textproduct: Cleveland

WHAT HAS CHANGED

The rainfall forecast has trended higher for portions of NE OH/NW PA Sunday. However, confidence in the location of the heaviest rainfall and the resulting greatest flooding risk is still relatively low at this point.

KEY MESSAGES

1) Several rounds of rain with some thunderstorms are expected through Sunday. Heavy rainfall will be possible at times with some flash flooding potential on Sunday. Isolated strong to severe storms are also possible Sunday afternoon into Sunday evening.

2) Periodic scattered rain chances and near normal temperatures are expected next week.

DISCUSSION

UPDATE... Convection ahead of the approaching surface low has organized into a QLCS across Southwest OH this evening, where several severe weather warnings have been issued. This activity appears to have peaked in intensity, and will be moving into a gradually more stable low-level airmass as it lifts towards Northwest and North Central Ohio through the late evening hours. We'll monitor the progress of these storms as they lift towards the Findlay, Marion, and Mt Vernon corridor, but in general believe the latest severe weather outlook from the SPC, which keeps probabilities just to our south/southwest, still holds tonight.

Most guidance remains in agreement that zone of low-level convergence and deformation to the north of the approaching surface low will lift into the vicinity of Northeast IN, Northwest OH, and far Southeast MI late tonight and pivot in that general area through at least Sunday morning, focusing showers with some embedded convection possible. The environment will be quite favorable for efficient rain rates in this area overnight tonight into Sunday morning. The last several HRRR runs have caught onto this feature and suggest a narrow band of 1-3" of rain is likely where this feature pivots, with locally higher amounts of potentially upwards of 5" possible with any more intense/stationary convection. Did adjust the forecast to increase rain amounts in the Toledo area through midday Sunday. Can not rule out the need for a short fused Flood Watch for the Toledo area over the next few hours if we can gain confidence in the placement of the heaviest rain and in locally more excessive rain occurring, though at this exact moment confidence is not high enough to go with one.

KEY MESSAGE 1... Low pressure will slowly shift east across the Midwest through Sunday, bringing multiple rounds of rain to the local area for the rest of the weekend. Any precipitation this afternoon into the start of this evening will be light, although rainfall rates will likely pick up as better moisture lifts into the area tonight. A few thunderstorms can't be ruled out, but severe weather is not anticipated tonight. By early Sunday morning, most spots across the area will see at least a quarter of an inch of rain with locations along and west of I-75 likely receiving up to 0.75" of rain. There are some signals for training and locally higher amounts of 1-2" along the far western fringe of the local area, although that higher precipitation axis may be to the west of the CWA. Will need to keep an eye on where swaths of heavier rain occur, but in general this initial round of rain will largely serve as a primer for heavy rainfall on Sunday.

A break in precipitation (or at least, lower coverage in shower activity) is likely Sunday morning, especially across north- central Ohio. By the afternoon, better upper level support will move over the region, allowing additional showers and thunderstorms to develop and move east through the rest of the afternoon and into the evening. This will be the window for the heaviest rainfall and likely the greatest flash flooding risk. Most of the area will receive 0.5 to 0.75" of additional rainfall Sunday afternoon/evening with some areas possibly receiving 2 or more inches of rainfall where showers and thunderstorms train. Latest guidance suggests that the highest rain amounts could fall across portions of NE OH/NW PA which would result in an enhanced flash flooding risk, but will need to see how high res models trend over the next 12-18 hours. Have opted against issuing a Flood Watch with this update since confidence in the placement of the heaviest rainfall/greatest training potential is still medium at best. Would like to see where the heaviest rain occurs tonight before making a final decision on any headlines. On Sunday, there is a Slight Risk (Level 2 of 4) of excessive rainfall/flash flooding across the majority of the local area.

There is still potential for isolated strong to severe thunderstorms Sunday afternoon into Sunday evening. Jet support will increase Sunday afternoon as the low meanders eastward into the Ohio Valley, resulting in increased shear. There's still some uncertainty with how much we destabilize given the potential for morning showers/thunderstorms. If we manage to clear out between rounds of rain then instability will be higher, but any lingering showers/clouds could result in lower instability and a lower severe weather threat. Based on the shear profile/wind field, any thunderstorms could produce damaging wind gusts and possibly a brief tornado Sunday afternoon/evening. There is a Marginal Risk (Level 1 of 5) of severe weather.

KEY MESSAGE 2... The low will finally lift northeast of the area on Monday, although persistent upper troughing will result continued chances of rain showers through much of Monday. A brief period of dry weather is anticipated on Tuesday before rain chances increase as a shortwave lifts into the region Wednesday. Scattered rain chances continue through the end of the week as an upper trough shifts east into the area Thursday/Friday. Temperatures will generally be near normal with highs in the 80s and lows in the 60s anticipated.

AVIATION /06Z Sunday THROUGH Thursday/

A mixed bag of conditions ranging from VFR to IFR is expected to impact this TAF period as a low pressure system moves east across the Ohio Valley. This morning, a broad area of showers with a history of reducing visibilities to IFR continues to push north across the area. There are scattered thunderstorms as well but given decreasing instability, not expecting any widespread thunder. In addition to the precipitation causing impacts currently, overall ceiling heights are gradually beginning to diminish to 1-3kft by the morning hours. Some terminals may see high end IFR ceilings, however confidence is fairly low given the spread in models compared to what is currently being observed.

On Sunday morning, there should be a notable pause in precipitation across the area before another round moves in for the afternoon and evening hours. Ceilings will remain in the MVFR range through the evening hours at all terminals. With this additional round of precipitation, visibilities should drop to MVFR but in well developed thunderstorms, expect IFR to LIFR visibilities given the very heavy rainfall potential. Given uncertainty in timing and placement of this second band, opted to handle much of the storm chance using TEMPO/PROB30. Near the tale end of this TAF period, conditions should begin to improve as the low pushes and showers begin to move out of the area.

Winds ahead of the surface low will be from the south-southeast at 5-10 knots with winds behind the low from the northeast at 5-12 knots. Gusty winds up to 20 knots are possible behind the low, likely impacting the far western terminals through sunset.

Outlook...Isolated to scattered showers and thunderstorms with potential for non-VFR continue Monday through Wednesday, primarily during the afternoon hours.

MARINE

Low pressure will move west to east south of Lake Erie tonight into Sunday, with winds becoming northeasterly around 10kts tonight, increasing to 15-20kts Sunday and Sunday night. Western and central basin wave heights will increase to 3-5ft Sunday night, decreasing to 1-3ft as northeasterly winds persist through Tuesday. Winds turn light and variable Wednesday with wave heights less than a foot.

CLE WATCHES/WARNINGS/ADVISORIES

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