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SYNOPSIS

Strengthening low pressure will move through the eastern Great Lakes tonight, dragging an arctic cold front through the region. Weak high pressure will build into the Ohio Valley Thursday and remain through the weekend while a trough of low pressure remains across the Great Lakes. A weak clipper system will then move through the Great Lakes Monday.

NEAR TERM /THROUGH THURSDAY NIGHT/

Evening Clipper and Linear Snow Squall:

Mid afternoon water vapor loops show the mid/upper shortwave associated with this clipper low diving through the western and central Great Lakes. As this shortwave continues to dive into the southern Great Lakes this evening, light snow will break out in the 21-22Z timeframe from NW to SE due to broad forcing for ascent beneath the exit region of a 140+ knot H3 jet streak. This will bring areawide snow for the evening, but the period of interest continues to be a potential intense linear snow squall along the arctic front mid to late evening. A lake-effect snow band that dropped a narrow strip of heavy snow along the lakeshore areas of Lake and Ashtabula Counties this morning and early this afternoon has mostly drifted offshore ahead of the arctic front. As the front crosses the lake this evening, it will capture the lake-effect band and rapidly push it inland which will be our potential snow squall set up. RAP BUFKIT forecast soundings show deepening instability in the 00Z to 03Z timeframe as 850-700 mb temps cool with resultant lake induced equilibrium levels rising above 7000 feet. This combined with strong Omega (lift) through a saturated DGZ and strong low-level convergence along the front all support the snow squall. Timing has slowed slightly among HREF CAMS, and expect the squall to push onshore from KTOL to KERI in the 01-02Z timeframe, reaching a KFDY to KCAK and KYNG line by 02-03Z and clearing the U.S. 30 corridor by 04Z. This will bring a brief period of heavy snow and gusty winds above 35 knots supporting whiteout conditions. Given the timing of this coinciding with New Years Eve festivities, we continue to heavily message the snow squall.

Lake-Effect Tonight through Thursday:

Behind the arctic front and snow squall, weak shortwave ridging and associated drier air and subsidence should largely shut down the snowfall, so expect most areas to be dry from about 06Z tonight through Thursday. Northwesterly boundary layer flow and moderate lake induced instability as equilibrium levels hover around 6-7 thousand feet will generate scattered snow showers and flurries in the higher terrain, inland primary snowbelt of far NE Ohio and NW PA, but additional accumulations will be about 1 inch or less. The exception will be in southern and eastern portions of Erie County and northern Crawford County where a well-modeled Lake Huron band could put down an additional 3 to 5 inches tonight and early Thursday morning before drifting east into NY as the flow backs.

Snowfall Totals:

As stated above, the bulk of the snow will occur this evening and early tonight associated with the clipper and lake enhanced snow squall along the arctic front. Expect additional amounts of 2 to 5 inches in much of north central and NE Ohio where the Winter Weather Advisory is in effect. Far eastern Cuyahoga County could see as much as 6 inches of additional snow, with generally 4 to 7 additional inches across Lake, Geauga, and Ashtabula Counties where Lake-Effect Snow Warning remains in effect. The bigger totals will be in NW PA where an additional 5-10 inches (locally up to 12) is expected. The greatest amounts will be in southern and eastern Erie County and northern Crawford County. Outside of these headline areas, amounts of 1 to 3 inches are expected in the rest of north central and Northwest Ohio.

Additional Lake-Effect Snow Thursday Night:

After the break for most areas Thursday, another weak mid/upper shortwave/clipper will progress through the Great Lakes Thursday night. Increasing moisture and convergence ahead of the associated surface trough and well-aligned westerly flow will generate an impressive band near or just offshore of NE Ohio and NW PA. There is uncertainty in the placement of this band and how far inland it will push, but another period of deep moisture and lift through the DGZ and increasing equilibrium levels supports at least a short window of heavy snow in parts of Lake, northern Geauga, Ashtabula, Erie, and northern Crawford Counties (if it makes it that far south). Have additional amounts of 2 to 5 inches for now Thursday night into Friday morning, with the greatest amounts in Erie County. This may need additional Advisories.

