Updraft: September 8, 2009 Archive

Salvaging summer

Posted at 8:02 AM on September 8, 2009 by Paul Huttner

Twin Cities NWS weather story today shows summer like temps east with scattered thunderstorms west.

You can't script holiday weekends any better.

We salvaged a bit of summer last weekend for Minnesota. Bright sun, warm breezes and temperatures near 80 degrees made for the perfect end to summer. Of the three big "summer" holiday weekends this year, Labor Day takes the prize. We had rain for at least part of Memorial Day and the 4th of July weekends this year.

Our summer surge looks like it will fade this week. A cold front is triggering showers and a few strong thunderstorms in western Minnesota and the eastern Dakotas today. The front will bring a chance of rain to the metro by Wednesday.

The pattern changes this weekend with a "cut-off" low spinning into the area. Cut-off lows are separated from the main jet stream, and tend to be erratic in movement. This weekends system may spin toward Minnesota Friday, move back west toward Colorado late Saturday, then surge back toward us brining more widespread rains by late Sunday and Monday.

The extended outlook hints that summery weather may make a cameo. There are signs we could see another mild dry weather pattern set up shop for the following weekend. It appears we're not done with summer like weather just yet.

PH

Forecast Update: Nicer weekend ahead?

Posted at 3:02 PM on September 8, 2009 by Paul Huttner

NOAA 5-day rainfall forecast shows over an inch of rain for much of Minnesota. This may change for the drier.

A cut-off low is a weatherman's woe.

I'm not sure who coined that phrase, but it's a good one. And this time the weatherman's forecast woe may come with a bonus; a nicer than expected weekend for Minnesota. Summer may just hang on another week.

The forecast models are having a duzy of a time trying to resolve a cut-off low pressure system in the northern U.S. this weekend. As is typical, the first solution was to just keep it moving along from west to east. This is a typical trend for numerical forecast models that like to keep weather systems moving along with the upper level flow. That would bring the low over Minnesota, and bring showery weather in the 60s and low 70s this weekend.

Now the models are building in an upper level ridge over Minnesota this weekend, and holding the cut-off back in the northern Rockies. If that happens, we may see more sun and temperatures near 80 again this weekend.

This latest solution makes more sense this early in September. Cold season cut-offs become more common in October and as we move through fall.

In the meantime, an upper wave is bringing showers and thunderstorms to the region. Look for our best chance of rain in the metro on Wednesday as the system moves through. It appears the heaviest rain will be in northern Minnesota, where over an inch could fall with this system.

Stay tuned to the saga of the cut-off low drama this week. The weekend forecast may change yet again.

PH