textproduct: Cleveland

WHAT HAS CHANGED

Eastern Ohio and Northwest Pennsylvania have been placed under a Marginal Risk (level 1 of 5) for isolated damaging winds with any stronger thunderstorms through this evening.

KEY MESSAGES

1) Isolated to scattered thunderstorms are possible through this evening, with isolated damaging winds possible with any more intense storms that are able to develop.

2) A brief period of quiet weather tonight and Sunday.

3) An unsettled weather pattern with multiple chances for thunderstorms is expected Sunday night through Wednesday. There will be some risks for severe weather, along with potential for heavy rainfall and flash flooding due to the repeated rounds of storms. There remains lower confidence in the exact timing, placement, and severity of storms early this week.

4) A cooler and drier pattern is favored to end the week.

DISCUSSION

KEY MESSAGE 1... As of 3 PM, a cold front extends from extreme Southeast MI and across Northwest OH. This front will sweep southeast across the forecast area through this evening. There is also a lake breeze boundary evident near the Lake Erie shoreline, especially northeast of Cleveland.

Isolated to scattered thunderstorms are expected to gradually evolve along the cold front as it sweeps across the area. We may also see a few showers or storms develop across southern portions of the area ahead of the front on the nose of higher theta-e air trying to advect in from the west-southwest, along with along the aforementioned lake breeze.

Warm and dry mid-levels, along with rather weak large scale forcing, are negatives for storm development and have led to activity being slow to get going so far. Jet support modestly improves after 5 PM as a very subtle shortwave progresses across the southern Great Lakes, so do expect coverage and intensity of showers and storms to increase at least somewhat into this evening as the front progresses east across the area. Activity should exit to the southeast between 9-11 PM with the front. Overall, POPs range from 30-60% across the area this evening, mainly in the 30-40% range but briefly higher across the Wooster/Akron-Canton/Youngstown areas.

Weak shear and the warm/dry mid-levels will make it difficult to see organized/intense thunderstorms this afternoon and evening. However, steep low-level lapse rates, moderate to strong MLCAPE, and strong DCAPE can support a few microbursts/downbursts if any more intense storms can play out. Confidence is low-medium.

KEY MESSAGE 2... A cooler and drier airmass briefly moves in for tonight and Sunday behind the front. There may be some patchy radiational cooling fog in the "usual spots" early Sunday morning. Otherwise, Sunday is expected to be rain-free until very late. Highs will again be well into the 80s on Sunday, but dew points will be about 10 degrees cooler than today.

KEY MESSAGE 3... The much-anticipated active pattern (some may call it a "ring of fire") is still on track beginning Sunday night. The pattern favors repeated rounds of storms with risks for both severe weather and heavy rain/flash flooding across the region through the first half of the week...however, would like to state quite clearly that these types of patterns feature plenty of uncertainty regarding the exact placement and severity of storms, as each round of storms will modify the environment and lay down boundaries that affect subsequent rounds. So the advice at this time is to be prepared for unsettled weather through the first half of this week, including potential for severe weather and flash flooding, but to continuously check back for updates as it's currently too early to have confidence in the details.

Aloft, ridging will be in place from the Rockies east across much of the South, with a modest trough over the Northeast. This will put our area beneath a band of enhanced west-northwest flow aloft for the first half of the week. At the surface, this evening's front will lift back north as a warm front Sunday night and Monday, waiver across the southern Great Lakes through Tuesday and into Wednesday, and finally push back south of the area late Wednesday or Wednesday night. Clusters of storms will be favored near and just south of the front, with some tendency in these types of regimes for clusters of storms or MCSs to dive south of the front into the deeper instability. The forecast has elevated chances for rain and storms for several periods beginning Sunday evening or night across the area, though in reality storm chances will be occasional from late Sunday through Wednesday with a combination of various shortwaves and daytime heating modulating when risks are higher or lower.

With the caveat that uncertainty increases farther out in time, current consensus has a few potential window of elevated rain and storm chances. An initial, weakening cluster of storms will attempt to spread in from the west-northwest Sunday evening into Sunday night. There is greater confidence in another cluster spreading in late Sunday night or early Monday. Beyond that, there's decent confidence in the next window for storms to develop or move in will be late Monday and Monday night. Confidence decreases too much to identify additional windows with much resolution, but the front is not expected to sweep south until Wednesday or Wednesday night, so the forecast maintains elevated storm chances Tuesday into Wednesday.

South of the front, a combination of a very warm and humid airmass beneath somewhat steeper mid-level lapse rates will support moderate to strong instability Monday through Wednesday. This will couple with moderate deep-layer shear to support risks for organized/severe convection. Precipitable water values increase to 1.50-1.90" Sunday night through Wednesday. That is not extreme, but still can support more efficient rain-rates and eventually a risk for flash flooding where training or repeated rounds of storms occur. This is overall a setup that can support impactful convective hazards (mainly in the form of damaging winds, potentially widespread, and/or flash flooding) across the broader region. However, there's lower confidence in the exact timing and placement. Currently, it appears that any storms between Monday afternoon and Tuesday evening would have the greatest overall risk to be severe and/or produce excessive rainfall across the local area.

The main "fail mode" with a setup like this is clusters of storms continuously diving southward into the deeper instability and largely remaining just to our west/southwest. This could limit how much instability can advect into the local area and end up focusing activity farther west/southwest than modeled. Currently, most guidance suggests we'll be able to lift the instability axis into at least parts of our area by Monday night, though trends will need to be monitored. Overall, the northeast end of our area has lower confidence in seeing heavy rain or severe weather than locations farther west/southwest.

KEY MESSAGE 4... A trough and surface high pressure are expected to build into the Great Lakes and New England Thursday into Friday, bringing a period of cooler and drier weather to end the week.

AVIATION /06Z Sunday THROUGH Thursday/

As a cold front exits to the east, high pressure will build over the area allowing for dry conditions for much of the period. As this system enters, skies are clearing and will remain generally clear through this evening. With residual moisture in the region, some MVFR visibility may develop at terminals that had rain on Saturday and can decouple before sunrise. There will be a chance for MVFR at all terminals but KCLE and KERI and have TEMPO groups in the TAFs.

For the end of the TAF period, the first in a series of systems will reach the area bringing increasing cloudiness before showers and storms arrive to the region. The only terminal with a chance for any TS is KTOL and have a VCTS there. Otherwise, will need to refine storm timing and aviation impacts in later TAF packages.

Winds through the period will be light and generally southwesterly.

Outlook...Periods of non-VFR conditions are expected through Thursday as several rounds of scattered showers and thunderstorms move across the airspace. Some storms could be strong to severe during this timeframe, especially on Monday.

MARINE

Northwest flow is present over the lake this morning with a cold front exiting the region. High pressure will briefly build over the lake today and flow will shift to the southwest by this afternoon. For tonight through Wednesday, the weather pattern appears fairly unsettled with several weak low pressure systems moving over or just south of the area. These systems will allow for southwest to west flow to persist through the middle of the week and will bring periodic shower and storm chances. There may be some marine headlines needed with the storm chances over the lake. A cold front will cross the area by Thursday and high pressure will build into the region toward the end of the week, allowing for northwest flow to take over. There could be some 2 to 3 ft waves with the cold frontal passage, which may lead to a brief moderate swimming risk.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...None.