textproduct: Cleveland

WHAT HAS CHANGED

Forecast remains largely unchanged. There will be severe weather potential across the area this afternoon/evening with all hazards possible. Additional rounds of severe weather possible Thursday and Saturday.

KEY MESSAGES

1) Severe weather potential across the region continues this afternoon/evening with additional rounds possible Thursday and Saturday.

2) Multiple rounds of precipitation through Thursday night will bring flooding potential to the region. A Flood Watch remains in effect for northwestern Ohio.

3) Temperatures remain above average through Saturday evening with cooler temperatures for Sunday and Monday. Highest potential for frost/freeze will be Sunday night into Monday.

DISCUSSION

KEY MESSAGE 1... Severe weather potential continues this afternoon into the evening with additional rounds possible Thursday and Saturday as a boundary wavers through the central Great Lakes through the early weekend. See below for a breakdown for each day:

Today: Northern Ohio and northwestern Pennsylvania continues to destabilize this afternoon as ample moisture advects in from the southwest. As this occurs, MLCAPE values will rise to 1000-1500 J/kg this afternoon with low and mid-level lapse rates between 6.0-7.0 C/km. Lapse rates of those values could inhibit some thunderstorm potential. Additionally, given the southwestern surface flow, there will be decent low level and deep layer shear, especially across northern Ohio into Pennsylvania, that will support organized convection with all hazards possible to include damaging winds, hail, and possibly a tornado or two. Thunderstorms are currently getting started across eastern Indiana and western Ohio early afternoon along a boundary across that area. As this moves eastward more into Ohio, should expect to see a increase in coverage and intensity. Timing wise, the thunderstorms should enter in the western portion of the CWA by 2-3PM and traverse across exiting into Pennsylvania by 8-9PM. Another round of thunderstorms are possible late tonight after midnight with support from a shortwave moving through the region. Though, severe potential associated with those should be limited given the much lower instability and lapse rates.

Thursday: Another round of severe weather is possible on Thursday as an upper level low moves through the Great Lakes during the afternoon. Showers and thunderstorms will be in the area for the majority of the day with scattered severe potential given the continued southwesterly flow. The main threat will be in the evening with damaging wind potential as a cold front sweeps through the region. Can't rule out the possibility of a brief tornado or two along and ahead of the line, though shear values will be better during the morning to early afternoon out ahead of the best instability. The severe weather potential should begin to diminish around sunset and move out to the east.

Saturday: The next round of severe potential will be during the afternoon on Saturday as a low pressure system moves across the Great Lakes. A warm front will lift northward through the region Saturday morning with a cold front later in the evening. All modes of severe weather are possible, though the main threat will be damaging winds along the cold front as it moves through given the strong low to mid level winds.

KEY MESSAGE 2... With plenty of moisture advection across the region through Thursday night, there will be potential for moderate to heavy rainfall with the potential for flooding. Precipitable water values will be around 1.0-2.0 inches that will support rainfall rates of 1-2 inches per hour in thunderstorms. With the potential for showers and thunderstorms to continue from late this evening through Thursday night, flow will become more parallel to the boundary situated north of the area and support the potential for training storms. Generally expecting this to stay north of US Route 30. Through Thursday night, rainfall totals will be around 1-2 inches with the higher end amounts closer to the lake shore. Higher amounts will be possible in thunderstorms as well. Latest guidance has trended northeastern Ohio and northwestern Pennsylvania to receive more rainfall, though this will be dependent on where thunderstorms set up over the region so confidence is lower in this.

KEY MESSAGE 3... Temperatures through Saturday evening will continue to be above average. Highs will be in the mid to upper 70s as we continue to see southwesterly flow across the region. Low pressure will move through the Great Lakes on Saturday sweeping a cold front through that will usher in a much cooler air mass. Temperatures will drop down to 5-10 degrees below average with highs in the upper 40s to mid 50s. Overnight lows for Sunday night into Monday will be the coldest of this stretch, dropping down into the lower 30s with some locations possibly seeing upper 20s. Given the growing season as begun across Ohio, frost/freeze headlines will likely be needed Sunday night with a lower potential for Monday night. Temperatures will begin to moderate on Tuesday rising to around seasonally average.

AVIATION /06Z Thursday THROUGH Monday/

The airspace starts with VFR conditions this morning with mid- level clouds across the region. Some isolated rain showers exist with some isentropic lift across Northeast Ohio into NW PA and there could be a brief shower at KYNG or KERI. The main show for today will be an incoming cold front that will allow for another round of showers and storms across the region. Early convection in NW OH should just be rain after dawn at KTOL and KFDY. However, convection should flare up over North Central Ohio and allow for some clusters of thunderstorms to move through the remaining terminals during the afternoon hours. Have some TEMPO groups timed in across the area for the best chance of TS. Behind the front, some wrap around precipitation could allow for rain to persist for the NE OH and NW PA terminals. Clouds will erode from the west during the evening hours. However, ceilings will persist down wind of Lake Erie and may fall to MVFR as winds shift to the west and northwest with the cold air advection.

Outlook...Periodic showers and thunderstorms with non-VFR are expected Saturday with rain continuing Saturday night through Sunday evening. This rain may mix with or change to scattered wet snow at times Sunday morning and again Sunday evening.

MARINE

Lake Erie remains along the northwestern flank of a high pressure ridge before a cold front sweeps SE'ward across the lake Thursday night. Behind the front, another ridge builds from the northern Great Lakes through Friday. Ahead of the cold front, winds trend S'erly to SW'erly around 5 to 15 knots with waves of 3 feet or less. Behind the front, winds veer to W'erly to N'erly and ease to around 5 knots. Accordingly, waves subside to 1 foot or less by daybreak Friday. On Friday, variable winds around 5 to 10 knots and waves of 2 feet or less are expected. These winds should trend onshore during the late morning through early evening due to lake breeze development.

During Friday night through Saturday morning, the ridge should exit E'ward and allow a warm front to sweep N'ward across Lake Erie. Mainly E'erly to SE'erly winds of about 5 to 15 knots ahead of the warm front veer to S'erly and freshen to around 10 to 20 knots behind the front. Waves of mainly 3 feet or less are expected, but occasional 4 footers should occur in open U.S. waters of the central basin based on forecast fetch. A strong cold front should sweep E'ward across Lake Erie Saturday evening through Saturday night and allow SW'erly winds around 10 to 20 knots to veer to W'erly and freshen to around 15 to 25 knots. Waves should build to as large as 3 to 7 feet and a Small Craft Advisory will likely be needed, especially east of The Islands.

Behind the cold front, a trough should linger over Lake Erie through Sunday night and be accompanied by W'erly to NW'erly winds around 15 to 25 knots. Waves as large as 3 to 7 feet should persist. On Monday, a ridge should build from the west and be accompanied by winds becoming variable and easing to around 5 to 10 knots. Waves are forecast to subside to 2 feet or less by sunset Monday evening.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Flood Watch until 8 AM EDT this morning for OHZ003-006. PA...None. MARINE...None.