Area Forecast Discussion
Issued by NWS Blacksburg, VA

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000 FXUS61 KRNK 241133 AFDRNK Area Forecast Discussion National Weather Service Blacksburg VA 633 AM EST Fri Feb 24 2017 .SYNOPSIS... Low pressure was over Missouri with a cold front trailing into the Southern Plains. By Saturday morning this low will be in the Great Lakes with front extending into western Virginia and into the Gulf of Mexico. High pressure returns to the area on Sunday. && .NEAR TERM /THROUGH TONIGHT/... As of 330 AM EST Friday... Satellite pictures showed some high clouds from Kentucky through central Virginia this morning but cirrus was thin enough to allow temperatures to drop to near the dew point. Patchy fog had developed and will continue to expand in coverage through sunrise. The fog that does develop will mix out and dissipate by mid morning. Scattered to broken stratocumulus is expected this afternoon. Clouds will increase overnight as a cold front approaches the region. Models have similar timing with the GFS a few hours faster than the other models. Have slowed down the onset of precipitation in southern West Virginia and southwest Virginia until after 09Z/4AM. Lifted index forecast was just below zero along the boundary late tonight with CAPES as much as 300 J/Kg so have left slight chance of thunder in before 7AM/12Z. As pressure lower over the Mid Atlantic region today and the narrow axis of high pressure retreats east, winds will turn to the south-southwest. Wind speeds will increase at higher elevations tonight as the pressure gradient tightens in advance of the front. Warmer guidance was used as the basis for maximum temperatures today. Clouds and mixing will keep temperatures mild tonight. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... As of 300 AM EST Friday... A shortwave trough will move from the Great Lakes region through much of the Northeast by early Sunday. A well advertised cold front will move east across our area Saturday and push out into the Atlantic ocean Saturday night into Sunday. The main batch of convection, a pre-frontal line will cross our area during the morning into the early afternoon. The cold front to cross late morning into the mid afternoon, and the associated 850 mb front to cross the area late afternoon into the evening. The latest Day 2 Convective Outlook from the Storm Prediction Center offers a marginal risk of severe weather across the central and northeastern sections of the forecast area with the passage of the cold front. Instability will be the main limiting factor but a conditional risk for localized damaging gusts is possible with the convective line during the morning. Winds will increase in the wake of this front, ushering in colder air by the afternoon, especially in the west. Used an non-diurnal temperature curve with areas in the west reaching early high temperatures with temperatures falling off in the afternoon. Eastern portions of the forecast area should realized their high temperatures in the afternoon times, but still experience falling temperatures before sunset. High temperatures on Saturday will range from the lower 50s in the northwest mountains to near 70s across the Piedmont. Actual highs will be dependent on the exact timing of the front. One of the challenging aspects of the forecast is whether there is a break in the action like suggested by ECMWF before upslope kicks in. Elected to keep continuity with lingering upslope showers across the west mountains persisting through the afternoon. Enough colder air will reach the highest peaks in this region for a mix with, or change over to, light snow. By Saturday night, snow showers and snow flurries are expected for the western upslope locations. Given how mild conditions will be prior to the arrival of snow showers, little if any accumulation is expected. Western Greenbrier County in West Virginia has the best chance for any measurable snowfall, with up to one-half inch possible. Low temperatures Saturday night will vary from the upper teens in the northwest mountains to the lower 30s in the Piedmont. The wind gusts at higher elevations may approach wind advisory levels at the highest elevations during the Saturday afternoon and Saturday night. However, most gusts across the mountains will be more in the 25 to 40 mph range with 20 to 30 mph across the Piedmont. High pressure builds over our area Sunday and shift east to the Atlantic coast Sunday night. Dry weather is expected on Sunday with plenty of sunshine. High temperatures Sunday afternoon will warm into the upper 