Area Forecast Discussion
Issued by NWS Charleston, WV

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349 FXUS61 KRLX 171736 AFDRLX Area Forecast Discussion National Weather Service Charleston WV 136 PM EDT Sat Mar 17 2018 .SYNOPSIS... Low pressure system brings rain and storms across the WV/VA/KY borders this afternoon and evening. Another system arrives Monday night through mid week. && .NEAR TERM /THROUGH TONIGHT/... As of 1140 AM Saturday... SPC has included Buchanan and Dickenson counties in VA under a slight risk for severe thunderstorms for this afternoon and evening. Models suggest that relatively high dewpoints in the lower 50s and low level warm advection, a hint of sfc-based CAPE, and very high deep layered shear around 70 knots. These parameters are enough to produce or sustain strong updrafts capable to produce large hail and/or damaging winds. Will highlight the severe storm threat in the HWO. As temperatures across the northern third of our CWA warm to above freezing levels, and rain showers exit the eastern mountains, will be canceling portions or all of the reminder winter weather advisory for FZRA. As of 1000 AM Saturday... Radar images show that the back edge of pcpn has moved east of portions of the winter weather advisory late this morning. Therefore, the threat for freezing rain has ended in southeast OH and portions of WV. Temperatures remain around or below freezing across the northwest quadrant of the area. FZRA still possible at least through noon. 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 SATURDAY/... 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 /18Z SATURDAY THROUGH THURSDAY/...
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As of 200 AM Saturday... Radar images show that previous pcpn already moved east of the area. Although satellite images show some breaks in the sky mainly across the south, IFR post-precipitation low stratus or fog will affect CRW and BKW, while MVFR ceilings should slowly lift at other sites such as HTS and EKN. Additional isolated showers or storms will be possible across southeast OH this afternoon. A sfc low pressure system and an upper level wave will provide enough instability to produce thunderstorms some strong across the extreme south portions of WV and southwest VA this afternoon and evening. Ceilings should improve across the north through tonight, with lower clouds lingering across the south. Wind will be fairly light, turning more N to NW this afternoon and evening. FORECAST CONFIDENCE AND ALTERNATE SCENARIOS THROUGH 18Z 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 17 18 19 20 21 22 23 00 01 02 03 04 EDT 1HRLY 13 14 15 16 17 18 19 20 21 22 23 00 CRW CONSISTENCY H H H H H H H H H M M M HTS CONSISTENCY H H H H H H H M H L L L BKW CONSISTENCY L L L L H H H L L L L L EKN CONSISTENCY H H H H H M H L L L L L PKB CONSISTENCY M M M M H H H H H M M M CKB CONSISTENCY L M H M M H H H H M M M AFTER 18Z SUNDAY... IFR possible in precipitation Monday into Tuesday.
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WV...None. OH...None. KY...None. VA...None.
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&& $$ SYNOPSIS...MZ/SL NEAR TERM...ARJ/MZ SHORT TERM...SL LONG TERM...SL AVIATION...ARJ is the U.S. government's official web portal to all federal, state and local government web resources and services.