textproduct: Cleveland

WHAT HAS CHANGED

The probability of precipitation has increased a bit Thursday through Saturday as models and ensembles slowly converge on a solution, though details remain of lower confidence.

KEY MESSAGES

1) Outside of a few light showers into Northwest PA today, dry and somewhat mild weather is expected through midweek.

2) Rain chances ramp up area-wide Wednesday night and Thursday. Cooler air flows in for Friday and the weekend as a combination of lingering wrap-around moisture and lake enhancement allows shower chances to continue, especially from North Central and Northeast OH into Northwest PA. While snow may mix in at times starting Friday, impactful accumulations are rather unlikely.

DISCUSSION

KEY MESSAGE 1... A cold front crossing the area early this morning will exit to the southeast by sunrise. Chilly northwest flow is supporting lake effect clouds into far Northeast OH and Northwest PA this morning, with a few showers into PA where moisture is a bit deeper. Locations west/southwest of roughly a Cleveland-Canton line will see a mostly sunny day. With the low-level ridge axis not really pushing into Northeast OH/Northwest PA until this evening some lake effect clouds will continue flowing in for much of the day, with continued minor shower chances in Northwest PA. West-northwest winds will be a bit brisk, especially through early this afternoon. There will be another cold frontal passage on Tuesday, though it's expected to be a dry frontal passage with little airmass change. Highs in the 50s with lows in the 30s/40s (largely above freezing) are expected through Wednesday. Tuesday will be the warm day, when portions of the area will likely get into the 60s.

KEY MESSAGE 2... A notable pattern amplification is still on track for the end of the week across the eastern U.S., bringing a return to more notable precipitation chances and the chilliest airmass we've seen so far this fall...and potentially some wet snowflakes.

Ridging will amplify from the eastern slope of the Rockies towards Hudson Bay starting on Wednesday, with a shortwave expected to round the amplifying ridge and drop into the Great Lakes and Ohio Valley Wednesday night and Thursday. This shortwave will bring an injection of polar (not arctic) air into the eastern CONUS while interacting/phasing with another wave in the sub-tropical jet Thursday into Friday. This will lead to a large, deepening, slow-moving trough over the eastern U.S. and southeastern Canada late week into the weekend. Ridging over the North Atlantic and a closed low near Newfoundland, often referred to as a -NAO, further supports a deep and slow- moving trough over the east that will be slow to exit. At the surface, a cold front is likely to cross the area late Wednesday night or Thursday as developing low pressure tracks through the Ohio Valley. This developing low pressure is expected to really begin deepening near the Mid Atlantic coast Thursday night into Friday. Chilly, moist cyclonic flow is expected to continue behind the low beneath troughing aloft through Saturday and into Sunday...there is improving agreement that surface ridging will begin working in on Sunday but that the ridge axis won't really move into the local area until Sunday night or Monday.

In terms of sensible weather, there are decent odds for rain showers Wednesday night into Thursday as the front and developing low move through the region. Behind this, an inverted trough axis is likely to extend towards the Great Lakes beneath the deepening upper-level trough into Friday. This will keep synoptic precip going, especially across eastern portions of the area. Synoptic precip is likely to shift east Friday night into the weekend, though some amount of north-northwest flow lake effect will continue and keep shower chances in the forecast south-southeast of the lake until the surface ridge axis works in Sunday night or Monday. Compared to prior runs, agreement among the non-GFS operational models and ensembles, including AI versions, has increased a bit. The GFS, with a much stronger and slower surface low that amplifies west of the Appalachians, is an outlier, with most other guidance coming into better agreement on the general scenario laid out above, with the low deepening well to our east but troughing maintaining influence through the weekend. Still, the phasing of shortwaves and development of low pressure is something guidance struggles with, so will watch for any adjustments back towards a more amplified solution that could increase QPF Thursday and Friday over the next few cycles. There's also improving agreement that some lake effect precip will continue through the weekend, though the impression is that precip should become more hit/miss and confined to areas downwind of the lake this weekend as we gradually lose synoptic moisture.

Am not expecting rain amounts or wind gusts to be especially impactful with this system though it will be wet, somewhat blustery, and generally unpleasant. The main talking point has been potential for some snow across the area, as it would be the first of the season. It should be too warm for the synoptic precip to mix with snow through most of Thursday night. 850mb temperatures bottom out at -4 to -7C Friday and Saturday as deeper cold works in, with moderation starting on Sunday. Temperatures aloft can support snow by late Thursday night or Friday, though the low-levels will be "warmer" given the lack of arctic influence and modification from the still-mild Great Lakes. Mainly rain is expected though wet snow or graupel may mix in at times, mainly away from the lake and during the overnight/morning hours. Notable accumulations are unlikely, though will need to monitor the higher terrain for a low- confidence light accumulation scenario if steadier precip/snow can occur during an overnight or early morning period. In general, highs in the 40s and lows in the 30s are likely late week and into this weekend. The NBM low temperatures are probably a bit too chilly Thursday and Friday nights, especially farther east where clouds/precip will be more widespread.

AVIATION /18Z Monday THROUGH Saturday/

Lake effect clouds linger across Northeast Ohio and Northwest Pennsylvania through this evening, with periodic MVFR ceilings possible at KERI over the next several hours. Once clouds dissipate, VFR conditions expected through the rest of the TAF period with occasional upper-level cirrus.

Northwest winds of 6-10 knots gradually dissipate to around 5 knots by late this evening. Winds quickly become southwest shortly after sunset following the passage of a warm front, gradually increasing to around 6-10 knots. A cold front swings through during the day Tuesday, with winds becoming westerly and then nearly northwest by Tuesday afternoon.

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

MARINE

Brisk northwest winds across the lake early this morning are expected to gradually shift west-southwest and subside today as brief high pressure builds in. Rough conditions prompting Small Craft Advisories are ongoing early this morning, though will gradually improve from west to east through the day. Will continue evaluating the end time of the advisories, as waves may not fall below 4 feet before some of the current expirations.

Winds increase back to 20-25kt out of the southwest tonight ahead of a cold front, with winds veering more west-northwest on Tuesday behind the front. Another round of Small Craft Advisories will be needed, though won't be issued until later this afternoon given the ongoing headlines. The next round of rough conditions will be Thursday and Friday, with brisk northeast winds shifting north-northwest behind developing low pressure. More Small Craft Advisories will be needed for this period, with lower but non-zero potential for a marginal gale.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...Small Craft Advisory until 3 PM EST this afternoon for LEZ146>149.