textproduct: Cleveland

WHAT HAS CHANGED

The following weather alerts have been issued:

- Wind Advisory for Cuyahoga, Lake, Ashtabula, and Erie (PA) Counties from 10 AM Monday to 7 PM EST Monday.

- Cold Weather Advisory for all of northern OH and NW PA that takes effect at 1 PM Monday for Morrow, Richland, Huron, and Erie (OH) counties west. Farther east, the advisory takes effect at 7 PM Monday. This advisory is in effect until noon Tuesday for our entire CWA.

- Winter Weather Advisory for Erie County, PA from 10 AM Monday to 7 AM Tuesday.

KEY MESSAGES

1) Below-normal temperatures will continue through Sunday. Dangerous wind chills as cold as -10F to nearly -20F are expected later Monday and especially Tuesday morning.

2) Blustery conditions are expected with scattered snow squalls possible on Monday.

3) Periods of lake-effect snow are expected downwind of Lake Erie, impacting Northeast Ohio and Northwest Pennsylvania at times through the upcoming weekend.

4) Outside the lake-effect snow, periods of widespread, accumulating snow should impact our region through the 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. An Arctic front is expected to sweep E'ward through our CWA between about daybreak and midday Monday and usher-in a colder air mass before a warm front sweeps NE'ward through our region Tuesday night. Prior to the warm front passage, overnight lows are expected to reach the 10F to 15F range around daybreak Monday and the 0F to 10F range around daybreak Tuesday. Daytime highs should reach the upper teens to mid 20's on Monday before temperatures tumble behind the Arctic front. On Tuesday, afternoon highs should reach only the 10F to 20F range. Lows should bottom-out near 5F to 10F Tuesday evening, before the warm front ushers-in a warmer air mass originating over the Gulf.

As for wind chills, these are expected to decrease to widespread sub-zero values and generally from west to east between mid-morning and mid-afternoon on Monday, behind the Arctic front. The coldest wind chills around -10F to -20F are expected later Monday into Tuesday morning. Somewhat "warmer" wind chills are then expected the rest of Tuesday and especially Tuesday night. On Wednesday, low-level WAA in the warm sector should contribute to highs reaching the lower to mid 30's before a strong cold front sweeps generally E'ward across our CWA Wednesday night. Behind the front, net low-level CAA is expected through the upcoming weekend and contribute to below-normal temperatures Wednesday night through Sunday. Additional sub- zero wind chills are possible, especially around daybreak Friday. Based on latest temperature and wind forecast trends, additional sub- zero wind chills are possible at times this Thursday night through upcoming weekend.

KEY MESSAGE 2... On Monday, the Arctic front should be accompanied by a burst of moderate to heavy snow as convergence/moist ascent along the front release at least weak potential instability in the lowest 1 km AGL and result in moderate to strong and maximized ascent at cloud temperatures near -10C to -15C. These snow showers should be accompanied by mean wind speeds near 20 to 30 knots in the 0-1 km AGL layer. Thus, snow squalls are possible. Quick snow accumulations of 1" or less are expected. Behind the front's passage, WSW'erly to W'erly surface winds are expected to gust up to 35 to 50 mph due to the following: several hours of rapid MSLP rises; steepening low-level lapse rates amidst low-level winds/CAA increasing with height, respectively, which will allow deeper mechanical mixing of the boundary layer to tap into stronger flow aloft. The strongest gusts are expected from the Lake Erie shore to roughly I-90 in northeastern Cuyahoga County through Erie County, PA due to the aforementioned reasons combined with onshore surface flow amidst lake-induced convective mixing of the boundary layer tapping into stronger flow aloft. Winds and gusts are forecast to ease Tuesday evening as an Arctic surface ridge builds gradually behind the front and the synoptic MSLP gradient relaxes, at least somewhat.

KEY MESSAGE 3... Lake-effect snow (LES) is ongoing over and downwind of Lake Erie late this afternoon. Ahead of the Arctic front, LES will continue to impact portions of western NY through early Monday afternoon amidst a SW'erly mean low-level flow and 850 mb temperatures hovering near -15C over the ~1C ice-free waters of Lake Erie. The LES is expected to intensify and become heavy at times tonight, especially after midnight, as low/mid-level moisture increases ahead of the front and attendant shortwave trough, which will allow lake-induced instability to increase. The E'ward passage of the Arctic front and attendant shortwave trough should be followed by 850 mb temperatures falling to near 22C below zero and mean low-level flow veering toward W'erly later Monday afternoon through evening. Thus, LES banding should settle slightly S'ward into most of the primary snowbelt of NE OH and NW PA, but especially Erie County, PA. The LES should be steady to heavy at times as low-level moisture remains abundant and contributes to sizable lake-induced instability. Resulting snow accumulations should be mainly 1-3", but up to 6" of snow should accumulate in far-northeastern Erie County, PA due to greater persistence of steadier LES banding. 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.

