textproduct: Cleveland

WHAT HAS CHANGED

A Severe Thunderstorm Watch has been issued for the western half of the forecast area through midnight tonight. Primary hazard will be damaging wind gusts, a tornado or two, and heavy rainfall.

Timing of thunderstorms into Northwest Ohio this evening has trended faster and the Slight Risk for severe thunderstorms (level 2 of 5) has been expanded east to around Vermilion. Raised low temperatures slightly the next couple nights given the warm and humid airmass. Lowered pops on Tuesday morning and portions of the area Tuesday afternoon given uncertainty in timing and coverage of showers and thunderstorms. QPF has also trended down across northeast portions of the forecast area through Wednesday.

KEY MESSAGES

1) There is a Slight Risk (level 2 of 5) of severe thunderstorms in Northwest Ohio this evening and tonight. Damaging wind gusts of 50-60 mph are the primary hazard.

2) Additional rounds of showers and thunderstorms through Wednesday will lead to the potential for localized flooding and scattered severe thunderstorms.

3) Muggy conditions will make temperatures feel uncomfortable at times through Wednesday with cooler and drier air returning to end the week.

DISCUSSION

KEY MESSAGE 1... 7:50 PM Update... An MCS is ongoing and moving roughly east-southeast across northern Indiana into Northwest Ohio this evening. The MCS has maintained strength as moving east with SPC issuing a Severe Thunderstorm Watch for the western half of the forecast area through midnight tonight. Primary hazard will be damaging wind gusts and a tornado or two. Can't rule out instances of heavy rainfall with isolated flash flooding, particularly in urban and well-saturated areas.

Previous discussion... Weak low pressure is located over NW Illinois with a warm front extending east across northern Indiana into western Ohio. The warm front is identified primarily by a swath of dewpoints in the lower 70s that is advecting northward today. An MCS is ongoing across Lake Michigan this afternoon and a Severe Thunderstorm Watch extends as far east as Williams County Ohio through 7 PM. The northern portion of the MCS is expected to outpace the reservoir of unstable air and the associated moisture advection. The southern portion of the MCS is more likely to maintain strength into Indiana but unclear at this time the extent it can hold together into NW Ohio. The instability gradient is expected to lift north along the I-75 corridor and possibly to the central highlands but only make slow progress to the northeast across Lake Erie tonight. CAMS have struggled with the handling of this MCS but best timing estimates are for a few thunderstorms to continue east along the advancing warm front into the I-75 corridor and possibly towards Mansfield between 8-11 PM. A general weakening trend is likely as we get past sunset and uncertainty remains regarding the coverage of severe wind gusts into this evening. In general the timing of thunderstorms has trended faster into NW Ohio.

Later tonight we expect to see a low level jet develop from Chicago into lower Michigan. This feature combined with the next round of shortwave energy moving through the quasi northwest flow aloft are likely to result in a rejuvenation of thunderstorms upstream across SW lower Michigan. Showers with scattered thunderstorms are expected to spread east across Lake Erie after midnight tonight while perhaps more robust convection still favors a southeast trajectory towards Central Ohio. Models over the last couple days have been highlighting a swath of heavier rain setting up just southwest of our forecast areas in Indiana/west central Ohio prior to 12Z.

KEY MESSAGE 2... The local area remains on the downstream side of an upper level ridge over the Rocky Mountains and Plains states through mid-week. This places the local area in a favorable region for additional rounds of showers and thunderstorms as the warm front stalls in the vicinity and multiple shortwaves move through the flow aloft. Timing of additional showers and thunderstorms is challenging beyond tonight and will be impacted by storm evolution, outflow boundaries, and placement of the stalled front. We do expect a break during the late morning/early afternoon on Monday. Moderate instability is expected to develop through the afternoon, especially across southern portions of the forecast area, with scattered thunderstorms possible during the late afternoon. A more organized severe weather threat could materialize during the evening ahead of a more substantial shortwave trough sliding through the Central Great Lakes. Good veering of the flow with height is expected along with around 40 knots of shear. Almost all of the forecast area is in a Slight Risk(level 2 of 5) for severe thunderstorms on Monday.

