textproduct: Cleveland

WHAT HAS CHANGED

A Heat Advisory has been issued for all of northern Ohio through Saturday evening.

KEY MESSAGES

1) Heat and humidity will continue today followed by temperatures not as hot Sunday into next week.

2) Scattered chances for showers and thunderstorms expected this weekend through early next week.

DISCUSSION

KEY MESSAGE 1... The "heat dome" or upper level ridge of high pressure that has brought so much heat and humidity this past week is almost done impacting our weather across the region. We will still have some lingering heat and humidity to contend with today with highs in the upper 80s to lower 90s. Our heat index values will be around 100 degrees, especially across northern Ohio. We have extended heat headlines with a Heat Advisory for today into this evening for all of northern Ohio. High temperatures will be closer to seasonable warm levels for early July starting Sunday through early next week in the lower to middle 80s. High temperatures may creep back up into the middle to upper 80s later next week. Overnight low temperatures will be slightly more comfortable next week in the lower to middle 60s away from the immediate lakeshore.

KEY MESSAGE 2... The active storm track has shifted southward back into the lower Great Lakes and Upper Ohio Valley region thanks to the "heat dome" sliding away from our area. This means that we will see several days of unsettled and stormy weather this weekend into early next week. There is a weak mid level disturbance riding over the top of the ridge into northwest Ohio this morning with some scattered convection. The expectation is for this area of general convection to move eastward through the morning hours and weaken. It will leave out some outflow boundaries which new convection will develop around this afternoon and evening. Given the deep layer shear and some healthy downward CAPE values, there is a marginal risk for a few strong to severe storms with damaging wind gusts later today.

A weak mid level short wave trough will approach the area from the west Sunday and Monday. This trough will keep a higher chance for scattered showers and thunderstorms in the forecast through Monday. Given the very moist airmass in place with PWATs of 1.5 to 2 inches any thunderstorm that does develop will be capable of producing locally heavy rainfall. There is a Marginal Risk (Level 1 of 4) for Excessive rainfall both today and Sunday.

High pressure will build into the Ohio Valley and lower Great Lakes region Tuesday and Wednesday with lower rain chances. A broad upper level trough pattern may develop towards the end of next week over the Great Lakes region with a weak cold front moving through late Thursday. Some higher POPs will return back in the forecast by then.

AVIATION /12Z Saturday THROUGH Wednesday/

The main aviation concern remains potential for convection. Overnight convection has largely dissipated, leaving a clean slate to start the day. There is increasing confidence in scattered to numerous thunderstorms firing from interior eastern OH into interior northwestern PA after 19 or 20z this afternoon, with impacts most likely at CAK and YNG (included TEMPO groups for TSRA) and possible at MFD (PROB30) before storms drift east out of the area this evening. More isolated activity is possible farther west this afternoon and evening, but confidence is lower so maintained a PROB30 group for TOL and FDY. Potential for TS impacts to CLE and ERI is non-zero this afternoon but is below 30%, precluding a TAF mention at this time. Did include VCSH at CLE to hedge a bit, as it's possible any afternoon thunderstorm development isn't too far south/east of the field. Additional showers and perhaps some thunder will try spreading in from the west overnight...for now, have a rather benign -SHRA mention at TOL, FDY, MFD and CLE late tonight into early Sunday. Some non-VFR mist may develop late tonight, but confidence in a period of clearer/calmer conditions is currently too low to include in TAFs outside of YNG and CAK.

Winds will start south-southwest today, but will shift more westerly through the afternoon and even gain a northerly component closer to Lake Erie. Winds will increase to 6-12kt during the day. Some stronger thunderstorms can produce brief and sporadic wind gusts over 40kt this afternoon and evening.

Outlook...Weak low pressure and a cold front move across the region Sunday and Monday, bringing occasional showers and thunderstorms. Non-VFR ceilings and visibility also possible Sunday night into Monday.

MARINE

West-southwest winds of 5-10kt this morning shift a bit more west-northwest this afternoon and evening as a weak cold front crosses the lake. Winds gradually turn east-northeast tonight into Sunday, and increase to around 15kt Sunday afternoon and evening as weak low pressure approaches from the west. Winds then persist out of the northeast early this week as low pressure slowly tracks through the upper Ohio Valley. High pressure builds in towards midweek. The current forecast keeps winds in the 10-15kt range and waves in the 1-3 foot range Sunday night through Monday night. Some guidance suggests a period of winds to around 20kt is possible Sunday night into Monday as low pressure makes its closest pass. If these trends continue we will need to nudge the wind and wave forecast up, and may get close to needing Small Craft/Beach Hazards headlines between the Islands and Willowick for a period of time. Any thunderstorms over the lake over the next few days can bring briefly higher winds and waves.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Heat Advisory until 8 PM EDT this evening for OHZ003-006>014- 017>023-027>033-036>038-047-089. PA...None. MARINE...None.