textproduct: Cleveland

WHAT HAS CHANGED

No major changes to the forecast this morning.

KEY MESSAGES

1) After rain exits to the east through this morning, another round of widespread showers is likely this afternoon/evening.

2) Lake effect showers take over tonight into the weekend as western portions of the area dry out. Snow will mix in at times late tonight through Saturday, especially away inland. Localized snow accumulations are possible Friday night into Saturday.

3) Dry weather and slowly warming up into next week.

DISCUSSION

KEY MESSAGE 1... A compact area of low pressure is tracking through the upper Ohio Valley early this morning, and will exit to the east today. A quick-moving batch of rain accompanying this low pressure is with us early this morning, but will exit to the east-southeast through midday. Aside from some northeast flow lake effect showers which are already taking shape off the western and central basin early this morning, there will be a brief lull in rain across the area around midday.

This lull won't last long, as a sharp inverted trough axis behind the departing low drops south-southwest across the area this afternoon and evening as an embedded shortwave aloft also crosses the region. This will bring another more widespread batch of showers to the area this afternoon and evening. It will be cold and unstable enough for lake enhancement, and some showers will likely have a convective component...especially west and southwest of Cleveland. Much of the area is expected to see another 0.10-0.25" of rain during the day today (between the exiting morning rain and afternoon/evening rain). Locations just west and southwest of Cleveland will see more due to lake enhancement. Most regional and convective allowing models have a localized area of 0.50-1.00" of rain where lake enhancement is most prominent and the forecast has higher amounts in the vicinity of Erie/Huron/Lorain/Richland/Ashland Counties today, as the flow direction, increasing instability, and synoptic support from the trough suggest that there will be decent lake enhancement in that area.

Temperatures will generally settle into the mid to upper 40s by sunrise this morning and will rise no more than a couple/few degrees. If anything, temperatures will backslide this afternoon as the trough brings rain and increased cold air advection. Northerly wind gusts will also increase to 20-30 MPH late this afternoon and evening just behind the passage of the trough.

KEY MESSAGE 2... We transition to a lake effect rain/snow shower setup to end the week and start the weekend. There should be a relatively drier period with limited lake effect for several hours tonight as we see a brief period of subsidence, drier low-level air, and shear behind this evening's trough. Winds are expected to become better aligned out of a north or slightly east of due north direction heading into Friday as deeper moisture returns, allowing lake effect to re-invigorate. Once lake effect starts flaring back up into Friday it will continue in some capacity through most of the weekend. Conditions will be most favorable for lake effect late tonight through Friday night as the heart of the upper trough moves overhead. 500mb temperatures bottom out near -30C Friday into Friday night over the region, which over lake waters ranging from 12-15C provides strong and deep lake-induced instability. The mid-levels will gradually begin to dry and warm on Saturday, though that probably won't begin to significantly curtail the intensity of lake effect until Saturday night and Sunday. Lingering minor lake effect may not fully end until Monday across far Northeast OH/Northwest PA, as that's when the surface high finally builds into the region.

In terms of where lake effect will go, this will generally be a shorter fetch event with north-northeast winds tonight into Friday gradually shifting north-northwest into Friday night and more northwesterly for the bulk of the weekend. A band of precip with connection to Lake Huron will be the main feature and should take shape tonight into Friday well west of Cleveland... possibly coming onshore as far west as Ottawa County and extending towards Tiffin initially. This connection is expected to drift east into the Cleveland and Akron metro area later Friday into Friday night, and then into the more traditional primary snowbelt of far Northeast OH for the weekend. There is also a signal on multiple models for convergence along the far northeastern lakeshore to focus a more organized band into eastern Erie/Crawford Counties in PA Friday into Friday evening as well. Outside of these potentially more focused bands activity will generally be less intense and not very organized, though showers will occur at times, especially in the higher terrain directly downwind of the lake. Given the precip will be lake-driven by Friday and into the weekend precipitation chances will trend to very low values across our Northwest Ohio and Central Ohio counties. A few showers may occur across Northwest OH on Friday beneath the heart of the trough aloft. Some very low precip chances are also in the forecast farther west on Saturday, as a shortwave rotating around the backside of the departing upper trough may bring just enough lift.

