Here it comes

20 years ago when I was a rookie forecaster in Chicago, a wise Air Force trained meteorologist named Forrest Archer taught me how to forecast snow. Us young bucks used to joke that Forrest would track the onset times from snow all the way to Siberia, as he wrote down the time snow started in Great Slave Lake in Canada's Northwest Territories, and followed it all the way to Chicago.

Arch would be proud today as we've been able to track the core of the coldest Siberian born arctic air mass through Nome, Alaska and all the way to Yellowknife on Great Slave Lake this morning. It's -40 in Yellowknife. No need to ask whether its Fahrenheit or Celsius as -40 is where the two scales meet. With the wind chill at -51F you can freeze your skin in just 30 seconds.

That core of cold air is heading right down over Minnesota this weekend. I'm always interested to see how well the models handle air this cold. The current GFS model puts the lowest temp forecast for the metro this weekend at -12 for Sunday morning. The same model has a forecast high Saturday of -1.

KMSP GFSX MOS GUIDANCE 1/17/2008 0000 UTC

FHR 24| 36 48| 60 72| 84 96|108 120|132 144|156 168|180 192

THU 17| FRI 18| SAT 19| SUN 20| MON 21| TUE 22| WED 23| THU 24 CLIMO

X/N 15| 4 8| -9 -1|-12 2| -7 5| -4 10| -4 10| 1 14 5 23

These arctic air masses modify somewhat as they move south, but with snow cover and a low January sun angle, my guess is they won't modify that much by the time this one gets to Minnesota. I would be surprised if we get as "warm" as -1F Saturday. I'm guessing more like -5F or so. And though -12F may hold for the inner core of the metro Sunday morning, places like Lakeville and Hutchinson could easily see -20F.

Forrest is probably tracking the arctic core right now. So am I.

PH

Yellowknife

Currently

Observed at: Yellowknife Airport 6:00 AM MST Thursday 17 January 2008

Clear

Temperature

-40°F

Pressure/ Tendency

30.39 inches↑

Visibility

15 miles

Humidity

55 %

Wind Chill

-51

Dewpoint

-50°F

Wind

NNW 2 mph