Spring Fever: First 40s of 2011 ahead

You could feel it in the air Friday afternoon.

Temperatures rose over 30 degrees and surged above freezing after a sub-zero start Friday. There is slush in the streets, water on the sidewalks and a run on windshield washer fluid at your local hardware store. You can almost taste spring in the air.

Get used to it. It looks like a major outbreak of spring fever is busting out all over Minnesota.

Why is it happening?

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Predominant northwest upper air flow this winter.

Winter (really) began in Minnesota on November 13th. That's when our upper air flow turned into the northwest, and began dealing shots of cold air and a barrage of snowstorms that would choke streets with snow and collapse the Metrodome. For 3 solid months winter has been relentless. Until today.

Our mean upper air flow has finally shifted into the west, brining a surge of Pacific air into the Upper Midwest. The change in air masses today was dramatic, with temperatures rising over 40 degrees in much of the region.

Upper air flow shifts into the west, bringing milder pacific air masses.

First 40s of 2011 likely:

The milder air will bring daytime high temperatures as much as 40 degrees warmer than earlier this week. 30s should spread statewide and southern (and maybe all of) Minnesota will have a shot at 40 in the coming days.

Models hinting at 40s as early as Sunday. (click to enlarge)

The best chances for a 40 degree temp surge appear to be Sunday, Tuesday, Wednesday and Thursday.

Even overnight lows may be near or above freezing next week!

Fog Factor?

When snow melts it releases additional moisture into the low levels of the atmosphere. That sets the stage for fog. On clear nights it may form as radiation fog. When the warm breezes blow over the cold snow pack, it may be advection fog.

Either way, there is a good shot at some relatively thick fog blankets in the next week, especially late at night and early in the morning.

If the fog burns off early in the morning, we'll see temperatures surge in the mild air mass in the afternoon sun, and 40s are possible. If the fog hangs tough into afternoon, temperatures may be held into the 40s. It will be a day-to-day nowcasting situation, but expect the possibility of some fog advisories in the next week.

Slop storm late next week?

The GFS model is tracking a low pressure system through Iowa by next Thursday/Friday. Right now it looks warm enough for the system to begin as rain in southern Minnesota and the metro, but maybe snow in central and northern MN. There may be a transition to all snow Friday, but it's way too early to tell.

The medium range forecast models are not nearly good enough temporality or spatially to pinpoint rain/snow areas a week out, and sometimes even 24 hours out! The state of the science of meteorology only allows us to say there might be rain and or snow in a week...and anyone who tells you otherwise is selling you a bill of goods.

The medium range models are much better with big temperature trends...like the well advertised and forecast thaw now underway.

It looks like the extended thaw and rain potential next week means our excellent outdoor ice (and our Friday night hockey games) will take a hit. I'll miss the outdoor ice...but I am ready for a warm up after our "real Minnesota winter of 2010-'11."

Enjoy the thaw, and stock up on washer fluid!

PH