textproduct: Cleveland

SYNOPSIS

Low pressure centered over the northern Great Lakes region will maintain a surface trough over the area through Friday. A very brief area of high pressure will push east on Saturday before another system moves from the Southern Plains northeast across the region on Sunday. High pressure returns for the start of next week.

NEAR TERM /THROUGH FRIDAY NIGHT/

9:30 PM Update...

Upgraded Lorain County to a Winter Weather Advisory and slightly increased snow totals to 2 to 4 inches in NE parts of the county since the main band should reorganize again over the next few hours as a fairly sharp trough crosses the lake, further increasing low-level convergence. This band will pivot from NE Lorain County through central and SE Cuyahoga, southern Geauga, northern Summit, northern Portage, and Trumbull Counties through 06 to 08Z before finally breaking up behind the trough.

Previous Discussion...

Happy Thanksgiving! Upgraded Portage County to a Lake-Effect Snow Warning since the main band has been impacting far northern portions of the county since late afternoon, and that will likely continue for several more hours with snowfall rates over 1 inch per hour at times. A surface trough has been rotating across the region, and this has aided in deepening the cold air, improving low and mid level moisture, and strengthening Omega (lift) and low-level convergence. The deepening cold air has raised lake induced equilibrium levels to 10-15 thousand feet, and this combined with the improved moisture and lift into the DGZ has finally allowed for optimal dendritic snow growth. Earlier today, the main band contained a lot of graupel, which limited the snowfall overall. Now, we are seeing snowfall rates of 1-2 inches per hour, so the most organized part of this event will likely be from now through about 08Z tonight. This main band should largely remain in place from the Cleveland area east-southeast to southern Geauga, northern Summit and Portage, and much of Trumbull Counties between now and 06 to 08Z where low-level convergence is maximized. Slight N and S drifts are possible. This area will see the highest snowfall totals, and forecast snow amounts still look to be on track. Farther NE, weaker bands will continue to stream into parts of Lake, northern Geauga, Ashtabula, southern Erie, and Crawford Counties. Snowfall rates in these could be 0.5 to 1 inch per hour at times. Another area to watch is NE Lorain County. The aforementioned main band across the Cleveland Metro area is affecting Avon and North Ridgeville at times, so a few inches are possible in these areas tonight. This will be monitored. Late tonight, winds will turn more NW behind the trough, and the shorter fetch should lead to the formation of weaker multiple bands. This will favor overall lower snowfall rates, but over a broader area of interior north central and NE Ohio and NW PA through the day Friday. So the main message is that periods of snow will continue in and near the headline areas through Friday, but the most organized and heaviest will probably be from now through the pre-dawn hours of Friday. Continue to limit travel. If you must travel, prepare for rapidly changing road and visibility conditions. Have a safety kit, and allow plenty of extra time to reach your destination.

Original Discussion...

The main focus will be continued lake effect snow across the snowbelt region through Friday and into Friday night, with the most impactful snow falling through tonight. A few wind gusts up to 45 MPH remain possible near the immediate lakeshore through the first half of tonight, for which a Wind Advisory remains in effect.

Outside of the Lake Erie snowbelt, flurries and scattered snow showers are expected this evening as a shortwave and weak surface trough cross the area. These may leave a dusting of snow, especially towards and after sunset. Some flurries and brief snow showers from Lake Michigan will likely continue to stream east-southeast across Northwest and North Central OH overnight tonight into Friday, with additional localized dustings where snow showers track. Lows will range from near 30 along the immediate lakeshore to low-mid 20s well- inland tonight, with wind chills in the 10s. Highs on Friday will be similar to or perhaps a degree or two warmer than today, mainly low to mid 30s, with mainly dry conditions outside of the minor Lake Michigan activity. Lows Friday night will range from the upper 10s well- inland to the mid 20s along the lake, with mainly clear and quiet conditions outside of the lake effect.

As for the lake effect...

Will start with changes to the forecast...based on current band placement and organization, have upgraded Trumbull County to a Lake Effect Snow Warning. Based on reports of 1-3" this morning, a period of no accumulating snow and melting this afternoon, and forecast new amounts of 1-4" in northern Ashtabula and 2-5" in northern Erie for the rest of the event, downgraded the two lakeshore zones to an advisory to reflect overall lower impacts in those lakeshore communities. Otherwise, all headlines remain as previously posted.

Activity is increasing in organization and intensity this afternoon as lift improves ahead of an approaching shortwave and surface trough...these features will cross early this evening, veering winds to a bit more of a west- northwest direction, especially over the lake. A secondary trough will drop across the lake around midnight, bringing another increase in synoptic moisture/lift and veering the winds more late tonight into Friday morning. The flow will remain west-northwest through Friday before starting to back more westerly Friday night as surface ridging builds in.

