textproduct: Cleveland

WHAT HAS CHANGED

A Marginal Risk for severe weather has been introduced across Northwest Ohio for late Monday afternoon/evening. A Slight Risk for severe weather has been introduced across a majority of the area for Tuesday afternoon/evening, with a Marginal Risk farther southeast.

KEY MESSAGES

1) Temperatures will be well above seasonal averages through early this week. The warmest days will be Monday and Tuesday when highs may approach daily records at a few sites.

2) Mainly dry with lower confidence shower and storm potential both today and Monday. Higher confidence and more widespread shower and storm potential is evident later Tuesday into early Wednesday, with potential for severe weather Tuesday afternoon and evening.

3) Drier and much cooler weather spreads in Wednesday and Thursday. Rain chances gradually return to the forecast Friday and Saturday, but with low confidence in the details that far out.

DISCUSSION

KEY MESSAGE #1:

Broad and prolonged deep-layer southwesterly flow has taken hold for the second half of the weekend and will continue through Tuesday, supporting well above-average temperatures. Today will be the first notably warm day, with highs in the low to mid 80s. Coverage of convection should be limited enough today to allow for a more uniform warm day than on Saturday. Monday appears to be the warmest day overall, with highs expected to range from the mid 80s to near 90. Tuesday will be nearly as warm as Monday, but temperatures aloft will cool just a touch, which along with likely some more clouds and greater afternoon convective potential keeps the forecast a bit cooler than Monday...still into the mid to upper 80s. Overnight lows tonight will range from the low to mid 60s inland to the upper 60s closer to the lake and in the more urban Cleveland metro...lows Monday night will only dip into the mid to upper 60s inland and stay in the upper 60s/lower 70s closer to the lake, especially in and around the Cleveland area. Even with the cooler lake, we typically see the mildest overnight lows in the lower terrain closer to the lake with southerly winds. Dew points will generally be in the low to mid 60s during peak heating hours today and Monday, which won't be enough to add much if any "heat index". Dew points creep up a bit more into the mid-upper 60s on Tuesday, so it will feel more humid.

Those who work outside or don't have adequate cooling will want to be ready for the much warmer temperatures Monday and Tuesday. Heat index values will be well shy of our 100 degree advisory criteria, but early season heat can have greater impacts. This is highlighted by the NWS Heat Risk product highlighting the area in moderate to borderline major risk for heat-related impacts.

KEY MESSAGE #2:

We are starting dry today. A weakening vort max is tracking to our south across the Ohio Valley early this morning, and should continue shearing out and drifting east as heights rise. Still, daytime heating will yield moderate and uncapped instability by this afternoon. Can't rule out some convection trying to fire across our southern counties as the vort max continues to pass just to our south through this morning as has been seen across southern Ohio, and from near the western lakeshore east across Northeast OH and Northwest PA this afternoon. Confidence in this convection occurring is not high with minimal forcing in the face of rising heights, with the forecast generally maintaining a 20-30% mention across parts of the area for it. If we do see any convection develop today it will quickly dissipate this evening with the loss of heating.

Monday will be another mainly dry day, with some convective potential during the afternoon and evening. The main focus will be Northwest and North Central Ohio late Monday afternoon and evening, as convection will fire to our west Monday afternoon and may push in before weakening. A weak shortwave moving across the central Great Lakes late Monday and Monday night may add enough lift to assist in carrying convection that develops upstream into Northwest/North Central Ohio. Can not rule out isolated convection Monday afternoon across eastern OH and into western PA where a pool of deeper moisture and greater instability is hinted at on several models, but confidence here is currently too low (<20%) for a forecast mention. A Marginal Risk (level 1 of 5) for severe weather has been introduced across Northwest Ohio for Monday afternoon/evening, driven by potential for damaging winds and perhaps isolated hail. This risk is supported by moderate instability and well-mixed low levels supporting downbursts and gusty outflow winds, and just enough flow farther west for storms to organize into multi-cell clusters. Convection should quickly wane Monday night, but with a shortwave passing just to our north the forecast hangs onto a low chance for some rain across Lake Erie and our northern counties overnight.

