textproduct: Cleveland

SYNOPSIS

A strong cold front sweeps southeastward across our region this morning. Behind the front, a trough lingers over and near Lake Erie through Sunday as a ridge builds from the north- central United States to the Ohio Valley. The ridge then builds eastward across our entire region Sunday night into Monday before departing to the east coast midweek

NEAR TERM /THROUGH TONIGHT/

- Lake-Effect Snow (LES) Warning remains in effect for NW PA from 7 AM today to 7 AM EST this Monday - LES Warning now in effect for the primary snowbelt of NE OH and Cuyahoga County from 10 AM today to 7 AM this Monday - Winter WX Advisory remains in effect for the secondary snowbelt of NE OH from 1 PM today to 7 AM this Monday - Winter WX Advisory remains in effect for Stark and Mahoning Counties from 1 PM today to 7 PM Sunday - Remainder of Winter WX Advisory in northern OH remains in effect from 1 PM today to 7 AM Sunday

In the mid/upper-levels, cyclonic W'erly flow aloft persists over the Lake Erie region and Upper OH Valley through tonight as embedded shortwave troughs affect our region and a primary shortwave trough axis approaches from MB, Canada and eventually the western Great Lakes. Closer to the surface, a shortwave trough axis in roughly the 925 to 700 mb layer will move from the northern Great Plains this morning toward New England and the Mid-Atlantic region by daybreak Sunday. At the surface, a strong cold front will sweep generally SE'ward across our region between roughly daybreak and late this afternoon as the preceding ridge continues to exit toward New England. Behind the front, a thermal trough develops over relatively-warm Lake Erie while an Arctic ridge builds from the north-central United States to the OH Valley and vicinity. Today's daytime highs will reach the mid 20's to lower 30's ahead of the cold front. The "warmest" highs are expected farther to the east and southeast in our CWA, where a later cold front passage will occur. Strong post-front low-level CAA will contribute to lows reaching mainly the 5F to 15F range around daybreak Sunday.

Early this morning, LES is organizing/strengthening gradually over Lake Erie and over portions of western NY amidst a cyclonic WSW'erly to SW'erly mean low-level flow of sufficiently-cold/moist air over/downwind of the ~3C lake, weak lake-induced CAPE (LICAPE), and low/mid-level moisture advection ahead of the front and aforementioned 925-700 mb shortwave trough axis. Isolated to scattered snow showers should accompany the front's passage as convergence/ascent along the front release weak potential instability located in the lowest 1 km AGL. Low-level convergence/ascent along the front will also enhance the Lake Erie LES. The LES will settle S'ward into our primary snowbelt counties during the mid- morning through late afternoon hours of today as the cold front's passage causes mean low-level flow to veer from SW'erly to W'erly. The LES will be steady to heavy at times per model soundings, which continue to indicate low-level convergence along the major axis or axes of LES banding will result in a crosshair signature (i.e. moderate to strong and maximized ascent will be collocated with a cloudy DGZ at least 0.5 to 1 km deep). During this evening through daybreak Sunday, the LES will settle over the snowbelt and vicinity in NE OH/NW PA as the mean low- level flow of progressively colder/sufficiently-moist air veers from W'erly to NW'erly and LICAPE grows to moderate magnitudes, due in part to the development of upstream moisture connections to Lakes Huron and St. Clair. The LES will be steady to heavy at times, with snowfall rates as high as 1-2" per hour, due in part to a crosshair signature. In addition to the LES, widespread snow will overspread our region from west to east this afternoon through very early early evening. This snow will be associated with moist isentropic ascent and frontogenetical convergence ahead of the aforementioned 925 to 700 mb shortwave trough axis. The frontogenetical convergence will result from flow in that aforementioned layer backing slightly from W'erly to WSW'erly ahead of the shortwave's axis. This backing of the 925 to 700 mb mean flow is still expected to be most-pronounced farther south in our CWA. The widespread snow should be steady to heavy at times, especially roughly along and south of U.S. Route 30, where the FGEN aloft and moist isentropic ascent should allow moderate to strong and maximized ascent to be collocated with a cloudy DGZ about 1 to 2 km deep, which should yield periodic snowfall rates up to 1" per hour. Note: as the widespread snow overspreads Lake Erie and vicinity, the seeder-feeder process and continued presence of at least weak LICAPE over the lake should enhance the aforementioned LES further for a time this afternoon and evening. The widespread snow will then exit our entire region from west to east between ~6 PM and midnight tonight as much drier air, especially in the 850 to 700 mb layer, overspreads our area behind the shortwave trough axis.