Temperatures:

Lows tonight will fall into the teens to single digits, with highs Thursday in the upper teens to low 20s in the deep arctic airmass. This will lead to subzero wind chills tonight and Thursday morning. Lows Thursday night will generally be in the teens.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/

The lake-effect snow from Thursday night/Friday morning should shift up the shoreline during the afternoon as the boundary layer flow backs ahead of a more defined area of surface ridging building into the Ohio Valley late Friday through Saturday. This will support mainly dry conditions Friday afternoon through the weekend. However, continued broad mid/upper troughing over the Great Lakes and Northeast CONUS and cyclonic flow around the Hudson Bay low will keep arctic air in place, with weak shortwaves continuing to pivot through the Great Lakes during the weekend. This will keep lake-effect snow bands going through the weekend, but a primarily SW to WSW boundary layer flow will direct the bulk of this into western NY. Kept chance POPS in NW PA at times from Friday afternoon into Sunday for snow showers to occasionally drift into that area, but otherwise, it will be dry and cold to start 2026.

Highs will be stuck in the mid to upper 20s Friday and Saturday, with lows in the teens Friday night and Saturday night.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

Surface ridging will maintain dry conditions Sunday outside of some lake-effect snow showers/flurries in NW PA. A weak clipper system still looks to drop through the Great Lakes Monday into Monday night, so maintained chances for snow showers, mainly in far northern Ohio and NW PA. This system has been trending weaker and warmer, so do not expect much accumulation. Thereafter, the lingering Great Lakes and Northeast CONUS trough will lift out for mid and late week as a quasi-zonal Pacific- based pattern takes over much of the country, so Tuesday and Wednesday continue to trend warmer, and this warming may continue the rest of the week leading to a short break in winter. Highs in the low to mid 30s Monday will likely reach the low 40s Tuesday and Wednesday.

AVIATION /00Z THURSDAY THROUGH MONDAY/

WNW'erly to NW'erly and predominantly cyclonic flow aloft, and embedded disturbances, affect our region through 00Z/Fri. At the surface, an Arctic front will sweep SE'ward through our region between ~00Z/Thurs and ~05Z/Thurs. Behind the front, a ridge builds from the north-central United States and vicinity into much of our region as a trough lingers over Lake Erie and vicinity through 00Z/Fri. Ahead of the front, our regional surface winds trend SW'erly around 10 to 15 knots with gusts up to 20 to 25 knots. Behind the front, NW'erly winds around 5 to 15 knots back gradually toward WSW'erly through 00Z/Fri in response to the building ridge. The NW'erly winds will gust up to 20 to 25 knots at times for several hours behind the front.

Widespread snow, steady to heavy at times, associated with the disturbances aloft, Arctic front, and lake-enhancement downwind of Lake Erie, will impact our region this evening. This widespread snow should end from northwest to southeast between ~03Z/Thurs and ~08Z/Thurs following the passage of the front at the surface and aloft. In addition, a narrower band of steady to heavy snow is expected along the surface front and should be accompanied by surface winds as strong as 20 knots gusting up to 30 knots for a brief time period. Visibility will range between MVFR and LIFR in the widespread snow and ceilings will range between MVFR and IFR in/near this snow. Behind the widespread snow, widespread ceilings in the 2kft to 3.5kft AGL range, primarily dry weather, and mainly VFR visibility are expected to accompany the building surface ridge. However, multiple bands of lake-effect snow (LES) of varying intensity are expected to stream generally SE'ward from Lake Erie and impact NE OH/NW PA and vicinity through ~13Z/Thurs. Thereafter, LES will stream generally ESE'ward and then E'ward from Lake Erie and impact far-NE OH, NW PA, and vicinity as mean low-level flow backs from NW'erly to W'erly. Visibility should vary between mainly MVFR and LIFR in the LES.

Outlook...Lake-effect snow with non-VFR should impact portions of NE OH and NW PA Thursday night into Friday and again this Sunday. In addition, periods of widespread snow with non-VFR may impact portions of northern OH and NW PA Thursday night and again this Sunday night into Monday.

MARINE

Rough marine conditions will continue across much of the lake tonight into Thursday as a cold front ushers in northwest winds of 25 to 30 knots. Elevated west to northwest flow of 20 to 25 knots will persist across the eastern and perhaps portions of the central basin through Friday night. Conditions will gradually improve by Saturday as west to northwest flow diminishes to 10 to 15 knots through Sunday. Winds will shift towards the southwest by Monday, 10 to 15 knots.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Winter Weather Advisory until 7 AM EST Thursday for OHZ010-011- 020>023-031>033. Lake Effect Snow Warning until 7 AM EST Thursday for OHZ012>014-089. PA...Lake Effect Snow Warning until 7 PM EST Thursday for PAZ001>003. MARINE...Small Craft Advisory until 7 AM EST Thursday for LEZ143>145. Small Craft Advisory until 4 AM EST Saturday for LEZ146>149.