textproduct: Cleveland

WHAT HAS CHANGED

Trended high temperatures up a degree or two for today and Tuesday in central and eastern portions of the area. The Marginal Risk for Severe Thunderstorms has been expanded across northern Ohio into Northwest Pennsylvania for this evening.

KEY MESSAGES

1) The hottest temperatures of the year arrive today and continue on Tuesday. The heat will break behind a cold front on Wednesday with below normal temperatures continuing into Thursday.

2) A few strong to severe thunderstorms are possible in Northwest Ohio and across the northern counties this afternoon and evening. The potential for severe thunderstorms returns on Tuesday afternoon with greater coverage of storms expected. Damaging wind gusts to 60 mph and hail are the primary concerns with severe thunderstorms.

3) Unsettled conditions are expected heading into the holiday weekend.

DISCUSSION

KEY MESSAGE 1... The local area resides in the warm sector today with a ridge over the Appalachians and 500mb heights of 585dm. A southwesterly pressure gradient supports warm advection with 925mb temperatures reaching 24-25C. Winds are expected to gust to 20-25 mph in the east and up to 30 mph in the west which will help to mix out dewpoints and keep humidity/heat index values in check. The high temperature forecast was raised by 1-3 degrees from north central Ohio into Northwest Pennsylvania for this afternoon with highs expected in the upper 80s to near 90 degrees and heat index values only running about a degree higher. With that said, this is the first near 90 degree day of the season and people will likely feel the effects of heat more easily. Several climate sites are forecast to be within a degree or two of record values(see the climate section below). The temperature forecast for Tuesday is a little more tricky as we have to contend with increasing cloud cover and higher chances of precipitation during the afternoon. Dewpoints also trend up closer to the mid 60s so humidity will be more noticeable. Due to the increasing clouds and moisture, temperatures will likely top out a couple degrees lower than Monday but heat index will be virtually the same.

The brief bout of near record highs will abruptly end on Wednesday behind a strong cold front. 850mb temperatures fall by 11-12C in 24 hours with a northwesterly flow off the lake. High temperatures are forecast to be 20-25 degrees cooler by Wednesday and remain cool on Thursday. Temperatures do gradually trend warmer heading into the holiday weekend but will be impacted by chances for precipitation.

KEY MESSAGE 2... Convection is ongoing this morning from the Upper Peninsula of Michigan extending southwest to Iowa ahead of low pressure located over western Wisconsin. A moist and unstable airmass advances eastward into the Central Great Lakes today as the trough over the Great Basin shifts east into the Plains states. Leading shortwave energy across northern Wisconsin tends to weaken while another shortwave is expected to move across Indiana and western Ohio later today. While we start the day capped, mixed layer CAPE of 800-1100 may sneak into northwest Ohio late this afternoon ahead of the shortwave which comes with increasing shear values. The better lift skirts Lake Erie and the lakeshore counties into this evening and may have to monitor for a few stronger storms moving east from Toledo towards Erie in the 4-9 PM window. While activity is generally expected to dissipate for the overnight hours, a moist and weakly unstable airmass resides overhead tonight so kept a low pop in the forecast through Tuesday morning.

On Tuesday surface low pressure is forecast to move northeast across Lake Superior with a cold front extending south through the Central Great Lakes. A pre-frontal trough with moderate instability moves into NW Ohio during the afternoon on Tuesday. Expecting good coverage of showers and thunderstorms to develop west of the I-71 corridor during the afternoon with around 2000 J/kg of ML CAPE and 20-30 knots of bulk shear. Thunderstorms will continue eastward through the evening. This looks to present a scattered wind and hail threat for Tuesday afternoon and evening from about 2-10 PM. Storm relative helicity values are slightly higher in the northeast with good veering of the flow with height and the Storm Prediction Center has included a low end tornado threat for that area.

Rain will linger along the cold front Tuesday night into early Wednesday with a drying trend through the day on Wednesday as broad high pressure expands south of Lake Erie.

KEY MESSAGE 3... Confidence in pattern evolution is low heading into the upcoming holiday weekend. Models depict southwesterly flow and moisture advection later Friday into Saturday ahead of a trough approaching from the Plains and a ridge along the East Coast. This will likely result in an unsettled pattern with periods of showers and thunderstorms. Timing is difficult this far out but could see the first round of precipitation Friday night into Saturday then additional precipitation possible later in the day on Sunday.

AVIATION /12Z Monday THROUGH Friday/

Mainly VFR expected for the TAF period but with some convective potential. Convection will likely develop to the west this afternoon and spread towards TOL and FDY early this evening before weakening. Have a window of -SHRA with a TEMPO for TSRA with gusty winds and more significant restrictions at TOL and FDY early this evening. It is uncertain how far east thunderstorms will get before dissipating, so included a PROB30 as far east as CLE and MFD for lower confidence potential. Once thunderstorms dissipate this evening, a decaying batch of lighter rain showers may continue east-northeast for a few more hours. Outside of convective potential, afternoon cumulus will likely produce a SCT sky around 040-050 at times today.

Winds are generally 5-10kt out of the south early this morning. Winds will shift south-southwest and increase to 12-18kt with gusts to around 25kt late this morning into this afternoon. Winds lose their gustiness tonight. There is low-level wind shear potential tonight beneath a 40kt low-level jet, especially across Northwest OH. For now included LLWS tonight for TOL and FDY where the strongest jet will be oriented. The low-level jet is marginally strong and timing of the surface decoupling is uncertain, so didn't include farther east yet.

Outlook...Non-VFR likely at times in showers/thunderstorms Tuesday into Wednesday. Non-VFR possible in showers on Friday.

MARINE

South winds are slightly elevated at 10-15kt early this morning and will continue today. Gusts up to 25kt are possible in the nearshore waters west of Cleveland this afternoon. Thunderstorms may reach western Lake Erie this evening, and could pack brief wind gusts over 35kt before dissipating while tracking east. Otherwise, southerly winds will remain slightly elevated at 10-15kt tonight into Tuesday. Winds increase a bit further to 15-20kt Tuesday afternoon, with gusts potentially up to 30kt in the nearshore waters west of Cleveland. Small craft headlines remain possible for Tuesday. There is additional thunderstorm potential spreading from west to east Tuesday afternoon and evening along and ahead of a cold front, again with potential for storms over the lake to pack strong wind gusts over 35kt.

Winds whip around to the north late Tuesday night into Wednesday behind the cold front, and gradually shift more northeasterly Wednesday into Thursday and more easterly for Friday. These winds are currently forecast to be around 15kt which would bring choppiness, but there is a chance winds trend up closer to 20kt Thursday into Friday, which could warrant some small craft/beach hazards headlines.

CLIMATE

High temperatures today and Tuesday will approach record values. The following are the records for May 18 and 19 at local climate sites.

Date Toledo Mansfield Cleveland Akron Youngstown Erie 05-18 95(1962) 92(1962) 91(1962) 92(1962) 92(1962) 89(1889) 05-19 92(1996) 88(1964) 88(1998) 91(1911) 89(1934) 90(1996)

CLE WATCHES/WARNINGS/ADVISORIES

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