textproduct: Cleveland

WHAT HAS CHANGED

The potential for accumulating synoptic snow this evening across eastern Ohio and northwestern Pennsylvania has continued to increase, transitioning to lake effect snow later tonight and Tuesday. A Winter Weather Advisory has been issued for most of the primary snowbelt, with a Winter Storm Warning for southern Erie County PA. Farther west, snow showers and a few snow squalls remain likely into early tonight. Adjustments have been made to the remaining Wind Advisories as we approach the end of the windy weather.

KEY MESSAGES

1) Strong gusty winds will gradually subside tonight into Tuesday.

2) A sudden return to wintry weather will take place through the rest of today and into tonight across the area. A quick-hitting system snow will impact eastern Ohio and northwestern Pennsylvania this evening. Elsewhere, scattered snow showers and perhaps a few snow squalls are expected late this afternoon into tonight. Travel impacts are possible across the area as the sun sets and temperatures drop.

3) Lake effect snow will develop across the primary west flow snowbelt tonight and continue Tuesday, tapering off Tuesday night.

4) Unseasonably cold conditions through Tuesday night.

5) Limited precipitation chances with a gradual warming trend expected Wednesday through the weekend.

DISCUSSION

KEY MESSAGE #1...

A Wind Advisory remains in effect until 8 PM today for northern and western portions of our forecast area, and until 8 AM Tuesday for Lake, northern Ashtabula, and northern Erie Counties. Winds have been generally gusting 40-50 MPH (strongest in the wind advisory) and will gradually relax starting this evening as the low-levels begin stabilizing after sunset, and as flow aloft eases a bit. The exception will be the eastern lakeshore, where the "warm" lake will allow deeper mixing and stronger gusts to continue. With one more push of stronger flow aloft overnight tonight into early Tuesday, expect occasional advisory-level gusts to around 50 MPH to continue near the lakeshore through early Tuesday.

KEY MESSAGE #2...

While the lake effect snow and associated headlines certainly catch the eye and grab the attention, do not want to neglect the rest of the area as we'll all see some snow through this evening, which along with lingering gusty winds and plunging temperatures can lead to travel impacts...a shock to the system after the recent warmth.

Starting with the synoptic snow across our east: A brief period of impressive lift ahead of an amplifying and negatively tilted shortwave, including decent mid-level frontogenesis briefly intersecting the dendritic growth zone, will lift northeast across eastern OH and western PA through this evening. Rain/snow is beginning to spread in quickly this afternoon, and will quickly turn steadier/heavier and change to all snow between 4-6 PM. While the warm ground will initially stave off impacts to roads, expect that to quickly change around and after sunset as temperatures plunge into the 20s. Along with continued gusty winds, am expecting travel impacts east of I-77 (especially from Mahoning County to Ashtabula County points east) from this synoptic snow after 5 or 6 PM. The steady snow should quickly exit between 9 PM and 11 PM. This synoptic snow may drop up to an inch as far west as near I-77, increasing to 1-3" across far eastern Ohio and to 2-4" (perhaps a touch more on the hilltops) across Northwest PA.

Elsewhere, there are plenty of snow showers on radar to our west and these will quickly spread east into and across our forecast area as the aforementioned upper-level shortwave and a sharp low-mid level trough axis swing through this evening. The low-levels will remain a bit unstable through this evening, given sufficient low-level moisture and steep low-level lapse rates in the lowest 8-10k feet. Anyone can see a quick, light accumulation of snow with these snow showers as temperatures drop into the 20s through this evening, with locally an inch or two possible (in short order) if a more organized heavy snow shower or squall can develop along the trough axis. Until 6 or 7 PM the warm ground should keep any road impacts to a minimum, but after that time potential for more intense snow showers to cover roads will increase. Along with visibility issues, which will be enhanced by the lingering gusty winds, some impacts to travel are likely across much of our forecast area this evening. As temperatures continue plunging overnight, untreated surfaces can turn icy. It is worth noting that these snow showers/squalls will continue all the way east across our area, so our eastern counties will likely see some snow from the synoptic snow shield first followed quickly by these trailing snow showers and squalls.

Flow off of Lake Michigan and troughing aloft will combine to allow flurries and some snow showers to continue overnight tonight into Tuesday across parts of our forecast area, with potential for another little uptick early Tuesday as another trough moves through. This activity should diminish Tuesday afternoon into Tuesday evening as surface ridging builds in from the southwest.

KEY MESSAGE #3...

There will likely be a period of lake enhanced snow late this evening as the snow showers and squalls associated with the trough axis discussed above move across the lake and then east-southeast into the primary snowbelt. Temperatures aloft will be quickly cooling as sufficient synoptic moisture lingers, supporting increasing intensity and efficiency of any snow flowing off the lake this evening. Some hi-res models suggest that briefly more organized west to east band or two may play out from near Cleveland points east during the first half of tonight, which could allow snow rates on the order of 1" per hour to briefly focus across parts of the Cleveland area and primary snowbelt early on in this event.

There should be a brief period around midnight tonight where lake effect snow loses organization and intensity due to a brief period of subsidence behind this evening's trough passage. Another trough approaches pre-dawn Tuesday into Tuesday morning, which should allow more focused lake effect bands to re-develop amid continued west to slightly west-northwest flow. Most models indicate multiple upstream moisture connections taking shape Tuesday morning. Activity likely peaks in organization and intensity again Tuesday morning, before subsidence behind the trough and negative diurnal influence during the afternoon hours causes activity to lose organization Tuesday afternoon. Plentiful moisture, instability, and lift (including in the dendritic growth zone), minimal shear, and weakening flow over the lake can support 1"+ per hour rates in organized bands Tuesday morning. There is some question of if these organized bands will be ongoing during the Tuesday AM commute or if they'll really rip just after the commute. Some commute impacts should be planned for from Cleveland points east-northeast Tuesday morning, though a couple hours' worth of difference in when the bands organize will determine how significant those commute impacts are. With a west to slightly north of due west flow Tuesday morning, suspect we'll see one band from near Cleveland points east-southeast into Geauga and towards northern Trumbull (possibly clipping northern Portage), with another band focused closer to Erie County PA. There will likely be be a significant change in accumulations and conditions heading east/northeast across the Cleveland metro.