By daybreak Sunday, fresh snow accumulations are expected to reach 1-5" outside the snowbelt. The greatest of these accumulations should be focused roughly along and south of U.S. Route 30, where the Winter WX Advisory remains in effect. Within the snowbelt of NE OH/NW PA, fresh snow accumulations should reach 3-7" by daybreak Sunday. The greatest of these accumulations are expected in the higher terrain just east of Cleveland and in the higher terrain of southern Erie County, PA, where upslope enhancement of snow will also be a factor.

SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/

Up in the mid/upper-levels, the prominent shortwave trough axis should sweep SE'ward across our CWA between daybreak and early afternoon on Sunday. Behind that shortwave trough axis, high pressure at the surface and aloft will build generally from the west through Monday night and as mentioned in the near-term section, the surface ridge will be associated with a rather cold air mass. However, on Monday, another shortwave trough should move SE'ward across our region and temporarily weaken the ridge at the surface and aloft. Daytime highs should reach only the 15F to 25F range on Sunday and the upper teens to upper 20's on Monday. Overnight lows should reach mainly the 5F to 15F range around daybreak Monday and 10F to the upper teens around daybreak Tuesday. The coldest wind chills of the seven-day forecast period are expected on Sunday and Monday. Wind chills as cold as 0F to -10F are expected around daybreak Sunday and as cold as the single digits above 0F to nearly -10F around daybreak Monday.

Dry weather is expected across most of our region during the short-term period, due in part to stabilizing subsidence accompanying the ridge. However, periods of LES will impact the snowbelt of NE OH/NW PA and vicinity on Sunday amidst NW'erly mean low-level flow of sufficiently-cold/moist air, weak to moderate LICAPE over Lake Erie, and upstream moisture connections to Lakes St. Clair and Huron. Thus, the LES will likely be steady to heavy at times. During Sunday night, the LES is still expected to shift N'ward to our primary snowbelt counties and vicinity as the mean low-level flow of sufficiently-cold/moist air backs gradually to W'erly. The LES should weaken due to synoptic low-level dry air advection and a lowering subsidence inversion accompanying the building ridge, which will weaken LICAPE. Between daybreak Sunday and daybreak Monday, additional LES accumulations are expected to be highly variable and range from a coating to 7". The greatest of these accumulations should be focused in the higher terrain of southern Erie and northern Crawford Counties in NW PA, due to a combination of upslope enhancement and a fairly prolonged upstream moisture connection to Lake Huron.

LES is expected to persist over and downwind of Lake Erie on Monday through most of Monday night amidst at least weak LICAPE and a sufficiently-cold/moist mean low-level flow that should vary between SW'erly and W'erly. Thus, the LES should be transient. Ahead of the aforementioned shortwave trough axis, moist isentropic ascent may allow scattered snow showers to occur outside the LES, especially in NE OH and NW PA. In addition, the seeder-feeder process should occur ahead of the shortwave trough axis and enhance the LES for a time. Additional snow accumulations of a coating to several inches are possible. The LES should weaken Monday night and end by daybreak Tuesday amidst weakening LICAPE due in part to a lowering subsidence inversion behind the shortwave trough axis.

LONG TERM /TUESDAY THROUGH FRIDAY/

Current odds favor dry weather this Tuesday through Wednesday as the above-mentioned ridge at the surface and aloft continues to exit E'ward. In addition, net low-level WAA along the backside of the ridge should be accompanied by highs in the upper 20's to mid 30's Tuesday afternoon and the upper 30's to lower 40's Wednesday afternoon. Lows should reach mainly the 20's around midnight Tuesday night and begin to moderate during the predawn hours of Wednesday morning as the aforementioned low-level WAA strengthens.

