Thursday, December 12, 2013

Fast Moving System

A quick moving system will be passing through the Midwest Friday and Saturday.  Computer models are still a little spread regarding how much snow and where.


National Weather Service offices have issued Winter Storm Watches and Winter Weather Advisories for parts of Kansas, Missouri, Illinois and Indiana.
Watch, Warning & Advisory - 3:49pm CT

Let me show you a couple computer model suggested snowfall totals and then I'll tell you how much I'm currently thinking.

European forecast agency's computer model.
ECMWF Snow Accumulation through 12pm CT Saturday.
(Click image to see larger version.)

ECMWF Snow Accumulation through 12pm CT Saturday.
(Click image to see larger version.)

ECMWF Snow Accumulation through 12pm CT Saturday.
(Click image to see larger version.)

National Weather Service's global forecast model.
GFS Snow Accumulation through 12pm CT Saturday.
(Click image to see larger version.)
NAM computer model:
NAM Snow Accumulation through 9pm CT Saturday.
(Click image to see larger version.)

NAM Snow Accumulation through 12pm CT Saturday.
(Click image to see larger version.)

NAM Snow Accumulation through 9pm CT Saturday.
(Click image to see larger version.)
It is interesting to note that all three of the above models try to move snow around the St. Louis metro area.


WHAT I'M THINKING:
The system will start to spread moisture north starting Friday afternoon.  I think most of the snow will come down as a wet, slushy snow.  The slushy snow will have a big impact on snow accumulation.  If temperatures end up being 2° to 3° colder than computer models are projecting, we could easily add another 1"-3" on to the totals shown below.

It should come to an end from early Saturday morning in Kansas City, late morning in St. Louis and Saturday afternoon in central Indiana.

Indiana:
  • Columbus: 2"-3" (Up to 4" not out of the question.)
  • Indianapolis: 3"-5"
Illinois:
  • Mt. Vernon: 2"-4"
Missouri:
  • Cape Girardeau: Up to 2" (Probably not much accumulation.)
  • Farmington: 3"-6"
  • Kansas City: 1"-4"
  • Perryville: 3"-5"
  • St. Louis: 2"-3" (A few locations up to 4")

FREAK-OUT-METER:
Indiana:
  • Columbus: 3
  • Indianapolis: 3
Illinois:
  • Mt. Vernon: 4
Missouri:
  • Cape Girardeau: 2
  • Farmington: 4
  • Kansas City: 3
  • Perryville: 4
  • St. Louis: 3

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