textproduct: Cleveland

WHAT HAS CHANGED

Main change to the forecast was to expand the Heat Advisory for Wednesday to include all of Northern Ohio.

KEY MESSAGES

1) Hot and humid conditions are expected over the next few days with heat indices approaching the low 100s. Little relief is expected overnight with lows in the low to mid 70s.

2) There is potential for multiple rounds of thunderstorms tonight through Friday with daily chances for severe weather and heavy rain.

DISCUSSION

KEY MESSAGE 1... Upper level ridge persists across the eastern CONUS allowing for continued heat and humidity to impact the region through Thursday. Temperatures at 850mb remain warm in the 20-22C range Wednesday before lowering slightly into the 18-20C range by Thursday. Daily afternoon highs warm into the low 90s on Wednesday and upper 80s on Thursday. There will be little overnight relief as lows settle in the low 70s each night. Despite the potential for early morning convection, have expanded the Heat Advisory to include the remaining counties in Northern Ohio for Wednesday. Confidence in morning showers and storms remains high, however guidance continues to show rapid clearing of lingering cloud cover by late Wednesday morning. There should be enough clearing to allow for temperatures to warm and heat index values to rise into the upper 90s to lower 100s. Additionally the entire forecast area remains under Major HeatRisk (Level 3 of 4) on Wednesday. Heat lingers into Thursday but confidence is currently too low to extend the Heat Advisory beyond Wednesday night.

KEY MESSAGE 2... A series of ridge riders will continue to crest atop the upper ridge axis through Thursday. These shortwaves will provide numerous chances for showers and thunderstorms into the end of the week. Daily chances for strong to severe storms exist given amble instability (2000 J/kg MLCAPE) and favorable bulk shear (30-35 knots) in the warm and moist environment. Some of the latest CAMs have hinted at isolated showers and storms entering Northwest Ohio tonight though there is low confidence in any strong to severe storms this evening. Hi-res guidance continues to show storms pushing into Northeast Ohio and Northwest Pennsylvania before daybreak on Wednesday. strong to severe storms are likely with the early morning round, particularly where the SWODY1 Slight Risk (Level 2 of 5) exists. Primary hazards will be damaging wind gusts and large hail. Some additional isolated showers and storms will remain possible in the wake of the morning convection, mainly across eastern zones, given the continued unstable and moist environment.

By Wednesday night, a cold front will begin to push southward across Lake Erie providing another window for strong to severe storms to impact the region. There remains a SWODY2 Slight Risk (Level 2 of 5) for severe thunderstorms on Wednesday. Primary hazards in thunderstorms associated with the cold front Wednesday night will be damaging wind gusts and large hail. There is a lower chance for tornadoes. Fairly widespread showers and storms will be ongoing Thursday into Friday. The severe weather threat area shifts further south to central Ohio by Thursday as the cold front sinks southward. Trending drier by the weekend as Canadian high pressure builds over the region.

With the warm and moist environment, PWATs will range between 1.5-2 inches. Any thunderstorms that move across the region will be capable of producing heavy rainfall. Localized flooding is possible where repeated rounds of thunderstorms occur.

AVIATION /18Z Tuesday THROUGH Sunday/

Regional radars depict scattered showers extending from Lake Michigan towards NW Ohio. These showers may impact TOL at times through 20Z with a low probability of a thunderstorm. Otherwise, can not rule out an isolated shower elsewhere but the trend will be towards mainly scattered mid-level clouds until late tonight. Southwest winds may gust to 20 knots at times through 22Z.

The next window of concern will be generally after 09Z when showers and thunderstorms move northwest to southeast across Lake Erie towards Northeast Ohio and Northwest Pennsylvania. Confidence is highest at ERI but showers or thunderstorms could also reach CLE and YNG. Thunderstorms in this time frame do have the potential to be strong to severe with brief IFR conditions and a wind shift to the northwest. By mid-morning, skies are expected to scatter out with generally VFR conditions. Isolated showers/thunderstorms may be possible later on Wednesday but confidence is low at this time. Winds will tend to be 10 knots or less out of the southwest except in the vicinity of thunderstorms.

Outlook...A cold front will settle south into area Wednesday night with thunderstorms possible, especially across NE Ohio and NW Pennsylvania. The chance for thunderstorms will continue Thursday into Friday with very low probabilities lingering into the weekend.

MARINE

Southwest winds with good marine conditions are expected on Lake Erie through midnight. There is some potential for stronger thunderstorms to cross mainly the central and east half of Lake Erie in the pre-dawn hours of Wednesday which could lead to erratic wind and wave conditions. Another round of stronger thunderstorms are also possible Wednesday night as a cold front settles south.

A gradual wind shift to the north will occur by Thursday night with winds decreasing into Friday. Northeast flow over the weekend could result in some choppy conditions with waves of 3 feet or less.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Heat Advisory until 8 PM EDT Wednesday for OHZ003-006>011- 017>021-027>031-036-037-047. Heat Advisory from 11 AM to 8 PM EDT Wednesday for OHZ012>014- 022-023-032-033-038-089. PA...None. MARINE...None.