textproduct: Cleveland

WHAT HAS CHANGED

Dew points and RH values were lowered through early this evening. Rain amounts in the forecast for Wednesday night have increased. Precip chances Thursday and Friday were increased a bit as confidence increases. Low temperatures Thursday night were raised across parts of the forecast area.

KEY MESSAGES

1) Dry and somewhat milder weather is expected through midweek.

2) Cooler with unsettled weather returning late week. While snow may mix in at times starting early Friday, especially in the higher terrain southeast of Lake Erie, impactful accumulations remain rather unlikely.

DISCUSSION

KEY MESSAGE 1... Small low pressure zipping out of Ontario and into Quebec today will drag a weakening cold front into the area today. This front will be dry, accompanied by little if any airmass change, and will likely wash out across the area into tonight. Today will be the warm day of the week with highs ranging from the upper 50s across Northwest PA to the low-mid 60s across most of northern Ohio. Minimum RH values will likely fall into the 30-40% range across Northwest OH this afternoon with slightly elevated westerly breezes...a reminder that the state of Ohio's open burn ban is in effect through November. Lows will largely dip into the 30s tonight, with highs in the mid to upper 50s on Wednesday. Rain ahead of the next system, discussed below, may begin encroaching on Northwest Ohio around sunset on Wednesday.

KEY MESSAGE 2... The combination of amplifying ridging from the eastern Rockies north towards Hudson Bay and a -NAO blocking pattern across the northwestern Atlantic still supports a notable change to much chillier and unsettled weather across the region for the second half of the week, lingering into the weekend. Guidance remains in good agreement on the big picture, as a trough begins to quickly dig into the eastern CONUS Wednesday and Thursday, with the trough evolving into a large closed low to end the week. Once this occurs, the trough/closed low will only slowly exit to the east through the weekend and into early next week.

A cold front is expected to push across the area Wednesday night or early Thursday as a developing wave of low pressure tracks through the upper Ohio Valley. This low pressure is expected to transfer to off the Mid Atlantic coast on Thursday, as an inverted surface trough axis hangs back towards the Great Lakes through Friday beneath troughing aloft. There is still some disagreement regarding exactly how quickly this low pressure develops and how far north/south it tracks...however, the overall amount of spread has decreased, with previous outlier models like the GFS (more amplified) and RRFS (farther south) coming into better agreement with the overall guidance suite. Surface high pressure is still on track to begin building in from the west Saturday night into Sunday behind the trough, but will likely not move overhead until Monday of next week.

Rain chances quickly ramp up Wednesday night as the developing wave of low pressure and a cold front move across the region. The placement and magnitude of rain Wednesday night will be contingent on exactly how quickly the low develops/deepens and where it tracks, and finer details are still to be worked out. There are hints at a swath of more moderate rain playing out just northwest of the developing low Wednesday night. Some guidance has more or less rain than our current forecast and further adjustments in either direction are possible. The low pressure exits east on Thursday so some breaks in the rain are expected, particularly farther west across the area where the majority of the day will be rain- free. However, the lingering inverted trough, initial north- northeast flow lake effect, and an embedded shortwave rotating through the region Thursday evening will keep opportunities for showers going, especially farther east across the area and south of the lake. There is high confidence in all precip falling as rain through Thursday, with lows Wednesday night mainly in the low- mid 40s with highs on Thursday in the mid-upper 40s. It will begin to turn blustery on Thursday with wind gusts to 30 MPH possible.

Precipitation will become increasingly lake-driven as we get to the end of the week and head into the weekend. Initial north- northeast flow will gradually turn northwesterly this weekend. Northwest OH will trend mainly or completely dry heading into the weekend while shower chances continue across much of the rest of the area. The higher terrain south-southeast of Lake Erie will see the most precip overall, with this type of flow supporting a spray of less-organized lake effect that favors the terrain. There's quite a signal among nearly all guidance for a Lake Huron connection bringing more persistent, organized, and intense lake effect to a smaller portion of the area. This will likely set up west of Cleveland Thursday into Thursday night and then drift around across the Cleveland metro and surrounding areas Friday into Saturday, before slowly shifting east across the more traditional Northeast OH snowbelt through the weekend. Instability becomes deep over the lake Friday into Saturday as 500mb temperatures bottom out around -30C over the 12-15C lake waters, so any organized lake effect will have intensity. The mid-levels begin gradually warming and drying later Saturday and beyond, meaning lake effect should begin loosing coverage and intensity through the second half of the weekend. That said, lingering lighter activity may take until Monday to fully wind down, especially downwind of Lake Huron.

Temperatures aloft become cold enough for snow late Thursday night into Friday, with 850mb temperatures bottoming out at -5 to -7C Friday into Saturday. The main limitation or uncertainty regarding snow involves near-surface temperatures, given the lack of Arctic influence and modification from the still-mild Great Lake waters. Given the temperatures aloft, it's likely we see some snow mix in where precip is occurring away from the lake each overnight/early morning period from Thursday night through Saturday night. With deep instability over the lake, any more intense or convective lake effect will likely mix with graupel, and that can happen down to the lakeshore and even during the "warmer" afternoon hours. Impactful accumulations remain rather unlikely. There remains a lower probability scenario for localized lighter accumulations if steadier or more intense precip impacts higher elevations during an overnight or early morning period. The greatest odds may be Friday night into early Saturday when 1000-500mb thickness values fall to an impressive <528dam. Highs are expected to range from the upper 30s to mid 40s Friday and Saturday before gradual modification begins Sunday. Overnight lows Thursday night will range from just below freezing across Northwest OH to mainly the mid to upper 30s elsewhere, with similar or perhaps slightly cooler values Friday night. Lows ranging from the upper 20s to mid 30s are generally in the forecast the rest of the weekend. It will remain blustery/brisk Friday into Saturday.

AVIATION /12Z Tuesday THROUGH Saturday/

VFR conditions and fair weather skies are expected today and tonight during this TAF period. Skies will be mostly clear with some passing high cirrus at times today into tonight. Winds will be light from the southwest to west 5 to 10 knots through this TAF period.

Outlook...Non-VFR will be likely with low ceilings and periods of rain showers Wednesday night through the weekend. Some wet snow showers may also be possible at the end of the week and weekend along with gusty winds up to 35 mph.

MARINE

Brisk southwest winds early this morning will shift westerly later this morning as a cold front pushes across the lake. Speeds of 15-25 knots will build 4 to 7 foot waves across the central and eastern basin, peaking this morning, and Small Craft Advisories are in effect from Vermilion points east. While the headlines expire by this evening, northwest winds remain a bit brisk tonight so it will remain choppy.

A brief break in rough conditions is expected on the lake on Wednesday. Northeast winds ramp up to 15-20kt Wednesday night, then gradually shift north and then northwesterly Thursday through the weekend. Speeds will generally be 15-25kt Thursday through Saturday, before more substantial weakening Sunday into early next week. Winds are forecast to be strongest Thursday afternoon and evening, when sustained values briefly approach 30 knots in the forecast. Small Craft Advisories will be needed starting Wednesday night or early Thursday, with the risk for a gale remaining low in the 10-30% range.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...Small Craft Advisory until 4 PM EST this afternoon for LEZ145>147. Small Craft Advisory until 10 PM EST this evening for LEZ148- 149.