textproduct: Cleveland

WHAT HAS CHANGED

Main focus for storms is trending slightly earlier than previous forecasts while the main cold frontal passage may be later into Thursday at this point.

KEY MESSAGES

1) Storms to fire ahead of a cold front this afternoon into early tonight with a severe potential.

2) High pressure for the end of the week and into the early weekend, but turning unsettled again Sunday through early next week.

DISCUSSION

KEY MESSAGE 1... Dewpoints will surge into the lower 70s today adding to the surface based CAPE for the region with a prefrontal trough that will also be working its way into and through the CWA. Meanwhile, a weak upper level trough axis will also track into the area from the west, aiding in the formation of a subtle surface low moving through northern Ohio towards western Pennsylvania later this afternoon. As convection fires, development of this surface low could aid in enhancement of it and/or add to additional areal coverage heading into the evening hours for the eastern CWA. Off the surface, low level jet enhancement also occurs after 21Z today while 0-6km shear increases to 45-55kts in this setup, supporting line segment/QLCS formation. Models also continue to show a dry layer of air between around 600-650mb with the CAPE stretching into and above this layer, adding a mechanism to enhance downdrafts and a damaging wind threat coupled with the low mid level flow in place. Going back to the aforementioned surface low development, this adds a backing element to the surface winds and adds to the low level helicity variable, so isolated tornadoes cannot be ruled out. As the convection exits overnight, another upper level trough axis digs into the southern Great Lakes from the west keeping shower and storm chances going in the southern zones Thursday as the frontal boundary lingers over central/southern Ohio.

KEY MESSAGE 2... High pressure moves in for Friday into the weekend, but weakness in the upper level mass fields brings back chances for showers/storms late Saturday and through early next week as the pattern becomes more unsettled once again. Low end POPs Sunday through Monday become more numerous and greater in coverage ahead of the next cold front around the Tuesday time frame. After cooler end of the week conditions, temperatures will push back into the mid 80s by Tuesday while dewpoint Sunday through Tuesday will be back into the upper 60s to lower 70s.

AVIATION /06Z Wednesday THROUGH Sunday/

VFR across the TAF sites early this morning with deterioration to IFR possible this afternoon and evening in showers and thunderstorms well ahead of a cold front. Favored a slightly later timing for tsra impacts to TAF sites, though could see a few sites needing to be bumped up a couple of hours east of I-71 as an early round of storms may develop along residual outflow boundaries from overnight convection.

The greatest potential for strong to severe storms will be along and east of the I-71 corridor where wind gusts up to 35 knots have been introduced. Targeted higher wind gusts in the 40 to 50-knot range may be needed in future updates if confidence in direct impacts increases.

Winds will generally favor a south to southwest direction today, increasing into the 10 to 15 knot range with periodic gusts of 20 to 25 knots possible later this afternoon.

Outlook...Non-VFR possible in low ceilings/fog Thursday morning. Additional scattered showers are possible through Thursday, generally along and south of the US-30 corridor. Non-VFR may return for the weekend in isolated to scattered showers and thunderstorms.

MARINE

There will be a brief window for a lake breeze this afternoon with a east-northeast wind 5 to 10 knots and a light chop of waves around a foot. Southerly winds will increase to 10 to 15 knots tonight, becoming west-southwesterly ahead of a cold front on Wednesday 15 to 20 kts. Marine zones offshore of Cleveland and eastward will see wave of 3 to 4 feet. A Small Craft Advisory may be needed for Wednesday. A broken line of storms are expected ahead of the cold front late Wednesday. Winds northwesterly 10 to 15 knots are expected in the wake of the cold front Wednesday night through Thursday night with wave heights 1 to 3 feet. High pressure will build over the lake on Friday with light northeast winds 5 to 10 knots and waves of 1 to 2 feet.

CLE WATCHES/WARNINGS/ADVISORIES

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