textproduct: Cleveland

WHAT HAS CHANGED

The system that will bring snow to the area through Thursday has continued to trend a bit stronger and slower-moving. This has led to a significant upward trend in the snowfall forecast for both the synoptic snow through this evening and the continuing lake enhanced snow through Thursday. Winter Weather Advisories and Lake Effect Snow Warnings have been expanded to cover much more of the area to account for these trends. No significant changes for the outlook from Friday through early next week.

KEY MESSAGES

1) Rain will continue changing to snow through this evening. The entire area will see a burst of accumulating snow through this evening, which along with quickly falling temperatures and gusty winds will lead to hazardous travel conditions.

2) Lake enhanced snow will continue through much of Thursday across Northeast OH and Northwest PA, leading to continued impactful accumulations of fluffy snow with the greatest additional snowfall in the higher terrain of the snowbelt.

3) Temperatures will rapidly fall into the teens tonight into Thursday morning with near to below zero wind chills, posing a minor cold exposure risk.

4) A cold weather outbreak is expected for this weekend into next week with several systems bringing additional rounds of snow, single digit low temperatures, and wind chills below zero.

DISCUSSION

KEY MESSAGE 1... A swath of light to moderate synoptic snow is evolving early this afternoon from IN into Northwest OH and southeast MI, aided by good synoptic lift ahead of a potent vort max that is continuing to gradually amplify and take on a more negative tilt to our west. Guidance has continuously trended slower and more amplified with this feature over the last 24-36 hours worth of runs, leading to the continued slower trend with the initial cold frontal passage and change to snow across the area but also allowing for a greater amount of synoptic snow area-wide through this evening behind the cold front.

The swath of snow taking shape to our west is expected to continue to gradually expand and intensify as it translates east-northeast across the forecast area through the first half of tonight. As of 3 PM, the arctic cold front extends from just west of Cleveland to just southeast of Findlay and is moving southeast at about 20 MPH. It should clear the eastern portions of our area between 6-8 PM. Mainly light rain (possibly mixed with a bit of wet snow) ahead of the front will quickly change to all snow with the frontal passage as temperatures quickly plunge below freezing and into the 20s. Temperatures will drop into the 10s quickly between about 9 PM and Midnight from northwest to southeast. Snow intensity will peak from west- east across the area for a few hours behind the front. Wind gusts of up to 35 MPH are expected amid the strong cold air advection this evening, strongest near Lake Erie and west of the I-71 corridor. Some enhancement from the lake and upslope should begin taking shape this evening in the higher elevations of Greater Cleveland and the primary and secondary snowbelts.

Snow accumulations through 1AM/6z Thursday, which captures the bulk of the synoptic snow, are expected to range from 1-3" across Northwest OH and our southern counties in Central OH to 2-4" across most of the area, with locally up to 6" possible in the higher terrain surrounding the Cleveland metro. The combination of rain changing to snow, rapidly falling temperatures/gusty winds, and a relatively quick accumulation of snow through this evening (peak snow rates with the synoptic snow of 0.5-0.75" per hour, perhaps up to 1" per hour in the higher terrain/upslope areas of the snowbelt) will lead to road conditions becoming hazardous across the entire area. Was slightly generous with a Winter Weather Advisory and included all counties that have a solid chance to see 3" or more of snow, with a Special Wx Statement for the rest of the area. While snow will become generally light and much more intermittent overnight outside of continuing lake enhanced snow downwind of Lake Erie, ran all advisories until at least 10 AM Thursday as poor road conditions will likely linger into the morning commute, especially away from the main drags. Some snow showers may continue west of the Lake Erie lake effect into Thursday, though will decrease from west to east as ridging builds in with any additional accumulations on Thursday expected to stay <1".

KEY MESSAGE 2... As mentioned above, an impactful period of synoptic snow (with enhancement from the lake and upslope into the higher terrain) will drop about 3-6" of snow on the Greater Cleveland area and Erie, PA along with the primary and secondary snowbelts through 1 AM/6z Thursday...with the greatest amounts in the higher terrain southeast of the lake. This will lead us into a continuing lake enhanced snow setup through much of Thursday, lingering into Thursday evening across Northwest PA.

