textproduct: Cleveland

WHAT HAS CHANGED

Much of the forecast remains on track with the convection tonight and 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 /18Z Monday THROUGH Saturday/

VFR conditions are currently seen across the region with a few sites seeing MVFR visibility due to smoke/haze. There maybe times through the overnight hours where visibility can drop to MVFR, though confidence is low in where and when that would happen, so opt to run with 6SM and haze through that time frame. Precipitation chances increase out west at KTOL and KFDY late tonight around 06Z and lasting through 13Z tomorrow morning. Confidence decreases in impacts to terminals to the as the precipitation will be decaying through the early morning hours. Showers and thunderstorms chances will increase mid morning through the afternoon from KCLE/KMFD, eastward with gusty winds and non-VFR conditions possible. A cold front will sweep through late in the TAF period for KCLE and precipitation chances will decrease with it.

Winds currently are light and at times variable across the region. Any predominate winds will be out of the southwest at less than 10 knots. A lake breeze will impact KCLE and KERI this afternoon, shifting winds to be out of the north through 02-03Z tonight. Winds will shift to be out of the south at less than 10 knots through 12Z. Mid-morning, winds will increase out of the south-southwest at 10-15 knots gusting up to 25 and persist through the majority of the day. Stronger gusts are possible in the afternoon, especially for terminals in eastern Ohio as thunderstorms begin to develop.

Outlook...Non-VFR likely in showers and thunderstorms through Tuesday afternoon. Some thunderstorms Tuesday afternoon may contain strong wind gusts. Residual non-VFR possible on Wednesday in rain showers across the eastern half of the area.

MARINE

Calm marine conditions are expected today, but south/southwest winds will begin to increase tonight as a warm front crosses the lake and a cold front approaches from the west. By 8 AM or so Tuesday morning, southwest winds to 15 to 25 knots (strongest winds in the open waters) are expected with waves likely building to 2 to 5 feet in the nearshore waters of the central and eastern basins of the lake. Small Craft Advisories will likely be needed during the day Tuesday and probably through much of Wednesday as flow shifts to the northwest behind the cold front. Winds will diminish Wednesday evening/night and expect much better marine conditions as winds remain below 10 knots Thursday/Friday.

CLE WATCHES/WARNINGS/ADVISORIES

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