Thursday, January 19, 2012

January 19-22 Significant Snowfall (Midwest, Great Lakes, Northeast Affected)

EDIT: NWS forecast office's are suddenly backing off snow totals. This graphic is now void and no new graphic will be issued today.

We will be seeing significant snowfalls come across the Midwest and Great Lakes before shifting to the Northeast. This will come as multiple systems converge on the region. We expect to see a clipper come south and deliver some significant snows to the Midwest as it takes in Gulf moisture. This Gulf moisture pretty much brings the clipper to a regular system status. Clippers are, after all, moisture starved. That is the big difference in the weather world between a clipper and a regular system. Factor in Gulf moisture and you have a fast moving system putting down heavy snows. But with the Gulf moisture comes the risk of a dry slot. A dry slot is dry air that will filter into the underbelly of the system, usually on the right side. When you see a comma-shaped storm on satellite imagery, that dry pocket that makes the storm look like a comma is the dry slot.
There will be two sides to this: Snow and Ice. We have outlined the WI/IL/IA border as a potential area where 10-12 inch totals may be sighted. This map is based off of ratios that may be just a tad higher than what we will see, so don't hold your breath for the 10-12 inches- that is merely a heads up. As the system progresses east I expect storm totals to be enhanced by some lake effect snow by Lake Michigan and a Lake Erie/Lake Ontario combination out in the Northeast.
For the Midwest i am anticipating a widespread 4-8 inches above I-80, with isolated 6-10 inches in the harder hit areas, which would be from the IA/IL/WI border point into Chicago. Icing will play a big and unfortunate role for the Midwest. I am anticipating 0.10 inches of ice to be commonplace from Central Illinois eastward into Ohio and parts of the Northeast. I did outline an area where 0.25 inches of ice may fall, but I put that there as I believe the hardest hit areas may approach that number (keyword is approach).
In the Northeast, there may be some icing close to the coast, but for now I don't believe I have the right to insert that ice potential there, mainly because of a lack of forecasting guidance at this time. The Northeast ought to wind up with a good 1-3 inches across a lot of the region, and 3-6 inches in inland areas. An isolated 6-8 inches cannot be ruled out by the Lakes.

I am thinking that the big winners of this storm will be primarily in East Iowa, South Wisconsin and North Illinois. Stick with me as I will mention some towns that are more on the smaller side.

Freeport, Illinois
Rockford, Illinois
Possibly Chicago's far NW suburbs

Monticello, Iowa
Dubuque, Iowa

Monroe, Wisconsin
Janesville, Wisconsin

New York---
Buffalo, NY
Rochester, NY
Possibly Utica, NY

('Winners' are listed from top to bottom in confidence of 'big' totals (outstanding from other regions))

1:00 PM (CST) Update to Late Week Winter Storm

We will update at 1:00pm CST

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New Stratospheric Warming Propagates Down to Lower Stratosphere

Here we have the stratospheric temperatures at the 5mb level. We can see a sharp spike in the past as well as a more recent, but more subtle, warming event. Whenever we get these times of stratospheric warming, we want to see the warming propagate (shift) down to the lower levels of the stratosphere. And in this case, that just happened.
70mb temperatures
Stratospheric temperatures at 70mb have spiked with this latest warming in the stratosphere. This is indeed an encouraging sign that the atmosphere may be getting tired of the continuous cold in the Poles and warm in the US. If we can see another Significant Stratospheric Warming (SSW) event (of which there has been chatter about one just over the horizon) propagate to the 70mb level, there is an increased risk of the pattern changing.
The thing is, however, if we get a SSW to happen, it would still take a good 2-4 weeks for the effects to even begin. That would mean February would be a virtual scratch. But luckily the stratosphere isn't the only variable we see to incite pattern shifts.