textproduct: Cleveland

WHAT HAS CHANGED

9:30 AM EST Jan 18th: Increased POP's to 20% to 40% across northern OH and NW PA to account for potential light snow showers amidst moist isentropic ascent preceding a low/mid-level shortwave trough axis. This shortwave trough axis is expected to sweep E'ward through our CWA early this afternoon through early evening. Any snow accumulations are expected to be less than one inch. Please see discussion below for further details.

6:34 AM EST Jan 18th: There are no impactful changes regarding this morning's forecast update. We are expecting a blast of frigid weather Monday through Tuesday night with dangerous cold wind chills possible. We will be watching closely for the development of a lake effect snow band over the central and eastern basin of Lake Erie Monday into Tuesday. This potential lake effect snow may try wobble closer to the lakeshore of far Northeast Ohio and Northwest Pennsylvania late Monday into Tuesday with some accumulating snowfall.

KEY MESSAGES

1) The main weather story over the next few days will be the frigid weather heading this way Monday through Tuesday night with dangerous cold wind chills as low as -10F to -20F possible.

2) A lake effect snow event will develop with very cold southwesterly flow over Lake Erie late tonight through Tuesday evening. This particular lake effect setup will mainly impact southwestern New York. The band of lake effect snow may wobble towards the lakeshore of far NEOH and NWPA late Monday into Tuesday with some accumulating snowfall.

3) Outside the lake-effect snow, there may be several waves of light snow showers from fast moving low pressure systems tracking across the Great Lakes this week and bring some light snowfall.

DISCUSSION

KEY MESSAGE 1... The coldest weather so far for this winter season is heading our way. This blast of frigid temperatures will arrive tomorrow and continue through Tuesday night. An Arctic front will move across the region early Monday. The daily high temperature for Monday will likely occur early Monday morning before the Arctic frontal passage. Most areas may climb briefly into the low 20s Monday morning ahead of the front. Temperatures will slowly fall behind the front through teens and into the upper single digits during the afternoon and evening. Wind chill values will drop below zero between -5F and -10F by late afternoon.

An Arctic high pressure system will move from the Midwest and build into the Ohio Valley Monday night and Tuesday. We are expecting the coldest temperatures Monday night into early Tuesday morning dropping down around or on either side of zero. Some locations may drop a degree or two below zero for the overnight low temperature. There will be a breezy from the west-southwest 8 to 15 mph Monday night into Tuesday morning that will likely cause dangerous wind chills between -10F and -20F. We will likely need a Cold Weather Advisory if forecast continues to trend this way. Despite skies being mostly sunny to partly cloudy on Tuesday, temperatures will only reach into the lower and middle teens for highs. Wind chills will still hovering around zero during Tuesday afternoon. It will again be very cold Tuesday night with overnight lows dropping back into the single digits areawide. We will recover fairly nicely with temperatures rebounding into the lower 30 on Wednesday.

KEY MESSAGE 2... An Arctic airmass will move over Lake Erie Monday through Tuesday evening. The overall low and mid level flow of this cold airmass will be from the west-southwest which generally favors a setup for lake effect snow to be more impactful towards southwestern New York. The forecast model guidance is in fair agreement that the lake effect snow will start to develop and organize over the central and eastern basin of Lake Erie by Monday morning. This lake effect snow will be near or just offshore of the lakeshore of far northeast Ohio and northwest Pennsylvania NEOH/NWPA with its trajectory heading towards the eastern end of Lake Erie and southwestern New York. We will have to watch this band of lake effect closely and nowcast the forecast late Monday into Tuesday. Some of the forecast guidance like the latest hi-res models do show the potential for this lake effect to wobble a little southward Monday evening through Tuesday morning. There is at least some potential for some accumulating snowfall for areas closer to the lakeshore of Ashtabula County and Erie County PA. Three to five inches of snowfall may be possible if this lake effect brushes along that lakeshore for a period of time before shifting back northeastward. The rest of the primary snowbelt closer to the lakeshore may see some passing light snow showers from lake effect but any snowfall will be light an inch or two.

KEY MESSAGE 3... There will be several chances this upcoming week for some general light snow and scattered snow showers periodically starting tonight. A low pressure system will track across the Great Lakes tonight through tomorrow and push an Arctic cold front through area early Monday. As this weather system and front moves through the region tonight through tomorrow, it will bring scattered snow showers areawide. Any snowfall will remain light with around an inch or less possible for most locations of northern Ohio and NWPA for this weather system. There could be some minor travel impacts and slick road conditions for the Monday morning commute with the scattered snow showers.

There will be a weather system mid-week that could bring light snow and scattered snow showers to the area. It will arrive late Wednesday through Thursday with another low pressure system that will track across the Great Lakes and a trailing cold front sweeping through the region. There could be some light snowfall around an inch or two with the mid week system that could have some minor travel impacts as well.

AVIATION /18Z Sunday THROUGH Friday/

Outside of TOL and FDY who will continue to see mainly MVFR ceilings this afernoon, VFR persists though with some ceilings of 040-050 floating around parts of the area. Clouds will fill in and lower to MVFR tonight with snow arriving late evening into the overnight with a clipper system. This snow will likely be accompanied by mainly MVFR ceilings and a period of IFR vsby, with accumulations of an inch or two across the area. Snow will become lighter into Monday morning, though an arctic front sweeping through from west-east 12-18z could bring scattered snow showers and squalls with brief but impactful vsby drops. Confidence in that increases farther east across the area, though some snow showers could accompany the front anywhere. Drier weather returns into Monday afternoon from the west/southwest, though MVFR ceilings may not clear as quickly.

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...Non-VFR possible in snow showers on Wednesday into Thursday. Non-VFR may linger across NE OH and NW PA through Thursday.

MARINE

An active marine period is in store as several systems move across the Great Lakes. The most impactful period appears to be Monday into Tuesday as an arctic cold front ushers in west to southwest winds of 30 to 40 knots with gusts up to 45 knots possible, particularly across the central and eastern basins of Lake Erie. In this update, the Gale Watch has been upgraded to a Gale Warning, and a Heavy Freezing Spray Warning has been issued for the ice-free areas of the central and eastern basins as lake air temperatures fall into the low teens behind the front on Monday and Monday night. A Low Water Advisory will also likely be needed for the western basin given the favorable southwest fetch.

Winds will begin to subside on Tuesday, though elevated southwest flow of 25 to 30 knots will remain possible across the eastern basin through much of the day. Another period of elevated southwest flow of 25 to 30 knots is possible Wednesday into Thursday, before winds subside to less than 20 knots by Friday.

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...None. PA...None. MARINE...Gale Warning from 7 AM to 7 PM EST Monday for LEZ142>145- 162>165. 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.