Saturday, December 15, 2012

December 20-22 Potential Blizzard Event

See the updated version HERE

I have upgraded my thinking of this winter event from a 'Significant Storm' to a 'Blizzard' event. I'll now explain why.

This is the ECMWF forecast for Hour 144, a.k.a. the evening of December 20th. We see a very strong storm system in northeast Illinois at this time with a minimum central pressure of 986 millibars- pretty strong for an onshore system. Let me first start off discussion of the model by saying I trust the ECMWF more than other models at the moment, as although all models have been having troubles, the ECMWF has historically outperformed most models in the past. The ECMWF shows a high pressure system in the Southeast, off to the east of Florida.

Moving quickly along, we now visit the ECMWF Ensemble prediction system, or the ECMWF EPS. This forecast is for the same timeframe as above- the evening of December 20th. We see our storm system is on the Michigan/Indiana/Ohio border, with a central minimum pressure of 998 millibars. Considering the ECMWF EPS is composed of 51 separate forecasts, and we are 144 hours away, the strength of this system that is being projected is astounding. It's not that common to see an average of 51 forecasts, 6 days out projecting such a strong storm system. The ECMWF EPS believes the system will be submerged in cold air, as shown in 850mb temperatures (colors). This, combined with tightening of isobars, makes me believe that a blizzard-like solution could evolve in the Upper Midwest and South Canada into Michigan.

The GFS model has not been mentioned, but for those wondering, it is similar to the ECMWF EPS solution above as far as placement of the system goes.

Going back to the ECMWF model, we can see that it is projecting very heavy snow to fall over some Midwestern states. Snow is shown as precipitation north of the dark blue 32 degree line:

ECMWF Precip/Temp forecast for the Morning of Dec. 20

ECMWF Precip/Temp forecast for the evening of Dec. 20

ECMWF Precip/Temp forecast for the morning of Dec. 21
I don't have access to snow depth forecasts from the ECMWF, but if I were to give a rough estimate of snow amounts from the above few images, I would predict the following accumulations for the following locations:

-Northeast IL: 6 inches+
-South WI: 5-8 inches
-Michigan: 5-8 inches+

Forecast Preference: ECMWF
Confidence: 55%



Teddyz1919 said...

Hey Andrew, I am in Milwaukee, looks to be a nasty NE wind for us here on top of the possible snowstorm, do the numbers look right to get a decent fetch off the lake to enhance the moisture and increase snow totals around here?? Also seems that most models are in agreement... What's your forecast confidence that this will pan out?? Would love a white Christmas for once!!

Randy the Random Dude said...

Could I have a link to where you got those ECMWF plots Andrew?

Teddyz1919 said...

Sorry didn't see your 55% confidence at the bottom!!! Does the fetch look favorable or no?? Thanks andrew

armando said...

Well not shocked that the midwest(as usual) will get a major possible snowstorm! Andrew could this storm either form a secondary or slide to the coast and strengthen so that the northeast and inland NJ could be affected by this? Thanks

Anonymous said...

What about a snow forecast for the Front Range on the 19th? which was totally skipped, we matter too.

Chris E. said...

Do you think it might be a rain to snow transition for south Wisconsin? Some of the 12z runs placed the low further north. I know it's still 144 hours away, but I'd still like to learn your opinion.


Anonymous said...

You're a little vague when you say Michigan... can you be a little more specific as to how much snow different areas of the state may recieve?