textproduct: Cleveland

WHAT HAS CHANGED

A couple strong to sever thunderstorms are possible this evening into the overnight with large hail possible. Strong gusty winds are likely behind a cold front on Friday. A colder weather pattern will return this weekend and continue into next week with scattered chances for light snow.

KEY MESSAGES

1) A developing storm system over the Ohio Valley will bring the scattered showers and thunderstorms this evening into overnight. A couple strong to severe storms may be possible with large hail as the main threat.

2)Strong gusty winds from the West will follow the passage of a cold front Friday morning.

3) Colder and seasonable-like temperatures will return this weekend through next week along with chances for scattered snow showers.

DISCUSSION

KEY MESSAGE 1... The unseasonable mild weather over the region will give fuel to a developing storm system over the Ohio Valley this evening into overnight. There is a stalled frontal boundary that stretches from NWOH eastward along southern lakeshore of Lake Erie this afternoon. North of this boundary, temperatures are stuck in the 30s. South of this surface boundary, temps have climbed into the upper 50s and lower 60s. A developing surface low is currently over the Cornbelt region of the Midwest. This low pressure system will deepen as it track northeastward towards Lake Michigan tonight.

Our attention later this evening into the overnight will be watching the strong to severe convection that is currently developing over the lower and central Ohio Valley this afternoon. The better thermodynamics and setup for severe weather will remain southwest of our local area down closer to the Ohio River this afternoon and evening. That area of stormy weather will eventually move northeast into northern Ohio and northwest Pennsylvania late this evening through very early Friday morning. We are expecting this convection to weaken for the most part as it moves into our local area later tonight. Scattered "general" thunderstorms are very possible tonight. There is a limited or marginal threat for a couple stronger storms with large hail as the main severe weather hazard. Average QPF expected this evening through early Friday morning will be a quarter to half an inch of rainfall.

KEY MESSAGE 2... A strong low pressure system will deepen to around 988 mb by later Friday morning over central Lake Michigan. A rather strong cold front will sweep from west to east across the area Friday morning. The cold frontal passage will be around 12z for NWOH and quickly push eastward and pass through NWPA before noon. Temperatures will start off mild in the 50s Friday morning and steadily fall after the cold front passage into 30s by late afternoon and evening. Later in the Friday afternoon and evening, scattered snow flurries or snow showers will be possible as the cold air advection and wrap around moisture from the storm system pushes into the area. There will likely be a good push of gusty winds up to 45 mph with the actual cold front pushing through. Gusty west winds will follow the frontal passage through the rest of the day Friday 20 to 30 mph with gusts over 40 mph for NEOH and NWPA. We have issued a Wind Advisory for areas along and west of I-71 for strong winds of 25 to 35 mph with gusts up to 50 mph possible on Friday.

KEY MESSAGE 3... Forecast model guidance shows a big weather pattern change with an upper level trough developing over the Great Lakes and eastern U.S. this weekend into next week. This pattern with the trough over the region will bring colder but seasonable temperatures for the middle and end of February. The trough over the Great Lakes will favor colder air moving over the lakes which will develop scattered lake effect snow showers this weekend continuing through Monday night or early Tuesday. Light snowfall accumulations of a few inches could be possible for the favor Snowbelt region. High temperatures will generally be in the 30s and overnight low temperatures in the teens and 20s.

AVIATION /18Z Thursday THROUGH Tuesday/

A stationary front will sink south of Lake Erie today, as LIFR fog/stratus briefly improves to MVFR across the area. Widespread dissipation of fog/stratus south of the boundary is unlikely, however, given continued boundary layer saturation, colder surface temperatures, and little mixing. Therefore, expect to see IFR and patchy LIFR conditions return this evening.

Showers and isolated thunderstorms will develop this afternoon in the warm sector southwest of the boundary ahead of a vigorous low pressure system. Development will spread out of the MS Valley and into the OH Valley, and push the stationary front north and eastward tonight. This will increase the chance of showers and isolated, embedded thunderstorms at most terminals, with most convection elevated. Therefore, small hail and winds gusting above 30 knots are likely in stronger storms.

As this system moves through the Great Lakes, an associated cold front will sweep the region Friday, which will help bring ceilings back above LIFR/IFR thresholds by late morning. Southeasterly winds will shift southwesterly through the day, gusting above 20kts, with conditions remaining sub-VFR behind the front as well.

Outlook...This system will move near the east coast Friday night, with a weak trough lingering over Lake Erie and a ridge building to the south. Expect periods of non-VFR conditions throughout the weekend, with the snow returning Sunday and Monday enhanced by a vigorous coastal low pressure system exiting the Mid Atlantic. High pressure will build across the region Tuesday.

MARINE

Colder air has returned over the lake with a stationary front now south of the lake this morning. This colder air has taken advantage of some added low level moisture, courtesy of the initial warm frontal passage on Wednesday, and dense fog has developed on the lake. This fog will last through the morning hours and a Marine Dense Fog Advisory has been issued through Noon. Outside of the fog, the lake should stay relatively steady state with light east flow and cooler temperatures over the lake for much of the day.

For Friday, a low pressure system will advance the stationary front north again with some oomph in a 45 kt low level jet and some warm advection once again to get temperatures into the 50s. This will allow for ice to continue to weaken across the lake and strong southwest winds around 25 to 30 kts will allow for movement of the ice fields. Any ice floes will be hazardous to folks on Lake Erie and may block or close established shipping channels. People are urged to stay off the Lake Erie.

The low pressure system will weaken over the region on Saturday and southwest flow will fall to around 10 to 15 kts. A strong low pressure system will move up the East Coast on Sunday into Monday and enhance the pressure gradient of the trough over the region, allowing for 15 to 20 kts of northwest flow on Sunday and Monday.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Wind Advisory from 7 AM to 7 PM EST Friday for OHZ003-006>012- 017>020-027>030-036-037. PA...None. MARINE...Dense Fog Advisory until 4 PM EST this afternoon for LEZ142>149-162>169.