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A cooler summer?

How’s this for going out on a shaky limb? The CPC, Climate Prediction Center, a division of NOAA in Washington D.C. is predicting a slightly cooler than average summer for much of Minnesota and the Dakotas. Based on sea surface temperature trends (a developing El Nino, a slow warming trend of equatorial Pacific Ocean water) and prevailing jet stream winds circulating around the Northern Hemisphere, there is a slight tendancy toward cooler than normal conditions close to home for the months of June, July and August. During an average summer we experience at least 13-14 days above 90 degrees. It’s entirely possible we’ll have fewer (stinking hot) days this summer, maybe 8-10, if you believe the guidance. If you have your heart set on a hot, blazing summer I would’t worry too much — in spite of best efforts these long range 90 day forecasts are not terribly accurate. Time will tell.

The same 90-Day Outlook suggests that precipitation amounts are literally a flip of a coin, a 50-50 chance of near normal rainfall — potentially good news for Minnesota’s farmers, and anyone with a lawn or garden. Considering southestern Minnesota is still suffering through a moderate drought, I find the last summer forecast vaguely reassuring.

Weather Headlines

• Memorial Day high temperatures ranged from 84 at Redwood Falls to 78 in the Twin Cities, 77 at St. Cloud, and a chilly, rainy 58 degrees at International Falls.

• The same front that sparked moderate/heavy rain & T-storms over far western and northwestern MN yesterday is weakening, a light shower or two possible today, no more than .03 to .05″ rain expected.

• Wind shift to the north means afternoon temperatures 10-15 degrees cooler than yesterday.

• Drier Wednesday, residual moisture may spark an isolated shower, most of the area stays dry.

• Mild Thursday on tap, but cooler, Canadian air pushes south by late-week.

• Canadian high pressure promises a relatively cool Saturday, in spite of sunny intervals highs may not climb out of the 50s (north) and 60s (south).

• Growing chance of showers/thunder by Sunday PM as milder air tries to return.

• Long-range computer guidance hinting at a string of 80s next week as more summerlike weather returns to Minnesota.

Paul’s Outlook

OK. What are we going to do for an encore? It was, by almost every measure, the sunniest, most outdoor-friendly Memorial Day weekend in recent memory. Most towns experienced 3 wondrous days in the row — not much humidity, gentle breezes, temperatures a few degrees above average. Showers and T-storms rumbled across far western and northern Minnesota, staying just north/west of the Brainerd Lake area most of the day. We lucked out, pure and simple. A well-timed bubble of Canadian high pressure acted like a giant atmospheric roadblock, forcing rain and embedded T-storms to detour to our south, west and north. Count the number of colleagues and friends nursing a beet-red sunburn today. I have a hunch the cool breeze prompted many Minneotans to forgo the sunscreen (there’s still a train of thought that one can only become sunburned – fried – on a hot, sunny day). In reality it’s just as easy to get a painful burn when it’s 60 or 70 degrees, if the sun is out and there are no thick, rain-producing clouds overhead. In theory the best day of the year to get a tan (or burn) is June 21, the Summer Solstice, when the sun’s rays are as direct, as far north, as they ever get.

We’ve picked up only .50″ of rain, two inches less than usual for a typical May, to date. The driest conditions are showing up south and east of the Twin Cities — much of southeastern Minnesota is experiencing a moderate drought, it’s even worse on the other side of the St. Croix River in Wisconsin. We’re heading into the rainy season (June is historically the wettest month of the year, with close to 4″ of rain). It also has the distinction of being the month with the highest probability of severe T-storms, hail and tornadoes. The pattern has been remarkably quiet so far this spring – a lack of significant Gulf moisture and high dew points is the main reason why we haven’t had to spend any quality time in the basement. At some point our luck will run out, odds are we’ll see our first tornado outbreak somewhere in Minnesota in the next week or two. Next week looks significantly warmer, perhaps a string of highs in the 80s. With the warmth will come a heightened risk of rough T-storms.

Today’s cool front looks unimpressive — it may sail through dry across much of the region, a few dribs and drabs of rain, not enough to spoil after-school activities or ball games. It will be cooler though, as much as 10-15 degrees cooler than yesterday. Lingering moisture may spark a stray shower or T-shower Wednesday, but Thursday looks springy enough with blue sky and highs well up into the 70s. The latest guidance is quite a shift from previous runs, showing the jet stream buckling nearby, plunging cooler, drier air back into Minnesota and Wisconsin late in the week. I could see another outbreak of light jackets up north by Saturday with a few towns registering lows in the 30s and highs in the 50s. This coming only 2-3 weeks from the Summer Solstice. It’s early (it always is, come to think of it) but Saturday appears to be the drier, sunnier day. A return flow of moisture and warmth may set off a smear of showers by late Sunday, although the timing of any weekend rain is still very much up in the air. We salvaged a memorable Memorial Day holiday — I hope you had a chance to catch up on outdoor loitering, grilling and tinkering. For now I guess that should be good enough.

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