A trough at the surface and aloft should overspread our region from the west on Wednesday night through Thursday. In addition, a cold front should approach our region from the Upper Midwest and vicinity on Thursday as net low-level WAA persists in northern OH and NW PA. Lows should reach the upper 20's to mid 30's Wednesday evening and be followed by moderating readings by the predawn hours of Thursday morning. Highs should then reach the lower 40's to 50F on Thursday as low-level WAA continues to strengthen due to deepening of the trough at the surface and aloft. A low-level return flow of warm and moist air from the Gulf should undergo isentropic ascent aloft, ahead of the front and primary trough axis aloft, and allow periods of precip to affect our region Wednesday night through Thursday. A mix of snow and rain is in our official forecast Wednesday night before changing to just rain on Thursday as temperatures and wet-bulb temperatures moderate via WAA at the surface and aloft. Will have to monitor this portion of the forecast closely, including how exactly the vertical profiles of temperature and wet-bulb temperature are projected to evolve.

At this juncture, it appears the cold front and primary trough axis aloft will sweep E'ward through our region Thursday night and be followed by a ridge at the surface and aloft building from the west through Friday. Lows should reach the upper teens to mid 20's around daybreak Friday. Highs should reach the upper 20's to mid 30's Friday afternoon. Additional periods of precip are expected Thursday night due to convergence/moist ascent along the cold front and moist isentropic ascent ahead of the trough axis aloft. Behind the surface cold front, rain should change to snow via the wet-bulb effect and CAA at the surface and aloft before widespread precip ends behind the trough axis aloft. Will monitor trends in NWP model guidance for accumulating snow potential. Overnight Thursday night into Friday, the environment should become cold and moist enough to support LES over/downwind of Lake Erie, but all of the following remain very uncertain at this time: mean low-level flow direction; LICAPE magnitude; placement, intensity, and amounts of LES.

AVIATION /12Z Saturday THROUGH Wednesday/

Overcast skies with ceilings around 1,500 ft are observed areawide and expected to persist through much of the TAF period.

Lake effect snow develops across the snowbelt region this morning, with periodic IFR visibilities expected within any snowbands. This will primarily impact KERI.

Meanwhile, a system will build in from the southwest, with widespread snow impacting the entire airfield. Visibilities will quickly tank to IFR and to as low as 1/2 SM at times. Snow will exit from west to east tonight, with conditions improving quickly. Lake effect snow will return primarily to the snowbelt region of Northeast Ohio and Northwest Pennsylvania, but a few snow showers streaming in off of Lake Michigan could impact other TAF sites at times tonight into Sunday morning.

Southwest winds of 10-15 knots are expected this Saturday morning with gusts up to 20-25 knots. These winds will gradually become west-northwesterly by this afternoon.

Outlook...Non-VFR conditions possible as Lake effect snow continues across Northeast Ohio and Northwest Pennsylvania through Monday night.

MARINE

Southwest winds currently around 10-20 knots will strengthen this morning, shifting to westerlies and peaking around 30 knots late this morning into the early afternoon. A Small Craft Advisory is in effect for the entire nearshore waters of Lake Erie to account for this. Toledo water level is forecast to drop to around the low water datum later this morning into the early afternoon, which is 8 inches above the critical mark for safe navigation. At this time, a Low Water Advisory is not expected for the western basin of Lake Erie.

Winds become northwest Saturday night through Sunday night and will generally be in the 15 to 25 knot range, though could approach 30 knots at times late Sunday morning into early Sunday afternoon, especially in the central basin where wave heights up to 6-9 feet may be possible. The Small Craft Advisory continues through Sunday night and Monday morning to account for this.

Southwest flow develops again on Monday and persists through the rest of the week. Wind speeds will oscillate with periods of wind speeds in the 20-30 knot range. Additional Small Craft Advisories are expected. There is increasing chance of gale force winds Thursday into Friday.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Winter Weather Advisory from 1 PM this afternoon to 7 AM EST Monday for OHZ010-020>023. Lake Effect Snow Warning from 10 AM this morning to 7 AM EST Monday for OHZ011>014-089. Winter Weather Advisory from 1 PM this afternoon to 7 AM EST Sunday for OHZ029>031-036>038-047. Winter Weather Advisory from 1 PM this afternoon to 7 PM EST Sunday for OHZ032-033. PA...Lake Effect Snow Warning until 7 AM EST Monday for PAZ001>003. MARINE...Small Craft Advisory until 1 AM EST Monday for LEZ142-143. Small Craft Advisory until 7 AM EST Monday for LEZ144>149.