textproduct: Cleveland

WHAT HAS CHANGED

Confidence in the placement and timing of severe weather potential today remains low relatively low. There's a possibility of an initial round of storms later this morning into early this afternoon and any evening/overnight convection will rely on how things pan out during the day. There is also increasing concern for stronger storms and flooding Wednesday into Thursday.

KEY MESSAGES

1) Multiple rounds of storms likely today through Thursday. Storms may be strong to severe at times, best chance this evening into tonight and on Wednesday afternoon/evening.

2) Multiple rounds of moderate to heavy rain may result in flooding, especially on Wednesday.

3) Above normal temperatures expected through Saturday with cooler temperatures returning towards the end of the weekend.

DISCUSSION

KEY MESSAGE 1... Unsettled weather with periodic showers and thunderstorm complexes are expected through Thursday as a frontal boundary wavers to the north of the local area and a series of shortwaves move across the boundary. Given the lack of forcing with the best upper level support to the north of the area, convection over the next couple of days will rely on mesoscale features and the resulting confidence in timing, placement, and strengths of storms remains low at this time.

Round 1 (Early Today): The actual first round of storms has exited the area, however the upstream convection over southern Wisconsin and Michigan will need to be monitored through this morning. It's possible that the overnight convection has left some lingering boundaries across the area so will need to keep an eye on the potential for enhanced convergence as this weakening convection moves in. It's possible that the atmosphere is still stabilized due to lingering cloud cover and a mid- level cap, but some elevated instability remains in place. Either way, will need to keep an eye on the potential for elevated storms that could produce gusty winds and hail this morning into this afternoon.

Round 2 (This Evening/Tonight): The severe weather potential later this afternoon into tonight will depend on how the early- day convection pans out. Early-day convection may help stabilize things later this evening. On the other hand, the convection could leave behind boundaries and a source for convergence for evening convection maintenance and growth. Additional convection will move in from the northwest this evening into tonight, although there is some potential for scattered showers and storms developing out ahead of the main line of convection at some point early to mid evening. There's quite a bit of disagreement in the forecast amongst CAMs, but overall confidence in the potential for precipitation in general is high for tonight. Despite the unfavorable diurnal timing, relatively high shear values due to a 50 knot LLJ moving into the northern portion of the CWA and deep moisture will result in a favorable environment for thunderstorm maintenance. With this round, damaging wind gusts will be the primary hazard but large hail and a few tornadoes cannot be ruled out given the wind field and lapse rates. Generally expect a weakening trend as the storms move into the area overnight. If stability stays in place, it may be more of a heavy rain scenario (see Key Message 2). There is a Slight Risk (level 2 of 5) of severe weather across northern Ohio with a Marginal Risk (level 1 of 5) over the remainder of the local area.

Round 3 (Wednesday): The air mass will change very little on Wednesday and if anything, moisture will increase and forcing may increase slightly as the aforementioned frontal boundary sags a bit further south. Moist and deep west/southwest flow will likely produce sufficient destabilization for scattered showers and storms on Wednesday and CAMs suggest that yet another complex of storms will traverse east across the local area Wednesday afternoon into Wednesday evening. As with previous days, damaging wind gusts and hail will be possible in these storms, although the severe weather threat will depend on mesoscale features that have not yet been resolved. There is a Slight Risk (level 2 of 5) of severe weather across interior NE OH and NW PA with a Marginal Risk (level 1 of 5) elsewhere.

Round 4 (Thursday): Additional showers and storms are possible as a cold front pushes east across the local area Thursday into early Friday. Instability may be a bit lower during this timeframe, but the upper level support will allow for potential for organized convection ahead of or along the cold front. There is a Marginal Risk (level 1 of 5) for severe weather on Thursday.

A brief break in convection is expected on Friday, but showers and storm chances return on Saturday as a cold front approaches and moves east across the region. Will need to keep an eye on potential for organized storms on Saturday in the upcoming days.

KEY MESSAGE 2... Moderate to heavy rainfall rates will accompany thunderstorms through Thursday. The deep, moist west/southwest flow will produce precipitable water values between 1.2 and 1.5 inches (possibly higher at times) through early Thursday. To add some context for how unseasonably high these PWATs are, the 90th percentile for PWATs at surrounding upper air sounding sites for mid-April are generally under an inch with daily maxima of up to about 1.25 inches. Storms should be relatively progressive today into tonight, although the efficient rainfall rates and multiple opportunities for storms could cause some rises on rivers/creeks/streams and cause some minor flooding issues in urban/poor drainage areas. Any precipitation today and tonight will help prime waterways and soils for additional precipitation on Wednesday. As of early this morning, 1-hr FFG values across the area are generally up to 1.5 inches (with locally higher values up to 2 inches) with 3-hr FFG values of generally 1.75-3 inches. Expect these values to decrease with any heavier rainfall this evening/tonight. There's also some potential for backbuilding/training Wednesday into Wednesday night, which would increase flooding concerns for localized areas. Confidence in QPF (especially axes of higher QPF values) is low and will depend on where storms occur, but several CAMs have at least 1 to 2 inches of QPF across portions of the area through early Thursday with locally higher amounts possible where repeated rounds of rain occur.

KEY MESSAGE 3... Persistent warm air advection will result in well above normal temperatures through Saturday. Instead of normal lower 60s for highs, highs will be in the 70s with lower 80s possible in areas that clear out a bit today and Wednesday. Cooler temperatures may materialize with persistent cloud cover and precipitation. It will be quite muggy thanks to dew points in the lower 60s. Temperatures will temporarily moderate to below normal values in the 50s Sunday and Monday, but guidance favors a warming trend by the middle of next week.

AVIATION /12Z Tuesday THROUGH Saturday/

Active stretch of weather expected through the TAF period with multiple possible rounds of thunderstorms, some strong to severe possible. The first round of showers with some embedded thunder will enter from the northwest this morning. Guidance has trended a bit earlier so have -TSRA or -SHRA begin ~12Z and exit this afternoon ~18Z. Have timed out impacts to terminals with the initial round of convection using PROB30 groups across western terminals and TEMPO groups for -SHRA across eastern terminals. The development on the next round of thunderstorms may hinge on what occurs this morning and early afternoon. As of right now, these thunderstorms will develop along and east of CLE around 03Z/Wed with a stronger area of thunderstorms pushing southward across Lake Erie starting at ~04-06Z/Wed. For the TAF, opted for a PROB30 group at all TAF sites for the evening/overnight possible convection. Strong to damaging wind gusts and IFR/MVFR reductions to cigs/vis will be possible in any stronger thunderstorm that moves over a terminal in this later timeframe.

Elevated southwesterly winds 12-18 knots with gusts 20-30 knots will remain in place through this evening. Highest wind gusts will occur this afternoon and in any convection. Winds shift southerly tonight and diminish to 10 knots or less through the overnight hours.

Outlook...Periods of non-VFR conditions are expected in showers and thunderstorms through Thursday.

MARINE

Southerly to southwesterly winds remain elevated between 15-20 knots through today. Given the offshore component, the highest wave heights will remain across the open waters of Lake Erie. Southerly to southwesterly winds 12-18 knots will remain across the lake through the end of the week as multiple systems move through the region. Periodic shower and thunderstorm chances will be present through Thursday.

CLE WATCHES/WARNINGS/ADVISORIES

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