Updraft: September 9, 2009 Archive

Weekend Forecast: Retrograde

Posted at 8:36 AM on September 9, 2009 by Paul Huttner (2 Comments)

European model shows upper low has moved back west into Montana late Saturday.

Here's a geeky weather term to throw out at cocktail parties this weekend. Retrograde.

That's what happens when weather systems move backwards in the atmosphere. In this case the system in question is a cut-off low that will move toward Minnesota Friday. The latest model runs then retrograde the system back to the west into Montana on Saturday.

Retrograding systems can be a forecaster's worst nightmare. Forecast models have a tough time accurately resolving the movement of these erratic systems. The computer models want to make nice and just keep things moving along in the flow. Retrograding systems throw a monkey wrench into that notion.

The resulting forecast differences can be striking. Will it be 65 and showery this weekend, or mostly sunny hazy humid and 75 to 80? You'll see a lot of local forecasters "splitting the difference" the next two days.

Here's the bottom line for you weekend forecast. If this system retrogrades all the way back into Montana Saturday we'll see a nice weekend here. I'm leaning toward that solution right now. We may get a shot of showers Friday evening as the cut-off approaches, and then look for more sun and warmer temperatures Saturday into Sunday. Showers may return Monday into Tuesday as the system wobbles back our way.

So here's my weather limb for this weekend.

Wednesday: A few scattered showers. High 77.
Thursday: Mostly dry and warmer. High 81.
Friday: Chance of showers late, especially west of the metro. High 80.
Saturday: Partly cloudy. High near 75 to 80.
Sunday: Mixed sun and clouds. High 75 to 80.

Stay tuned. This forecast may change yet again!

PH

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Evening Forecast: Scattered showers

Posted at 2:57 PM on September 9, 2009 by Paul Huttner (2 Comments)

A fading cool front is washing out over southern Minnesota this evening. The front still has enough oomph to serve as the focus for scattered showers and a few thunderstorms through this evening. Local downpours will occur under storms with a humid air mass this evening.

Thursday into Friday still looks dry at this point. Then a quirky cut-off low will approach the area Friday night into Saturday morning. It will be a close call for showers Friday night into Saturday morning, before the system moves backwards into Montana by Sunday. The latest model runs today bring rain right up to the western edge of the metro Friday night, and then pull it back into the Dakotas Saturday. That would leave us with a sunnier drier weekend with temperatures close to 80 by Sunday afternoon.

Stay tuned to this quirky system and the weekend forecast!

PH

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