30s in the northern mountains to the mid 50s in the Piedmont. On Sunday night, south to southwest winds will be on the increase again as the influence of the high pressure wanes, and another potential shortwave trough approaches from the west. At this time, the ECMWF and GFS keep the moisture to our west. Low temperatures Sunday night will have readings from the mid 20s across the mountains to the lower to mid 30s across the Piedmont. && .LONG TERM /MONDAY THROUGH THURSDAY/... As of 300 AM EST Friday... There still remains difference in the model guidance regards the precipitation potential on Monday and Monday night. The GFS has back off on its agressive southern stream system heading northeast, and has increased its moisture with the north stream shortwave heading east out of the Ohio Valley. The ECMWF is weaker with northern shortwave and slower regarding southern stream feature, with precipitation arriving Monday night. Decreased pops for Monday as suggested with Superblend and continued chance of rain for Monday night. Through Wednesday, the region is expected to remain in a deep southwest flow in advance of a developing trough across the Central Plains states. The GFS continues to be more progressive in depicting pieces of energy streaming across the area, each with the potential for additional rounds of precipitation, especially on Wednesday. Our forecast will continue to reflect the superblend solution that accounts for these features, but on a diluted magnitude. Wednesday afternoon into Wednesday evening, the main upper trough and associated cold front are expected to race across the area. Look for another a line of convection to move through the region, with the potential for isolated thunderstorms. Gusty winds from the northwest are again forecast to develop in the wake of the cold front. Anticipate upslope rain and snow showers across portions of southeast West Virginia, south into the northern Mountains of North Carolina late Wednesday night, into and through the day on Thursday. Placed isolated to scattered pops in the northwest for Friday and dry out Friday night. Temperatures during this portion of the forecast will trend from near normal on Monday to around 10 to 15 degrees above normal for Tuesday and Wednesday. Thursday will be slightly cooler with readings around five degrees above normal. Cooling trend expected into Friday with temperatures returning towards normal. && .AVIATION /12Z FRIDAY THROUGH TUESDAY/...
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As of 625 AM EST Friday... Temperatures dropped down close to dew points in most locations overnight despite some scattered high clouds. Patchy MVFR fog was reported in southeast West Virginia, southwest Virginia and northwest North Carolina early this morning. Lowest confidence that fog will develop is at KROA. The fog will mix out and lift shortly after sunrise with VFR conditions by 14Z/9AM. Bufkit soundings showed scattered to broken VFR stratocumulus this afternoon. Cloud cover will continue to increase overnight as high clouds from showers and thunderstorms in the Tennessee and Ohio Valleys spread east. Medium to low confidence how fast ceilings may lower to MVFR in the mountains overnight. Front and associated precipitation will not arrive until after 09Z/4AM. Will continue to indicate AMD NOT SKED at KLYH due to persistent ASOS equipment issues. Extended Aviation Discussion... Showers and isolated thunderstorms will cross the Mid Atlantic region on Saturday and will be east of KLYH and KDAN by 00Z/7PM. Drier weather and increasing northwest winds follow behind the front on Saturday night through Sunday morning. High pressure will cover the region behind the front for late Sunday into Monday with lighter winds. A warm front is expected to stay near us Monday night into Tuesday keeping a threat of showers around with sub-VFR possible.
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&& .CLIMATE... As of 345 AM EST Friday... February 24 Record Highs: Bluefield 71 (1961) Danville 79 (2012) Lynchburg 79 (2012) Roanoke 80 (1985) Blacksburg 73 (1975) && .EQUIPMENT... As of 700 PM EST Thursday... The automated observation system at Lynchburg (LYH) continues to experience problems. Electronics technicians will investigate further on Friday. && .RNK WATCHES/WARNINGS/ADVISORIES... VA...None. NC...None. WV...None. && $$ SYNOPSIS...AMS NEAR TERM...AMS SHORT TERM...KK LONG TERM...DS/KK AVIATION...AMS/WP CLIMATE...WP EQUIPMENT...AMS is the U.S. government's official web portal to all federal, state and local government web resources and services.