Weather whiplash ahead? Season’s first fall storm may bring heavy rains

Welcome to Minnesota.

If we had to explain our recent climate to newcomers it might be a difficult job. In the past 2 years we’ve gone from flood, to drought, to flood and back to drought again. It’s a pendulum of extremes. On or off. All or nothing.

That’s why it comes as no big surprise to me that after three months of drought, it looks like our weather pattern is ready to swing back to the other (wetter) extreme. October looks to have a very different character than last summer. A much wetter and cooler weather disposition is only 72 hours away.

+5 degrees – temps vs. average at MSP in September

3 to 5 inches - rainfall deficits across southern Minnesota since late June

2 to 3+ inches – NOAA rainfall forecast in the next 7 days in Minnesota

Image: Twin Cities NWS

Image: Twin Cities NWS

Summer’s swan song?

Our late summer affair lingers through Wednesday. September slides into the weather books warm and dry, the 4th straight warmer than average month at MSP Airport. Our late summer weather pattern holds through Wednesday. We’ll enjoy two more days with plenty of sun, and mild temps in the 70s which are about +10 degrees vs. average for early October. The air mass is also desert dry…with dew points in the 30s and even 20s.

Here’s the Euro model forecast from Weatherspark.

Image: Euro data via Weatherspark

Fall storm winds up by Thursday

A western storm is pounding the Pacific Northwest with flooding rains. A significant piece of that storm’s energy will slide east over the rockies by Thursday. The center of low pressure will wind up near Denver, then move northeast toward Minnesota by the weekend.

Ahead of the low, a significant rain shield will develop over the Upper Midwest by late Wednesday night and Thursday.

Image: NOAA GFS model via College of Dupage

These more widespread “stratiform” rains cover more territory than the spotty “convective” rains of summer. As the low moves in Friday and Saturday, waves of rain may be heavy at times. That could lead to some (welcome?) multi-inch rainfall totals by late Saturday. Some areas of Minnesota may soak up as much rain in the next week as they have in the past 3 months.  A 2 to 3.5 inch rainfall bull’s eye right over Minnesota?

Here’s the 7-day rainfall forecast from NOAA’s Weather Prediction Center. (WPC)

Image: NOAA WPC

 October weekend chill to follow

The first weekend in October looks unseasonably chily. Temps Saturday may crash from the mid 60s into the 50s Saturday afternoon on a developing blustery raw… and wet northwest wind.

Image: Euro data via Weatherspark

Again this weekend, Sunday looks like the sunnier, nicer day.

Cooler wetter October?

Overall the character of October looks much cooler and wetter. Right now looking at the maps..and trends in the Arctic Oscillation I’d place my bets on October coming in near or even cooler than average…and wetter than average. The 16-day GFS cranks out an impressive 3.83 inches of rainfall.

Image: NOAA GFS model via IPS Meteostar

If this verifies, we may see some positive signs in mitigating Minnesota’s late summer drought of 2013 by Halloween.

Stay tuned.