textproduct: Cleveland

SYNOPSIS

A trough lingers over Lake Erie today as a ridge builds from the north-central United States. The ridge then builds eastward across our entire region tonight through Monday. However, on Monday, a separate trough should sweep southeastward over and near Lake Erie, and weaken the ridge temporarily.

NEAR TERM /THROUGH MONDAY/

- Winter Weather Advisory remains in effect for Stark and Mahoning Counties until 7 PM EST this evening. -The Winter Weather Advisory has been upgraded to a Lake Effect Snow (LES) Warning for Lorain, Medina, and Summit Counties, and is in effect until 7 AM this Monday. - LES Warning remains in effect until 7 AM this Monday for Cuyahoga, Portage, Geauga, Lake, Ashtabula Counties in NE OH and Erie and Crawford Counties in NW PA. - The Winter Weather Advisory for Trumbull County remains in effect until 7 AM this Monday. Considered upgrading this advisory to a warning, but less-persistent LES and a snow shadow in the lee of the higher terrain of Geauga County and vicinity should limit additional snow accumulations in Trumbull County.

Aloft, a shortwave trough axis extending from Georgian Bay to the southwestern Great Lakes at 3 AM EST this morning moves generally ESE'ward to eastern NY and eastern PA by sunset this evening. Behind the shortwave trough, a ridge builds from the northern Great Plains and vicinity through sunset Monday evening. However, another shortwave trough should advance SE'ward from the northwestern Great Lakes to eastern Great Lakes between daybreak and sunset on Monday and weaken the ridge temporarily. At the surface, a trough lingers over Lake Erie today as an Arctic ridge continues to build from the north- central United States to the OH Valley. This ridge will then build generally E'ward across our entire region tonight through Monday. However, on Monday, a separate surface trough accompanying the latter shortwave trough should sweep generally SE'ward over/near Lake Erie and weaken the ridge temporarily. This weather pattern at the surface and aloft will allow below- normal temperatures to persist across northern OH and NW PA. Morning lows mainly in the 5F to 15F range are expected today and Monday. Afternoon highs should reach only the mid teens to mid 20's today and the upper teens to upper 20's on Monday. Wind chills are expected to be as cold as -5F to -10F around daybreak this morning and as cold as 0F to -10F around daybreak Monday morning.

The above-mentioned weather pattern evolution at the surface and aloft will maintain a sufficiently-cold/moist mean low-level flow for continued lake-effect snow (LES) over and downwind of ~3C Lake Erie through sunset Monday evening and cause the mean low-level flow direction to be variable. The LES will be steady to heavy at times, especially through this evening, and again between daybreak and sunset on Monday, when low-level moisture is expected to be greater/deeper and promote moderate lake- induced CAPE (LICAPE). Upstream moisture connections to Lakes St. Clair and Huron will contribute to periods of steady to heavy LES through this evening. During periods of heavy LES, snowfall rates up to 1-2" per hour are expected, especially through this evening, as model soundings continue to depict a crosshair signature (i.e. low-level convergence along the major axes of LES bands yielding strong and maximized ascent collocated with a cloudy DGZ about 1 km deep). Mean low-level flow is expected to veer gradually from W'erly or WNW'erly to NNW'erly through this early evening and allow multiple bands of LES to impact the snowbelt of NE OH/NW PA and vicinity. Later this evening through daybreak Monday, mean low-level flow will back gradually to W'erly, which will allow LES bands to drift N'ward and eventually impact only our primary snowbelt counties and vicinity. Fresh LES accumulations through daybreak Monday are expected to be highly variable and primarily amount to 4" or less. However, additional snow accumulations of 5-8" are expected in heavier and more- persistent LES, which should be focused across the following areas: northern Lorain, southwestern Cuyahoga, northern Medina, and central Summit Counties through this afternoon due to frictional surface convergence/resulting mesoscale low-level frontogenesis along the southwestern shore of Lake Erie, which should contribute to upstream generation of a heavier snow band that will then stream over the aforementioned areas; the higher terrain just east of Cleveland due to a combination of upslope enhancement of LES and an upstream moisture connection to Lake St. Clair for a time; the higher terrain of southern Erie County and northern Crawford County in PA due to upslope enhancement of LES and an upstream moisture connection to Lake Huron for a time. Note: light/scattered LES showers originating over Lake Michigan should impact locations roughly along and southwest of a Toledo to Mansfield to Millersburg line through about daybreak this morning, but any associated snow accumulations are expected to be less than 1".

On Monday, LES over/downwind of Lake Erie should continue to shift N'ward and eventually stream NE'ward into primarily portions of western NY as mean low-level flow backs from W'erly to SW'erly. However, during the SW'erly flow regime, the LES may brush the lakeshore at times from roughly Lake County, OH through Erie County, PA. Moist isentropic ascent ahead of the above-mentioned and latter shortwave trough axis should trigger scattered snow showers over NE OH and NW PA on Monday. The moist isentropic ascent-related snow and weak to moderate LICAPE over Lake Erie should lead to the seeder-feeder process and enhancement of the LES. Additional snow accumulations between daybreak and sunset on Monday should be 3" or less. Outside the LES and moist isentropic ascent-related snow, fair weather is expected today through sunset Monday evening as stabilizing subsidence accompanies the aforementioned ridge.

