656 FXUS61 KCLE 260246 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 946 PM EST Sat Nov 25 2023 .SYNOPSIS... High pressure moves off the Middle Atlantic Coast tonight. Low pressure moves across the Great Lakes region with its cold front crossing the region through Sunday evening. A trough lingers over the area as another cold front moves east Tuesday. && .NEAR TERM /THROUGH SUNDAY NIGHT/... Slightly cooler than forecasted across the region with much of the CWA seeing partly cloudy to clear skies. Expect cloud cover and warm advection to increase through the overnight. So expect lows to bottom out through 06Z then remain steady or slowly warm through sunrise. Previous Discussion... High pressure is expected to continue to influence weather across the area into Sunday morning as it slowly drift off the Mid-Atlantic Coast. This will keep conditions dry through tonight with clouds building in as a low pressure and associated cold front approach from the west. Overnight lows will drop into the upper 20s. On Sunday, an upper level trough and associated low pressure system will begin to impact the area. Onset of precipitation ahead of the cold front is near 15Z for western counties, which will then spread east. With this update, the progression of the cold front east has slowed a bit, which will keep showers primarily liquid until late Sunday evening into the overnight hours. Overall rainfall total will be near 0.2-0.3" so there are no concerns with flooding. Highs on Sunday will reach into the low to mid 40s, with the exception of NW OH as the arriving cold air begins to impact those counties earlier. By Sunday evening, the cold front will move east across the area with much colder air expected to push southeast across the area behind it. Models suggest 850mb temperatures dropping to -8 to -10C. With these colder temperatures moving in at the tale end of precipitation, expect some rain/snow mix Sunday evening/early night. No accumulation is expected with this initial transition. At the tale end of this period, lake effect snow potential begins to materialize with EQL near 8kft and lake induced instability over 300 J/kg. The overall flow between 06-12Z Monday is not the most ideal fetch set up, but wouldn't be surprised to see 0.5-1" of snow in higher elevations of the snowbelt. The bulk of snow is expected to occur in the short and long term periods, but found it worth noting the onset time here. Sunday night lows will drop into the mid to upper 20s. && .SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/... On the large-scale, upper-level trough axis and associated surface cold front will have crossed the region and departed to the east by 12Z Monday, with strong cold air advection areawide on Monday. The broader upper-level trough still encompassed the Great Lakes and much of the northeast quadrant of the CONUS. Another shortwave trough on the backside of the larger trough originates out of the upper Midwest, diving southeast across the Great Lakes region Monday night and Tuesday, with the large trough axis moving off to the east coast by Tuesday night. In general, this will result in cold and blustery conditions areawide, as well as accumulating lake effect snow for the primary snowbelt of Northeast Ohio and Northwest Pennsylvania. Getting into more details...lake effect precipitation is likely ongoing by 12Z Monday with precipitation type either in the process of transitioning or already fully transitioned to snow. Strong cold air advection should bring surface temperatures into the low 30s on Monday before quickly dropping into the 20s for the duration of this event, making temperatures and precipitation type a non-issue for this lake effect event. Flow should initially be out of the west (around 270-280 deg) and 850 mb temps around -8 to -9C will initially contribute to modest lake-induced instability, though strong low-level flow off of Lake Erie and greatest lift below -10 C main initially result in lower snow ratios and less efficient accumulations on Monday. As the shortwave approaches from the northwest, flow becomes a little more more southwesterly (ranging 250-270 deg) Monday afternoon through early Monday night. Ahead of the trough, flow becoming more southwesterly should allow lake effect to conform to a singular band hugging the lakeshore, with accumulating snow mainly in Lake, northern Ashtabula, and Erie, PA, though increased surface convergence along the lakeshore and gradually increasing lake-induced thermodynamics (e.g. CAPE, equilibrium heights, etc.) should