textproduct: Cleveland

WHAT HAS CHANGED

The severe weather and flash flooding potential for Sunday continues to trend slightly more favorable but will need to see how the weather today progresses before considering Flood Watches.

KEY MESSAGES

1) Several rounds of rain with some thunderstorms are expected through Sunday. Heavy rainfall will be possible at times with some limited Flash Flooding potential on Sunday. Strong to severe storms are also possible Sunday afternoon.

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

DISCUSSION

KEY MESSAGE 1... A low pressure system approaching the region today will be the culprit in producing showers and storms this weekend with heavy rainfall and strong to severe storm potential both on the table. Showers will start scattered on Saturday with the main, vertically stacked surface low remaining well west along the Mississippi River. Some mid-level vorticity advection will help support some occasional showers today ahead of the low but rainfall should be relatively light today for those that see anything. The main show will start tonight as the low advances east and additional moisture enters the region. Forecast soundings across northern Ohio show PW values over 2 inches tonight, which means that any rain that does occur will be heavy, efficient rain. Any rain that develops will be moving south to north with some speed but if recurring rain trains over the same areas, then there will be flooding concerns tonight, mainly in Northwest Ohio.

The trends for Sunday for heavy rainfall and strong to severe storms is going up with this forecast package. The low will pass to the south of the forecast area on Sunday. However, a deformation band of precipitation will be on the north side of this low, which will be well supported by the left exit region of one upper level jet and the right entrance region of another upper level jet. This broader support should allow for widespread coverage of rain across the region on Sunday with efficient rainfall rates and have a higher QPF forecast to reflect these concerns. It would not be surprising for most folks to get at least one inch of rain this weekend but recurring rain episodes for any location would open up the potential for multiple inches of rain and an increased risk for Flash Flooding. On the severe threat, the low pressure system and upper level jet support are indicative of a decently sheared environment that could allow for strong to severe storms to develop. The main concern for severe storms will be the instability. Rain and clouds across the region may limit the overall instability in the region and in turn the severe potential. However, there are hints that there could be a break in shower activity on Sunday morning, especially for the eastern half of the forecast area. If this break does materialize, then the severe potential for Sunday will continue to trend upward. The main storm concerns for Sunday will be strong to damaging wind gusts and even a low end concern for a tornado.

As of this morning, the area is delineated in a WPC Slight Risk for Excessive Rainfall for today and Sunday and an SPC Marginal Risk for Severe Weather for Sunday. There is potential for a Flood Watch to be needed across the area, depending on how the rain evolves today/tonight.

KEY MESSAGE 2... The upper trough that will move through the region this weekend will amplify Sunday night into Monday and eventually form an upper level cut off low over the Tennessee Valley. This feature will meander over the Ohio Valley next week and have enough lift to allow for daily rain chances on Monday and Tuesday. This low will get absorbed by an upper trough entering the region on Wednesday. This upper trough will support a surface trough across the region, which should allow for additional rain chances on Wednesday, Thursday, and Friday. None of the days next week will be a washout, but there will be scattered rain on the scope that could allow for a brief impact. Temperatures should be near normal in the 80s, perhaps slightly cooler if there is more rain/cloud activity on a given day.

AVIATION /06Z Saturday THROUGH Wednesday/

Scattered light showers have begun to creep into the western portion of the area, however are not causing any reduced conditions. These showers should dissipate over the next few hours as they lift north. This afternoon into the evening, showers and thunderstorms will gradually become more widespread as a low pressure system approaches the Ohio Valley from the west. Initial activity should be scattered so opted to handle any reductions in visibilities with TEMPOs or PROB30s. At any terminal impacted by these thunderstorms, visibilities could briefly be reduced to MVFR/IFR distances. Near the end of this TAF period, MVFR ceilings between 2-3kft are expected to push east and reduce conditions tonight. Highest confidence in thunder potential will be this afternoon into the evening, however models suggest some instability advecting into the area late, potentially prolonging that thunder potential.

Southeast winds tonight of 5 knots or less will gradually increase today to be sustained at 5-10 knots. Local gusts up to 20 knots are possible across western terminal through this evening. Near the end of the period, winds will gain a more easterly component but remain 5-10 knots.

Outlook...Occasional non-VFR in showers and thunderstorms tonight through Sunday night. Scattered showers and thunderstorms with potential for non-VFR continue Monday through Wednesday, primarily during the afternoon hours.

MARINE

Low pressure centered over Illinois will continue to move east today into tomorrow, moving just south of the Lake Erie lakeshore which will keep the entire basin north of the center of the system. Given the positioning of Lake Erie in relation to the low, winds today will generally be from the southeast at 5-10 knots before gaining a more east-northeast component tonight. As winds shift to this position late today into tonight they will also increase to 10-20 knots with the strongest winds expected in the western basin. This will result in waves building to 2-4 feet by Sunday morning. This period may need a very brief Small Craft Advisory, but given a bit of uncertainty in the timing of the low have opted to not issue this morning. As the center of the low shifts east on Sunday, winds will become more north-northeast and persist at 15-20 knots across the lake into Monday. This stretch of onshore flow may result in waves of 3-5 feet building across the western and central basins. With that direction as well, rip currents may be a concern along beaches in these areas. Will have to monitor future model guidance to determine the need for any marine headlines. By Monday, high pressure begin to nudge back into the area, allowing for calm marine conditions to return across Lake Erie.

CLE WATCHES/WARNINGS/ADVISORIES

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