Area Forecast Discussion
Issued by NWS Charleston, WV

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468 FXUS61 KRLX 191908 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 308 PM EDT Mon Mar 19 2018 .SYNOPSIS... Low pressure system will bring unsettled weather to the region into Thursday. High pressure takes control late week with another low pressure system next weekend. && .NEAR TERM /THROUGH TUESDAY/... As of 213 PM Monday... An area of low pressure, currently over the mid-Mississippi Valley, will move into the region on Tuesday. Associated clouds and precipitation will spread east early tonight and then continue across the region through much of Tuesday. With little in the way of clouds today, temperatures have warmed a few degrees above what was expected. These warmer than expected readings may play a role in what form the precipitation falls across the highest elevations tonight into Tuesday. Dewpoint temperatures are still quite low and not sure if the latest models have a handle on the evaporative cooling that should take place as the precipitation pushes into the area. Have leaned toward the cool side of guidance tonight. However, have increased the readings by a degree or so to reflect the warmer afternoon temperatures. Even with the lowest portion of the atmosphere cooling to freezing or below, models suggest temperatures just above the surface will remain above freezing through the period. This results in the precipitation becoming a wintry mix across the highest elevations of our northern West Virginia mountain counties after midnight tonight and then continuing into Tuesday. Could see a tenth or so of freezing rain with some sleet and snow as well. After consultation with our neighbors, have issued a Winter Weather Advisory mainly for ice for tonight into Tuesday. && .SHORT TERM /TUESDAY NIGHT THROUGH THURSDAY/... As of 345 AM Monday... As a surface low passes by to our south, a portion of it breaks off and gets picked up by an upper level low across the middle Ohio River Valley Tuesday into Wednesday. Not a lot of confidence in just how this will evolve -- such as where any heavier bands of snow may set up. For the day on Tuesday, have mostly rain, with a brief wintry mix across the northern mountains early on. Cold air then surges in Tuesday night, changing precipitation over to snow for everyone by Wednesday morning. This Tuesday night time period has a decent bust potential on snow amounts due to temperatures. Specifically, just how quickly will temperatures fall after a warm day on Tuesday, and how soon will snow be able to start accumulating. The NAM shows very robust frontogenesis on the NW side of the surface low -- which should drive a mesoscale band of precip across the Tri-state and coal fields Tuesday night. Think temperatures will be too warm for significant accumulations with this, but intensity could partially overcome that. Other area of concern is SE Ohio...where the changeover to snow will happen first. Models showing very wide range of accumulations here, with a low end near 2 inches and high end over 6 inches. Went with amounts of 2-4 inches for now, with the hope that details will resolve better with future models runs and totals can be trended toward higher confidence solutions. Will go with a broad HWO mention of snow Tuesday night into Wednesday. The surface low opens up and exits to the east Wednesday into Thursday with northwest flow snow showers lingering. Could get another decent area of snow across the southern mountains and coal fields Wednesday night, but again models have some variability, ranging from around 2 inches to over 4 inches. Did not put a whole lot of faith in model based snow accumulations during the daylight hours, as the late March sun angle and warm ground has a tendency to greatly reduce accumulations during the day. && .LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... As of 245 PM Monday... High pressure briefly builds and passes through Friday for a dry day, though continued NW flow aloft evens out any solar insulation and continues to keep temperatures near normal. Then, another system attached to a weak short wave affects the area during the weekend. Models diverge a bit on location/track for this weekend`s system in regards to local impacts. While models agree that over- running style rain showers will fall in this region, the boundary upon which warm/moist Gulf air over-runs may be closer (more rain, possibility for snow upon onset with moisture reaching further northward into cooler air) or further to the SW (later arrival of rain and more showery in nature on the back- end). Chose a middle-of-the-road solution with a slight preference to the 12z ECMWF, thus we`re somewhat warmer than a general blend. The boundary may meander back up into the area at the start of the work week with ridging/WAA, keeping shower activity going at least in the southern zones && .AVIATION /19Z MONDAY THROUGH SATURDAY/... As of 124 PM Monday... VFR conditions with light surface winds through 00Z, although areas of MVFR cigs will likely develop across the mountains after 21Z. Clouds should thicken and lower with MVFR conditions in rainshowers will spread north after 00Z. By 08z, MVFR conditions will prevail across much of the area with patchy IFR or even LIFR conditions in the mountains as well as the southern coalfields. After 09Z, the precipitation will changeover to a wintry mix of sleet and freezing rain across the higher elevations of the northern West Virginia mountains. After 12Z, conditions across the lowland counties to the west of the mountains should improve as southeast downslope winds prevail. Gusty southeasterly winds will develop after 02Z particularly across the higher terrain, with occasional gusts in the teens to lower 20 kt range. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z TUESDAY... FORECAST CONFIDENCE: High through 00Z, then Medium. ALTERNATE SCENARIOS: Timing of precipitation and associated restrictions may vary from forecast. 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 H H H H H H H H H M M L HTS CONSISTENCY H H H H H H H H H M M L BKW CONSISTENCY H H H H M M M M M M L L EKN CONSISTENCY H H H H H H H H H H H L PKB CONSISTENCY H H H H H H H H H H H L CKB CONSISTENCY H H H H H H H H H H H L AFTER 18Z TUESDAY... IFR possible in precipitation Tuesday afternoon through Thursday. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...Winter Weather Advisory from 2 AM to 2 PM EDT Tuesday for WVZ523-526. OH...None. KY...None. VA...None. && $$ SYNOPSIS...ABE/JSH/MC NEAR TERM...JSH SHORT TERM...MZ LONG TERM...MC AVIATION...JSH is the U.S. government's official web portal to all federal, state and local government web resources and services.