Area Forecast Discussion
Issued by NWS Charleston, WV

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413 FXUS61 KRLX 171041 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 641 AM EDT Sat Mar 17 2018 .SYNOPSIS... Low pressure system brings a wintry mix early this morning, changing to mostly rain by late morning. Another system arrives Monday night through mid week. && .NEAR TERM /THROUGH TONIGHT/... As of 630 AM Saturday... Added some thunder to the Tri-State region early this morning as a few lighting strikes are being detected in the shower activity moving in from the west. Also updated temps through this morning based on current obs and trends... using the LAV to help time the freezing line moving northward. As of 200 AM Saturday... A surface low will cross the lower Ohio River Valley this morning, with moisture overrunning a warm front extending through Kentucky and into southern WV/VA. This should begin driving precipitation into the forecast area from the W/SW around or just before sunrise. Leaned pretty heavy on a blend of high res models for POPs through the period. Main change was to slow down incoming precipitation by a couple hours. This first wave of precip should gradually lift from SW to NE across the forecast area through this afternoon. Then expect a second wave of precip -- mainly across the south -- as the surface low passes by to our south and an upper level shortwave trough crosses. All of the above was not a super difficult forecast... the difficult part comes in precip type. Could not really find any models that had a good handle on current temperatures across the forecast area, which makes it hard to have much confidence in them going forward. Add in a bit of wet bulbing as the precipitation starts and things get even more complicated. Ended up using a blend of short term models and the ECMWF MOS, and then making some hand adjustments to go cooler in spots that are already below guidance. We never really get into warm advection at the surface, but as winds pick up through mid morning we should be able to mix down slightly warmer air off the surface so have some non-diurnal trend going for more exposed areas. As for those temperatures just off the surface, should remain above freezing across the southern 2/3 of the forecast area which will keep the falling precipitation liquid, with freezing rain possible generally north of I-64 where temps will be starting out below freezing. Across the northern third of the forecast area, went with a period of sleet as wet bulbing occurs and then gradually transition to freezing rain and then finally rain by late morning or early afternoon. With the lead upper level wave models actually show a cold pocket at 850mb crossing the north which may limit freezing rain and lead to more of a sleet to plain rain transition as surface temperatures warm to around 40F this afternoon. Added in thunder across the south late this afternoon with the surface low. Models showing adequate instability with 200-500 J/kg CAPE. Combined with 60-70kts 0-6km bulk shear and the surface boundary in the vicinity, would not be surprised to see some developed convection and maybe even some gusty outflows across the southern coal fields. For now, no changes planned to winter weather advisory, but will need to watch surface temperatures closely as the precip moves in this morning. && .SHORT TERM /SUNDAY THROUGH MONDAY/... As of 230 AM Saturday... Overall drier weather starts to take hold on Sunday, with high pressure building into the region. Cloud cover, and moisture will increase across the area on Monday, with southeasterly flow developing, there is the possibility of a light wintry mix developing Monday across eastern zones. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... As of 235 AM Saturday... Models continue to differ with system Monday night/Tuesday with track and timing of low pressure system, which will create rather soggy weather to start the long term. Depending on track of low, could be looking at the possibility of a wintry mix across the higher terrain and northern zones late Monday night/early Tuesday, before transitioning to rain area wide as the day progresses. Precipitation will gradually change over to snow by Tuesday night into Wednesday, with light accumulations possible across the higher terrain counties and N WV zones. Drier weather takes hold for the end of the long term period. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/... As of 200 AM Saturday... Messy forecast as a surface low approaches and then passes by to our south. Overrunning moisture will lead to MVFR to IFR ceilings moving in through the day. Expect rain across the south, with some pockets of freezing rain where surface temps are below freezing. Across the north, expect a period of sleet, which will transition to freezing rain then rain through the morning. Ceilings should improve across the north later today into tonight, with lower clouds lingering across the south. Wind will be fairly light, starting off generally NE this morning and then turning more N to NW today. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 12Z SUNDAY... FORECAST CONFIDENCE: Medium. ALTERNATE SCENARIOS: Timing and level of restrictions could vary. 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 10 11 12 13 14 15 16 17 18 19 20 21 EDT 1HRLY 06 07 08 09 10 11 12 13 14 15 16 17 CRW CONSISTENCY H H H H M H H H H H M M HTS CONSISTENCY H H H M H H H H H H M L BKW CONSISTENCY H H H H H H H H L H L L EKN CONSISTENCY H H H H H M L L M H L L PKB CONSISTENCY H H H H H M M M H M L M CKB CONSISTENCY H H H H H H H L L H M M AFTER 12Z SUNDAY... IFR possible in precipitation Monday into Tuesday. && .RLX WATCHES/WARNINGS/ADVISORIES... WV...Winter Weather Advisory until 1 PM EDT this afternoon for WVZ006>011-014>020-027>032-039-040-521>526. OH...Winter Weather Advisory until 1 PM EDT this afternoon for OHZ066-067-075-076-083>087. KY...None. VA...None. && $$ SYNOPSIS...MZ/SL NEAR TERM...MZ SHORT TERM...SL LONG TERM...SL AVIATION...MZ is the U.S. government's official web portal to all federal, state and local government web resources and services.