Expect the lake effect to continue inching south through this evening, push south a bit more substantially overnight tonight, hold nearly steady in location through Friday, and then start shifting east-northeast Friday night. Activity will peak in intensity through the first half of tonight as instability increases/deepens and as cooling temperatures aloft allow for improved snow growth and higher snow to liquid ratios. Snow rates of 1 to briefly 2 inches per hour are possible within the more organized bands through midnight tonight. Conditions become slightly less conducive for lake effect overnight tonight resulting in perhaps a modest downtrend in organization and intensity, with a more notable period of some subsidence and drier boundary layer air expected for several hours during the day Friday. This, along with high temperatures near freezing, should lead to snow accumulations and impacts notably decreasing during the day Friday. One last uptick in organization and intensity is possible into Friday evening as winds begin backing, lengthening the fetch over the lake and increasing convergence near the shoreline. However, building ridging will likely put a lid on how prolonged or intense this uptick is Friday evening into Friday night.

There are currently three bands of lake effect evident on radar...a primary one across the western basin into the Cleveland area, extending east-southeast towards Trumbull County...another from eastern Lake/northern Ashtabula into southern Erie and northern Crawford...and a third clipping northeastern Erie County PA. Between, less organized and more cellular snow showers are ongoing. The southern band near Cleveland is and likely will remain the most intense. Expect the ongoing bands to inch south through this evening. As winds veer more west- northwest overnight into Friday we will likely see these bands push farther south and then break apart into a mix of weaker and more narrow multi-bands and more general upslope snow showers. The exception is the current primary southern band, which may maintain some organization into Friday morning across parts of central/southern Cuyahoga County, northern Summit/Portage Counties and into most Trumbull. Some light accumulations are in the forecast as far southwest as northern/eastern Lorain, northern Medina, central Summit, central Portage, and northern Mahoning County to account for some uncertainty regarding how far south this band may push Friday morning before likely breaking up by midday. One or two more organized west-east bands may re-develop Friday evening into Friday night from the Cleveland area points east, though intensity shouldn't be too crazy by then (rates perhaps in the 1/2" per hour range).

No major changes to the overall snow totals, though given an increasingly short fetch and onshore component to the strong flow off the warm lake, lakeshore communities will continue to generally see lesser accumulations. This is one area where overall totals trended notably down from the prior update. Given current organization into Trumbull County totals there increased just a bit, enough to prompt the warning upgrade. Otherwise, the flavor of the event remains the same as previously laid out with peak amounts across the higher terrain of the primary snowbelt, with localized storm totals over 12" in northeast Ohio and up to 20" in southeastern Erie County PA. Will also need to monitor northern Portage over the next several hours, as if good banding settles into there this evening the route 82 corridor would likely see 5-8" of snow, which would need a warning. The current end time of headlines of 7 PM in Ohio may be a bit awkward if we see a last gasp uptick in intensity Friday evening, though will allow future forecasts better evaluate that.

SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/

The main focus for the short term forecast period is the increasing likelihood of widespread light to moderate accumulations of wet snow late Saturday afternoon through early Sunday morning across the entire area, with the greatest impacts expected Saturday evening and Saturday night and the highest accumulations expected across Northwest Ohio.

A flat shortwave and associated (fairly weak) surface low will lift east-northeast out of the upper Mississippi Valley and into the southern Great Lakes Saturday night into Sunday. Most of our precipitation with this system will come courtesy of warm/moist advection and lift within the warm conveyor belt ahead of the shortwave and surface low between late Saturday afternoon and early Sunday morning. A mid-level dry slot will overspread the area Sunday morning, allowing for a decrease in precipitation intensity and perhaps even some dry breaks. The low pressure's accompanying cold front crosses Sunday afternoon/early evening, with colder air aloft returning amid west-northwest flow as a weak mid-level deformation zone grazes the forecast area. This will bring some returning light precip chances late in the day Sunday that give way to (relatively minor) lake effect across the snowbelt Sunday night.

Temperatures aloft are forecast to remain cold enough for mainly or all snow through this event, though mid-level warm air may get close to the route 30 corridor east of Mansfield during the day Sunday. That said, it will be surface temperatures that will be most impactful to precip types and potential snow ratios/accumulations. Expect everything to start as snow Saturday afternoon and evening. Surface temperatures will likely climb above freezing from southwest to northeast between 3-9 AM Sunday, with surface temperatures especially likely to warm quicker once precip rates start diminishing in the dry slot. It's likely precip will start mixing with rain (especially outside of Northwest Ohio) by Sunday morning, with a rain/snow mix forecast through most of Sunday...transitioning back to snow (where precip remains, primarily in the snowbelt) Sunday night.

