textproduct: Cleveland

SYNOPSIS

A warm front will move through the area this evening before a cold front approaches from the west tonight into Thursday. This front will settle near the Ohio River for Thursday into Friday before a low pressure system forms and lifts this feature north as a warm front Friday night.

NEAR TERM /THROUGH THURSDAY NIGHT/

7:45 PM Update... There are a multitude of things we are keeping an eye on. In the observations, we are watching the progress of the warm front, which has moved into the southwest part of our forecast area. There is a sharp T/Td gradient across this from with around 75/60 T/Td behind the front. As the warm front lifts northeastward, should see a sharp increase in temperature and dew point (which will contribute to an increase in instability tonight.

Convection has already been ongoing for a few hours to our west and southwest, especially in IN/IL and points to their south. This may seem far away but strong wind flow is resulting in very fast storm motions. Latest model guidance projects convection impacting the I-75 corridor as early as 02Z. Severe weather remains possible with damaging winds and a few tornadoes being the primary weather hazards of concern. Wet conditions and high rainfall rates should lead to at least minor flooding for a good portion of the area, but the greater flash flooding risk continues to trend a bit lower (still possible especially in Northwest Ohio but should remain isolated), due to relatively fast storm motions and gradually decreasing rainfall rates through the overnight hours.

Previous Discussion... The first round of showers and thunderstorms has exited stage right this afternoon after a round of rain spanning 0.50-1.50", some nuisance flooding, and some small and isolated large hail. The main warm front to help trigger these storms is into central Ohio and will continue to extend north across the forecast area this evening. The advancement of this warm front will be key to the severe weather threat across the area tonight. Temperatures in Mount Vernon have crossed the 70 degree mark and Marion has exceeded 60 degrees, but the gradient is tight with Findlay still below 50 degrees and closer to the 40s near Lake Erie. The front should advance to near Lake Erie by 8-9 PM and the western two-thirds of the forecast area should reach at least 60 degrees and some instability should build with 1000-1500 J/kg of SBCAPE, where 70s could still be achieved. This will be plenty of instability to work with, as a strongly sheared air mass continues to develop across the Ohio Valley with a 70 kt low level jet at 850 mb entering tonight and mean 0-3 SRH values exceeding 400 m2/s2. A line of convective development continues to blossom across Illinois and Missouri and it will continue to expand north and east with time this afternoon. This will organize and be the main show that will enter a favorable atmosphere for severe weather. Therefore, the Enhanced Risk remains for the western forecast area with the Slight Risk expanding to the east from there. All severe weather hazards remain on the table with a few tornadoes embedded within a line of convection, damaging wind gusts, including some significant severe over 65 kts, and large hail. The timing will be into Northwest Ohio around 8 PM and extending east through the night around I-71 by Midnight and into the overnight. The trend in the forecast is that these storms are more likely to move through faster than previously anticipated and the flash flood threat may be more conditional and slightly lessened. However, will keep the flood watch with the overall wet pattern through the weekend and will monitor for hydrological hazards tonight.

The cold front will be into the area Thursday morning and will move southeast. The bulk of the storms will be southeast of the area during the daytime hours and the Day 2 Severe Risk has been removed from the area with the forecast trending dry. Highs in the 60s may be achieved early in the day. The front will be to the south of the forecast area on Thursday night but will be a focus area for new rain development that may push north through the night. Some efficient rainfall should enter the southern forecast area and there could be some conditional flooding for Central Ohio, as highlighted by a Day 2 Slight Risk of Excessive Rainfall.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/

