Discussion... Sunday morning will see some snow showers in BLF possibly LWB with cigs dropping to IFR at times, while MVFR cigs improve to VFR with clouds clearing east of the mountains by 15z. Winds remaining up through the day, with another surge of higher gusts expected by Sunday evening around dusk. Mountain snow showers coming to an end by Sunday evening. Northwesterly winds finally abate by late Sunday night, as high pressure builds in from the southwest. Conditions then transition to VFR Monday through Wednesday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...Wind Advisory from 4 PM this afternoon to noon EST Sunday for VAZ007-009>020-022>024-032>035. NC...Wind Advisory from 4 PM this afternoon to noon EST Sunday for NCZ001-002-018. WV...Wind Advisory from 4 PM this afternoon to noon EST Sunday for WVZ044-507-508. && $$ SYNOPSIS...WERT/WP NEAR TERM...WERT/WP SHORT TERM...DS LONG TERM...JH AVIATION...RAB/WP is the U.S. government's official web portal to all federal, state and local government web resources and services.