textproduct: Cleveland

WHAT HAS CHANGED

Snowfall is trending a little higher Wednesday afternoon through Thursday, with a faster transition from rain to snow on Wednesday. Temperatures Wednesday night and Thursday are also trending colder.

KEY MESSAGES

1) A mild and breezy day is expected Tuesday with a quick shot of rain showers in the afternoon and evening, especially in NE Ohio and NW PA.

2) Widespread rain will arrive early Wednesday transitioning to snow by early afternoon, with snow continuing into Thursday while gradually transitioning to lake effect snow Thursday afternoon into Thursday night.

3) Temperatures will rapidly fall Wednesday afternoon, with below zero wind chills likely Wednesday night into Thursday.

4) Even colder air is possible this weekend into early next week as well as additional rounds of snow.

DISCUSSION

KEY MESSAGE 1... A rather strong northern stream mid/upper shortwave trough will dive through the Upper Midwest and Great Lakes Tuesday and Tuesday night, with the associated surface low passing north of Lake Superior Tuesday and lifting through eastern Ontario Tuesday night. As the warm front lifts through the region Tuesday morning ahead of the system, strengthening warm air advection and a tight pressure gradient will lead to gusty SW winds developing. Decent mixing into a 45-50 knot low-level jet as temperatures warm will allow winds to increase to 15-20 knots with gusts of 25-30 knots. Locally stronger gusts are possible Tuesday afternoon in NW Ohio and near downslope favored areas near the lakeshore. In terms of rainfall with this system, that will not be very impactful since there is a lack of moisture. Some light rain will occur with a frontogenesis band Tuesday afternoon and evening as mid-level forcing from the right entrance of a 120-130 knot upper jet streak squeezes out a band of showers along the weak trailing cold front. The bulk of this will likely move through between about 21Z and 03Z Tuesday evening, with the greatest coverage in NE Ohio and NW PA. Temperatures will warm into the low/mid 40s in the warm sector Tuesday afternoon, and this will be the last mild day for quite some time.

KEY MESSAGE 2... The big system of the week will arrive early Wednesday and will signal a return to winter, with impacts lingering through Thursday night. As the mid/upper trough over the Great Lakes continues to deepen Wednesday, a second cold front will plow through the Great Lakes and Ohio Valley regions. This front will slow as shortwave energy diving into the base of the digging longwave trough combined with a strong pool of trailing arctic air triggers a wave of low pressure to develop on the front. This low will develop in the vicinity of the Lower Ohio Valley Wednesday morning and lift into New England by Thursday morning while transferring its energy to a strengthening coastal low. As moisture advection and isentropic ascent increase early Wednesday, widespread rain will spread in before sunrise. This rain will changeover to snow from west to east, starting in NW Ohio Wednesday morning, with the changeover reaching the OH/PA border by 21Z. This has trended several hours faster compared to previous forecast guidance, so confidence is increasing for widespread, accumulating snow Wednesday. Given the faster changeover, snowfall amounts have been slightly increased.

The heaviest and most widespread snow will likely fall Wednesday afternoon into Thursday morning as the mid-level deformation zone pivots through the region with deep wraparound moisture and strong mid-level vorticity. This combined with lake enhancement from a NW boundary layer flow across Lake Erie and 850 mb temps crashing to -19 to -21 C will boost snowfall. This will significantly impact the Wednesday evening commute, with additional impacts lingering for the Thursday morning commute as the steadiest snow winds down from west to east. Besides the falling snow, NW winds gusting up to 25 knots at times will also lead to blowing snow and poor visibilities.

Total snowfall Wednesday through Thursday afternoon should at least average 1-3 inches areawide, with 4-6 inches possible in parts of north central and NE Ohio through NW PA.

As the deeper moisture exits from mid Thursday morning through the afternoon, the synoptic snow will transition to lake-effect snow as the NW flow and strong cold air advection continues. This will be more localized as is typical for lake-effect, but additional accumulations are likely in upslope favored regions of the primary and secondary snowbelts in NE Ohio and NW PA Thursday afternoon. This will gradually end Thursday night as shortwave ridging briefly builds into the region.

KEY MESSAGE 3... Another impact with this midweek system will be the strong blast of arctic air. Morning highs in the upper 30s to around 40 Wednesday will fall through the 20s in the afternoon, with lows in the teens Wednesday night. Temperatures are trending colder Thursday, with highs only in the teens to low 20s. This will support wind chills between 0 and -5 Wednesday night into Thursday morning and subzero again Thursday night.

KEY MESSAGE 4... Arctic air will remain in place this weekend and into next week, and likely beyond, as the mid/upper air pattern strongly amplifies over North America. The pattern will feature a strong mid/upper ridge in the NE Pacific and Alaska, with a downstream deep mid/upper trough over central and eastern North America. This is a classic pattern for cross polar flow to send a lot of arctic air through central and eastern parts of the United States, and the coldest air of the winter usually occurs with such patterns. After a brief warm up to the upper 20s to around 30 Friday and Saturday, expect highs in the teens and low 20s to return Sunday and Monday, with several days of below zero wind chills likely again.

Several clipper systems will bring bouts of at least light snow Friday through early next week, with locally heavy lake-effect snow likely in the primary snowbelt east of Cleveland through NW PA as well.

AVIATION /00Z Tuesday THROUGH Saturday/

VFR across the TAF sites this evening with VFR to persist through the TAF period. Light rain showers are possible at ERI Tuesday afternoon, though no vsby impacts are expected.

Otherwise, the main concern will be the potential for gusty south to southwest winds on Tuesday. Winds will increase to 15 to 22 knots, with periodic gusts of 30 to 35 knots likely late Tuesday morning and afternoon. A marginal window for LLWS is possible overnight as west to southwest 925 mb winds of 35 to 40 knots briefly arrive across the area, though opted against inclusion at this time. Stronger 925 mb southwest winds of 45 knots will arrive late Tuesday morning and afternoon, though elevated surface winds greater than 15 knots precludes LLWS mention.

Outlook...Non-VFR expected in rain late Tuesday night into Wednesday. Non-VFR will continue into Thursday as rain transitions to snow showers late Wednesday, most numerous east of the I-71 corridor. Non-VFR may return in snow showers on Friday, and again on Saturday.

MARINE

Southwest winds will ease slightly and briefly tonight dropping to 10-20kts and keeping the higher wave heights of 3-6ft well east of the islands and out beyond the nearshore water zones. Small Craft Advisories will drop this evening into tonight, but likely only for a short period of time. Southwest winds again increase Tuesday ahead of a pair of cold fronts to 20-30kts, and wave heights 3-5ft again east of the islands. The second and stronger cold front Wednesday brings a wind shift to northwesterly at 20-30kts and wave heights in the 4-8ft range in the central basin and 3-6ft in the eastern and western basins. Winds return to offshore directions by Friday at around 15-25kts, keeping the open waters at 3-6ft but the nearshore zones 1-2ft.

CLE WATCHES/WARNINGS/ADVISORIES

OH...None. PA...None. MARINE...Small Craft Advisory until 7 PM EST this evening for LEZ144>148. Small Craft Advisory until 3 AM EST Tuesday for LEZ149.