The main potential for convection out of the next few days will be Tuesday afternoon into Tuesday night. The cold front will approach Tuesday evening and cross from northwest to southeast Tuesday night into early Wednesday. Forcing will not be tremendously strong as a potent shortwave passes through the upper Midwest and northern Great Lakes, but will be greater than prior days thanks to the approaching cold front. There's good agreement in uncapped and moderate to strong instability developing Tuesday afternoon across the area due to strong heating of a warm and moist airmass, with modestly stronger flow aloft fostering up to 30kt of effective deep-layer shear.

Generally expect convection to fire along and ahead of the cold front approaching from the northwest Tuesday afternoon and spread in late Tuesday afternoon and evening. More isolated activity may develop farther east during the peak heating hours, though forcing that far ahead of the front will be minimal so confidence is lower. Convection should gradually lose intensity after sunset, though most of the area should see some showers and thunder as the front progresses through. The SPC has placed a good portion of the area, west of approximately an Ashtabula to Mansfield line, in a Slight Risk (level 2 of 5) for severe weather, with a Marginal Risk (level 1 of 5) farther southeast. Damaging winds are expected to be the main concern. Deep-layer flow will be parallel to the approaching front with precipitable water values climbing to near or above 1.50", above the 90th percentile of climatology for mid-May. This could support localized training convection with a heavy rain risk too.

KEY MESSAGE #3:

Shower potential exits to the southeast on Wednesday as the cold front exits. High pressure builds into the Great Lakes and Northeast later Wednesday and persists through Thursday, bringing cooler and drier conditions locally. A more unsettled pattern likely returns for the end of the week or weekend as a subtle trough digs into the central U.S., with ridging aloft focused off the East Coast. However, guidance disagrees considerably on the timing and intensity of any systems that move through the more active flow locally, with some guidance also taking longer to displace the aforementioned high pressure as well and keeping us drier. Overall, after below average temperatures for Wednesday and Thursday a warming trend is expected to begin on Friday. Rain chances gradually return to the forecast Friday into Saturday, though will need refined in the coming days.

AVIATION /12Z Sunday THROUGH Thursday/

Patchy MVFR fog at a few terminals this morning will improve through 13Z. Scattered showers and thunderstorms are moving east through Central Ohio and may pass within the vicinity of MFD through 13Z. There is not enough confidence that these will hold together to reach CAK but will be monitoring evolution over the next hour or two. There remains a low potential through the afternoon for a few additional stray showers and thunderstorms to develop in an arc from Toledo to Cleveland to Youngstown between 19-22Z but coverage is expected to be low. TAFs will need to be amended as timing and location of any thunderstorms are determined. Otherwise, most sites will have a VFR sct-bkn cloud deck of 3500-5000 feet between 17-21Z. A warm front lifts north tonight with clearing skies.

South to southwest winds of 5-10 knots will continue with western terminals more likely to see gusts to 18-20 knots between 17-21Z. ERI is the exception and is expected to see a wind shift off the lake at 280-290 degrees for the afternoon. Winds will drop below 10 knots again tonight and back to southerly.

Outlook...Non-VFR possible in isolated showers and thunderstorms Sunday afternoon and evening, though chances are lower. Non-VFR likely at times in showers/thunderstorms late Tuesday into Wednesday.

MARINE

Light southwest winds today will back to southeasterly at 10-15 knots tonight. Southwesterly winds on Monday increase to 10-20 knots on the western half of the lake. Winds may ramp up just a little more on Tuesday ahead of a cold front and will need to monitor the need for a Small Craft Advisory. The offshore flow will keep the higher waves over the open waters on Tuesday with winds decreasing as the flow shifts to northwesterly behind the front on Wednesday. Conditions will be somewhat choppy with 2-4 foot waves Wednesday night into Thursday with northeasterly flow ahead of high pressure building to the north.

CLIMATE

High temperatures on Monday 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.