616 FXUS61 KCLE 161154 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 654 AM EST Wed Dec 16 2020 .SYNOPSIS... Low pressure will slowly move through the Ohio Valley today and linger through Thursday, as a stronger low pressure system develops over the southeastern United States and moves off the East Coast. High pressure will build into the region for Friday and Saturday. Another low pressure system enters the Great Lakes region for the second half of the weekend. && .NEAR TERM /THROUGH THURSDAY/... Bumped up timing of PoPs in NW Ohio slightly as snow enters the Findlay area. Snow will expand over the next several hours as moisture and lift overcome the near-surface dry air. Otherwise, forecast remains on track and the previous discussion remains valid. Previous Discussion... Low pressure over the lower Ohio Valley will move slowly northeast today, bringing inclement weather to the region with widespread snowfall. Ahead of this low, high pressure over Canada remains fairly influential across the region with dry easterly flow and surface dew points in the teens across the forecast area. As low pressure enters, a plume of moisture is entering the area from the southwest, helping to re-saturate the low levels and isentropic lift is allowing for snow to develop in central Indiana and southwest Ohio. The area of snow will overspread the western half of the forecast area this morning and up to an inch of snow is expected in the I-75 corridor. Elsewhere, the low continues east along the Ohio River and will allow more sufficient moisture to enter the region. The supporting upper trough comes closer to the region with the left exit region of the upper jet over the upper Ohio Valley this afternoon and evening. This will bring ample lift across the region to generate widespread snowfall with a more favorable air mass in place. Will continue with a forecast of generally 1 to 3 inches of snow across the region. However, with just a slight westward shift in the positioning of this system, believe that portions of the Mahoning Valley and Crawford County PA will see a bit more snow than previously forecasted and have issued a Winter Weather Advisory for Stark, Mahoning, Trumbull, and Crawford Counties for late this morning through early Thursday morning for 3 to 5 inches of snow. The maximum will be in far southeast Mahoning County, where 6 inches is possible. Conditions will be least favorable during the Wednesday evening commute as snow settles in across the region and snowfall rates in advisory areas could be half inch or more per hour tonight. The supporting upper level jet quickly exits the region tonight and the more impactful snow should follow suit. However, the surface low pressure system will linger across the region tonight into Thursday. With a still saturated air mass in place, this should support scattered snow showers through the end of the near term forecast period. There is some concern that clouds could lose ice within them by Thursday, as the upper levels dry, and snow may actually switch over to more drizzle across the region (and perhaps freezing drizzle, where surface temperatures are cold enough) and will maintain a mixed forecast for Thursday. Temperatures through the period will be a few degrees below normal in the 30s for highs. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... Surface low pressure/inverted trough over the area will begin to lift northeastward out of the region Thursday night into Friday as high pressure builds into the area from the west. Lingering lift and low level moisture warrants slight chance pops diminishing into Friday. Models indicating that there may be some mid level moisture for a while and ice in the clouds, possibly a seeder-feeder mechanism, for mainly snow as a p-type, although moisture becomes shallow towards Friday morning with freezing drizzle possible for a brief time. Ridging builds across the region Friday through Saturday before a sharp shortwave trough moves from the northern Plains through the Great Lakes, developing a surface low that will track just north of the area. The attendant surface trough/cold front will swing east across the area Saturday night, with precip chances increasing through the day Saturday from west to east. Temperatures should be warm enough for mainly rain, possibly mixing with snow overnight into Sunday morning behind the trough/front. Highs Friday will be in the mid/upper 30s across most of the area. Highs Saturday will be near 40 across the area. && .LONG TERM /SUNDAY THROUGH TUESDAY/... Aforementioned trough will move northeast out of the area on Sunday, as high pressure quickly builds east late Sunday and Sunday night. A low amplitude trough tries to dig south through the Great Lakes while ridging persists across the Ohio valley, which may end up bringing some lake effect/enhanced precip to the snowbelt Monday night/Tuesday. Temps will be near 40 Sunday and Tuesday, with low/mid 40s expected in between on Monday. && .AVIATION /12Z Wednesday THROUGH Sunday/... Snow has begun entering from the southwest this morning with IFR snow and vsbys at KFDY. Snow will continue to develop and overspread the area through the day today with trends to IFR for most locations and perhaps down to LIFR by this evening. Have sped up snowfall and drop to non- VFR a bit across the area with more pessimistic conditions starting an hour or two earlier than originally forecasted. The most impactful snow will be at the KCAK and KYNG terminals this evenings and have introduced some 1/2 mi snow windows when the best push of snow is expected. As the forcing supporting the snow leaves the region tonight, have ended snow at each of the terminals by the end of the TAF period but IFR or LIFR ceilings should linger and snow and drizzle will develop across the region for Thursday. Winds will generally remain light at the terminals today, mostly east to northeast. KTOL may have some gusts to 20 knots early. Outlook...A mix of snow, drizzle, and freezing drizzle accompanied by non-VFR is possible through Thursday night. Non- VFR possible with snow and/or rain showers Saturday afternoon through Sunday. && .MARINE... No changes to ongoing headlines as east/northeast flow ramps up over the lake ahead of approaching low pressure from the south. Winds will be peaking through this morning before subsiding a bit towards midday. As the low passes southeast of the Great Lakes tonight, winds ramp up again out of the northeast late tonight through Thursday, which could necessitate a small craft advisory at some point late Thursday, but confidence is low at this time. Winds become light/variable Thursday night/Friday as high pressure builds over lake, but quickly become southerly later Friday/Friday night as the high shifts east of the area and a trough approaches from the west. Southerly winds persist through Saturday before the trough cross the lake Saturday night into Sunday, with winds becoming southwest through Sunday night. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...Winter Weather Advisory from 10 AM this morning to 4 AM EST Thursday for OHZ023-032-033. PA...Winter Weather Advisory from 10 AM this morning to 4 AM EST Thursday for PAZ003. MARINE...Small Craft Advisory until 1 PM EST this afternoon for LEZ142>145. && $$ SYNOPSIS...Sefcovic NEAR TERM...Sefcovic SHORT TERM...Greenawalt LONG TERM...Greenawalt AVIATION...Sefcovic MARINE...Greenawalt