textproduct: Cleveland

WHAT HAS CHANGED

Heat indices trended a bit higher for northwest Ohio on Wednesday, with peak heat indices exceeding 100 degrees along and west of I-77. Additional Heat Advisories will likely be needed for Wednesday.

KEY MESSAGES

1) Heat indices will peak in the mid 90s to low 100s today and Wednesday, resulting in Major HeatRisk conditions (level 3 of 4).

2) Periodic showers and thunderstorms return Friday and continue through the weekend.

DISCUSSION

KEY MESSAGE 1... A closed off mid/upper-level high with 500mb heights near 600 dam will drift southeastward into the Great Lakes and Ohio Valley region today and tomorrow. This high will be responsible for upcoming heat.

For today, temperatures will reach the 90s areawide, except for near the lakeshore in Northeast Ohio and Northwest Pennsylvania where temperatures will be a bit cooler. Heat indices will be broadly in the mid to upper 90s, with low 100s more likely towards Northwest Ohio. The Heat Advisory area/time is unchanged with this forecast package.

On Wednesday, temperatures will once again be in the 90s, though maybe a couple degrees warmer in parts of Northwest Ohio and central Ohio. Humidity is forecast to be higher, contributing to more widespread heat indices exceeding 100, including areas along and west of I-77. However, it could get close to 100 for locations farther east, including the Youngstown area. Additional Heat Advisories are expected for a larger area on Wednesday. Heat indices may reach 105 heat indices in parts of Northwest Ohio, so may need to consider an Extreme Heat Warning for that area.

The upper high will gradually flatten and dissipate over the Ohio Valley through the rest of the week. A weak cold front passes south Wednesday night but it will remain hot with highs in the low 90s, except cooler closer to Lake Erie in Northeast Ohio and Northwest Pennsylvania. The cold front will bring slightly lower humidity, at least compared to today and Wednesday, which will limit heat indices to the low to mid 90s.

KEY MESSAGE 2... An upper-level trough centered over eastern Quebec will slowly drift southwestward over the weekend as the ridge weakens locally and becomes entrenched over the western CONUS. Broad northwest flow ensues in between these two features, with several shortwave troughs expected to move southwest across the Great Lakes region. At the surface, a cold front also approaches from the north, settling across the region this weekend. This setup will promote a stormy pattern, though uncertainty remains due to nature of a weakly forced setup. Model ensembles are keying in on a more pronounced shortwave moving through on Saturday, with the highest PoPs around 60-70% Saturday into Saturday night. Modest mid-level flow and instability could yield an organized severe weather threat, so this weekend is worth keeping an eye on.

AVIATION /06Z Tuesday THROUGH Saturday/

VFR conditions will be prevalent across the region with some scattered high clouds expected through the TAF period. Winds will be light and variable through 14-16Z today, then become predominately out of the west-soutwest at 5-10 knots for the remainder of the TAF period. KERI will see increased sustained winds at 10-15 knots and gusts up to 20 knots with flow being off the lake. Gusts there should diminish after 01Z tonight with sustained winds around 10 knots out of the southwest.

Outlook...VFR expected through Wednesday. Non-VFR visibility possible Wednesday night and Thursday due to wildfire smoke. Non-VFR likely starting Friday night in showers and thunderstorms.

MARINE

Conditions across Lake Erie will stay fairly quiet for the week as high pressure continues to builds into the region. Winds will be out of the southwest today at around 10 knots for the central and western basins with waves at 1-3 feet. The eastern basin open waters will see increased winds around 15-20 knots due to the southwesterly flow and waves building to 3-5 feet. The near shore zones across the lake will range from around a foot with winds at 5-10 knots in the western and central basins to 1-3 feet with winds 10-15 knots in the eastern basin.

Winds and waves will begin to subside late tonight into Wednesday, diminishing to around 10 knots and 2 feet or less by Wednesday afternoon. Light and variable winds are expected across Lake Erie from Wednesday evening through Friday night. A cold front will approach the region from the north with winds and waves building Saturday into Sunday.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Heat Advisory from noon today to 8 PM EDT this evening for OHZ003-006>011-017>019. PA...None. MARINE...None.