textproduct: Cleveland

WHAT HAS CHANGED

Winter Storm Watches have been issued for Cuyahoga, Medina, Summit, Geauga, Lake, and inland Ashtabula Counties in NE Ohio and Erie County in NW PA. The watches are in effect from 6 PM Sunday through 4 AM Tuesday in Ohio and from 10 PM Sunday through 7 AM Tuesday in PA. Confidence continues to increase for periods of light snow late tonight and Sunday transitioning to bands of heavy lake enhanced snowfall Sunday night through Monday night.

KEY MESSAGES

1) Light snow develops tonight and Sunday, but accumulations will be minimal and low impact. Heavier lake enhanced snow Sunday night through Monday night could bring significant accumulations to inland parts of the NE Ohio and NW PA snowbelts, with snow covered roads and reduced visibilities.

2) Weak systems Tuesday night through Thursday will bring periods of rain and snow showers, with light accumulations.

3) Warmer and drier conditions expected Friday into the weekend.

DISCUSSION

KEY MESSAGE 1... Winter returns for the end of the weekend and start of the work week as colder air and deep moisture wrapping around a major East Coast blizzard leads to periods of heavy lake enhanced snowfall in northern Ohio and NW PA.

Starting off this evening, broad mid/upper troughing covers the northern CONUS east of the Rockies with an upper low in the central Great Lakes. This broad cyclonic flow pattern is circulating colder but mainly dry conditions into the region. By tonight, a southern stream mid/upper shortwave trough currently crossing the Lower Mississippi Valley will phase with the aforementioned northern stream mid/upper low in the central Great Lakes and broad/deepening mid/upper trough. This phasing combined with strong low-level convergence along the Mid Atlantic coast will lead to a rapidly deepening surface low lifting from the vicinity of the North Carolina Outer Banks Sunday morning to coastal Maine by Monday night. While this system will make national headlines for its crippling blizzard conditions from New Jersey to Maine, it will also have some interesting impacts to northern Ohio and NW PA.

Light snow tied to mid-level warm air advection and isentropic ascent near the left exit of a 130-140 knot H3 jet streak will gradually lift northeastward into the region this evening and early tonight, but little to no accumulation is expected before a lull in the roughly 03-09Z period. A more widespread area of light snow is expected to develop in Michigan late tonight and Sunday morning as the mid/upper trough and resultant forcing and moisture deepens over the southern and central Great Lakes in response to the phasing. This will slowly pinwheel into northern Ohio and NW PA Sunday from west to east as the trough and PVA aloft continue to deepen overhead. Deep synoptic moisture will wrap into the region through the day, which when combined with the broad PVA overhead, will support frequent periods of light snow. The strongest combination of synoptic forcing and moisture transport will be occupied by the main East Coast storm to our east, so this will keep the snow light Sunday, with marginal temperatures in the mid 30s leading to minimal accumulations. Up to 0.5 inches is possible on grassy and elevated surfaces by Sunday evening with mainly wet roads, keeping this portion of the event low impact.

The nuisance snow will become more impactful later Sunday evening, and especially Sunday night through Monday night as a more classic lake enhanced set up takes shape. Much colder air will advect into the region as the deepening east coast storm moves northward, and this combined with well aligned N to NW boundary layer flow across Lakes Huron and Erie, deep synoptic moisture, and continued lift from the deep, negatively tilted trough overhead will support a transition to bands of heavy lake enhanced snows. A possible TROWAL could further enhance the banding. Pattern recognition increases confidence in significant accumulations over upslope favored areas of the primary and secondary snowbelts. Hoisted Watches for Cuyahoga, Medina, Summit, Geauga, Lake, and inland Ashtabula Counties in Ohio, and Erie County in PA based on where probabilistic data gives the highest probabilities for greater than 6 inches of snow, but headlines (probably Advisories) may be needed for bordering counties as well. This will be monitored. At this point, people should prepare for worsening travel conditions Sunday night across inland north central and NE Ohio and NW PA, with significant impacts to the Monday morning and evening commutes. Roads will be snow covered and slippery, and gusts up to 40 mph Monday could lead to some blowing and drifting where bands persist. The snow will gradually taper off Monday night as brief ridging and drier air work into the region.

KEY MESSAGE 2... There remains some uncertainty with the midweek pattern, but a Clipper system looks to dive through the central Great Lakes Tuesday night into Wednesday. Light snow (mainly in NE Ohio and NW PA) could bring some light accumulations Tuesday night before ending as some scattered rain showers Wednesday as temperatures warm. A stronger Clipper system may phase with some southern stream energy Thursday and support potentially heavier, more widespread precip, but confidence in the temperature profile and resultant precip type, as well as the track of the system and details of the phasing is low at this time.

KEY MESSAGE 3... A quasi-zonal flow pattern should develop Friday into Saturday ahead of another trough and surge of arctic air by later in the weekend. This will allow temperatures to warm into the 40s Friday and perhaps low 50s in some areas by Saturday, along with mainly dry conditions.

AVIATION /06Z Sunday THROUGH Thursday/

MVFR ceilings continue across terminals with some isolated areas of IFR visibilites as light snow showers push eastward across the region. MVFR conditions due to both reductions in ceilings and visibilities will continue through the TAF period. Expect for windows where visibilities are further reduced to IFR in heavier pockets of snow showers, primarily across western TAF sites. Anticipate for areawide IFR ceilings to develop late in the TAF period this evening.

Generally west to northwest winds 5-10 knots continue through this morning. Northwest winds increase to 10-12 knots Sunday afternoon.

Outlook...Periodic snow with non-VFR expected through Tuesday night. Non-VFR likely on Wednesday in snow changing to rain/snow with a clipper system. Non-VFR may return again on Thursday as another system moves through the region.

MARINE

Main concern over the next several days will be the increasing north to northwest flow of 20 to 30 knots across Lake Erie Sunday night into Monday as a trough sweeps southeast through the region. This will lead to abrupt southerly shifts of the ice across Lake Erie, especially on Monday. Winds will diminish to 10 knots or less Monday night, before shifting towards the southwest on Tuesday, and increasing into the 15 to 25 knot range by Tuesday night into Wednesday. Winds may gradually favor a more westerly direction by Thursday, and maintain a modest speed of around 20 knots.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Winter Storm Watch from Sunday evening through late Monday night for OHZ011>014-020-021. PA...Winter Storm Watch from Sunday evening through Tuesday morning for PAZ001-002. MARINE...None.