textproduct: Cleveland

WHAT HAS CHANGED

Snow has moved into all areas a couple of hours faster this morning but now looks to end faster tonight. The bulk of the widespread snow will be over by Midnight with just some lingering light snow through the night. Forecast snowfall totals have increased to 10-15 inches across the region, with the greatest amounts on a Mt. Vernon to Meadville line.

KEY MESSAGES

1) Widespread heavy snow will bring major travel impacts to the region today before tapering off tonight. Lake enhanced snow showers will linger in Northeast Ohio and Northwest Pennsylvania Monday, with additional light snow accumulations expected.

2) Temperatures will drop below zero Monday night and Tuesday morning with wind chill values of -10 to -20 bringing a significant cold exposure risk.

3) Prolonged cold with occasional light snow is expected through next weekend, creating elevated risks for cold exposure and damage to infrastructure.

DISCUSSION

KEY MESSAGE 1... The much talked about snowstorm is underway this morning. Regional radar and surface observations indicate that snow is reaching the ground areawide. Snow has been steadily increasing here at the office over the past hour. The snow began a couple of hours faster than previous forecasts since wet bulb effects were able to moisten the low-levels, and this faster start is part of the reason why snowfall amounts have been increased.

The snow so far has been driven by broad moisture advection and isentropic ascent in the mid-levels, with infrared satellite and water vapor loops currently showing a broad conveyor belt of mid-level moisture streaming from the Texas Gulf coast northeast through the Tennessee and Ohio Valleys. As the remnants of the southern stream mid/upper shortwave fully phase with the northern stream mid/upper trough digging through the central CONUS later this morning, a coupled mid/upper jet structure will develop over the Mississippi Valley vicinity and move toward the Ohio Valley. The very strong upper divergence beneath this coupled jet will strengthen mid-level (700-500 mb) frontogenetic forcing, and this will set up a band of much heavier snowfall to the immediate NW of the track of the deepening surface to 850 mb low. The latest NAM, RAP, and HREF guidance remain consistent in tracking the surface low from East Tennessee this morning through northern and central West Virginia by late afternoon, with the 850 low following a path just to the NW of that. This gives high confidence that the band of heaviest snowfall beneath the aforementioned mid-level frontogenesis will set up along a Mt. Vernon to Meadville line from about mid morning through evening. Snowfall rates will increase to about 1 inch per hour during this window, and this combined with the faster start this morning will lead to storm totals of 10-15 inches. Even farther NW on the edge of this enhanced frontogenesis band, the overall synoptic lift and moisture advection combined with the dry snow ratios greater than 20:1 will lead to a solid 8 to 13 inches in much of north central and NE Ohio and NW PA, with 7 to 10 inches in far NW Ohio, so increased the forecast areawide. One other thing to point out is thunder snow potential. Looked at a RAP forecast sounding near Youngstown for this afternoon which will be right within that frontogenesis band. The sounding did not show any instability, but given the degree of forcing and moisture advection in that area (the sweet spot), would not be surprised if some -EPV develops and causes some convective snow bursts with a clap of thunder. This will be the largest and most widespread snowstorm to impact our area since February 2022!

The snow will rapidly taper off from west to east tonight as the low and associated forcing move toward the New Jersey coast and a coastal low attempts to take over. This process will strip away the moisture faster, which is why the synoptic snow will end faster tonight than previously forecasted other than some lingering light snow showers. Nevertheless, travel impacts will continue through the night as NW winds increase to 15-25 knots, with occasional gusts to near 30 knots, allowing for some minor blowing and drifting of the dry, fluffy snow. This will especially be true in NW Ohio and near the lakeshore. After a lull much of the night, some wraparound moisture and strong cold air advection across Lakes Huron and Erie will set up some lake enhanced and lake-effect snow showers in upslope favored regions of the inland primary snowbelt of NE Ohio and NW PA. This will develop by 09-12Z Monday and continue through midday Monday. Confidence in the amount of lake enhanced/effect snow has decreased since there is no lingering TROWAL feature, the best moisture strips away quickly, there is quite a bit of boundary layer shear, and Lake Erie is ice-covered. This will probably limit additional snow accumulations across the snowbelt Monday to 1 to 2 inches, with locally up to 3. The snow showers will shift up the shoreline Monday afternoon as the flow backs to SW before ending by Monday night.

KEY MESSAGE 2... A deep mid/upper trough will be reinforced across the central and eastern CONUS in the wake of the storm downstream of persistent strong ridging offshore of the West Coast extending up to Alaska. This will send a renewed pool of arctic air into much of the country east of the Rockies as cross polar flow continues. This combined with fresh, deep snowpack and SW winds eliminating any warming from Lake Erie will allow for widespread below zero temperatures Monday night and Tuesday morning. The current forecasted lows may not be cold enough (it has been trending colder), so we could see temperatures below -5 to -10 in a number of locations if trends continue. This along with SW winds gusting to 15-25 knots at times will produce wind chills as low as -20, so cold weather headlines will be needed Monday night into Tuesday.

KEY MESSAGE 3... The aforementioned ridge/trough pattern and cross polar flow will keep arctic air locked in place through next weekend. This will be the coldest stretch of weather since late December 2017 through early January 2018. Daily highs will struggle to rise out of the low and mid teens through next Saturday, with some single digit highs on Wednesday and Thursday. Lows will fall below zero each night, with wind chills of -10 to -20 at times. This prolonged cold will significantly increase risks for cold exposure and infrastructure damage. In terms of snow chances, frequent weak shortwave troughs and clipper-type systems will bring bouts of light synoptic snow areawide, with periods of lake- effect snow showers in the NE Ohio and NW PA snowbelts. Details of these systems are unclear at this time, but the most defined systems look to be late Tuesday and Wednesday night.

AVIATION /12Z Sunday THROUGH Thursday/

Widespread is ongoing with visibilities ranging from 1 1/2 SM to as low as 1/4 SM at times. As deeper moisture arrives from the southwest, should see visibilities under 1 SM become more persistent later this morning and through the afternoon, with periodic visibilities down to 1/4SM at times. Snow ends from west to east this evening and by midnight, leaving behind a stratus deck with MVFR ceilings. Lake effect snow is likely to develop across portions of Northeast Ohio and Northwest Pennsylvania Monday morning into Monday afternoon, with variable visibilities between 1-4 SM. Cyclonic flow around 10-12 knots become northwest tonight through Monday.

Outlook...During the rest of Monday through Thursday, additional periods of snow with non-VFR are possible, especially in NE OH and NW PA, where periodic lake-effect snow may occur downwind of mainly ice-covered Lake Erie.

MARINE

East-northeast flow becomes 15-20 knots today. Winds become northwest on Monday and then southwest on Tuesday. Southwest winds should generally be around 20-30 knots, though there is a very low chance for gales (5-10%), especially in the far eastern basin. There is also a low chance for low water in the western basin as well. West winds of around 15 knots on Wednesday become northwest Thursday into the weekend.

Ice will continue to thicken through next weekend as several bouts of cold air impact the region. Stronger southwest winds on Tuesday may break up and shift the ice northeastward away from the southwestern shoreline of Lake Erie.

CLE WATCHES/WARNINGS/ADVISORIES

OH...Winter Storm Warning until 7 AM EST Monday for OHZ003-006>008- 017. Winter Storm Warning until 10 AM EST Monday for OHZ009>014- 018>023-027>033-036>038-047-089. PA...Winter Storm Warning until 1 PM EST Monday for PAZ001>003. MARINE...None.