Friday will be a lull to the active weather for most of Northern Ohio and Northwestern Pennsylvania as the boundary stalls out to the south in Southern Ohio. There maybe some scattered precipitation throughout the day in Central Ohio, through most will stay dry. A surface low and boundary will start to move northeastward from the lower Mississippi Valley as a strong LLJ moves into the region. This will bring back ample moisture from the south back into Northern Ohio. Heavy rainfall will return to the region with the strong moisture advection for starting late Friday night and early Saturday morning. In turn, most of the CWA will continue to be in a MRGL risk for excessive rainfall on Friday and a SLGT risk on Saturday. There will be a flash flood and river flooding threat across much of the region, with the highest probability across areas west of Interstate 71. Total rainfall forecast for Friday through Saturday night will be from 2-4" across the region. There does lie a small, isolated risk for severe weather across the far southwestern counties of the CWA which warranted a MRGL risk from SPC, though it will be largely overshadowed by the heavy rain threat. The best opportunity for any sort of severe weather will be during the afternoon timeframe on Saturday as temperatures start to climb with the southerly flow. An approaching cold front from the northwest will start to push everything out to the east late Saturday night.

Temperatures on Friday will fall a bit from earlier in the week as we will be on the northern side of the boundary with highs in the 50s across the region. On Saturday, temperatures will rebound with the southerly flow and high will reach into the mid to upper 60s. Parts of Northwest Ohio may not hit the 60s as the approaching cold front could keep the high temperatures down some.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

The aforementioned cold front from the short term will be entering the region from the northwest driven by a much larger upper level trough that will be digging down into the Great Lakes region Sunday night into Monday. A couple weaker low pressure systems and associated cold fronts will move through the region with the upper level trough through the beginning of the week. The initial cold front on Sunday will drive out most of the precipitation in the region throughout the day. There may be some lingering showers on the back end in Eastern Ohio and Northwestern Pennsylvania. A secondary, weak low pressure system will move into the region on Monday with a more widespread, though low probability, chance for precipitation across the region. The northerly flow behind the system and with a high pressure building to the west, will bring down much colder air leading to the opportunity for a rain/snow mix during the morning and overnight hours Monday and Tuesday. Rain/snow showers will persist in the snowbelt through Tuesday night as the high builds eastward across the region. Temperatures will be below average to start next week with the the cold air advection.

AVIATION /00Z Thursday THROUGH Monday/

VFR conditions are observed areawide at around 00Z, with midlevel clouds. South to southeast winds generally in the 20-25 knot range this evening and overnight except in Erie County where gusts to 40 knots will be possible.

A line of thunderstorms will move west to east across the area, generally consisting of ceilings around 2-5kft, visibilities in the 2-6SM range, and the potential for gusts in the 35-50 knot range, especially for the western part of the forecast area where confidence is higher in stronger thunderstorms. General tendency should be for thunderstorms to weaken in intensity as they move east across the area overnight tonight. The cold front will move through the area late in the TAF period with rain coverage decreasing and winds veering while remaining with elevated gusts. MVFR ceilings should still remain for a couple hours after the bulk of the thunderstorms exit late tonight into Thursday morning but should quickly improve to VFR conditions by mid to late morning. West winds will gust to around 20-25 knots behind the cold frontal passage before diminishing close to sunset.

Outlook...Non-VFR ceilings may continue across the region Thursday night into Friday with some non-VFR visibility possible in showers and storms south. Non-VFR more likely areawide in showers and thunderstorms Friday night into Saturday. Non-VFR ceilings are expected to continue into Sunday.

MARINE

A Small Craft Advisory is still active for the entirety of the nearshore zones through Thursday morning when the western half will fall off and Thursday night for the eastern half. Winds will be predominantly out of the south this evening at 15 to 25 before increasing to 20 to 30 knots ahead of an approaching cold front. Behind the cold front, winds will shift out of the west and subside to 10 to 15 knots throughout the day on Thursday. Winds will continue to decrease into the overnight hours and Friday morning and veer to out of the north at 5 to 10 knots. Winds will stay light through Friday before increasing Saturday morning to 10 to 15 knots. There will be another shift in the winds Sunday morning with a passing cold front bringing the winds out of the north at 10 to 15 knots which will continue through Monday.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Flood Watch through Sunday morning for OHZ003-006>011-017>021- 027>032-036>038-047. PA...Wind Advisory until 6 AM EDT Thursday for PAZ001-002. MARINE...Small Craft Advisory until 8 AM EDT Thursday for LEZ142>145. Small Craft Advisory until 8 PM EDT Thursday for LEZ146>149.