Area Forecast Discussion
Issued by NWS Charleston, WV

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000 FXUS61 KRLX 202134 CCA AFDRLX Area Forecast Discussion National Weather Service Charleston WV 252 PM EDT Tue Mar 20 2018 .SYNOPSIS... Low pressure system will bring unsettled weather to the region into Wednesday night. High pressure takes control late week, followed by another low pressure system next weekend. && .NEAR TERM /THROUGH WEDNESDAY/... As of 235 PM Tuesday... Upper level low exits northeast WV this evening, but second upper level low passes south of the area tonight and Wednesday. That system will maintain a surface low pressure center over central WV through tonight, before transferring its energy to the coastal system on Wednesday. Precipitation moves back into the area tonight, changing over to snow within several hours, even faster north, as heights fall. The trick of the forecast is how fast surface temperatures fall, how low they get by dawn Wednesday, and how much they will climb on early spring insolation on Wednesday. This will make a big difference in snow accumulations, will will be elevation dependent as it is. Forcing wise, a vort lobe comes up the east side of the upper level low tonight, with the much of the mountains and adjacent lowlands to the west in the favored diffluent area northeast of the upper level low. A deformation area setting up northwest of the forecast area tonight will pivot back into southern and central portions of the area from the west Wednesday morning. The fall of temperatures just west of the mountains ahead of the upper low tonight, and temperatures across southern portions of the area Wednesday morning as the deformation area pivots in, will be crucial in snowfall amounts for these area during these times. With a warm layer aloft early on, a brief period of freezing rain may precede the snow tonight over the southern to central mountains. Blended NAM raw and a MOS consensus for surface temperatures, which are close to the previous package, save for a bit faster cool down tonight. No changes to warnings and advisories at this time, other than the expiration of the earlier high terrain advisory. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY/...
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As of 240 PM Tuesday... As the upper low departs off the coast towards the Atlantic Canada, snow showers will end early Wednesday night, while high pressure moves in from the southwest. Heights will rise, but only a modest temperature recovery can be expected. However, temperatures will remain below normal for the end of the week. Developing mid latitude cyclone over the central plains pushes eastward for the extended portion of the forecast but the short term is defined by dry weather.
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&& .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... As of 240 PM Tuesday... Warm frontal precipitation from the maturing low pressure system arrives in earnest on Saturday that may start off as snow or a wintry mix early Saturday morning. Strengthening closed low off the coast forces this system to the south of us, keeping the area out of the stronger warm air advection, and more subject to the cooler airmass north of the warm front. This system will push to the south fairly quickly, replaced by high pressure and dry air returning once again for the beginning of the work week. && .AVIATION /19Z TUESDAY THROUGH SUNDAY/... As of 235 PM Tuesday... While the TAFs show a snowstorm coming, accumulations will be on colder surfaces such as grass and elevated metal surfaces. Mountain sites EKn and BKW will see more accumulations, versus the lowland sites. The precipitation moves in tonight, near 00Z south to around 03Z north, starting as rain and then changing to snow south, and generally all snow north. Southern sites will switch to all snow around 06Z, except by 03Z at BKW. Expect widespread IFR conditions in snow overnight and Wednesday morning, including several hours of VLIFR in heavy snow 2 to 3 hours either side of daybreak Wednesday. Conditions will start to improve early Wednesday afternoon, though not much through 18Z Wednesday. Low pressure over the area will result in cyclonic, or counterclockwise flow, so directions will vary from northwest to southwest over southern sites, south of the low, and northeast across northern sites, north of the low. That northeast flow will be gusty at times this afternoon, and again Wednesday morning. By early Wednesday afternoon, surface flow will vary from west to southwest across the south, and north to northeast across the north, as surface low pressure starts to pull east of the area. Cyclonic flow aloft will vary likewise, moderate from the east to southeast across northern sites this afternoon. By early Wednesday afternoon, light flow aloft will be northeast across the north, and northwest across the south. as low pressure starts to pull east of the area. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z WEDNESDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: Timing of precipitation and associated restrictions may vary from forecast. Winds may vary from forecast with the cyclonic flow around low pressure right over the area. 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 EDT 1HRLY 14 15 16 17 18 19 20 21 22 23 00 01 CRW CONSISTENCY M L H L L M M H M M M L HTS CONSISTENCY H H H H M H H H L L H L BKW CONSISTENCY M M M M M M M M M M M M EKN CONSISTENCY H H H H H H H H H H M L PKB CONSISTENCY H H H M M M M M M M H L CKB CONSISTENCY H H H H H H H H H H H L AFTER 18Z WEDNESDAY... IFR possible in precipitation into Wednesday night. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...Winter Storm Warning from 8 PM this evening to 11 PM EDT Wednesday for WVZ032-039-040-516-518-520>526. Winter Weather Advisory from 1 AM to 8 PM EDT Wednesday for WVZ005>007-013>015-024>026. Winter Weather Advisory from 8 PM this evening to 8 PM EDT Wednesday for WVZ008>011-016>020-029. Winter Weather Advisory from 8 PM this evening to 11 PM EDT Wednesday for WVZ027-028-030-031-033-034-515-517-519. OH...Winter Weather Advisory from 1 AM to 8 PM EDT Wednesday for OHZ083-086-087. Winter Weather Advisory from 8 PM this evening to 8 PM EDT Wednesday for OHZ066-067-075-076-084-085. KY...Winter Weather Advisory from 1 AM to 8 PM EDT Wednesday for KYZ101>103-105. VA...Winter Weather Advisory from 8 PM this evening to 11 PM EDT Wednesday for VAZ003-004. && $$ SYNOPSIS...TRM/26 NEAR TERM...TRM SHORT TERM...26 LONG TERM...26 AVIATION...TRM is the U.S. government's official web portal to all federal, state and local government web resources and services.