Mild to wild: 70s give way to northern snow & 1st Metro freeze by Saturday

82F & 77F for highs in the metro last weekend

+1.9F temps vs. average at MSP in September

16th straight month above average in MInnesota

70s linger through Wednesday in southern MN & the metro

Cold front - season's coldest air mass sails south by Thursday

Accumulating snow potential by Thursday AM up north

Season's 1st metro frost likely by Saturday AM

Sibieran snow cover running below average - what it may mean for Minnesota this winter

High fire danger in western Minnesota again

Source: Twin Cities NWS

Roller Coaster week ahead:

Get ready for another ride on the Minnesota Roller Coaster.

September warmth lingers into the 1st 3 days of October this week. Highs will push 70 in the metro and southern Minnesota today and 70s will linger Tuesday & Wednesday. There may be just enough sun & southerly air flow to boost temps to the upper 70 to near 80F in some spots by Wednesday.

Source: Twin Cities NWS

October may have arrived on the calendar, but thermometers won't show it through mid week.

Season' coldest air mass oozes south:

Our next Canadian import sails south Thursday as the season's coldest air mass pushes south.

Low pressure will spin through northern Minnesota Wednesday night. Behind the low, sub freezing air will slide south. There should be enough moisture...and enough cold air to produce the first (heavy?) accumulating snow north & west of a Grand Forks to Ely line by Thursday morning.

Source: NOAA GFS model output via wxcaster.com

A huge bubble of frosty high pressure sends temps plummeting by Friday. 30s will return to the metro by Friday morning, and the season's 1st frost/freeze in the "inner core" of the metro appears to be a lock by Saturday morning. Right now I am forecasting temps near 30F at MSP Airport Saturday morning, with 20s in the suburbs.

Siberian snow cover running below average:

As we begin to piece together the winter outlook from the weather lab this month, one early trend is for below average snow cover in Siberia so far this fall.

Source: Rutgers Snow Lab

Recent studies seem to show a link between extensive Siberian snow cover in fall and cold air outbreaks in winter in the USA. A cold snow covered Siberia may kink the jet stream and send pulses of arctic air south into the USA.

Last winter you may recall I reported that Siberian snow cover was running well below average, and suggested it may not be a severe winter like many were projecting.

So far this fall, Siberian snow cover may favor a warm bias again this winter.

There are a lot of climatological "plates spinning in the air" now when it comes to our winter outlook. A (slowly) developing El Nino, PDO & AO phases, the lowest Arctic Sea ice on record and Siberian snow cover are just a few. All of these variables are running against the background hum of decadal climate changes that tend to produce warmer outcomes in winter at high latitudes.

You may recall last October I saw trends that lead me to the conclusion that the winter was likely to show wild swings, and be milder than many were forecasting. It turned out I was too conservative on the magnitude of the mild signals.

Heres' an excerpt from my winter outlook last October.

(In retrospect, I should have made this the headline!)

Decadal Trends: Our changing winter climate?

Juxtaposed over the technical and dynamic factors that may control winter weather are so called decadal trends, which lean strongly in favor of milder winters with less snowfall for Minnesota.

Some facts from the past decade include:

-7 of the past 10 winters have featured significantly below average snowfall in the metro, (70% bias toward less than average snow in the past 10 years)

-In those years the average winter snowfall has been 33.6"

(Roughly 22" below the 30 year average of 55.9"!)

-6 of the past 10 winters have featured above average temperatures

(60% bias toward milder than average winters the past 10 years)

-Minnesota winter nights got a lot milder in the past 30 years! (1981-2010 data set) Overnight low (minimum) temperatures in January average a full 2 to 4 degrees F warmer than the previous 30 year (1971-2000) data set.

Variable: Decadal trends in winter temps and snowfall in Minnesota

Potential effect on Minnesota winter: Milder winters temps (especially at night) and a apparent bias toward lower winter snowfall totals.

Trend for 2011-'12: Increased odds for a milder winter with less snow than 2010-'11.

Rather than giving you a "moving target" outlook every few days or weeks, I'll issue an outlook, stick with it and be accountable for the outcome.

Stay tuned in the next few weeks as we try and nail down a winter forecast that has some "predictive value."

PH