Lake effect snow will gradually shift towards the eastern lakeshore Tuesday evening and night as ridging builds in, with some accumulations likely continuing Tuesday night near the lakeshore but at a reduced rate as moisture and instability decrease.

These were not easy advisory and warning decisions for a number of reasons. The low-levels look slightly dry during this event and winds over the lake stay quite strong through early Tuesday. There will also likely be periods where subsidence and/or diurnal factors negatively influence the snow. However, the thermodynamics are supportive of intense and efficient lake effect when organized bands are able to establish. Overall, suspect the heavier snow will be pushed well inland. Upgraded southern Erie County PA to a warning, as they will do well with the synoptic snow this evening and have the longest fetch/most terrain to work with. Went with an advisory everywhere else in the primary snowbelt, and added Trumbull. Where organized bands can sit for any amount of time, additional accumulations from the lake effect of over 6" and perhaps up to 12" are doable through Tuesday or Tuesday night...if band organization struggles, additional amounts from the lake effect will be on the order of a more spread out couple/few inches. There were enough negative considerations to mainly stick with advisories, though future shifts will need to closely monitor for organized banding/localized overperforming and be ready to upgrade if needed. Ran the PA headlines through most of Tuesday night, though expect limited impacts in Ohio after about midday Tuesday.

KEY MESSAGE #4...

Temperatures will plunge into the 20s quickly this evening, with lows in the upper 10s/lower 20s tonight with minimum wind chills in the single digits. Highs on Tuesday will mainly stay in the 20s. Lows Tuesday night will fall into the 10s for most of the area but with minimal wind/wind chill consideration. While these values are well shy of headline criteria, the cold will be quite jarring and should be a consideration for those with outdoor holiday plans on Tuesday.

KEY MESSAGE #5...

No significant changes to the forecast were made beyond the next couple of days, with a gradual warming trend and low-impact weather expected through most of the weekend. A more organized system may move through Sunday into Monday.

AVIATION /00Z Tuesday THROUGH Saturday/

Cellular type snow showers moving in from the west in a clockwise flow while a south to north swath of snow is moving through eastern Ohio and western Pennsylvania. IFR to LIFR as the eastern snow exits to the east, but highly variable conditions expected in the cellular snow showers. Brief IFR visibilities expected in and out of these snow showers and will have to cover these with TEMPO groups as their time frames are limited. Lake enhanced/lake effect snow expected tonight and Tuesday but POPs are lower and will not cover with SHSN even in TEMPO groups that far out at this time, but the best chances will be CLE/YNG/ERI after 12Z Tuesday. Winds still on the gusty side, generally out of the west gusting 30-40kts tonight and 20-30kts Tuesday.

Outlook...Lake effect snow showers continue on Tuesday with non-VFR. Non- VFR returns late Tuesday night into Wednesday night with the next warm front.

MARINE

A robust low pressure system and associated cold front will continue to exit the region this evening. This system will continue to bring strong synoptic winds with the strong low level jet and pressure rises behind the surface low. Gale force winds are starting to be achieved across Lake Erie and winds may increase a touch further to 40 kts this evening. Therefore, the Gale Warnings will continue as previously issued. Strong southwest flow has allowed for water levels to drop in the western basin of Lake Erie to about 2 feet below low water datum. Water levels will remain below the critical mark for safe navigation tonight and the Low Water Advisory will also remain as previously issued.

High pressure will build into the region for Tuesday and allow for a reduced pressure gradient and winds should ease across the lake. There will still be 15 to 20 kts of west flow in the system transition and the Gale Warning will need to be replaced with a Small Craft Advisory. Southwest flow should be relax to 10 to 15 kts on Tuesday night and end any marine hazards. A warm front will cross the lake on Wednesday and southerly flow will be around 15 kts for most of the day. It may be more difficult to mix down any stronger winds with the cold lake and a marginally warmer air mass. High pressure will enter the region for Thursday and light southwest flow will be expected on the lake. Low pressure with a cold front will enter for Friday and winds will shift to the northwest and increase. The resultant waves could rise to 3 to 4 ft and a Small Craft Advisory may be needed. High pressure and a warm front will enter for Saturday, allowing for easterly flow before the warm frontal passage.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Wind Advisory until 8 PM EDT this evening for OHZ003-006>011- 013-014-017>020-027>030-036-037. Winter Weather Advisory until 2 PM EDT Tuesday for OHZ011>014- 023-089. Wind Advisory until 8 AM EDT Tuesday for OHZ012-089. Winter Weather Advisory until midnight EDT tonight for OHZ033. PA...Wind Advisory until 8 PM EDT this evening for PAZ002-003. Wind Advisory until 8 AM EDT Tuesday for PAZ001. Winter Weather Advisory until 5 AM EDT Wednesday for PAZ001- 003. Winter Storm Warning until 5 AM EDT Wednesday for PAZ002. MARINE...Gale Warning until 8 AM EDT Tuesday for LEZ142>149-162>169. Low Water Advisory until 8 AM EDT Tuesday for LEZ142>144- 162>164.