textproduct: Cleveland

WHAT HAS CHANGED

6:09 PM EDT May 4th Update...

Periods of isolated to scattered showers and thunderstorms are expected through daybreak Tuesday, which warranted a slight increase in POP's. Also increased forecast low temperatures slightly for overnight tonight since increasing cloud cover and persistent low-level warm/moist air advection from the Gulf are expected to limit nocturnal cooling through daybreak Tuesday morning more so than the previous forecast depicted.

KEY MESSAGES

1) Severe weather possible this afternoon into the late evening, though thunderstorms are expected to be isolated to scattered.

2) Widespread showers and thunderstorms expected Tuesday into Wednesday. Nuisance flooding possible with minor river flooding possible across the region.

3) Cooler temperatures expected the second half of the week with scatttered frost possible.

DISCUSSION

KEY MESSAGE 1...

Periods of isolated to scattered showers and thunderstorms are expected through Tuesday morning as weak to moderate CAPE, including elevated CAPE, is released by the following: moist isentropic ascent ahead of shortwave trough axes aloft, enhanced moist isentropic ascent aloft associated with the development of a SW'erly LLJ at/near 850 mb between about midnight and daybreak Tuesday morning; low-level convergence/moist ascent along surface trough axes accompanying the shortwave troughs, established downshear outflow boundaries, and along a cold front that will enter far-northwestern portions of our CWA by late Tuesday morning. Surface dew points were mainly in the mid 40's to lower 50's F as of about 6 PM EDT, but will climb to the lower to mid 50's F during the course of this evening as greater low-level moisture, originating over the Gulf, continues to overspread our region fairly slowly. SPC has highlighted a slight risk of severe thunderstorms for the area west of a roughly Sandusky to Tiffin, OH line, while the rest of our OH counties are in a marginal risk of severe thunderstorms. Trends in forecast model soundings continue to depict moderate effective bulk shear, fairly-steep mid-level lapse rates near 7C/km, steep low-level lapse rates stemming from recent diurnal convective mixing of the boundary layer, moderate DCAPE, and weak to moderate boundary layer CAPE will contribute to an environment favorable for multicell storms and perhaps a few supercell thunderstorms capable of producing marginally-severe hail and damaging straight-line wind gusts in northern OH. The severe thunderstorm threat should end late this evening, in response to boundary layer stabilization via nocturnal cooling. The potential for severe storms in NW PA still appears to be very limited since slower low-level moisture return from the Gulf should result in less CAPE, including elevated CAPE, there through this evening.

KEY MESSAGE 2...

A cold front will enter the region Tuesday morning and there will be widespread showers and thunderstorms that afternoon into the evening. There will be a brief dry period late Monday night into Tuesday morning, but rain will return from the west mid day tomorrow. The front will be slowly moving to the east and may cause some nuisance flooding and possible river rises across the region. QPF for Tuesday through Wednesday morning will is around 0.75-1.50" with amounts east of the I-71 corridor over an inch possible. The cold front will move out to the east late Tuesday night and rain will slowly end from west to east across the region.

KEY MESSAGE 3...

Behind the cold front on Wednesday, temperatures will drop to below average through the end of the week. Global models have 850 temperatures dropping down to around -2C by Friday morning. Thursday and Friday morning will be the coolest of the week, with temperatures dropping down into the mid to upper 30s with some locations down into the lower 30s. Frost potential will be possible those days, though with lingering cloud cover, may be more isolated.

AVIATION /06Z Tuesday THROUGH Saturday/

Rain will increase in coverage over the next few hours, especially across western and central terminals. This may cause some brief MVFR, but generally expect VFR with mainly light rain. Removed thunder early this morning given little to no instability in the latest analysis.

After a lull in the rain showers in the roughly 12-15Z timeframe, expect another round of rain to spread in from west to east. This will be a much more widespread and longer lasting period of rain, setting up a wet afternoon and evening with cigs and vis gradually falling to MVFR and eventually IFR. Some thunderstorms could develop on the front edge of this rain shield at KMFD, KCLE, KCAK, KYNG, and KERI, so kept TEMPO groups.

S to SW winds will gust to 20-25 knots at times this morning before gradually turning NW late this morning through the afternoon as a cold front moves through the region. Wind speeds will decrease through the afternoon, becoming NE around 3 to 5 knots by early tonight.

Outlook...Periodic rain showers with non-VFR are expected through Saturday. Occasional thunderstorms are possible Friday afternoon and evening.

MARINE

Southwest winds 10 to 20 knots are expected through early Tuesday morning. Marginal Small Craft Advisory conditions may periodically occur this evening and tonight, however confidence is too low to warrant a headline at this point. Gusty winds are possible in any thunderstorms that move over the lake this evening into tonight. Winds will shift to the northwest and diminish below 10 knots Tuesday afternoon with variable winds 10 knots or less expected Tuesday evening through Wednesday night. West/northwest winds under 15 knots will develop Wednesday through Thursday with southwest winds developing Friday into early weekend.

CLE WATCHES/WARNINGS/ADVISORIES

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