Posted at 5:35 PM on January 3, 2013
by Paul Huttner
-3.5F temps vs. average so far in January at MSP
+13 minutes increase in evening daylight since December 15th
+1 minute per day daylight increase next 2 weeks
65.8% snow cover now in the USA (lower 48 states)
18.7% last year on this date
30F possible by Friday afternoon in the metro and southern Minnesota
January Thaw 30s possible Monday through Thursday of next week
Arctic Invasion? -10F to -15F possible in the metro Janaury 15th-20th time frame?
Temps will gradually respond as arctic air eases in the Upper Midwest Friday. Highs should bump 30 by Friday afternoon from near the metro south into Iowa.
So far January is running a good -3.5F below average. This has the look and feel of a real January so far. Now if we could just get some more snow for snow lovers? There's a chance of a little snow next week but the models don't favor anything huge in the cards just yet.
Fellow MPR meteorologist Craig Edwards likes to talk about "high quality snowflakes." We got some Thursday as advancing arctic air managed to squeeze out a dusting of "arctic fluff."
It's amazing how efficient arctic air is at "paving the way" for its arrival by squeezing out scant amounts of atmospheric moisture into pretty snowflakes.
Check out the close up view on the Weather Lab fence Thursday, which appears to show some star shaped "stellar dendrites."
The physics of snowflakes is as close as we get to weather heaven on this earth I think. Creating unique, intricate stunningly beautiful snow crystals out of thin air in sub freezing temps? Pure magic.
Here's a great look at what science of snow crystals under different conditions from one of my favorite websites, snowcrystals.com
Growing snow cover:
Recent storms have brought respectable snow cover to the USA. With 65.8% now snow covered compared to last year's 18.7% on this date, It looks like a real January across the USA this year.
Thursday's NASA MODIS Terra image to clearly shows the white coating from space.
January Thaw next week:
All signs still point to a January Thaw next week in Minnesota.
After a seasonably cool weekend with highs in the 20s, 30s are likely next Monday through Thursday.
Will the widespread snow cover across the central US hold down temperatures during a warm spell? In other words, if there's no snow cover in Nebraska and Iowa, then a warm spell might get up to 45 degrees, but with snow cover south and west of us, it might get only to the upper 30s? How much of an effect does that have on temperatures?
So the Jan. 15-20 "Siberian Express" is now an "Arctic Invasion," and the expected -20F to -31F is now a wimpy -10F to -15F ?!
Snow cover has a significant effect on temps. Yes, temps would be a good 5 to 10 degrees warmer without snow cover to the south. We use correction factors for snow cover in our temp computations.
That said...snow cover is thinning in some areas to the south, and that may lessen the impact next week.
Don't read too much into the verbal changes.
All indications are we're still looking at a good chance of sub-zero air starting about January 15th. The latest GFS runs peaks at -21F on the 17th....and keep teens below into the 20th.
The GFS operational model we use usually overestimates cold outbreaks 1-2 weeks out. But there is plenty of -20F or colder air up north. It's very possible that any shift into a northerly flow will bring bitterly cold, and possibly prolonged sub-zero air into Minnesota by mid-month.