textproduct: Cleveland

WHAT HAS CHANGED

Still keeping an eye on the cold front and timing, but no major changes with the thunderstorm forecast late Thursday into Thursday night this issuance.

KEY MESSAGES

1) Weak trough axis in upper level flow ahead of the cold front late Wednesday night into Thursday.

2) Thunderstorms expected late Thursday into Thursday night with a potent cold front moving through the region.

DISCUSSION

KEY MESSAGE 1... Late tonight, have POPs introduced with a weak batch of PVA in the northwest flow aloft, kicking off showers concentrated mainly south of the CWA. The northern fringe of this precipitation potential clips the CWA with low end but non-zero chances. Meanwhile, there is simultaneously a warm air advection shower component that will be moving northeastward through the CWA on Thursday expanding the low end POPs to much of the CWA. Most areas are likely dry during the late Wednesday night/Thursday time frame ahead of the cold front, but the mention of showers cannot be excluded from the forecast.

KEY MESSAGE 2... The Slight Risk Day 2 from SPC has been expanded a few counties further to the east towards the I-77 corridor of the CWA. Still looking at 50-70kts deep layer shear which will be the primary driver for the severe threat. SBCAPE has been one of the parameters in question which may take until 21Z Thursday to materialize as the low level warm layer needs to erode while an elevated mixed layer will already be in place. Cold front moves southeastward into the CWA after 23Z Thursday with the developing line of thunderstorms beginning in the northwestern zones of our area. This will be a multi threat scenario with wind, hail, and tornadic potential all possible in a high SRH environment. Along with this severe threat will be PWATs which will hit the 1.5 inch mark, and thus an excessive rainfall potential threat as well.

Cold front passes, and temperatures drop back into the 30s again with brief light wet snow as the precipitation with the cold front exits Thursday night. After another chilly day Friday, temperatures will be on the upward trend again through the weekend and into early next week.

AVIATION /12Z Wednesday THROUGH Sunday/

WNW'erly to NW'erly flow aloft and embedded disturbances affect our region through 12Z/Thurs as a surface ridge continues to exit slowly E'ward. Variable amounts of mid/upper-level cloudiness are expected in association with the disturbances. Our regional surface winds trend light and variable through ~14Z/Wed. Thereafter, S'erly to SW'erly winds around 10 to 15 knots are expected through 12Z/Thurs. The development of a nocturnal and SW'erly low-level jet of about 40 to 50 knots at/near 925 mb is expected to result in low-level wind shear region-wide after ~03Z/Thurs. Widespread VFR and dry weather persist in northern OH and NW PA for most of the TAF period. However, after ~08Z/Thurs, widespread MVFR ceilings should form and isolated to scattered rain showers may develop as the low-level jet enhances moistening isentropic ascent.

Outlook...Non-VFR with periods of rain and/or snow are expected on Thursday through early Friday afternoon. Scattered thunderstorms are possible on Thursday, especially during the afternoon through evening.

MARINE

Primarily S'erly to SW'erly winds around 5 to 15 knots are expected through Thursday afternoon as a high pressure ridge exits slowly E'ward. Waves remain 3 feet or less. A strong cold front should sweep SE'ward across Lake Erie Thursday evening and cause SW'erly winds around 10 to 20 knots to veer to NW'erly to N'erly and freshen to around 15 to 25 knots. Waves should build to as large as 3 to 6 feet and a Small Craft Advisory should be needed. Behind the front, a strong high pressure ridge should build from the northern Great Plains and vicinity through Friday. Winds should be primarily NW'erly to N'erly and ease gradually to around 5 to 15 knots by Friday evening. Waves initially as large as 3 to 6 feet should subside to 3 feet or less by sunset Friday evening.

On Saturday through Sunday, the ridge should continue to impact Lake Erie as the embedded high pressure center moves from the Upper MS Valley toward VA and vicinity. This will allow a warm front to drift generally N'ward across Lake Erie Saturday night. Accordingly, winds around 5 to 15 knots should back gradually from N'erly to SW'erly to S'erly. Waves should remain 3 feet or less.

CLE WATCHES/WARNINGS/ADVISORIES

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