NEAR TERM /THROUGH TODAY/
9:30 PM Update...

The forecast remains on track overnight. Most of the lake-effect has ended in NE Ohio as expected, and lingering showers will end in NW PA overnight as the high builds in. Winds should stay up just enough to avoid widespread 30s in NW and north central Ohio based on current observations, so just kept patchy frost at this time along and west of the central highlands. Dew points are running a bit higher than forecast, and that will also help limit how far below 40 lows can drop, so we seem to be okay without an advisory.

6:30 PM Update...

The forecast remains on track this evening. Scattered lake- effect rain showers will continue east of Cleveland through NW PA given northwesterly flow across Lakes Huron and Erie, but increasingly dry air and a lowering inversion combined with backing flow as the Canadian high builds in from the west will gradually confine the activity to NW PA through Midnight. The current PoPs reflect this trend well.

Original Discussion...

An upper-level trough currently working through the eastern Great Lakes will exit east towards Quebec tonight into Sunday as fairly strong surface high pressure builds into the Ohio Valley.

In terms of clouds and precip chances, there's plenty of diurnal cumulus ongoing this afternoon with lake effect clouds and showers streaming southeast off the lake, especially from eastern Cuyahoga County points northeast through the primary northeast OH snowbelt into northwest PA. The diurnal cumulus will dissipate fairly quickly with sunset this evening. The lake effect will gradually shift east and diminish this evening and tonight as the trough pulls away and high pressure builds in, leading to instability decreasing as the column also trends drier. Activity may ebb and flow a bit through the evening as a couple of subtle vort maxes drop across the lake, though by later this evening and overnight the overall trend will be for a significant reduction in coverage and intensity of any lake effect. A rumble of thunder or two remains possible through the early evening across northwest PA. Sunday and Sunday night will largely be partly to mostly clear and dry. As a weak shortwave passes over or just north of Lake Erie overnight Sunday night into early Monday it may add enough synoptic moisture and lift for a bit of lake effect to redevelop near the Erie County PA lakeshore, so did introduce a 20% POP for Sunday night there.

Lows tonight will be impressively chilly for early September, especially across our western counties where locations outside of the Toledo urban heat island and away from the immediate lakeshore should fall into the mid to upper 30s. Farther east, higher dew points and more clouds downwind of the lake will keep lows warmer, generally in the 40s with 50s up against the lake. Highs will warm several degrees from today for Sunday, with mid 60s to low 70s expected. Lows Sunday night will generally range from the mid 40s to mid 50s, warmest up against the Lake Erie shoreline. The airmass is chilly enough for a frost concern late tonight into the pre-dawn on Sunday across our western counties where dew points should fall into the 30s. The main limiting factor is a modest pressure gradient keeping a bit of a wind going tonight, which is enough of a limiting factor to preclude a Frost Advisory at this time. Still, suspect lower-lying areas and river valleys will decouple a bit more and likely see patchy frost, which is noteworthy this early in the season. Put out a Special Wx Statement for some of our southwestern counties where confidence in patchy frost is highest to add a bit more visibility to the potential for some early-season frost.

SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/
NW'erly flow aloft impacts our CWA on Monday as a ridge at the surface and aloft builds very slowly from the north-central United States and vicinity. A potent shortwave trough embedded in the flow aloft and the attendant surface trough axis will advance SE'ward across our region, with the disturbance's influence expected to be greatest over eastern Lake Erie, NW PA, and far-NE OH. This is where a few showers and thunderstorms may occur during the morning through early evening hours as convergence/ascent along the surface trough axis release weak to moderate boundary layer CAPE, including sizable marine boundary layer CAPE over ~73F Lake Erie, amidst moderate to strong deep layer bulk shear. Thus, strong to severe thunderstorms may occur and this potential will be monitored closely. Fair weather is expected elsewhere as stabilizing subsidence accompanies the aforementioned ridge. Late afternoon highs are expected to reach the lower to mid 70's in NW PA and the mid 70's to lower 80's in northern OH.

