Welcome to Decemberrrrrr.
Or as us weather geeks like to say, happy meteorological winter!
December 1st marks the start of meteorological winter or the three coldest months of the year in the northern hemisphere. (Dec-Jan-Feb) During December average temperatures drop about 10 degrees in Minnesota. In the Twin Cities, the average high is 32 today...22 by New Year's Eve. Average lows dip from 22 to 6! (Ouch!)
We see about 10 inches of snow on average in the Twin Cities during December, but of course that number can vary wildly from year to year. What's that old saying...there really is no average weather...just a bunch of random extremes?
The winter solstice occurs on December 21st at 5:38pm. This will feature the lowest sun angle and shortest daylight of the year...then the days get longer!
At least December usually gets sunnier. November is our cloudiest month of the year with just 39% of possible sunshine on average. In December that number climbs to 42%...January 53%. Skies get sunnier as cold dry arctic air tends to take hold. At least there's hope for brighter days ahead!
November 2010: Mild again
Temperatures in Twin Cities averaged +2.8 degrees in November. This marks 8 of the past 9 months dating back to our rare snowless March that temps have been above average in the metro and Minnesota.
We shoveled 9.8" of snow in November in the Twin Cities. That's almost dead on the November average, which is 10".
Heavy snowfall totals west of the metro on November 29 & 30.
The forecast models are advertising the potential for our next snow maker Friday and Friday night. A clipper like system will slide east from Montana/Wyoming Friday, and will likely spread a shield of snow east as warm air tries to overrun our cold dome near the surface. It looks like all snow with this one...no pesky rain/snow line to deal with.
This colder system should feature a drier more powdery snow. The snow:water ratio could be 15:1 with this system...meaning it will take less water to pile up a few inches.
The forecast models are cranking out the potential for about .30" to .50" of liquid equivalent or so somewhere in southern Minnesota by Saturday morning. You can do the math to see that could be a "plowable" snow event. Somebody in southern Minnesota could see the potential for 3" to 6" with this system...but it's too early to say where (or if?) that may happen.
The forecast tracks of clippers are notoriously fickle, and precip amounts otften too high in early model runs. I'll have to see a few more model runs to see if the system tracks further south. The models have a tendency to steer these systems south over time. If it does...that could spell the difference between placing the heavier snow band in the metro...or along the I-90 corridor in southern Minnesota.
The "meteorologically responsible" thing to do at this point is to alert for the possibility of snow...and leave the "inches" forecast until a few more model runs (hopefully) agree on the storm track and precip output.
Stay tuned, but be prepared for the possibility of slick travel and "shovelable" snow Friday PM (& PM rush hour!) into Saturday morning.