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BIG TICKET COLD AND SNOW...

The United States is now in the grips of what's known as a positive TNH pattern. The +TNH reflects large-scale changes in both the location and eastward extent of the Pacific jet stream which in this case significantly limits the flow of mild Pacific air into North America. At the same time, it enhances the southward transport of cold Canadian air into the north-central United States.


In a nutshell, with a +TNH the axis of prominate ridges and troughs become aligned in such a way that a strong ridge develops along the west coast and a mean trough is established over the plains/Midwest (not the east). There's also a stable southeast ridge near Florida (which keeps the southeast mild).

The surface temperature departures for the +TNH in January are cold central and west.

The +TNH is aided and abetted by a strongly negative EPO (Eastern Pacific Oscillation) which strengthens and expands the west coast ridge.

The negative EPO teleconnects to the west coast ridge and large Arctic highs which deliver cold air intrusions.

Here's what the 500mb pattern is projected to look like February 1st. That is a text book +TNH

The ridge off the west coast and east coasts drives the trough and its cold air into the Midwest. We pay for that with the EURO indicating temperature departures of 30-35 below normal across Iowa and western Illinois February 2nd.

If the EURO verfies, (STILL A BIG IF) those departures translate to lows of 13 to 19 below zero the morning of February 3rd. Daytime highs the 2nd remain below zero in all but my far southern counties.

Serious wind chills would also be a by-product with readings 25-35 below zero.

The GFS is already showing odds of sub-zero cold of 50 percent in the south to 80 percent in the far north. Pretty strong odds a week out from the event. But I stress, strong is not a gaurantee of such severe cold. I will continue to monitor!

The Climate Prediction Center has a large part of the Upper Plains and Midwest in a high risk hazardous temperature outlook February 1st-3rd.

The 6-10 day outlook January 30th -February 4th

The 8-14 day outlook February 1st-7th. The next 2 weeks don't look fun unless you are a polar bear.

If the cold is not enough, there appears to be several chances for snow which in total the next 2 weeks could exceed what we have seen over the entire winter so far. These are the ensemble snowfall forecasts from the EURO, GFS, and Canadian over the next 15 days. There is remarkably good consistency between all three models over the two week period. Sometimes it's hard to get that a day ahead of an event let alone 15 days.


The EURO

The GFS

The Canadian