result in this band gradually intensifying through the night. The best thermodynamics are expected late Monday night into Tuesday morning when the shortwave trough is overhead. Peak equilibrium heights of 15kft, lake-induced CAPE of 1000 J/kg, 850mb temps of -12 to -14 C contributing to 850-sfc differences of 21 deg, and 700-sfc differences of 33 deg are expected. As the shortwave trough move overhead, flow becomes more northwesterly late Monday night through Tuesday (280-290 deg, perhaps even 300 deg by early Tuesday afternoon). This is also when the best lift is expected (18Z NAM BUFKIT omega values up to -50!) when peak intensity and snowfall rates are expected, with snowfall rates of up to 1-2"/hr. Lake effect snow weakens rapidly Tuesday evening/night as high pressure and warmer temperatures aloft build in from the west. A winter storm watch has been issued for Cuyahoga, Lake, Geauga, Ashtabula, Erie PA, and Crawford PA. The greatest confidence is for Erie, PA where there is a chance for accumulating snow for the entire duration of this event from Monday morning through early Tuesday night. Currently have 10-13" for all of Erie County but would not be surprised to see much higher totals. I expect forecast totals for Erie, PA to go up down the road as we get into range of hi-res model guidance. The next tier of confidence would go to Lake and Ashtabula, mainly because they have chances to accumulate snow at most points of this event. Uncertainty with Crawford, PA revolves around how much snow that are able to accumulate before the shortwave trough comes in. Then eastern Cuyahoga and Geauga are the lowest confidence of the counties in the watch. Those two counties are likely to observe most of their snowfall accumulations Tuesday morning, as that shortwave trough moves through and switches flow to more northwesterly, which is likely to be shorter duration (around 12-18 hours). Winds will be breezy, with gusts around 30-35 mph possible areawide and up to 40 mph near the lakeshore. This may cause blowing and drifting of snow throughout the duration of the event, making travel even more difficult. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... A small and compact shortwave trough may dive southeast across the Great Lakes on Wednesday, which may result in another round of light lake effect snow across the primary snowbelt on Wednesday and Wednesday night. High pressure briefly builds in Thursday and Thursday night before the next low pressure system lifts northeast out of the lower Mississippi Valley, impacting the region with rain areawide sometime Friday through Saturday. && .AVIATION /00Z Sunday THROUGH Thursday/... VFR conditions area expected into Sunday morning. NW OH will see the non-VFR conditions arrive by late morning with rain likely arriving with it. These non-VFR conditions spread eastward through the afternoon and evening. As the cooler air arrives in the wake of the cold front expect to see ceilings drop to IFR or lower. The rain will end from west to east after 03Z Monday. Winds through mid morning will remain light and variable. As the cold front approaches winds from the south increase to 5-12 knots. At KERI winds will be a tad higher with gusts up to 25 knots possible. Outlook...Lake effect snow with MVFR/IFR conditions are anticipated across NE OH into NW PA Sunday night through Tuesday night. && .MARINE... High pressure continues to the east coast this evening into tonight. Low pressure moving across the Great Lakes brings a cold front across Lake Erie Sunday afternoon through Sunday night. South to southwest flow increases to around 15 knots ahead of this front on Sunday. With the frontal passage, winds shift to out of the west, quickly strengthening to around 25-30 knots. These winds become northwest Monday night and Tuesday, weakening to less than 20 knots by Tuesday night. Currently holding with forecast max wind speeds of around 30 knots on Monday, though it's very close to gale force especially 12-18Z Monday east of The Islands. Flow becomes southwest by Wednesday morning, quickly strengthening to around 20-25 knots wobbling between southwest and west through the end of the week. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...Winter Storm Watch from late Sunday night through late Tuesday night for OHZ011>014-089. PA...Winter Storm Watch from late Sunday night through late Tuesday night for PAZ001>003. MARINE...None. && $$ SYNOPSIS...Campbell/MM NEAR TERM...Campbell/MM SHORT TERM...Saunders LONG TERM...Saunders AVIATION...MM MARINE...Saunders