188 FXUS61 KCLE 151757 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 1257 PM EST Tue Dec 15 2020 .SYNOPSIS... High pressure over the Great Lakes will continue to shift east of the region tonight. Low pressure will enter the Ohio Valley on Wednesday and linger through Thursday as a stronger low pressure system moves through the East Coast. High pressure will build into the region on Friday and remain over the area until the next system enters on Saturday afternoon. && .NEAR TERM /THROUGH WEDNESDAY/... Today's forecast remains on track with cloudy skies and temperatures lingering in the low 30s. Began to update the near term forecast with newer model data to reflect precipitation chances in the near term. Primary chances account for the NAM/ECMWF shifting the stronger low further west. A full analysis of these systems will be complete in the next update. Previous Discussion... High pressure entering the region from the northwest has allowed for the drier air to enter the area. A push of colder air ahead of this high has allowed for cooler temperatures across the region and with this air mass over Lake Erie, some lake effect clouds remain the only relevant weather today. These clouds will slowly erode from the west today as high pressure pivots east and drier air enters. Given a colder start to the day, temperatures will be slightly cooler than yesterday with highs in the low to mid 30s. High pressure continues east tonight and low pressure approaches from the southwest. Winds will back around to the southeast and clouds will advect in from the southwest. Expecting lows back into the 20s but with clouds in the west, will go with low to mid 20s east and more upper 20s west. An upper trough moving through the central CONUS will support a pair of lows across the eastern United States on Wednesday. The show that has been garnering the most attention is what will be the stronger low moving through the southeastern US that will bring heavy snow to the East Coast. However, our main concern is a weaker low/trough that will enter the Ohio Valley on Wednesday and bring accumulating snowfall to our region. There is increasing confidence in widespread snowfall with minor accumulations across northern Ohio and NW PA. This system will bring good low-level moisture across the region with fairly good saturation to 600 mb. In addition, the weak surface low plus left exit region of the upper jet will allow for ample lift across the area, primarily in this area of saturation. This combination will support precipitation across the region in the form of snow on Wednesday. Therefore, have bumped up PoPs on Wednesday to a mix of likely/categorical (60-90 percent) across the area and have snowfall accumulations across the region of generally one to two inches across the area with higher amounts (2-4 inches) in the Mahoning Valley into Crawford County PA through Wednesday night. One concern for this snowfall forecast is that there are some indications (Mostly the recent NAM runs and to some extent the ECMWF) that the stronger low to the east could be pulled a little further west and some better snow could reach the eastern portions of the forecast area. This is shown with some of the higher numbers in the probabilistic snow and not the official forecast but there is a low chance of a higher impact event, which will need to be watched for Wednesday. && .SHORT TERM /WEDNESDAY NIGHT THROUGH FRIDAY NIGHT/... The main surface low will be pulling away from the region off the east coast Wednesday night, while the secondary negatively tilted upper trough will lift northeast across the Ohio valley. Models are in good agreement of keeping a secondary surface trough or low over the area late Wednesday night through Thursday night before shifting northeast while filling. This may provide a tricky weather situation for the forecast area, which persistent weak low level lift and copious low level moisture, and mid level moisture shifting off to the east with the main system. Model soundings suggest a 9-18 hr period late Wednesday overnight/early Thursday afternoon through Thursday afternoon/early evening where there may be a loss of cloud ice and drizzle potential, with surface temperatures hovering in the upper 20s to low 30s bringing the potential for freezing drizzle at times. This will need to be watched closely over the next 24 hours, but have introduced chance/slight chance freezing drizzle mixing with snow at times for this period. We may regain some cloud ice late Thursday afternoon evening, switching everything back to mainly snow or rain before the lift moves out of the area and dry conditions prevail. High pressure will build northeast across the area late Thursday night through Friday night with dry conditions expected. Highs Thursday may reach the mid 30s across the bulk of the area, but some locations will hover near freezing. Highs Friday will be in the mid to upper 30s with return flow/WAA into the area late in the day. && .LONG TERM /SATURDAY THROUGH MONDAY/... Ridging will build east away from the area Saturday and an upstream cold front will push east across the area Saturday night. Precip chances may increase ahead of the front through the day Saturday, although recent runs of the ECMWF/GEM are showing a drier solution for the local area with stronger forcing/better moisture focused on the southeast CONUS. Weak ridging/quasi-zonal flow regime returns to the area Sunday with some more return flow into Monday before a northern stream mid/upper trough digs east across the Great Lakes late Monday. This may bring a brief shot of colder air and some lake effect/enhanced precip just beyond the period. Highs will be in the low 40s over the weekend, with mid 40s possible Monday ahead of the trough. && .AVIATION /18Z Tuesday THROUGH Sunday/... VFR conditions are currently spread across the area, with a few patches of lower ceilings resulting in MVFR conditions. High pressure dominating the area today will continue to move northeast overnight as a low pressure system moves in from the southwest. With the approach of this low, ceilings will gradually begin to drop to MVFR heights from southwest to northeast tomorrow morning. This low pressure will also bring an influx of moisture across the area and resultant precipitation, again spreading from southwest to northeast. Primary precipitation type will be snow across the area, although some rain may mix in for the western terminals with surface temperatures hovering just above freezing. With this update, every terminal, except for KERI, has the mention of snow. The heaviest of snow is expected to occur in the afternoon hours tomorrow, which may result in visibilities and ceilings dropping to IFR conditions at the far end of this TAF period. Winds across the area will shift between northeast to easterly through the period. In general, sustained winds of 5 to 10 knots are expected for terminals KCLE to KMFD and west. An enhanced low level jet across the eastern portion of the area will allow for sustained winds of 10 to 15 knots, gusting to 20 knots beginning Wednesday morning through the end of the TAF period. Outlook...Non-VFR expected to return Wednesday into Thursday as low pressure moves through the Ohio Valley. && .MARINE... Northwest winds continue to subside from west to east across the lake this morning. Have let the small craft advisory for a good portion of the lake expire early this morning, and expect the expiration of the remainder of the advisory for the area later this morning. Light northerly winds persist today before becoming more northeasterly to easterly tonight and increasing into Wednesday. Winds will back northeasterly Wednesday night into Thursday as low pressure passes to the southeast of the lake. Winds will subside Thursday into Friday as high pressure builds across the lake. Winds will increase out of the south Friday night into Saturday ahead of a weak cold front that will cross the lake Saturday afternoon/evening. Winds will become southwest behind the front Saturday night into Sunday. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Sefcovic NEAR TERM...Campbell/Sefcovic SHORT TERM...Greenawalt LONG TERM...Greenawalt AVIATION...Campbell MARINE...Greenawalt