SHORT TERM /MONDAY NIGHT THROUGH WEDNESDAY/

During Monday night, the shortwave trough will exit SE'ward from the eastern Great Lakes region as the above-mentioned ridge aloft continues to build from the north-central United States and vicinity. At the surface, the ridge will crest E'ward through our region. Primarily dry weather is expected as stabilizing subsidence accompanies the ridge. However, LES is expected to linger over/downwind of Lake Erie through the wee hours of Tuesday morning and then dissipate by daybreak as LICAPE wanes via synoptic low-level dry air advection and a lowering subsidence inversion in the wake of the shortwave trough axis. Before dissipating, the LES should impact portions of our primary snowbelt counties at times, especially roughly along and north of I-90, as the mean low-level flow of cold and moist enough air varies between SW'erly and WSW'erly. Nighttime LES accumulations should be 2" or less. Lows should reach the upper single digits to lower 20's around daybreak Tuesday.

Dry weather is expected Tuesday through Tuesday night as the surface portion of the above-mentioned ridge exits E'ward, the ridge aloft crests E'ward over northern OH and NW PA, and stabilizing subsidence continues to affect our CWA. Low-level WAA on the backside of the surface ridge should be accompanied by afternoon highs in the upper 20's to mid 30's on Tuesday. Lows should reach the lower 20's to lower 30's by midnight Tuesday night before readings moderate during the predawn hours of Wednesday morning as a deepening trough at the surface and aloft begins approaching from the west and causes low-level WAA to strengthen.

On Wednesday, the narrow trough at the surface and aloft should move quickly E'ward across our region and be followed by ridging at the surface and aloft building from the Upper Midwest and vicinity by the afternoon and early evening. Afternoon highs should reach the mid 30's to lower 40's as net low-level WAA persists. Note: moist isentropic ascent ahead of the trough axis aloft and convergence/sufficiently-moist ascent along the surface trough axis may trigger a few wet snow and/or rain showers over/near eastern Lake Erie and NW PA Wednesday morning through early afternoon.

LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/

During Wednesday night through Thursday, the ridge at the surface and aloft exits E'ward as another deepening trough at the surface and aloft and the attendant strong cold front approach from the northern Great Plains and eventually the western Great Lakes. Lows should reach the 20's to lower 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 lower 50's 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 will 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 at the surface and aloft moderate via WAA. 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 and influence surface precip type.

At this point, 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 lower 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 front and trough axis aloft. Behind the surface cold front, rain should change to snow as the atmospheric column cools 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.

For Friday night through Saturday, the ridge should exit E'ward and be followed by cyclonic W'erly flow aloft, embedded shortwave disturbances, and surface troughing overspreading northern OH and NW PA from the west. LES should end Friday night as LICAPE wanes via a N'ward warm front passage and strong low-level WAA on the backside of the departing ridge. Lows should reach mainly the mid teens to mid 20's Friday night, prior to the warm front passage. On Saturday, low-level WAA should allow afternoon highs to reach the upper 30's to mid 40's.

Periods of synoptic snow and/or rain should occur Friday night through Saturday in relation to the following: moist isentropic ascent along the upper-reaches of the warm front and ahead of the shortwave trough axes; convergence/moist ascent along surface trough axes accompanying the shortwave troughs. Will also 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 and influence surface precip type.

AVIATION /18Z Sunday THROUGH Friday/

Lake effect snow showers continue for the eastern portion of the CWA impacting terminals from just east of KCLE through KERI dropping visibilities down to IFR and LIFR at times in the heaviest bands. A band will start to take shape from a Lake Huron connection this afternoon that will target areas in NE OH and NW PA and as far south as KCAK. To account for this, a TEMPO group for LIFR visibilities has been included in KCAK and KYNG through 22-23Z tonight. KERI will see continued lake effect snow showers through the TAF period with a brief break after 00Z tonight as the band wavers.

In the western portion of the CWA, conditions have improved to VFR with clearing skies. Ceilings will be moving in from north to south from Michigan this afternoon that will impact the western terminals, though ceilings have been VFR with occasional MVFR.

For the majority of the terminals, conditions should improve by tomorrow morning as high pressure begins to build into the region. Ceilings will begin to lift and settle around 070-100 for the remainder of the TAF period. Winds will be predominately out of the west to northwest through tomorrow morning then back to be more southwesterly through the remainder of the period. Expect gusty winds up to 20-25 knots beginning around 13-15Z.

Outlook...Non-VFR conditions in lake effect snow showers in NE OH and NW PA through Monday night. Non-VFR possible Thursday as a low pressure system brings rain into the region.

MARINE

A Small Craft Advisory remains in effect for the entire nearshore zones of Lake Erie due to the elevated winds and waves. Water temperatures remain at, or below, 40 degrees across much of the lake, with air temperatures in the upper teens to low 20s. As a result, there is a minor risk for freezing spray through Sunday morning.

Winds will become northwesterly overnight and increase to 20-25 knots on Sunday. Winds may briefly increase to 30 knots across the central basin, but will decrease to 10-15 knots by the evening and becoming westerly. Waves will steadily subside from 2-4 feet Sunday to 1-3 feet Sunday night. Winds will become southwesterly on Monday and increase to 25-30 knots. Waves build to 3-6 feet in the nearshore zones, and 6-9 feet the open water zones. Occasional waves 11-15 feet are possible. The Small Craft Advisory has been extended to Monday night to account for these conditions. These conditions will continue through Wednesday, with gale-force winds likely across the lake on Thursday and Thursday night.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Lake Effect Snow Warning until 7 AM EST Monday for OHZ010>014- 020>022-089. Winter Weather Advisory until 7 AM EST Monday for OHZ023. Winter Weather Advisory until 7 PM EST this evening for OHZ032- 033. PA...Lake Effect Snow Warning until 7 AM EST Monday for PAZ001>003. MARINE...Small Craft Advisory until 11 PM EST Monday for LEZ142-143. Small Craft Advisory until 4 AM EST Tuesday for LEZ144>149.