Thursday, January 17, 2019

Winter Storm Watch

NWS has already issued a Winter Storm Watch for the entire area beginning tomorrow (Friday) at 3:00 pm CST and running through noon on Saturday. Heavy snow with 4-8” and locally heavier totals. Blowing snow may also be an issue on Saturday.

 

For the Chicago area:

  • Snow begins tomorrow afternoon. The heaviest snowfall rates will be overnight. Lake-effect snow is a major wildcard, especially on Saturday.
    • The evening commute could be tricky. It might not be piling up too much by then, but even an inch of sticking snow on a Friday evening commute can make for looooooooong delays on the roads. The airports will see some delays and cancellations too.
  • Snow totals through Saturday night should be in the 3-6 inch range. Totals of 6-8+ would not be a surprise. The chance of a bust (<1-2”) is low – less than 10%. But the chance of a boom (>8”) is moderate – about 30%.
    • A little bit – or lack – of lake-effect snow can make a big difference. Getting a precise read on that in advance is impossible

 

I’ll send an update tomorrow morning as the guidance is refined, but as this point I would expect an upgrade to a Winter Storm Warning and relatively little change in the overall picture.

 

Other notes:

 

  • Lake-effect snow is an issue given the strong NE wind and warm water. Lake-prone areas are in play for bursts of very heavy snow and totals that exceed the average across the area.
  • Air travel disruptions are going to be hard to avoid. The entire eastern half of the continental U.S. is going to be fighting rough weather for the next 1-3 days.
    • Snow/ice from Dallas to Philly, NYC and Boston
    • Heavy rain and thunderstorms everywhere else: Houston to Atlanta to Florida to the Carolinas
  • Roads are going to be tough on Friday until the PM commute clears and the plows can catch up. Some roads will be snow-covered on Saturday, and heavy bands of lake-effect will make for sporadic white-out conditions, but overall road conditions should be fine by Saturday afternoon.
  • A corridor from central Illinois through Indianapolis and northern Indiana to Cleveland and Pittsburgh and upstate NY, is a good bet to see more than a half-foot of snow. Northern PA and upstate NY are a good bet to see more than a foot of snow.
  • Cold weather is locked in for the next two weeks. We’ll have at least a few rounds of snow, punctuated with cold outbreaks.
    • I don’t see any reason to put stock in long-range models because unlike the 1-/7-/10-day models they’re just not very good. But given that the arctic has returned to “normal” and this is “triple split” of the PV, you’d think we would have more episodic cold/snow than in prior years with a similar cold/snowy pattern. Also, winter in eastern North America had a very mild start, and it’s already more than halfway over. It wouldn’t surprise me if there is another big flip back toward mild weather by early-/mid-February.

 

Local odds of >4 inches are >70%:

 

 

 

Regional odds of >8 inches:

 

 

 

For my two polar-vortex enthusiasts:

 


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