textproduct: Cleveland

WHAT HAS CHANGED

Slowed down timing of showers and storms tonight with better storm potential after daybreak tomorrow. Quite a bit of uncertainty still remains in the potential for severe weather tomorrow.

KEY MESSAGES

1) Multiple rounds of showers and thunderstorms expected tonight through Tuesday. Severe storms are possible, but there continues to be quite a bit of uncertainty in timing and coverage.

2) Below average temperatures arrive mid-week before gradually returning to near normal this weekend.

DISCUSSION

KEY MESSAGE 1... As high pressure departs off the Mid-Atlantic Coast today, an upper level trough will begin to dig south across the Great Lakes region. This trough will support a deepening low centered over Ontario and will aid in the development of upstream convection in the region beginning today. Remnants of this convection are expected to move into the far northwestern counties in the CWA late tonight, where SPC currently has a Day 1 Marginal Risk (1 of 5). There remains uncertainty with how organized this convection will remain given the lack of instability during a non- diurnally favorable time, but some gusty winds up to 60 mph will be possible. By the time they move east of the I-75 corridor, expecting them to be primary rain showers and sub-severe, but cannot rule out a few isolated rumbles of thunder.

On Tuesday, the associated cold front is expected to push east across the area, acting as a focal point for additional convection to develop. Confidence is high that there will be storms given the synoptic support that this trough will provide, the tricky part is the extent and magnitude of the severe risk over the area. In the mid-levels, a vort max will push east ahead of the trough axis providing mid-level support at the same time a strong (35-45 knot) LLJ moves over the area. This coupled with dewpoints climbing into the upper 60s to low 70s on Tuesday should allow for thunderstorms development, especially east of I-75 where there is the greatest potential for destabilization to occur by Tuesday afternoon.

The tricky part about the Tuesday forecast is a result of uncertainty regarding how the decaying overnight/early morning convection will impact destabilization across the area. If cloud cover lingers longer than it is currently forecast to, then there could be less instability that develops come the afternoon, limiting the overall robustness of storms across the area and placing the axis of severe storms further to the southeast. On the flip side, if the cloud coverage clears quickly and instability quickly increases, the region could see a shift in the severe potential to include areas further west.

Opted to ride the middle ground with this forecast package with some cloud coverage lingering, but instability still increasing to over 2000 J/kg given the strong WAA and moisture expected. With all of that, SPC has maintained the Day 2 Enhanced Risk (3 of 5) for the extreme far southeastern counties and a Slight Risk (2 of 5) for the bulk of the remainder of the area with the exception of the Toledo metro area. With this setup, the favored storm mode would be a large MCC with the primary threat being damaging winds up to 70mph and potentially a few embedded tornadoes. There is a non-zero chance for isolated large hail. Will have to monitor overnight convection trends to get a better grasp on the potential tomorrow.

KEY MESSAGE 2... Behind the robust cold front that moves east tomorrow, temperatures are expected to cool quite a bit, falling well below average for this time of year on Wednesday and Thursday. Ahead of the boundary, 850mb temperatures of 17-19C will push out of the region as 850mb temperatures closer to 7-8C push south. This quick change in temperatures will result in breezy conditions and a quick shift in surface temperatures as well. Highs on Tuesday will climb into the low to mid 80s, but will struggle to get out of the low to mid 70s through Thursday with overnight lows expected to drop into the 50s. This setup may also result in lake enhanced showers impacting portions of the snowbelt given the very warm lake temperatures. As high pressure returns late Thursday into Friday, temperatures will slowly climb back to near normal for this weekend with highs expected to be in the 80s once again.

AVIATION /00Z Tuesday THROUGH Saturday/

VFR conditions are largely expected through the first half of the TAF period for most sites. There is some MVFR haze with residual wildfire smoke over Lake Erie that is extending into KERI, but should end once the land breeze develops later this evening. Winds will start southerly around 10 kts or less.

Beyond the initial VFR forecast, very low confidence forecast in the evolution of shower and storm activity after 08z Tuesday. So far this evening, shower and storm activity has underperformed in the upper Midwest, favoring Iowa and Illinois or the Upper Peninsula of Michigan, leaving Wisconsin dry. Previous guidance favored storm activity in this region developing and moving southeast through the Great Lakes into the airspace late tonight. However, activity has been slow to develop and much of the night may remain dry and have pushed back rain timing at the terminals. The question then turns to when will storms develop with the prefrontal trough on Tuesday. If there is no convection overnight, then storm potential may increase earlier in the day before exiting the region and have slightly moved up TS timing at all terminals. There could be some additional showers and storms with the cold front toward the end of the TAF period, but this is too low of confidence to include in the TAF at this time. Winds with the trough on Tuesday will be southwesterly with gusts to 25 kts and changing to the west behind the feature.

Outlook...Residual non-VFR possible on Wednesday in rain showers across the eastern half of the area.

MARINE

Conditions across Lake Erie are currently pleasant with winds around 5 knots out of the west with waves less than 1 foot. As a warm front moves south to north across the region tonight, winds will increase to 15-25 knots out of the southwest with stronger winds possible in the open waters. Waves will also build in the near shore to 3-5 feet with occasional waves around 6 feet. A Small Craft Advisory has been issued for the entire near shore zones starting at 8AM Tuesday. The zones to the west of the Islands will be in effect through 4PM, while zones to the east through Ripley, NY will be in effect through 10PM Wednesday. This is due to strong northwesterly winds behind the cold front late Tuesday that will keep winds and waves elevated. Additionally, a Beach Hazards Statement has been issued for Lorain eastward from 8AM Tuesday through 8PM Wednesday due to the potential for high rip currents. Conditions will begin to improve late Wednesday night into Thursday as high pressure builds in. Winds will be out of the north at 5-10 knots with waves less than 2 feet.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Beach Hazards Statement from 8 AM EDT Tuesday through Wednesday evening for OHZ010>012-089. PA...Beach Hazards Statement from 8 AM EDT Tuesday through Wednesday evening for PAZ001. MARINE...Small Craft Advisory from 8 AM to 4 PM EDT Tuesday for LEZ142- 143. Small Craft Advisory from 8 AM Tuesday to 10 PM EDT Wednesday for LEZ144>149.