501 FXUS61 KCLE 160148 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 948 PM EDT Wed Apr 15 2020 .SYNOPSIS... An eastward-moving cold front should exit the entire local area by nightfall this evening. Behind the front, high pressure builds eastward through Thursday. Thursday night, developing low pressure moves from the southern Great Plains to the Middle Mississippi River Valley as the associated warm front approaches our region from the southwest. The front should stall just south of northern Ohio and northwest Pennsylvania on Friday, allowing the low to track toward the Upper Ohio Valley. && .NEAR TERM /THROUGH THURSDAY NIGHT/... Cold front is now east of the area and most of the precipitation is now east of the area as well. A little feature now passing over the lake onto the shore over eastern Cuyahoga County has some interesting characteristics. There appears to be an apex in the center with cyclonic rotation to the northeast and anticyclonic rotation to the southwest. This activity appears to be putting down a quick burst of snow as it moves through the area. Some lake effect is expected over the northeastern snowbelt areas overnight. Only minor changes with this update to temperature trends. Previous Discussion... Cyclonic westerly flow aloft persists over our CWA the rest of today and tonight as an extensive longwave trough resides over much of eastern Canada and the eastern United States. A shortwave disturbance embedded in the longwave trough should exit our CWA to the east by around nightfall this evening. At the surface, a cold front extended southwestward from just west of Lake Ontario to northwest and west-central OH as of 3:30 PM EDT this afternoon. This front should also exit our CWA by around nightfall this evening as the front continues sweeping eastward. Isentropic lift ahead of the front and shortwave disturbance, along with lift along the cold front itself will combine with sufficient moisture to continue generating a swath of precipitation across our CWA. This widespread precip will end gradually from west to east through this early evening. Given surface dew points in the upper teens or 20's at onset of precip, expect any rain to quickly mix with and then change to wet snow as an efficient wet-bulb effect occurs. This should especially be the case north of US-30. Little or no snow accumulation is expected through this early evening. However, an inch or two of snow may accumulate in the higher terrain of northwest PA. Any snow accumulations should be confined to grassy surfaces. A burst of steadier snow remains possible as model soundings suggest lift could be maximized in or very near the dendritic snow growth zone for about an hour, especially for areas east of I-77 and north of US-30. Once precip begins, temperatures should drop from the 40's into the 30's. Behind the cold front, a surface high pressure ridge will build from the west. This will allow fair weather to return to most of our CWA later this evening and overnight tonight. However, a northwesterly to westerly low-level flow of unusually-cold air over Lake Erie is expected to direct light to perhaps moderate lake effect snow showers over the snowbelt of northeast OH and northwest PA late this evening into Thursday morning. A lack of abundant low-level moisture should limit lake-induced CAPE and lake snow intensity. Nevertheless, a coating to an inch or two of lake effect snow accumulation is possible, especially along grassy surfaces in the higher terrain of northern Geauga County and northwest PA. Low temperatures should reach the lower 20's to lower 30's tonight. Thursday and Thursday evening, high pressure at the surface and aloft continues to build over our region. A lowering subsidence inversion and decreasing low-level moisture will contribute to lake snows ending over the snowbelt by late morning. Little or no additional snow accumulation is expected during the daylight hours of Thursday. Once lake snows taper-off, fair weather is expected for the whole CWA through Thursday evening as skies trend partly to mostly cloudy. Thursday afternoon highs are forecast to reach the lower to mid 40's, but upper 30's are expected in the higher terrain of northwest PA. && .SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/... Main focus of the short term period is early Friday morning through Friday evening, with accumulating snow looking more likely, especially west of I-71. The highest snow totals are likely to be found west of I-75. A disturbance will move southeast out of the Northern Rockies tonight and move east across the Central Plains as a large upper trough continues to slowly meander east across the Hudson Bay. Models have begun to come into agreement on an axis of precipitation extending from North-Central IL, eastward to West- Central OH. Timing has appeared to slow down, with the heaviest precipitation expected Friday morning in western OH. Strong isentropic ascent and frontogenesis between the 850-700mb levels is expected during this timeframe which could easily be supportive of snowfall rates in excess of 1" per hour. There are several limiting factors for significant snow accumulation in our area. Omega fields appear to be maximized just below the DGZ in areas like Toledo and Findlay which could inhibit efficient snow production. Since precipitation onset has slowed down, the heaviest snow could occur following sunrise, which could limit snow accumulations to mainly grassy and elevated surfaces. Snow will begin to mix in with rain by late Friday morning, then becoming all rain by Friday afternoon. Rain may switch over to a rain/snow mix over the southeast portion of the area Friday evening and overnight as the system exits to our east and wraps cold air behind it. For now, going with storm total snow accumulations of 2 to 3 inches west of I-75, 1 to 2 inches west of I-71, and up to an inch elsewhere. More details will be forthcoming over the next day as models begin to converge on timing and an axis of heaviest precipitation. Behind the system, high pressure will arrive into the Ohio Valley on Saturday with highs more seasonable, but still below average in the low 50s with mostly sunny skies. On Sunday, clouds and the chance for rain returns as a trough swings down from the Upper Great Lakes, reaching the area by Sunday evening. Ahead of the trough, southwesterly flow will pump up temperatures into the upper 50s and perhaps low 60s. && .LONG TERM /SUNDAY THROUGH WEDNESDAY/... Weak surface high pressure returns on Monday and Tuesday while upper level troughing continues to have an influence on the area. Seasonable temperatures in the upper 50s are expected with some pockets of sun. By Wednesday, another piece of shortwave energy will be ejected from the upper level trough, leading to a chance of showers Wednesday morning. Following this disturbance, upper level troughing finally looks to loosen its grip as an upper level low develops in the Desert Southwest. Temperatures Wednesday will be seasonable once again in the upper 50s to low 60s. && .AVIATION /00Z Thursday THROUGH Monday/... A cold front will continue to push east of the area this evening shifting winds to west-northwest across the area. Snow/rain showers ahead of the front will be exiting to the east of the area as well. Mainly diurnal cumulus clouds/showers are being reported west of the cold front and expecting this activity to gradually weaken and diminish as the sun sets this evening. Winds will be diminishing as well. Ceilings improve to VFR west of the cold front. Otherwise, generally VFR expected across much of the area except at Erie where some lake effect snow showers will persist overnight. Outlook...Non-VFR possible in widespread rain and/or snow Thursday night through early Saturday morning and again Sunday into Monday. && .MARINE... Winds over the lake will become northwest this evening 10 to 15 knots, becoming westerly and increasing to 15 to 20 knots by late Thursday morning and afternoon. A SCA will likely be needed along along several zones on the eastern basin of the lake starting Thursday afternoon and lasting until the overnight hours. Winds will decrease back to 10 to 15 knots by Thursday evening into the overnight period, then quickly shift easterly Friday morning and northeasterly through much of the day Friday 10 to 15 knots as low pressure skirts just south of the lake. Behind the low, winds shift back towards the northwest and diminish to 5 to 10 knots Friday night. By late Saturday morning, winds increase out of the west/southwest 15 to 20 knots and remain southwesterly through Saturday. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...None. PA...None. MARINE...None. && $$ SYNOPSIS...Jaszka NEAR TERM...Jaszka/Lombardy SHORT TERM...Kahn LONG TERM...Kahn AVIATION...Jaszka MARINE...Kahn