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 should occur Wednesday night, amidst a favorable thermodynamic environment and SW'erly to W'erly mean low-level flow behind the strong cold front passage. Thermodynamics and kinematics should remain favorable for periods of LES through this upcoming weekend. Multiple shortwave trough passages should cause mean low-level flow to vary between 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.

KEY MESSAGE 4... Outside the LES and aforementioned Arctic front-related snow showers, additional periods of snow are expected this evening into Monday due to moist isentropic ascent preceding an E'ward- moving shortwave trough axis. This snow should accumulate 1" or less. Additional 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 Wednesday night's cold front. Additional snow accumulations should occur, but exact amounts are uncertain at this juncture.

AVIATION /00Z Monday THROUGH Friday/

A low pressure system moving across the Great Lakes region will bring a stratus deck with MVFR ceilings accompanied by periodic light, snow. Steady snow will occur overnight, producing visibilities in the 1-3 SM range. An arctic cold front will then swing through Monday morning through the early afternoon, with snow becoming showery. Visibility reductions with snow showers will be brief and periodic, with the potential for visibilities of 1 SM or less. High pressure builds in behind the front, with conditions improving to VFR from southwest to northeast as clouds scatter out. Lake effect clouds persist across the primary snowbelt with heavy lake effect snow primarily impacting the Erie, PA lakeshore Monday night.

Southwest winds 7-15kt this afternoon shift a bit more south- southwest at 5-10kt tonight. These winds increase to 10-15kt with gusts 20-25kt ahead of the arctic front early Monday, then shift more west-southwest and increase to 15-25kt with gusts 30-35kt (up to 40kt near the eastern Lake Erie shoreline) behind the front later Monday morning/afternoon.

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

MARINE

Southwest winds in the 10-20kt range continue through this evening. Southwest winds ramp up to 15-25kt late tonight into early Monday, shifting a bit more west-southwest behind an Arctic cold front that will sweep across the lake during the morning and midday hours. West- southwest winds will increase to 30-40kt with gusts 40-50kt behind the front through Monday afternoon, with the strongest winds across parts of the central and eastern basins. Winds subside a bit Monday night into Tuesday, but still remain 15-28kt out of the southwest with 30-35kt gusts, especially over open waters across the central and eastern basins. Wave heights may still peak as high as 15 feet in the open waters across eastern Lake Erie. The arctic air spreading over the lake and elevated winds/waves will lead to favorable conditions for heavy freezing spray Monday and Monday night. Gale and Heavy Freezing Spray Warnings remain as posted, and will add a Low Water Advisory from 7 AM to 10 PM Monday for the western basin in conjunction with the west-southwest flow gale.

Southwest flow remains brisk at 15-28kt through Tuesday before subsiding to 10-20kt for a time Tuesday night. The next low pressure tracks through the Great Lakes on Wednesday. South-southwest flow ramps back up to 20-30kt behind a warm front Wednesday morning, with winds shifting more westerly late Wednesday into Wednesday night at 20-30kt behind a cold front. Westerly winds will remain 20-30kt through Thursday as another round of Arctic air spreads in.

Generally moderate ice growth is expected across Lake Erie over the next several days, with the limiting factor to rapid ice growth being strong winds. This will also likely cause significant drifting of existing ice.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Cold Weather Advisory from 1 PM Monday to noon EST Tuesday for OHZ003-006>009-017>019-027>029-036-037. Cold Weather Advisory from 7 PM Monday to noon EST Tuesday for OHZ010>014-020>023-030>033-038-047-089. Wind Advisory from 10 AM to 7 PM EST Monday for OHZ011-012-014- 089. PA...Cold Weather Advisory from 7 PM Monday to noon EST Tuesday for PAZ001>003. Wind Advisory from 10 AM to 7 PM EST Monday for PAZ001-002. Winter Weather Advisory from 10 AM Monday to 7 AM EST Tuesday for PAZ001-002. MARINE...Gale Warning from 7 AM to 7 PM EST Monday for LEZ142>145- 162>165. Low Water Advisory from 7 AM to 10 PM EST Monday for LEZ142>144-162>164. Small Craft Advisory until 7 AM EST Monday for LEZ146>149. Gale Warning from 7 AM Monday to 1 AM EST Tuesday for LEZ146>149-166>169. Heavy Freezing Spray Warning from 7 AM Monday to 1 AM EST Tuesday for LEZ146>149-166>169.