Depending on storm evolution, a trailing rain threat could linger into Monday night, particularly closer to Central Ohio. With the potential for a stronger round of storms on Monday evening/night, did lower pops to chance for most of the daytime on Tuesday. The airmass remains very moist with PW values rebounding to near 2 inches but confidence in placement of storms is low by this time. The more active storm track could be just south of the area on Tuesday but will need to be monitored. Coverage is likely to increase again Tuesday night. Then one more opportunity for thunderstorms is in the forecast on Wednesday afternoon ahead of the eventual cold front. Storm total rainfall amounts through Wednesday are over 2 inches across southwest portions of the forecast area but could see localized totals of 3 or more inches over several days. Will need to monitor the potential for flooding as the week progresses and areas become saturated.

KEY MESSAGE 3... This active stretch of weather will be characterized by warm and muggy conditions. Dewpoints return to the 70s on Monday and heat index values will be near 90 degrees across portions of northwest and north central Ohio. Elevated humidity levels will continue (at least in Ohio) through Wednesday. Temperatures will settle back into the 70s to end the week and bring some relief from the higher humidity.

AVIATION /00Z Monday THROUGH Friday/

A cluster of strong to severe thunderstorms is knocking on the doorstep of eastern terminals with the 00Z TAF issuance. Maintained TEMPO groups for TSRA impacts at KTOL/KFDY between 00Z/Mon and 03Z/Mon. Confidence in the MCS maintaining its strength as it moves east-southeast towards central Ohio terminals remains low, but kept PROB30 groups in all of TAF sites excluding KYNG/KERI. There will likely be future AMDs as tonight evolves. Strong wind gusts to 35-40 knots will be possible in strongest thunderstorms. Any severe thunderstorm that moves over a terminal will be capable of producing 50+ knot wind gusts. Highest confidence in severe wind gusts will be at KFDY this evening.

Beyond the next 6 hours or so, the forecast gets very uncertain. Guidance is continuing to suggest another area of showers and thunderstorms moving across terminals Monday morning, possibly into later Monday morning. However, exact details in timing and location are hard to parse out at this time given ongoing convection across the airspace. Given low confidence, opted to maintain PROB30 groups for a few hours across all TAF sites for any TS impacts Monday morning. Conditions are expected to remain VFR outside of any SHRA/TSRA.

Outlook...Periods of non-VFR conditions are expected through Thursday as several rounds of scattered showers and thunderstorms move across the airspace. Some storms could be strong to severe during this timeframe.

MARINE

A warm front will lift across Lake Erie tonight, waiver across the southern Great Lakes through at least part of Wednesday, and then sag south late Wednesday or Wednesday night. Winds will shift southwest behind the front tonight and remain generally west- southwest until the cold front sinks south later this week. Winds will be a bit elevated at 10-15kt late tonight through Monday evening, pushing waves to 1-3 feet in the central and eastern basins. Clusters of storms moving over or near the lake and their mesoscale impacts to pressure and winds may cause a period or two of more enhanced winds to 20kt or so over the lake, particularly late tonight into Monday morning. This could lead to a brief period of 3 to 5 footers across parts of the central or eastern basin. Given the convective influence on the pattern, confidence in a period of winds closer to 20kt and/or waves of at least 4 feet is too low for any headlines, though the potential for a brief period of Small Craft Advisory/Beach Hazard Statements will continue to be evaluated. Winds may briefly turn more northerly early Tuesday as the front briefly pushes south before wavering back north. Winds will be a bit elevated (at least 10 to 15kt, and perhaps briefly up to 20kt) out of a more northerly direction behind the front Wednesday night through Friday, bringing a period of choppier conditions.

CLE WATCHES/WARNINGS/ADVISORIES

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