Posted at 6:07 PM on November 29, 2012
by Paul Huttner
40F high at MSP Airport Thursday at 3:12pm
Fog & freezing drizzle possible early Friday AM
40s this weekend as milder air surges north
50s likely on Monday - peak of early "December Thaw"
California storm sending waves of rain and snow ashore through this weekend
Pineapple Express feeding tropical moisture into West Coast storms
A Big Maybe but at least one model hinting at snow chances for Minnesota late next week
Too early to be credible about snow chances next Thursday night/Friday...but worth watching
Icy start Friday?
Things could get a little icy in spots Friday AM in the metro and much of Minnesota.
Low level moisture is pushing north, and fog and some freezing drizzle and a few snowflakes are quite possible. Precip will be light in this mixed weather grab bag Friday morning...but it doesn't take much to ice up a few roads and sidewalks. Be careful driving...and walking early Friday morning.
Poised for the big thaw:
40 felt nice Thursday. It's amazing how good 40 in Minnesota feels after a chilly sub freezing run.
This weekend will feel more like late October or early April at times as milder air pushes north. High will push well into the 40s this weekend from the metro south. It won't shock me to see an eager bank thermometer or two flashing 50F in the metro this weekend.
By Monday 50s will be widespread in southern Minnesota, and 60F is possible south of the metro.
The best chances for rain come Saturday and again Monday...but overall rainfall totals look to be less than .25".
After the thaw the GFS hints we turn colder again next Tuesday as highs fall back into the 30s, but the Euro holds mild air in place with a week long thaw.
Either way the brief December chill won't last...warmer air appears ready to ease north again by next Wednesday & Thursday.
California storm a boon for snow lovers!
I've been hammering the massive California storm in my posts this week. Here's another angle from my MPR colleague Dr. Mark Seeley in a preview of this week's Weather Talk on how snow lovers will appreciate the massive snow dump. I added the italics.
Topic: A snow lover's forecast
The National Weather Service in Medford, OR issued the following forecast for Mt Shasta in California this weekend. For snow lovers it must have brought all smiles, but look at the wind speeds!
-Friday Snow showers. The snow could be heavy at times. Temperature falling to around 15 by 4pm. Wind chill values as low as -13. Windy, with a south southwest wind 80 to 85 mph decreasing to 70 to 75 mph in the afternoon. Winds could gust as high as 115 mph. Chance of precipitation is 100%. New snow accumulation of 23 to 29 inches possible.
-Friday Night Snow. The snow could be heavy at times. Low around 14.
Wind chill values as low as -13. Windy, with a south southwest wind
70 to 80 mph, with gusts as high as 115 mph. Chance of precipitation is 100%. New snow accumulation of 21 to 27 inches possible.
-Saturday Snow. The snow could be heavy at times. High near 19.
Windy, with a southwest wind 75 to 80 mph, with gusts as high as 115 mph. Chance of precipitation is 100%. New snow accumulation of 22 to
28 inches possible.
-Saturday Night Snow. The snow could be heavy at times. Low around 17. Windy. Chance of precipitation is 100%. New snow accumulation of
29 to 35 inches possible.
-Sunday Snow. The snow could be heavy at times. High near 18. Windy.
Chance of precipitation is 100%. New snow accumulation of 11 to 17 inches possible.
-Sunday Night Snow showers likely. Cloudy, with a low around 9. Windy.
Somehow putting out a forecast of a 12"+ "megastorm" for Minnesota in winter suddenly feels... inadequate.
Rumors of snow late next week?
Call it "A big maybe" at this point.
GFS runs Thursday hinted at some "phasing" of upper air and surface systems near Minnesota late next week. If that happens...and it's a big if a week out...there could be a chance of some significant snow next Thursday night or Friday on Minnesota.
It could also be just a passing forecast model fantasy...especially from the notoriously dicey GFS Model.
Still, the overall pattern suggests something may be in the cards. It's (always) too early for apocalyptic headlines a week out, but this one may be worth watching.
Forecasting snow: Tougher than hurricanes
People often ask me "What's the toughest thing to forecast Paul?"
My quick answer is always "snow storms."
Snow systems are highly complex animals. Storms tracks, moisture, temperature profiles and upper air energy all have to come together to get heavy snow. If just one element is missing, or if a storm track moves just 50 miles...or enough warm air works north to raise temperatures 2 degrees...it can be the difference between an inch of rain and a foot of snow.
These big beautiful beasts of winter are challenging to forecast. Forecasting hurricane tracks 3 days out actually proves more accurate than forecasting snowfall totals 3 days ahead.
That's why here at the Weather Lab we use the "24 hour rule."
Before a storm, I'll let you know about potential timing and the relative size of the storm. If there is a potential for significant snow...or heavy snow I'll say that if I think it's credible a few days in advance. That gives you, our customers, good longer range planning capability for a possible event.
As we approach 24 hours before the snow flies, I'll issue an more specific "inches" forecast. Why 24 hours? 24 hours is about where overall forecast accuracy..the "state of the science" that is meteorology...and having adequate time to plan ahead for a storm are "optimized."
You may hear forecasters throwing around multiple "inches forecasts" days in advance. 6" to 12" becomes 3" to 6" becomes 1" to 3" and back again. It gets to the point where that approach has little value...except to entertain and confuse.
The "meteorological reality" is that snowfall forecasting accuracy dramatically increases about 24 hours before the event. Even then, forecasting snow is one of the toughest forecasts we make as meteorologist.
It's also one of the most entertaining things I've ever done in my life. Instant gratification or widespread public ridicule is only a few hours away!