Archives — Chief Meteorologist Eric Wilhelm's Blog

Here's a collection of all the graphics I have shared on social media and on TV today.Temperatures and precipitation, showing timing of transition from rain to freezing rain and sleet to snow: [wpvideo pAt4oCHW]Check out that temperature plunge: Timing and impacts: Computer models' ice accretion forecast. Enough to make things very slick but likely not enough for widespread utility interruptions. What's the difference between sleet and freezing rain? Freezing rain occurs when there is a deep enough warm layer aloft, allowing the precipitation to remain liquid until it hits the ground, where it freezes on contact. Sleet occurs when the warm layer is shallower, meaning there is time for the rain to refreeze into ice pellets. Freezing rain is much more problematic. [wpvideo pGtvoC1I]Bridges and overpasses ice up first because they are exposed to the cold air on all sides. The snow forecast: A Winter Storm Warning will go into effect for the whole area. Wind chills will be rather harsh during the weekend. [wpvideo 7xm4yzUh]

Good morning! I wanted to share some thoughts on a storm that will impact the region Friday into Saturday....a storm that is very complicated and will likely bring a variety of precipitation types before it departs. It'll be quite a wild ride at the end of the week and into the weekend. Temperatures will soar into the upper 50s Thursday afternoon. High temperature forecast:You know at this time of the year temperatures like that are not likely to stick around for very long. Indeed a fresh batch of pure arctic air will descend into the lower 48 states Thursday into Friday, setting the stage for a battle of the air masses. Storms love to form along temperature gradients like that. An area of low pressure will get organized over the Lower Mississippi Valley Friday morning and then head north. They key to getting the details of the forecast right will be determining when the arctic air wins over the warmer air.Let's walk through what is possible and likely.

LIKELY

Temperatures will start mild Friday and any precipitation that occurs in the morning will be rain.
Temperatures will start falling at some point Friday, but I'm not sure if it's in the morning or later in the day. This has big implications for the TYPE of precipitation that will occur Friday afternoon and evening.
We will likely get snow from this system, but when the changeover to snow occurs and how much snow falls is something we don't have high confidence in right now.

POSSIBLE

The cold air is slower to arrive, thanks to a farther west storm track. This delays a changeover to snow, but opens up the possibility of an extended period of mixed precipitation/ice Friday night.
The cold air overwhelms the warmer air, pushing the storm track east. This would result in a changeover to sleet/freezing rain sooner and also a quicker change to snow by the end of the day Friday. Our region could be in the bulls eye for heavy snow Friday night and Saturday morning.

On the table:a) A "nuisance" event with some inconveniences for travelers Friday night into Saturday...a period of sleet and/or freezing rain followed by some snow but not a tonb) A major winter storm with a period of icing followed by several inches of wind-driven, heavy snow.I lean toward option "A" but can't rule out option "B" yet.

MODELING

Both the European and GFS (American) models have a swath of hefty snow with this storm, it's just a matter of where. The European is option "A" described above. The GFS is more option "B".European model (ensemble mean):GFS (ensemble mean): Why do I lean toward the European model idea? For starters, it "wins" over the GFS more often than it loses. It's been fairly consistent with the idea when above for a few runs now. It also has the support of some other modeling, which is a good sign.Let's look at the odds of certain amounts of snow, according to the European.At least 1": About 50-80% for our region.At least 3": Roughly 10-40%.At least 6": Generally 10% or less.The takeaway from this data: A "big" storm of a half foot or more is unlikely for eastern Ohio and western PA but can't be ruled out yet. Don't forget, even if the Euro has the right idea on snow, ice may still be a concern. Overall confidence in the details on this storm is low to medium this morning but will increase over the next 24-36 hours. One thing for sure, the cold air WILL win at some point. It looks very cold for a few days behind the system. Then...a nice thaw later next week.