Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 090220 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 920 PM EST Fri Dec 8 2017 .SYNOPSIS... Digging upper trough/cold front Saturday/Saturday night, and again early next week after a brief, modest warm up on Monday. One last cold shot late week may be the last in this series. && .NEAR TERM /THROUGH SATURDAY/...
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As of 920 PM Friday... Trimmed PoPs along eastern edge of forecast area overnight into early Saturday morning, per current trends with low pressure system moving up the middle Atlantic states. Trended overnight temperatures down a bit over the middle Ohio Valley and dew points up a bit throughout overnight and Saturday. As of 705 PM Friday... The HiRes WRF models better reflected the mid to high overcast, and was utilized overnight. Forecast otherwise on track. As of 205 PM Friday... Bulk of the activity today falls to the south and east of the forecast area with an expansive area of frontogenesis stretching from the lower Mississippi Valley to the mid Atlantic coast. Northwestward extent of the precipitation shield will be dictated by the sheared out vorticity maximum embedded in the 500hPa flow, which will encroach into the far eastern counties/mountains of the CWA into the tonight and early Saturday periods. Carry less than an inch type snowfall accumulations for these areas, and favored the non convective GFS for placement of the POPs. Upper wave digs into the Great Lakes, bringing the next round of snow, which falls largely in the short term forecast period. Setting up for a convective snowfall event with increasing 925-700hPa lapse rates in the 7-8C/km range by 00Z Sunday. This suggests a squall type nature, but again, this will ramp up more in the third period, where the bulk of the accumulations are expected. May warm advect briefly before the arrival of the cold front, so that warranted rain/snow mix in the grids during the afternoon for the lowlands in daytime temps reaching the mid 30s.
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&& .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY NIGHT/... As of 255 PM Friday... Cold front over eastern half of the cwa will continue to move east and exit Sunday morning. Snow showers with and behind the front will persist, especially in the upslope areas of the eastern and northern mountains. Most areas should see a dusting to an inch in heavier showers with 2-4 inches in the upslope areas. Strong NW winds with 30-40mph gusts are possible, especially on the ridge tops. Vsbys will lower in blowing snow and wind chills will be close to advisory criteria. Front exits Sunday morning along with any left of snow showers or flurries. Weak ridging will take place During the day on Sunday and conditions will improve from west to east Sunday and Sunday night. && .LONG TERM /MONDAY THROUGH FRIDAY/... As of 255 PM Friday... A brief warmup on southerly flow on Monday out ahead of the next clipper/cold front system moves through the area on Tuesday. Temperatures Monday will top out in the upper 30s to mid 40s. This warm up will be short lived however with the front and and upper trough moving through Tuesday into Wednesday. This system will bring the threat for more snow, with possibly the entire forecast area seeing some sort of accumulation. Models indicate that there is a potential for some snow squall activity with the front as it passes through. The active pattern continues through the week, with a brief break Wednesday before the next system pushes through on Thursday, Thursday night into Friday. Temperatures stay cold enough for more snow or a rain snow mix with this system. && .AVIATION /02Z SATURDAY THROUGH WEDNESDAY/... As of 705 PM Friday... Mid to high cloud shield from a low pressure center moving up the middle Atlantic seaboard will persist overnight, before moving east on Saturday. A cold front, and digging upper level short wave trough approaching from the west, will bring the return of mid and high cloud Saturday afternoon. By the end of the TAF period, 00Z Sunday, the front may reach HTS, and be close to CRW and BKW, as it will have a sort of northwest to southeast orientation owing to the digging upper level trough, as it moves east. This is reflected in ceilings lowering to near MVFR at HTS, with a wind shift to the west, and snow showers or even snow squalls may reach HTS by 00Z Sunday, with IFR possible near the end of, or just beyond, the TAF period. Otherwise VFR expected per weakening surface high pressure between the middle Atlantic low, and the cold front approaching from the west. Light and variable surface flow between the systems will become light southwest ahead of the cold front late Saturday. It will shift to west with the passage of the cold front at HTS near the end of the TAF period, and may become quite gusty if a snow squall arrives. Light northerly flow aloft in the mountains and westerly flow aloft over the lowlands overnight, will become light southwest throughout the area by early Saturday morning. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 00Z SUNDAY... FORECAST CONFIDENCE: High. ALTERNATE SCENARIOS: The cold front, and associated MVFR to IFR conditions, and gusty winds in snow showers and snow squalls, may arrive at HTS near the end of the TAF period. The lower confidence reflected in the table below at BKW reflects the proximity of an IFR to MVFR cloud deck along the eastern slopes of the mountains, associated with the middle Atlantic low, overnight. EXPERIMENTAL TABLE OF FLIGHT CATEGORY OBJECTIVELY SHOWS CONSISTENCY OF WFO FORECAST TO AVAILABLE MODEL INFORMATION: H = HIGH: TAF CONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. M = MEDIUM: TAF HAS VARYING LEVEL OF CONSISTENCY WITH MODELS. L = LOW: TAF INCONSISTENT WITH ALL MODELS OR ALL BUT ONE MODEL. DATE SAT UTC 1HRLY 00 01 02 03 04 05 06 07 08 09 10 11 EST 1HRLY 19 20 21 22 23 00 01 02 03 04 05 06 CRW CONSISTENCY H H H H H H H H H H H M HTS CONSISTENCY H H H H H H H H H H H M BKW CONSISTENCY M M M M M M L M L L L L EKN CONSISTENCY H H H H H H H H H M M L PKB CONSISTENCY H H H H H H H H H H H M CKB CONSISTENCY H H H H H H H H H H H M AFTER 00Z SUNDAY... IFR possible in snow showers Saturday night, mainly in the mountains, where it will be more persistent, and then again Monday night through Tuesday, again mainly in the mountains. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...TRM/MPK/26 NEAR TERM...TRM/26 SHORT TERM...JS LONG TERM...JS AVIATION...TRM is the U.S. government's official web portal to all federal, state and local government web resources and services.