Fair weather is expected CWA-wide Monday night through Tuesday night as the ridge at the surface and aloft continues to build from the north-central United States and is accompanied by stabilizing subsidence. The surface ridge axis is expected to shift from near the western Great Lakes and Lower OH Valley toward the northern and central Appalachians. Overnight lows are expected to reach mainly the upper 40's to upper 50's around daybreak Tuesday. Late afternoon highs on Tuesday are forecast to reach the mid 70's to 80F in NW PA, the upper 70's to mid 80's in NE OH, and mainly the 80's farther west. A weak synoptic MSLP gradient and sufficient daytime heating of surface air over surrounding land are expected to allow a lake breeze to occur over/within several miles of ~73F Lake Erie during the afternoon through early evening. Thus, relatively-cool highs are expected within the lake breeze. Overnight lows are expected to reach mainly the 50's to lower 60's Tuesday night as net low-level WAA on the synoptic scale impacts our CWA through the short-term period in response to the projected evolution of the weather pattern at the surface and aloft.

LONG TERM /WEDNESDAY THROUGH SATURDAY/
The core of the aforementioned ridge aloft is expected to move slowly from the central and northern Great Plains toward the northeastern and Mid-Atlantic states during this period. This is expected to allow our CWA to remain along the western flank of the attendant surface ridge, which should remain anchored in vicinity of the northern and central Appalachians. Accordingly, net low-level WAA is forecast to continue to impact our region. In addition, current odds favor fair weather in northern OH and NW PA as stabilizing subsidence accompanies the ridge. However, NHC expects a tropical cyclone to develop over the Bay of Campeche and western Gulf of Mexico during the early to middle portions of the week of Sunday, September 8th. The eventual remnant low of this expected tropical cyclone may move from the Lower MS Valley toward the Lower OH Valley late in the week. Forecast confidence in this remnant low delivering unsettled weather to our CWA by Friday or Saturday is very low. Trends in NWP model guidance will be monitored closely in the coming days.

Temperatures are expected to trend above-normal. Daily highs are forecast to reach the 80's to lower 90's on Wednesday through Saturday. The coolest readings are expected over/very near Lake Erie since lake breeze development is expected each late morning through early evening. Morning lows on Thursday through Saturday are forecast to reach the 50's or 60's.

AVIATION /06Z Sunday THROUGH Thursday/
VFR across the TAF sites early this morning with VFR to persist through the TAF period. Lake-effect clouds continue to stream off of Lake Erie, though coverage remains mostly scattered, apart from ERI where bkn to ovc ceilings of around 5kft may persist into mid-morning. Otherwise, only some high cirrus will arrive from the west by later this morning and afternoon.

Winds are generally light and variable across the TAF sites early this morning apart from ERI where northwest winds of around 10 knots remain. Winds will increase out of the northwest by later this morning and afternoon, 10 to 12 knots with gusts of 20 to 22 knots possible.

Outlook...Mainly VFR expected through Thursday.

MARINE
A Small Craft Advisory and Beach Hazards Statement remain in effect until 8 PM EDT this evening from Vermilion to Avon Point, and until 8 PM Sunday for Avon Point to Ripley. A trough lingers over Lake Erie through Sunday morning. Lake-effect rain showers are expected to continue to stream generally SE'ward or ESE'ward over/downwind of central and eastern Lake Erie. The showers may be accompanied by waterspouts. Simultaneously, NW'erly winds around 15 to 25 knots back gradually toward W'erly and ease gradually to 10 to 20 knots. Waves as large as 3 to 6 feet are expected through Sunday morning. A ridge begins to build over Lake Erie from the Upper MS Valley later Sunday through Monday.
However, another trough should sweep SE'ward across the lake on Monday and interact with the ridge. Winds around 10 to 20 knots are expected to vary between WSW'erly and WNW'erly during the rest of Sunday with waves as large as 3 to 5 feet. On Monday, winds are forecast to vary between SW'erly and NW'erly and be as strong as 15 to 25 knots as the MSLP gradient tightens in response to the aforementioned ridge/trough interaction. Waves as large as 3 to 7 feet are forecast and the Small Craft Advisory east of Avon Point may have to be extended into Monday.

By early Tuesday morning, W'erly to NW'erly winds are expected to ease to 5 to 15 knots behind the trough and then become variable in direction and ease further to around 5 knots by midday as the ridge continues to build over Lake Erie. Waves of 3 feet or less are expected. Variable winds around 5 to 10 knots and waves of 2 feet or less are expected Tuesday afternoon through Thursday as the ridge continues to affect Lake Erie and the core of the ridge shifts from near the Upper OH Valley toward the northeastern United States.

CLE WATCHES/WARNINGS/ADVISORIES
OH...Beach Hazards Statement through this evening for OHZ011-012- 089.
PA...Beach Hazards Statement through this evening for PAZ001.
NY...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for LEZ146>149.