Portions of the area are likely to see their first wintry precip of the season over the next couple of days. 850mb temperatures fall to -5 to -7C early Friday through early Saturday, before moderating a couple of degrees for the rest of the weekend. 1000-500mb thickness values fall to an impressive <528dam Friday and Friday night. This is cold enough to support snow, though the issue remains the boundary layer temperatures given a lack of Arctic influence and modification from the warmer than average Great Lake waters. Low temperatures will struggle to dip to freezing or below (outside of the highest terrain in Northwest PA) where flow off the lake and cloudiness occurs. The overall expectation remains that snow or graupel will mix in at times away from the immediate lakeshore from late tonight/ early Friday through at least Saturday morning, with the higher terrain of the snowbelt perhaps still seeing some flakes Saturday night into early Sunday. Precipitation will tend to be mainly rain near the lakeshore and during the afternoon hours. However, with deep cold air aloft and plenty of instability Friday through early Saturday the lake effect will be quite convective, which can cause snow or graupel to mix in through the daylight hours on Friday and even near the lakeshore at times.

In terms of any accumulations, we will primarily need to monitor the Lake Huron connection into parts of Northeastern Ohio late Friday into early Saturday. In most areas, the warm ground and "mild" boundary layer will preclude accumulations or keep them minimal and slushy. If a focused band of heavier lake effect can focus on an area for a period of time between late Friday and early Saturday there is potential for more legitimate accumulations on a localized basis, perhaps on the order of a couple of slushy inches in a narrow swath. There is uncertainty regarding both if this scenario occurs at all and where it may occur, so the current forecast just has a broad area of very light accumulations in the higher elevations of interior Northeast OH. Otherwise, some light and slushy accumulations can't be entirely ruled out during the day Friday if a more organized band of precip can impact the higher terrain east of I-79 in PA. Beyond that, the higher terrain east of I-79 will likely see lows near or a bit below freezing Friday night into Saturday morning, so even a lighter snow could accumulate a bit there into early Saturday. The airmass trends slightly milder for Saturday night and Sunday as lake effect likely loses intensity, so the odds of any accumulations Saturday night into Sunday appear lower than they are Friday night.

Highs on Friday will range from the upper 30s to mid 40s, with temperatures trending a degree or two warmer each day Saturday and Sunday but staying in the 40s. Overnight lows will generally be in the low to mid 30s across Northeast OH and Northwest PA downwind of the lake through the weekend. Locations farther southwest of the lake effect will likely see some sub-freezing lows, especially where clouds are able to clear more readily.

KEY MESSAGE 3... While it remains a bit uncertain when the last of the lake effect completely ends, there's high confidence in several days of dry, tranquil weather into next week as high pressure takes control. Temperatures will gradually moderate into next week.

AVIATION /06Z Thursday THROUGH Monday/

Rain, moderate at times, continues to expand northeast across the area as low pressure tracks across southern Ohio. In the heavier showers visibilities can drop to MVFR at times and can not rule out brief IFR but that is not expected to be the prevailing. Ceilings will lower to MVFR through 12Z and remain there through the duration of the TAF period. Rain will become more showery during the afternoon and timing will need to be adjusted. Another trough will swing south across the area between 20-00Z bringing another round of more organized showers. Some locations may see a couple hour period of IFR behind this trough on Thursday evening.

Winds will start out as northeasterly at 10 knots or less, back to northwesterly by Thursday morning with some gusts to 20 knots at times during the afternoon. Winds will set up out of the north behind the trough passage during the afternoon and evening with some locations gusting between 20-30 knots, especially near the lake.

Outlook...Non-VFR will linger across Northeast Ohio and Northwest Pennsylvania through the weekend. Some wet snow showers may also be possible Friday night into Saturday morning.

MARINE

Northeast winds 15-20kt early this morning will increase to 20-30kt this afternoon and evening as a sharp trough drops across the lake. This feature will focus lake enhanced showers as it drops across the lake, and waterspouts may be possible for a brief window with the trough passage. Waves will peak at 5 to 8 feet this afternoon and evening, largest east of the islands. High-end Small Craft Advisories are in effect for all nearshore waters of Lake Erie through at least early Friday. Winds shift more northwesterly for Friday and the weekend. Speeds may briefly dip to 10-15 knots Friday morning, before increasing to 15-25kt later Friday into Saturday. Winds should gradually weaken Sunday into early next week as high pressure builds in. We will likely need another round of Small Craft Advisories for portions of the lake Friday night and Saturday.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...Small Craft Advisory until 10 AM EST Friday for LEZ142-143-148- 149. Small Craft Advisory until 1 PM EST Friday for LEZ144>147.