textproduct: Cleveland

WHAT HAS CHANGED

No major changes to this forecast package and still expecting another round of convection into this evening, a strong cold front to come through Saturday, and freeze potential Sunday night and Monday night.

KEY MESSAGES

1) Convection beginning this afternoon with another severe potential through the evening hours.

2) A strong cold front with another round of severe weather expected Saturday, along with significant temperature drops behind the cold front.

3) Frost/Freeze confidence growing for Sunday night and Monday night in the chillier Canadian airmass.

DISCUSSION

KEY MESSAGE 1... Currently awaiting the erosion of a mid level cap from north central Ohio eastward at the time of this issuance, and with heating occurring, instability that results is expected to result in another round of storms. Modest low level jet exists ahead of an eastward propagating surface trough and 0-6km bulk shear remains on the higher side at 50-60kts. This will combine with the buoyancy after the mid level cap erodes for another round of storms east of I-75 with isolated severe thresholds possible. Peak window for this will be 18Z-02Z Friday with activity winding down tonight in a stabilized environment that will stretch through Friday. This thermal surface trough will bring temperatures slightly cooler by around 5F heading through the afternoon Friday.

KEY MESSAGE 2... Another warm front and a brief residence period in the warm sector for Saturday ahead of an airmass changing cold front that will track through the CWA. After a quiet Friday, this will put the region back into the threat for severe weather with increasing low/mid level flows and renewed buoyancy in the afternoon hours with dewpoints back towards the 60F mark. Cold frontal timing will be around 16Z through 23Z give or take an hour or two, and expecting line segments and mainly a wind threat. The warm sector destabilization is going to play a key role in how this evolves, however, and only in a small area of slight from the SWO D3.

KEY MESSAGE 3... In the wake of the cold front, a much more seasonably cold airmass expected to drop into the Great Lakes under Canadian high pressure, and will see 850mb temperatures that have consistently been in the upper single digits to low teens to fall into the -7C to -12C range by Monday morning. Currently have low temperatures by Monday morning to be in the mid 20s to lower 30s, and with the growing season now begun, the need for Frost and Freeze products is increasing in confidence. This could now carry over into Monday night/Tuesday morning for the eastern half of the CWA as the surface high pressure will only be getting east of the CWA Tuesday morning to allow for surface return flow. Some warm air advection off the surface in the lower levels should be enough to keep a second freeze threat out of the western half of the CWA. As the POPs exit Sunday, some wet snowflakes could fall Sunday evening for the far eastern CWA. Monday high temperatures may not get out of the upper 30s for the far eastern portions of our NW PA counties. Temperatures rebound into the 60s primarily after Monday and into mid week next week.

AVIATION /18Z Thursday THROUGH Tuesday/

At the surface, a weak trough lingers over our region before a cold front sweeps SE'ward across northern OH and NW PA between ~22Z/Thurs and ~06Z/Fri. Behind the front, a ridge builds from the northern Great Lakes through 18Z/Thurs. Our regional surface winds trend SW'erly around 10 to 15 knots ahead of the front. These winds will gust up to about 20 to 25 knots at times, especially before 23Z/Thurs. Behind the front, W'erly to NW'erly winds around 5 to 10 knots are expected for several hours before becoming light and variable. However, a Lake Erie lake breeze is expected to develop after ~16Z/Fri and impact locations within several miles of the shoreline, including KCLE and KERI.

Isolated to scattered rain showers and thunderstorms are expected along and ahead of the surface front, while scattered rain showers associated with the upper-reaches of the front should linger for roughly two to four hours after the surface front passage. Brief MVFR to LIFR should accompany showers and especially storms. Thunderstorms will be capable of producing brief and erratic surface wind gusts up to 30 to 50 knots. VFR are expected outside the showers/storms.

Lingering low-level moisture from recent rainfall and our regional surface winds becoming weak or calm should allow widespread radiation mist/fog and nocturnal stratus to develop over our region and generally from north to south between ~07Z/Fri and ~11Z/Fri. Widespread MVFR to LIFR are expected with these low clouds and mist/fog. VFR should return after ~14Z/Fri as diurnal convective mixing of the boundary layer erodes the low clouds and mist/fog.

Outlook...Periodic rain showers and thunderstorms with non-VFR are expected during the predawn hours of Saturday morning through Saturday evening. Additional periods of rain with non- VFR should occur overnight Saturday night through Sunday evening. Rain may mix with or change to scattered wet snow at times Sunday morning and again Sunday evening.

MARINE

Modest southwest flow continues across Lake Erie this morning ahead of a cold front. This cold front will allow for more shower and storm activity across the lake today before flipping light flow to the northwest tonight. Weak high pressure will enter on Friday keeping winds below 10 kts and variable. A warm front will enter on Friday night and restore southerly flow to the lake. This southerly flow will increase on Saturday ahead of a cold front and there is potential for 20 kts of offshore flow. The cold front will cross the lake on Saturday night and shift flow to the west. A trough will remain over the lake on Sunday and keep westerly winds elevated in the 15 to 20 kt range and could be enough to generate some 4 ft waves for the eastern half of the lake. There could be the need for a Small Craft Advisory. High pressure will build into the region for Monday and shift winds to the northwest and allow for them to diminish.

CLE WATCHES/WARNINGS/ADVISORIES

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