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 /00Z Wednesday THROUGH Sunday/

The main concern for aviation weather and possible impacts to area terminal will be the potential of several rounds of scattered convection over the next couple of days. There is some uncertain on timing and what areas may be impacted. The next round of showers and storms that we will be watching will come in late tonight through early Wednesday morning, mainly affecting NEOH and NWPA between 08z and 13z. We have mentioned PROB30 groups at CLE, YNG, and ERI for that potential of brief MVFR/IFR conditions with the heavier convection. Otherwise, the rest of the area will stay VFR with scattered to broken high and mid level clouds passing through during the next 24 hours. Additional scattered convection may develop again towards the end of this TAF window later tomorrow afternoon or evening for NEOH and NWPA but uncertainty remains on the timing and location at this time. Winds will be from the south and southwest 5 to 10 knots with a few gusts up to 20 knots during the midday and afternoon hours on Wednesday.

Outlook...A "backdoor" cold front will slowly move across the area from the northeast towards the southwest on Thursday. Scattered showers and storms may bring non-VFR conditions and impacts Wednesday night through Thursday night. High pressure and fair weather will return Friday 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.