A push of seasonably moist air, on the nose of a strong low to mid- level jet beneath a period of coupled jet support aloft, does support a decent period of steady snow late Saturday into Saturday night from west to east across the area. The nature of the snow, primarily driven by warm air advection, does argue for increasingly low snow ratios and perhaps general under-performing, which makes us skeptical of more robust snow amounts output by models such as the NAM (which has quite a bit more mid-level frontogenesis and banding potential than most other models). That said, there are still enough "positives" that a widespread accumulating snow is becoming rather confident for the entire area. The ground will be cold enough for road accumulations, particularly Saturday night, so some impacts are on the table. The general flavor of the forecast is a 1-3" snow across Northeast OH and Northwest PA, increasing to 3-5" across Northwest OH, where somewhat more prolonged/intense lift is favored by most guidance (to go along with a slower warming of surface temperatures through the event). A Winter Weather Advisory is likely for parts of Northwest Ohio. While considered less-likely, if additional guidance trends towards showing stronger lift and more mid-level frontogensis (like the NAM does), the potential for amounts to approach warning criteria around Toledo and advisory criteria farther east than currently expected is there.

Highs on Saturday will generally reach the low to mid 30s. Lows Saturday night will be early, in the upper 20s and lower 30s. Highs on Sunday will range from the mid 30s to near 40, with lows Sunday night falling back to a very chilly upper 10s to mid 20s range.

LONG TERM /MONDAY THROUGH THURSDAY/

The main potential weather impact next week will be a shortwave and associated surface low passing to our south and southeast on Tuesday. Most guidance suggests this shortwave will be fairly broad and unphased, leading to weaker low pressure that perhaps tries spreading some light snow towards our southern and eastern counties. A more phased solution could bring lighter snow to much of the area and more moderate accumulations from eastern Ohio into Northwest PA, though odds of that are on the lower side with the weaker solution currently favored. Otherwise, generally colder than normal weather continues with the next cold front (with perhaps a bit of rain or snow) looking to move across the area on Thursday.

AVIATION /00Z Friday THROUGH Tuesday/

Lake-effect snow will continue to bring frequent MVFR to IFR conditions to NE Ohio and NW PA tonight and Friday. The heaviest squalls and lowest visibilities will affect KCLE, KCAK, and KYNG from now into early Friday morning as a main band of heavy snow slowly sags across the area, bringing the best chance of IFR at times. The heaviest snow will be south of KERI, but nearly continuous light to occasionally moderate snow tonight and Friday will support mostly MVFR there, with shorter periods of IFR. Slow improvement is expected late Friday afternoon, but these snow showers will continue until after the TAF period.

For the rest of the region, snow showers will be much more intermittent tonight and Friday, with mostly VFR dominating. Lake-effect snow showers from Lake Michigan have the best chance at reaching KFDY, so have more periods of MVFR there tonight into Friday compared to KMFD and KTOL, but all sites will see passing snow showers and brief reductions at times.

WNW winds will continue to gust to 20-30 knots through tonight at times, gradually decreasing to 15-25 knots during the day Friday.

Outlook...Non-VFR ceilings will continue across parts of Northeast Ohio and Northwest Pennsylvania through Saturday morning. A low pressure system will enter the Great Lakes region this weekend, bringing light to moderate snowfall areawide late Saturday afternoon through Sunday morning, with lake effect snow lingering across Northeast Ohio and Northwest Pennsylvania through Monday.

MARINE

West winds around 25-35 knots across Lake Erie with gale-force winds primarily across the eastern half. The Gale Warning was canceled early west of Vermilion and replaced with a Small Craft Advisory. Elsewhere, the warnings were unchanged.

Due to the continued strong westerly winds, a Low Water Advisory remains in effect on the western basin of Lake Erie through 4 AM Friday. Water levels will oscillate near the critical mark through at least this evening.

High pressure with good marine conditions will be over Lake Erie on Saturday for a brief window. Southerly winds ramp up to 30 knots Saturday night as low pressure tracks from the southern Plain into the Central Great Lakes. Winds veer to westerly Sunday and northwesterly Sunday night and additional Small Craft Advisories are likely Saturday night through Sunday night.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Winter Weather Advisory until 1 PM EST Friday for OHZ010. Lake Effect Snow Warning until 7 PM EST Friday for OHZ011>014- 022-023. Wind Advisory until 1 AM EST Friday for OHZ012-089. Winter Weather Advisory until 7 PM EST Friday for OHZ021-089. PA...Wind Advisory until 1 AM EST Friday for PAZ001. Winter Weather Advisory until 1 AM EST Saturday for PAZ001. Lake Effect Snow Warning until 1 AM EST Saturday for PAZ002- 003. MARINE...Low Water Advisory until 4 AM EST Friday for LEZ142>144- 162>164. Small Craft Advisory until 10 PM EST Friday for LEZ142>146. Gale Warning until 10 AM EST Friday for LEZ147>149-167>169.