Updraft: April 14, 2011 Archive

Blustery April forecast; Ice out update; major warm up?

Posted at 9:17 AM on April 14, 2011 by Paul Huttner
Filed under: Ice out, Springtime, Winter/spring 2011

Two steps forward, one step back.

That chilly breeze you feel today is our latest reminder that the Spring of 2011 is taking its sweet time to show up. It may feel more like March out there for the next 48 hours in Minnesota at times.

A slow moving low pressure system will track through Missouri & Illinois over the next 48 hours.

The system will impact Minnesota weather with windy, cool wet weather and some snow...but not the heavy metro "snowmageddon" advertised by some weather models over the past week.

Thursday: Expect a chilly northeast wind from 15 to 25 mph today. Showery weather in southern Minensota, dry air from the metro north with a mix of sun & clouds.

Radar image and dew point contours overlay shows "desert dry" air north.

Friday: Showers increase from west to east. Dry air near the metro may hold rain at bay much of the day. Rain showers change to wet snow overnight.

Best chances for accumulating snow in the eastern Dakotas to Duluth where several inches may fall. Maybe a slushy inch in the metro by Saturday morning.

Potential accumulating snow near Duluth.

Major winter storm in eastern Dakotas?

Saturday & Sunday: Saturday will start blustery and cold, but the weather will improve as the weekend wears on.

Look for a return to sunshine Saturday, and brisk NW winds will ease by late afternoon. After morning temps in the 30s (and wind chills in the 20s) highs should struggle to reach 50 by around 4pm.

Sunday should feature a sun-cloud mix with lighter winds and temps in the lowers 50s by afternoon.

Searching for spring: Major warm up in sight?

Okay this is going way out on a limb...but with everybody searching for spring I thought I'd pass along this ray of hope for much warmer weather.

The GFS (yes... the model we don't trust lately that has been overpredicting snowstorms) is hinting at a possible major warm up in about two weeks.

The GFS seems to be better at identifying high amplitude temperature trends than handling potential low pressure systems.

The GFS paints a big, (high amplitude) high pressure ridge over the central USA sometime around April 29th-30th. If that verifies, we could see a big warm up...maybe our first real taste of late spring or early summer like temps in Minnesota. The pattern suggests 70s, and maybe even the first 80 degree readings of 2011 for the metro.

GFS: Major upper air ridge & warm up April 29th?

It may be weather fantasy at this point...but it's all we've got and I'll take it! I'll keep an eye on a potential warm up in the next week or so.

Stay tuned....

Ice out reaches the metro:

Southern Minnesota lakes have been ice free for about a week now, and the thaw is moving north by the day.

-Albert Lea Lake ice out was Friday April 8th
-St. Olaf Lake ice out Sunday April 10th

Some metro lakes are now ice free, pretty much on schedule.

-Lake Calhoun ice out occurred Sunday April 10th
-White Bear Lake ice out occurred Wednesday April 13th
-Lake Minnetonka still had partial ice cover as of Wednesday

Open water on Excelsior Bay Monday evening with ice in the distance looking north.

Here's the latest, updated list of ice out for Minnesota from the Minnesota Climatology Working Group.

What defines "ice out?

"Ice out" is defined in different ways according to the Freshwater Society in Navarre.

Here's how they define ice out on Lake Minnetonka.

"On Lake Minnetonka, the ice is designated as "out" when it is possible to travel by small boat from any one shore to another shore through any passage on the lake. Ice-out dates have been determined using this method since 1968. Previous methods include: when the ice was 50% gone, when a boat could circle Big Island, when a boat could travel between Wayzata and Excelsior, when a car fell through the ice and by visual
observations from a number of lake locations."

Today, April 14th is the median (average) ice out date for Lake Minnetonka. Oddly enough, the ice has never gone out on the lake on April 15th. Last year the ice was out on Tonka April 2nd.

Tonka ice out facts. (Click to enlarge)

Ice melts from the bottom!

I was surprised to learn several years back that ice actually melts form the bottom up!

Here's a great description from the MN Climate Working Group.

How Lake Ice Melts

"Ed Swain, of the Minnesota Pollution Control Agency describes the process of freezing and thawing lakes.

In the late fall, the lake loses heat to the atmosphere, and then on a day or night when the wind is not blowing, ice forms. The ice gets thicker as long as the lake can continue to lose heat.

In most Januaries and Februaries, snow both reflects sunlight and insulates the lake. With a thick snow layer, the lake neither gains nor loses heat. The bottom sediment is actually heating the lake water slightly over the winter, from stored summer heat.

Around March, as the air warms and the sun gets more intense, the snow melts, allowing light to penetrate the ice. Because the ice acts like the glass in a greenhouse, the water beneath it begins to warm, and the ice begins to melt FROM THE BOTTOM.

When the ice thickness erodes to between 4 and 12 inches, it transforms into long vertical crystals called "candles." These conduct light even better, so the ice starts to look black, because it is not reflecting much sunlight.

Warming continues because the light energy is being transferred to the water below the ice. Meltwater fills in between the crystals, which begin breaking apart. The surface appears grayish as the ice reflects a bit more light than before.

The wind comes up, and breaks the surface apart. The candles will often be blown to one side of the lake, making a tinkling sound as they knock against one another, and piling up on the shore. In hours, a sparkling blue lake, once again!"

PH