Area Forecast Discussion
Issued by NWS Charleston, WV

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618 FXUS61 KRLX 091757 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 1257 PM EST Sat Dec 9 2017 .SYNOPSIS... Digging upper trough/cold front pushes through today and tonight, and again early next week after a brief warm up on Monday. One last cold shot late week may be the last in this series. && .NEAR TERM /THROUGH TONIGHT/... As of 915 AM Saturday... No changes this morning. Light snow likely making it into the southern mountains near Flat Top, and into the GReenbrier Valley and Pocahontas mountains. As of 415 AM Saturday... The main weather maker in the eastern third of the CONUS remains an expansive zone of frontogenesis across the South. The extent to which this southern system effects our region is limited by dry mid- levels - chance pops featured only in Pocahontas through early afternoon. An axis of high pressure extends up the Ohio Valley, keeping us dry elsewhere. An amplified upper-level trough digging through the Great Lakes region and into the Ohio Valley kicks this Piedmont system offshore Saturday, allowing for a brief period of sct/clearing skies during the afternoon. Pressure and height falls ahead of the trough erode surface high pressure and induce southwesterly low-level flow, allowing for modest warm air advection through the early afternoon. So, have taken aftn temperatures slightly warmer with guidance - especially where clearing is favored. Cold air advection (steepening lapse rates) behind the digging trough`s accompanying cold front coincident with a low-level plume of high RH off Lake Michigan opens the door for scattered snow showers and perhaps a few convective snow squalls later Saturday afternoon through the overnight hours. Low freezing heights limit mixed precip potential, and more intense squalls would locally cool atmosphere so have opted for majority snow over other precip types during onset spare for isolated spots of mixed precip near the Tristate and Big Sandy basin. Low- to mid- level winds turn more northwesterly with the passage of the trough aloft, so upslope is enhanced across northern mountain zones from roughly 05 to 10Z Sunday morning. 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. && .SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 400 AM Saturday... Snow showers will linger in the mountains on Sunday morning, but generally the day will see improving conditions with decreasing clouds as short wave pushes well to our east. Although we will see some sunshine, temperatures will stay about 10 degrees below normal. Flow shifts SW overnight on Sunday and warm air advection kicks in on Monday. Temperatures will climb back up to near normal values out ahead of another cold front. Forecast guidance is in good agreement with the cold front pushing through overnight Monday and early Tuesday morning. The initial short wave with the front may kick off a few snow showers mainly across the Northern Forecast area, but amounts with this first wave will be quite light with little to no accumulation. && .LONG TERM /TUESDAY THROUGH SATURDAY/... As of 410 AM Saturday... Much colder air filters in behind the cold front on Tuesday. Deep upper trough sinks over the area Tuesday afternoon. NW flow with a fetch off Lake Michigan will advect moisture into the region. Early forecast model soundings indicate fairly unstable soundings in the low to mid levels with strong lapse rates. This could set the stage for wide spread snow shower activity from late Tuesday afternoon through early Wednesday morning. Could see some snow squall activity as well and current timing could impact the Tuesday afternoon commute. The active pattern continues through the week, with a brief break Wednesday before a clipper system pushes through late in the week. && .AVIATION /18Z SATURDAY THROUGH THURSDAY/...
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As of 1245 PM Saturday... Upper level trough digging into the Great Lakes to bring rounds of intermittent snow showers to all terminals beginning after 22Z today, with IFR or worse visibilities a strong bet in said snow showers. In the lowlands, where the POPs are not as high as the mountains, covering the intermittent snow showers in TEMPO groups. Mountain terminals are prevailing IFR in snow. Winds and wind gusts are expected to increase into the overnight period, with gusts in the 15-25kt range, highest again in the mountain terminals. MVFR ceilings persist through the 15Z Sunday. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z SUNDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: Timing of snow showers and IFR may vary slightly from forecast. May need IFR in prevailing for lowlands. 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. UTC 1HRLY 18 19 20 21 22 23 00 01 02 03 04 05 EST 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00 CRW CONSISTENCY H H H H H M L L H M H M HTS CONSISTENCY H H H M L M M M H H M M BKW CONSISTENCY M M M M M M L M M M L M EKN CONSISTENCY H H H H H H H M L L L L PKB CONSISTENCY H H H H H M L M L M H M CKB CONSISTENCY H H H H H H M L L L M M AFTER 18Z SUNDAY... Another wave Monday night/Tuesday is forecast to have similar, squally snow showers producing IFR conditions, favoring the mountain terminals.
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&& .RLX WATCHES/WARNINGS/ADVISORIES... WV...None. OH...None. KY...None. VA...None. && $$ SYNOPSIS...MPK/MC NEAR TERM...26/MC SHORT TERM...MPK LONG TERM...MPK AVIATION...26

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