Thursday, December 5, 2013

Major Winter Storm Taking Shape

A major winter storm for the Midwest is in the process of getting underway.

A strong cold front has ushered through Missouri, Illinois, Indiana and Kentucky.  Temperatures in the 60°s and 70°s yesterday will be replaced by falling temperatures through the day to the upper 20°s and lower 30°s.

Moisture is already starting to fall across Missouri and Illinois.  A friend in Cape Girardeau told me it has already started to sleet as of 12:30pm CT and there are multiple reports of sleet around the St. Louis metro area.

Moisture and cold temperatures are the big headache for forecasters around the region.  We know there will be moisture, but how much?  We also know there will be cold air, but how much cold air will there be and where will it be above the surface?  The answers to those questions will determine how much and what kind of precipitation will be seen.

There are many facets to the next 24 to 36 hours.  The first round, starting now, is going to produce rain, freezing rain and sleet.  This will continue through the evening.  I think much of it will fall in the form of sleet, especially north of a Poplar Bluff -- Cape Girardeau -- Evansville, IN line.

Freezing rain will end up being a significant problem for areas south of that line including the Missouri bootheel, western Kentucky, northeast Arkansas and northwest Tennessee.  The freezing rain should start later this afternoon (once the temperature reaches 32° and below) and continue for some areas through Friday morning.  I think it is totally possible for some areas, especially in western Kentucky and Pemiscot/Dunklin counties in Missouri to see 0.5" to 0.75" of ice and I wouldn't be surprised if a few locations go higher.

Here is a look at a meteogram for Paducah, Kentucky looking specifically at freezing rain accumulation.

Paducah, Kentucky Meteogram
(Click to see larger version.)
Each line represents a separate computer model run indicating what it projects for freezing rain/ice accumulation.

While not the 2009 Ice Storm, this much ice will NOT be fun.  Make sure you have leave your cell phones, laptops and tablets charged in case power does go out.  I suspect there will be power outages from northeast Arkansas through the bootheel in to western Kentucky.

Further north sleet will be the issue this afternoon.  Sleet will fall from Missouri to Indiana during the afternoon and evening.  Here is a look at the meteogram for Cape Girardeau looking at sleet accumulation.
Cape Girardeau Meteogram
(Click the image to see larger version.)
Again, each line represents a different computer model run.

Sleet is not as bad as freezing rain, but still not fun to drive on.

Sleet is always a killer to snow forecasts but I think in this situation it may not hurt the snow forecast too much.  The reason being this is going to come through in two waves.  First is sleet/freezing rain and then it will be snow.

The models this morning are narrowing in on the target for the heaviest snow.  I think the target has shifted slightly north of what they were showing before.  Now the heaviest band of snow could go through Farmington, Missouri through southern Illinois in to south-central Indiana.

Here is a look at how much moisture will be available for snow production from various computer models.
(Click image to see larger version.)
(Click image to see larger version.)
In some cases the models have up'ed the moisture and in other cases they have dropped.  Bottom line, I do think there is going to be some pretty good snow overnight through Friday late afternoon.

Here is a closer look at how much snow accumulation the European forecast agency's computer model is projecting through 7pm ET Friday.
12z ECMWF - Snow accumulation through 6pm CT.
(Click image to see larger version.)
12z ECMWF - Snow accumulation through 6pm CT.
(Click image to see larger version.)

12z ECMWF - Snow accumulation through 7pm ET.
(Click image to see larger version.)
My forecast is going to stay pretty close to what it was before.

SNOW FORECAST
Snow accumulation through Friday evening.

ILLINOIS:
  • Marion: 8"-12"
INDIANA:
  • Bloomington: 7"-11"
  • Columbus: 7"-12"
  • Indianapolis: 4"-6"
KENTUCKY:
  • Paducah: 1"-2"
MISSOURI:
  • Cape Girardeau: 5"-9"
  • Farmington: 7"-12"
  • Perryville: 7"-10"
  • Poplar Bluff: 4"-6"
  • St. Louis: 2"-4"

FREAK-OUT-METER

ILLINOIS:
  • Marion: 6 
INDIANA:
  • Bloomington: 7
  • Columbus: 7
  • Indianapolis: 5
KENTUCKY:
  • Paducah: 8
MISSOURI:
  • Cape Girardeau: 6
  • Farmington: 6
  • New Madrid: 8
  • Perryville: 6
  • Poplar Bluff: 6
  • St. Louis: 4
How much do you think will fall at your location?

As always, you can get more information by following my Twitter account, @johndissauer.

2 comments:

We had sleet all day in Perryville, changed to snow about 2 hours ago. Relative traveling from St. Gen to St Mary 20 mph all the way home. Inch predictions for the area still the same John?

Hopefully 10+ of the white stuff near the Chaffee area... I could pass on the other...

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