The general slower and more amplified nature of the system in recent guidance, with models coming into better agreement on the closed low aloft tracking over southern Lake Erie or far northern Ohio late tonight into Thursday, has led to the general setup for lake enhanced snow to continue to look more favorable for continued impactful accumulations through Thursday. Some modest synoptic lift and deep synoptic moisture to above 700mb persists into Thursday afternoon before exiting from west to east, so this is really more of a lake enhanced snow setup than a classic banded lake effect snow setup. 850mb temperatures plunging to -18 to -20C across the area by late tonight and Thursday will lead to modest to moderate lake induced instability, with lake-induced equilibrium levels climbing to 7-8k feet. While the amount of instability and EL heights aren't anything earth-shattering, the snow should be fairly high-ratio and efficient, with added contributions from the lake and upslope allowing it to add up through Thursday. Generally, am expecting continued light to moderate snow to continue across a good chunk of North Central/Northeast Ohio (as far west/ southwest as Sandusky and Wooster) and Northwest PA into Thursday morning. Activity will then gradually start to subside from west to east Thursday afternoon and evening, though will not entirely shutoff across Northeast OH until Thursday evening and a bit later into Thursday night across Northwest PA. Wind gusts up to 30 MPH, especially near the lake, will continue through much of Thursday leading to some blowing/drifting snow.

Mean low-level flow will initially whip around to the north- northwest this evening, gradually backing to a more northwest direction through tonight and eventually more west-northwest by Thursday afternoon. Targets for the heaviest snow in this type of flow will be: 1) The higher terrain southeast of Lake Erie in both the primary and secondary snowbelt due to well-aligned low-level flow in a favorable direction for upslope. 2) Where a Lake Huron connection sets up (perhaps as far west as the eastern Cleveland suburbs the first half of tonight before gradually working east into Northwest PA by Thursday)...and 3) potentially the western lakeshore towards Sandusky and southeast into parts of the secondary snowbelt (i.e. portions of Lorain/ Medina/Summit). While the lakeshore will generally see less snow than the higher terrain inland, the lake being colder now along with some synoptic component to the snow for most of the event should allow for at least moderate accumulations close to the lakeshore. Snow rates likely won't be out of control late tonight through Thursday, though will commonly reach 0.5" per hour within more organized lake enhanced snow and could still peak at 1" per hour on an isolated basis...most likely where any bands (especially the Lake Huron connection) interact with the higher terrain. Snow rates diminish more substantially within lingering snow late Thursday afternoon and evening.

Additional accumulations from the lake enhanced snow late tonight through Thursday evening will vary quite a bit and will be greatest in the higher terrain and lightest near the lakeshore...ranging from 1-3" as far west/southwest as Erie and Huron Counties to 2-6" across Great Cleveland and the snowbelt of Northeast Ohio, with 4-8" generally across Northwest PA. This will push storm total accumulations to 4-12" across Greater Cleveland and the Northeast OH snowbelt to 6-15" across Northwest PA. Locally higher amounts can not be ruled out in the higher terrain given this setup has a fair amount going for it and has been trending up quickly over the last 12-24 hours. Went with warnings for all of Northwest PA and much of Northeast OH, including Cuyahoga County and surrounding secondary snowbelt counties. Will need to see how things play out across Erie and Huron Counties, as some models suggest enhanced convergence near Sandusky focusing better snow and leading to greater than 6" across parts of those counties. Will also need to keep an eye on Trumbull County, though these lake enhanced setups often downslope into most of Trumbull and don't produce quite as much there as counties just to the north and northwest.

KEY MESSAGE 3... As mentioned above, the cold front moving through today will usher in colder air with 850 mb temperatures as low as -20 C into the region tonight. This will translate to surface low temperatures in the teens. With elevated northwest winds in the region of 15 to 25 mph and gusts to 35 mph, there will be a notable impact to wind chills. Wind chill values will fall to 5 to -5 F overnight and into the Thursday morning commute. This will pose a minor cold exposure risk to those outdoors.

