textproduct: Cleveland

WHAT HAS CHANGED

Included falling temperatures in the forecast through the day Friday. Wind gusts have trended down slightly.

KEY MESSAGES

1) Chance of showers and thunderstorms Thursday evening into early Friday. A few stronger storms are possible with wind gusts to 50 mph.

2) A cold front will cross the area Friday bringing strong gusty winds and showery conditions.

3) The coldest air of the season will arrive this weekend and a mix of frost/freeze conditions are expected on Sunday morning.

DISCUSSION

KEY MESSAGE 1... A few showers will exit to the south through this evening. A cold front extends from near Pittsburgh to north of Columbus at 3 PM and will continue to move south tonight as high pressure builds across the Upper Great Lakes. Scattered thunderstorms have filled in towards Columbus and should mostly remain south of the local area.

Thursday will be dry to start the day. Low pressure is expected to track out of the Mid-Mississippi Valley towards lower Michigan by Thursday evening. Initially there will be a dry low level flow out of the east with isentropic ascent increasing aloft during the afternoon. Showers will spread west to late afternoon through the evening as the warm front lifts north to near Lake Erie. A few thunderstorms will also be possible during the evening, especially across the north near the front.

The Storm Prediction Center does have a Marginal Risk of Severe Thunderstorms highlighted across portions of northern Ohio. The timing for this risk is late Thursday night with any thunderstorms occurring along or just ahead of the cold front generally after 2 AM Friday. The wind field will be strong initially with 40-45 knots of sheer aloft. The limiting factor for thunderstorms will be instability with surface based CAPE of only a few hundred joules. Have adjusted the forecast to indicate a non-diurnal temperature trend with temperatures peaking on Friday during the early morning hours ahead of the cold front. Even without thunderstorms, some stronger wind gusts may accompany showers and there is potential for a few wind gusts of 40-50 mph.

KEY MESSAGE 2... Low pressure will continue across the eastern Great Lakes on Friday, pulling a strong cold front east across the local area. Showers will accompany the front crossing the area during the morning. Strong cold air advection will occur behind the front with 850mb temperatures falling by about 10C between 06-18Z Friday. The surface low however is not as deep as previous runs and the upper level trough remains positively tilted and elongated to the deep south as it crosses the Central Great Lakes. Mixing depths behind the front on Friday are only up to about 4K feet with winds of 30-35 knots through that depth. Wind gusts of 30-35 mph are expected through the day on Friday with temperatures falling into the 50s by afternoon.

A secondary trough swings south across Lake Erie during the evening with winds shifting from northwest to northerly. This is the window of strongest winds on Lake Erie and lakeshore areas will see winds gusting to 35-45 mph Friday night. In addition, this secondary trough will result in a flare up of lake enhanced rain showers. Coverage of showers will be fairly high for several hours then becoming focused across north central Ohio overnight as winds shift around to the north/northeast. This includes flow off Lake Huron which prolong scattered showers through Friday night and extended a low chance pop into Saturday morning for favored areas.

KEY MESSAGE 3... The coldest air of the season arrives behind the cold front. Temperatures at 850mb will range from -2 to -6C at 12Z Saturday before gradually starting to rebound over the weekend as the trough shifts east. Temperatures on Friday night will tend to bottom out in the upper 30s for inland portions of northern Ohio but may reach the lower 30s in Northwest Pennsylvania. In general expecting precipitation to fall as nearly all rain as we lose ice in the cloud aloft late tonight.

High pressure builds overhead Saturday into Saturday night which will result in a favorable radiational cooling set-up. Saturday night lows are forecast to be near freezing for much of inland northern Ohio and Northwest Pennsylvania. This may result in frost or the first freeze of the season and potentially end the growing season for some locations.

AVIATION /06Z Thursday THROUGH Monday/

A warm front is expected to lift across the area this evening. Ahead of this front, MVFR ceilings are widespread early this morning and will generally continue through midday. Ceilings will try to lift/scatter out for a time this afternoon, and do bring some sites up to a brief window of VFR. Ceilings will likely lower back to MVFR across the board this evening along and ahead of the incoming warm front. The warm front may be accompanied by some mainly light rain showers. The greater potential for showers and even some embedded thunderstorms that can bring visibility restrictions appears to be late this evening into the overnight. The warm front will lift out of the area, with a brief window of warmer and more unstable conditions ahead of a quickly approaching cold front that will cross early Friday. Guidance is quite pessimistic with widespread low ceilings (IFR or LIFR at most TAF sites) Thursday night into Friday morning, though the current TAFs lean a bit less pessimistic for now as it can be difficult to see such low ceilings in a robust warm sector this time of year.

Northeast winds early this morning will gradually shift more east-southeast through the day today, and then more south- southwest behind the warm front this evening into tonight. Speeds will generally remain 10 knots or less through today before increasing to 10-15kt with some 25kt gusts behind the warm front tonight.

Outlook...Occasional non-VFR expected to continue in periods of rain showers and lower ceilings through Friday night. Winds may gust over 30kt at times Friday afternoon through early Saturday.

MARINE

Northeast winds of 15-20 knots are expected overnight. Waves generally build to 2 to 5 feet with the highest wave heights expected from the Islands to Willowick where a Small Craft Advisory has been issued between 10 PM and 6 AM tonight.

Winds veer around to the south on Thursday evening as a warm front lifts north and southwest winds increase to 25-30 knots overnight. A strong cold front comes through in two segments on Friday, first with a wind shift to the west/northwest Friday morning, then a shift to the north with a stronger push of cold air Friday night. Backed off on winds slightly with this system with only a brief period of gales now forecast for Friday night as the strength of the low pressure system has trended weaker and farther to the east. Will still monitor trends as we are close to gale force and may still need a warning for at least a portion of Lake Erie.

Small Craft Advisories will be needed through most of Saturday as waves are slower to come down. Otherwise high pressure builds overhead for the remainder of the weekend with improving marine conditions.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...Small Craft Advisory until 6 AM EDT early this morning for LEZ144>146.