Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 180839 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 339 AM EST Sat Nov 18 2017 .SYNOPSIS... A warm front lifts north across the area this morning, followed by a strong cold front overnight. Colder temperatures follow this front for Sunday along with windy conditions, starting tonight. High pressure builds in from the southwest late Sunday into Monday. && .NEAR TERM /THROUGH TONIGHT/... 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. && .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 /09Z SATURDAY THROUGH WEDNESDAY/... As of 1230 AM EST Friday... VFR conditions will continue through 19z Saturday, then MVFR conditions with convection will enter the forecast area. 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. Until then, ceilings should mainly be VFR. Winds will increase from the southwest Saturday as the front approaches and the large high pressure shifts into the western Atlantic. By afternoon, low end gusts can be expected at most TAF sites. Low-level winds will strengthen considerably during the later portion of the TAF valid period as a strong 850mb LLJ approaches the region with the front. Areas of low-level wind shear can be expected. Visibilities will be VFR for the most part, although a brief period of MVFR-IFR will be possible in heavier rain showers late Saturday. Will not include any thunder at the TAF sites given the lack of indicated instability. 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... A strong cold front moves across the region Saturday night into Sunday. This will lead to several impacts to aviation, including a period of rain changing to mountain snow showers (possible -SHSN at Bluefield) and a frontal wind shift to northwest with wind gusts further increasing areawide. Best chance at sub-VFR conditions is Saturday night into Sunday. For Sunday, may see a continuation of sub-VFR stratus in the western Appalachians, with breezy/gusty northwesterly wind conditions areawide also continuing. May see mountain snow showers coming to an end later Sunday afternoon. Northwesterly winds finally abate by late Sunday evening. Conditions then transition to VFR Monday through Thursday. && .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...WP NEAR TERM...WP SHORT TERM...DS LONG TERM...JH AVIATION...AL/KK/RAB

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