KEY MESSAGE 4... An amplified and persistent ridge on the west coast and into Alaska will support a deep trough over the eastern U.S. the end of this weekend into the first half of next week, with the mean troughing generally expected over the Great Lakes. The trough will be deepest Monday into early Tuesday. This will lead to a cold pattern with occasional snow chances, both from systems moving through and lake effect at times.

Snow chances: A clipper will bring potential for light snow accumulations to the entire area Friday, with modest snow shower potential lingering Friday night. Another cold front crosses on Saturday with snow shower potential. Outside of lake effect in the primary snowbelt there should be a relative lull in snow potential Saturday night and Sunday. Another cold front may bring some snow showers on Monday, with lake effect into the snowbelt behind it. There is hope for another relative break in the pattern on Tuesday, with hints of the next system arriving from the west-northwest around midweek.

Temperatures: After another night with lows in the 10s Thursday night, Friday through early Saturday will bring a relative break in the colder air with highs trying to sneak above freezing outside of the higher terrain of Northeast OH/Northwest PA. A period of very cold weather (coldest of the winter thus far) then arrives Sunday through Tuesday, with modest improvement Wednesday. Daytime highs struggling to get out of the 10s along with lows in the single digits are expected for much of the area. The coldest night may be Monday night, when a few spots could make a run at 0. Sub-zero wind chills are likely late this weekend into early next week, with potential for Cold Weather Advisories at some point as we get a better handle on exact temps/winds.

AVIATION /00Z Thursday THROUGH Monday/

Conditions across the region have deteriorated the past few hours down to IFR-LIFR as the cold front has cleared much of the region. Most sites have transitioned to snow as a result outside of KYNG and KERI, but will do so in the next couple of hours. Persistent IFR-LIFR conditions are expected through much of the early morning hours for sites from KCLE and eastward due to lake enhanced snow showers. For sites to the west (KMFD, KFDY, and KTOL), conditions will improve to MVFR at least by early morning with the western most transitioning quicker. The current IFR- LIFR are driven by low ceilings at less than 1kft and visibility dropping down to 1 mile or less in the snow showers. Ceilings should begin to rise across the region tomorrow morning, though visibility will still be an issue in the snow showers creating IFR conditions. Blowing snow will also be an issue as winds will be gusting upwards of 20-25 knots out of the northwest through much of the TAF period.

Conditions will improve to MVFR towards the end of the TAF period for most sites outside of the snow belt where a few snow showers may be continuing.

Outlook...Non-VFR expected to continue on Thursday, most widespread east of the I-71 corridor in lake effect snow showers. Non-VFR likely in snow showers on Friday and Saturday. Non-VFR may linger across NE OH and NW PA on Sunday.

MARINE

Small Craft Advisories in place. Northwest winds 20-30kts as a cold front charges across Lake Erie for the remainder of today and wave heights back into the 4-8ft range for the central basin, and 3-6ft for the western and eastern basins. Heavy Freezing Spray Warning out for tonight into early Thursday in high winds, near freezing lake temperatures, high wave heights, and air temperatures in the upper teens. Winds gradually ease Thursday, then become southwesterly/offshore Friday 15-25kts. During this time frame, open water wave heights will be 3-6ft, and nearshore zones will be 1-2ft. Southwest winds continue 15-25kts parallel to the shoreline through the weekend, bringing the 3-6ft wave heights into the nearshore zones east of Cleveland.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Winter Weather Advisory until 10 AM EST Thursday for OHZ008- 018-028>031. Winter Weather Advisory until 1 PM EST Thursday for OHZ009-019. Lake Effect Snow Warning until 7 PM EST Thursday for OHZ010>014-020>022-089. Winter Weather Advisory until 7 PM EST Thursday for OHZ023-032- 033. PA...Lake Effect Snow Warning until 1 AM EST Friday for PAZ001>003. MARINE...Small Craft Advisory until 4 PM EST Thursday for LEZ142>144. Heavy Freezing Spray Warning from 10 PM this evening to 2 PM EST Thursday for LEZ144>148-164>168. Small Craft Advisory until 7 PM EST Friday for LEZ145>149.