textproduct: Cleveland

WHAT HAS CHANGED

Widespread minor snow accumulations with minimal impacts are expected today. Thus, increased POP's to 60%. The rest of the forecast remains largely unchanged. Additional widespread accumulating snow is still forecast this Thursday night through Friday, but exact accumulations and related impacts remain uncertain.

KEY MESSAGES

1) Below-normal temperatures are expected to persist through this upcoming weekend.

2) Periods of accumulating snow are expected today through Tuesday and again this Friday through weekend.

DISCUSSION

KEY MESSAGE 1... Net troughing aloft, associated with an abnormally-cold air mass, remains entrenched over eastern Canada and will impact at least most of the eastern United States through this upcoming week, including northern OH and NW PA. Accordingly, below-normal temperatures are expected to persist in our CWA. For context, our normal highs are near 35F and normal lows are near 20F this time of year. At the surface, a ridge exits slowly from our region and toward the northeast United States through tonight before a weak cold front sweeps E'ward through our region on Tuesday. Behind the front, another ridge builds from the north- central United States and vicinity through Wednesday night. Net low-level WAA ahead of the front will contribute to daytime highs reaching the 20's today and tomorrow, respectively. Wednesday's daytime highs should reach the upper teens to lower 20's in the net low-level CAA regime behind the cold front. Overnight lows should be near 15F to 20F around daybreak Tuesday and reach mainly the single digits above 0F around daybreak Wednesday and Thursday, respectively. The ridge should exit slowly E'ward Thursday through Thursday night before an Arctic front sweeps SE'ward through our region on Friday. Low-level WAA on the backside of the ridge and ahead of the front should contribute to daytime highs reaching the 20's on Thursday and overnight lows near 10F to 15F Thursday night. Friday should be the "warmest" day of the week with highs reaching the upper 20's to lower 30's before the Arctic front passage. Behind the front, an Arctic ridge should affect our region through Sunday as the core of the ridge moves from the north-central states toward the northeast United States. For example, widespread sub- zero minimum wind chills should occur this Saturday and Sunday.

KEY MESSAGE 2... Widespread light snow, associated with weak, moist isentropic ascent preceding the axis of a shortwave trough aloft, is expected to traverse our region from west to east today, between about mid-morning and late evening. This snow should last for several hours at a given location and total one inch or less. Behind the widespread snow, a sufficiently-cold/moist low-level air mass may allow limited lake-effect snow (LES) to develop over mainly ice-covered Lake Erie and stream generally E'ward across far-NE OH and NW PA this evening through daybreak Tuesday amidst W'erly mean low-level flow. Additional accumulations from this LES should be one inch or less. During the day on Tuesday, additional periods of light snow are expected due, in part to the following: the release of weak potential instability in the lowest ~1 km AGL via convergence/moist ascent along the above-mentioned surface cold front; moist isentropic ascent ahead of the axis of another E'ward-moving shortwave trough aloft. Additional snow accumulations from this activity should be one inch or less.

Current odds favor dry weather Tuesday night through Thursday based on the aforementioned projected weather pattern evolution at the surface and aloft. During Thursday night through Friday, additional widespread snow is expected due to the following: moist isentropic ascent ahead of a SE'ward-moving shortwave trough axis aloft; the release of weak/shallow surface-based potential instability via convergence/moist ascent along the Arctic front. Exact accumulations from this round of snow remain uncertain. However, latest NBM probabilities for at least one inch of snow are 70% or greater across NW PA, NE OH, and much of north-central OH, while probabilities are lower farther west. The largest probabilities for at least 4" of snow in our CWA are around 30% to 40% in NE OH and NW PA. We will continue to monitor trends in NWP model guidance in the coming days.

During Friday night through this upcoming weekend, periodic and scattered LES showers should target our CWA amidst a mainly NW'erly mean low-level flow of sufficiently-cold/moist air over/downwind of the primarily ice-free waters of Lake Michigan and any ice-free waters of Lakes Huron and Erie. Given the expectation of extensive ice cover on Lakes Erie and Huron, LES intensity and amounts should be limited.

AVIATION /12Z Monday THROUGH Friday/

Areawide VFR conditions will gradually deteriorate as widespread light snow showers and low-level cloud cover move overhead from the west. Expect VFR ceilings to drop to MVFR across terminals late this morning into this afternoon from west to east. Widespread light snow showers may occasionally drop visibilities to the MVFR/IFR range. Can't rule out IFR ceilings persisting late tonight across southern terminals (KMFD/KCAK/KYNG). Southerly to southwesterly winds will remain in the 5-10 knot range through the TAF period.

Outlook...Periods of non-VFR expected in low-level clouds and/or snow showers through Thursday. Non-VFR likely Thursday night into Friday as a cold front moves through the region.

MARINE

Extensive ice cover on Lake Erie (~95%) will continue to thicken through the week as persistent cold temperatures remain in place. Winds will generally remain southwesterly at 8-12 knots today and tonight before turning northwesterly on Tuesday as a cold front pushes east across the lake. High pressure builds across the region allowing for northwesterly winds 5-10 knots to continue Tuesday through Wednesday afternoon. Winds remain light at 5-10 knots out of the west Wednesday afternoon through early Thursday. Westerly winds increase to 15-20 knots by Thursday evening ahead of a deepening low pressure system tracking through the Great Lakes region.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...None.