Saturday, January 4, 2014

Major Winter Storm To Hit Midwest

You've likely heard about it for days.  A major winter storm is taking aim on the Midwest and now we are twenty-four hours from it's arrival.

First and foremost, in my opinion the BIGGEST impact from this storm is going to be the barbaric cold air coming down from the arctic for Monday and Tuesday.  Temperatures projected to be experienced early in the week haven't been felt in this part of the country for nearly 20 years (if not longer).

Temperatures Monday morning are expected to drop well below zero.

12z ECMWF - Projected low temperatures Monday morning.
(Click the image to see larger version.)
Don't expect the air to warm much through the day Monday.  Many locations, especially in central Indiana will struggle to reach -5° during the afternoon.  We're talking temperatures in some locations of Indiana, Illinois and Missouri 40° to 50° below normal.
12z ECMWF - Temperature departure from normal Monday afternoon.
(Click the image to see larger version.)
The most asked question I have received in last three days is about snow.  Yes, there is going to be snow across much of the Midwest.  My concern is not so much with the snow, but instead when people go out to shovel the snow... Spending 30-45 minutes clearing their driveway and not being prepared for below zero temperatures and wind chills -20° to -35°.  Frost bite will be a BIG concern Monday morning along with exposure.

SAY IT AIN'T SNOW

Now to get on to what everyone wants to know.  "How much snow are we getting?"

I have been holding off on putting out numbers until close to the event because the storm still had a few wobbles in it and I didn't feel comfortable putting out numbers I didn't feel confident in.  Now that we are within 24-hours from the start of the storm, and now that all the morning computer model runs are in, I feel a bit more confident with the numbers.

I have gone over 26 computer models from this morning's runs and have come up with the snow matrix below.
(Click the image to see larger version.)
In the snow matrix you can see how much snow I think the computer model is suggesting.  It includes a blending of snow ratios I think we could be dealing with.  Due to the cold air coming in towards the tail end of the system, we could see snow ratios as high as 23:1 in some locations.  At the same time, some locations near the Ohio River, could see several hours of rain mixed in.

Keep in mind, the numbers on the snow matrix is not my forecast.  Here is what I am thinking as of this morning.

ILLINOIS:
  • Mt. Vernon: 8"-11"
INDIANA:
  • Columbus: 7"-10"
  • Indianapolis: 8"-11" (Wouldn't be surprised by a 12" amount somewhere.)
  • Lafayette: 8"-12"
MISSOURI:
  • Cape Girardeau: 4"-7"
  • Poplar Bluff: 4"-7"
  • St. Louis: 6"-10" (An 11" amount wouldn't surprise me.)
The majority of snow in Illinois, Indiana and Missouri will end by Sunday night and will start anywhere from Saturday evening through early morning Sunday.

I mentioned rain mixed in for some areas.  Some of the data is suggesting temperatures will be warm enough at the start to keep things rain until the cold air arrives.  Once it does so, rain should quickly change over.  Also, in southern Indiana (Columbus) it could start as snow early morning Sunday, change over to rain for a few hours, then change back to snow by Sunday afternoon.  For Columbus, if the changeover to rain does not happen, we could add another 2" to 3" of snow to the total I mentioned above.

FREAK-OUT-METER:
Normally the Freak-Out-Meter is based off precipitation but this time the numbers are going to be a little higher because I'm combining snow with the dangerous cold air coming in.

Keep in mind, the Freak-Out-Meter is based on a 0-10 scale.

ILLINOIS:
  • Mt. Vernon: 7
INDIANA:
  • Columbus: 7
  • Indianapolis: 8
  • Lafayette: 8
MISSOURI:
  • Cape Girardeau: 6
  • Poplar Bluff: 6
  • St. Louis: 8
BOTTOM LINE
  • Snow will being Saturday night through Sunday morning.  It will continue through Sunday afternoon/night.
  • Winds will increase and there will be drifting snow.
  • COLD air will arrive Sunday and linger through Tuesday.  Wind chills will drop to -30° to -40° in some areas.
  • Because of the cold air coming, be sure to not have your gas tank on empty.  Gas could freeze if your car is parked outside.
  • Be extremely careful when you go out to shovel snow Sunday evening and Monday morning.
As always, for more frequent updates follow me on Twitter: @johndissauer.

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