textproduct: Cleveland

WHAT HAS CHANGED

The Wind Advisory has been allowed to expire at 7 PM as wind gusts have decreased.

Forecast confidence continues to increase that the coldest air mass of this winter season will impact northern OH and NW PA this Friday and upcoming weekend.

KEY MESSAGES

1) Dangerously-cold wind chills as low as -15 to -20 are expected through Tuesday. Confidence continues to increase in a prolonged period of sub-zero wind chills beginning Friday and into early next week.

2) Periods of lake-effect snow are expected downwind of Lake Erie through this upcoming Monday and should impact Northeast Ohio and Northwest Pennsylvania at times.

3) In addition to the lake-effect snow, periods of widespread accumulating snow should impact our region through this upcoming weekend.

DISCUSSION

KEY MESSAGE 1... Primarily below-normal temperatures are expected through Sunday, as net and deep troughing aloft, associated with an unusually- cold air mass, persists over eastern Canada and impacts at least most of the eastern United States, including the Great Lakes and OH Valley. At the surface, our CWA is expected to primarily reside in the cold sector based on the latest projected mid latitude cyclone track. However, a warm front is still expected to sweep NE'ward through our region Tuesday night and be followed by the E'ward passage of a strong cold front Wednesday evening into Wednesday night. A stronger, reinforcing cold front is expected to sweep SE'ward through the Lake Erie region and Upper OH Valley this Friday.

Prior to the warm front passage, lows are expected to reach the single digits above 0F around daybreak Tuesday, when wind chills near -15F to -20F will be most widespread in our CWA. Afternoon highs should reach only 10F to the upper teens on Tuesday. Lows should bottom-out near 5F to 10F with wind chills as cold as 0F to -5F Tuesday evening, before the warm front ushers-in a warmer air mass originating over the Gulf. On Wednesday, low-level WAA in the warm sector should contribute to highs reaching the lower to upper 30's before the aforementioned strong cold front passage. Below-normal high and low temperatures are then expected Wedneday night through this upcoming Monday. For example, low temperatures should reach the single digits below 0F in many northern OH and NW PA locales around daybreak Saturday and Sunday, respectively. Sub-zero minimum wind chills will likely be a daily occurrence this Friday through Monday. Forecast trends will continue to be monitored for the need for additional cold weather alerts.

KEY MESSAGE 2... Lake-effect snow (LES) showers are expected to persist amidst a cyclonic W'erly to WSW'erly mean low-level flow of sufficiently- cold air over/downwind of the ~1C ice-free waters of Lake Erie through this evening. Thus, LES showers will impact much of the primary snowbelt of NE OH and NW PA, especially along/near the lakeshore from near the Cuyahoga/Lake County line through Erie County, PA, due to frictional surface convergence. The LES will be heavy at times, with snowfall rates up to 1" per hour, due in part to greater/deeper low-level moisture contributing to sizable lake- induced instability. Additional LES accumulations are expected to be 1-4". Greatest additional snow accumulations are expected in far- northeastern Erie County, PA due to greater persistence of LES showers. Considered expanding the Winter Weather Advisory W'ward and S'ward in the primary snowbelt, but the showery/periodic nature of the LES and expected mean low-level flow direction should limit additional snow accumulations to 3" or less.

During Tuesday morning through Tuesday night, the LES, amidst continued favorable thermodynamics, should shift back N'ward and out of our region as mean low-level flow backs to SW'erly ahead of another shortwave trough poised to approach the Lake Erie region generally from the west. Most of Wednesday should feature a brief hiatus from LES as the warm sector overspreads Lake Erie and causes ice-free lake surface to 850 mb temperature differences to shrink to less than 13C for a time. Renewed LES development is expected Wednesday night through Thursday night, amidst a favorable thermodynamic environment and W'erly to SW'erly mean low-level flow behind the strong cold front passage. Thus, the LES should impact at least portions of the primary snowbelt of NE OH and NW PA at times and produce up to several inches of fresh snow accumulation. Thermodynamics and kinematics should remain favorable for periods of LES this Friday through upcoming Monday. Multiple shortwave trough passages should cause mean low-level flow to vary between primarily SW'erly and NW'erly. Therefore, LES should impact NE OH and NW PA at times. However, exact mean low-level flow direction and LES placement, intensity, and amounts remain uncertain at this time. Note: surface winds should remain strong enough over Lake Erie to prevent the lake from freezing-over completely through early next week.

KEY MESSAGE 3... Periods of widespread snow, outside the aforementioned LES, should impact northern OH and NW PA overnight Tuesday night through next Sunday due to moist isentropic ascent ahead of shortwave trough axes, moist isentropic ascent along the upper- reaches of the warm front Tuesday night, and low-level convergence/moist ascent along the expected cold front passages Wednesday evening into Wednesday night, and again on Friday. Note: a surface-based melting layer should develop in the warm sector and become deep enough for rain to mix with snow at times Wednesday afternoon into evening. Our official snowfall forecast, which is valid through Thursday night, calls for a coating to 3" of fresh snow accumulation outside the LES. General snow should yield additional accumulations this Friday through upcoming weekend, but exact amounts remain uncertain at this juncture.

AVIATION /00Z Tuesday THROUGH Saturday/

A band of heavy lake enhanced snow is ongoing across Lake Erie with the Erie, PA shoreline experiences occasional IFR visibilities over the next couple before before is lifts northward away from Erie. Elsewhere, occasional MVFR ceilings are expected through the overnight period as high pressure builds in and overall cloud cover tends to diminish. West- southwest winds of 10-15 knots with gusts to 20-25 knots decrease by Tuesday night.

Outlook...Areawide light snow is expected on Wednesday, followed by lake effect snow impacting Northeast Ohio and Northwest Pennsylvania Wednesday night through Friday. Areawide light snow may occur on Friday into Saturday.

MARINE

A Gale Warning remains in effect on Lake Erie, expiring at 7 PM west of Cleveland and 4 AM from Cleveland to Erie, PA. The strong west southwest winds have resulted in low water conditions on the western basin of Lake Erie and a Low Water Advisory remains in effect through 10 PM. Conditions will be monitored this evening and there is a chance the Advisory may need to be extended a few extra hours. Due to arctic air over the region, a freezing Spray warning is also in effect for the east half of Lake Erie through 4 PM Tuesday. Ice growth is expected to continue both along the shoreline and eastward on the open waters overnight with very cold air over the region.

Winds will remain elevated for much of the week on Lake Erie between 20 and 30 knots. The lake will be positioned between high pressure to the south and a trough to the north on Tuesday, with a warm front lifting north on Wednesday and another cold front pushing back south Wednesday night into Thursday. A stronger arctic front will cross Lake Erie on Friday. Periods of freezing spray will continue with considerable ice growth expected on the lake through the weekend.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Cold Weather Advisory until noon EST Tuesday for OHZ003- 006>009-017>019-027>029-036-037. Cold Weather Advisory until noon EST Tuesday for OHZ010>014- 020>023-030>033-038-047-089. Wind Advisory until 7 PM EST this evening for OHZ011-012-014- 089. PA...Cold Weather Advisory until noon EST Tuesday for PAZ001>003. Wind Advisory until 7 PM EST this evening for PAZ001-002. Winter Weather Advisory until 7 AM EST Tuesday for PAZ001-002. MARINE...Gale Warning until 7 PM EST this evening for LEZ142>145- 162>165. Low Water Advisory until 10 PM EST this evening for LEZ142>144- 162>164. Gale Warning until 4 AM EST Tuesday for LEZ146>149-166>169. Heavy Freezing Spray Warning until 4 PM EST Tuesday for LEZ146>149-166>169.