Tuesday, July 27, 2010

Siren-Free Wednesday (Tuesday storm recap)

* 48 tornadoes so far in 2010 across the state of Minnesota since June 17 (twice as many as average for the entire year).

* Numerous reports of minor wind damage and large hail Tuesday, 3-4" rains near Detroit Lakes.

* Cool frontal passage today on gusty northwest winds - HALF as much water in the air as yesterday as dew points drop off through the 50s. Much better!

Foreboding Sky. WeatherNation meteorologist Todd Nelson snapped this picture of the approaching squall line as it approached St. Michael, temperatures dropping 10-15 degrees in a matter of minutes as a "gust front", the leading edge of rain and hail-cooled air swept across town.
Straight Line Winds. According to Star Tribune weather spotter Mark Robokoff, over 1" of rain fell on the Milaca area, winds may have gusted as high as 60-70 mph, snapping off 4-6" diameter trees. More extensive wind damage was reported in the Balsam Lake, WI area, where pine trees were toppled by the extreme winds.

Tuesday Flash Flooding. 3-4" rains engulfed the Detroit Lakes - Pelican Rapids - Perham area Tuesday, nearly a month's worth of rain falling in less than 6-8 hours. Flood warnings were issued for this region, reports of standing water in fields and standing water on area highways.

Wind Damage. The "W" icons show the location of high wind reports (straight-line winds, no tornadoes) from Tuesday afternoon/evening - the strongest storms tracking off north of the Twin Cities.
Damage Reports. The Chanhassen NWS has a chronological list of hail/wind reports from Tuesday's squall line, which raced east at 40-50 mph. All the details are here.

SPC Reports. All those blue dots are wind damage reports - no confirmed tornadoes in Minnesota, in spite of the tornado watch issued around 4 pm. The reason for the tornado-no-show? Wind shear was marginal, in spite of ample instability and low-level moisture. No "supercell" thunderstorms developed ahead of the main squall line. More from SPC here.

Blazing Saddles. Every reporting station (except Alexandria) registered 90s yesterday, 93 in St. Cloud, 94 in Minneapolis, Eden Prairie and Redwood Falls. Dew points rising into the mid 70s created a heat index of 100-105 across the southern third of the state, where heat advisories were issued.


To quote Kurt Vonnegut, "and so it goes." We got roughed up (a little) yesterday, the roughest storms rumbling off to the north of the Twin Cities. There were reports of a few funnel clouds up in Otter Tail county (near Earnhart) but no confirmed touchdowns - that I could find. Straight-line winds gusted as high as 71 mph (lot's of reports of minor damage from Sauk Centre to Milaca to Balsam Lake, WI).

SPC issued a tornado watch, to err on the side of safety, but in the end there just wasn't enough instability and wind shear to spin up tornadic thunderstorms. Flooding rains swept through the Detroit Lakes area during the morning hours (prompting flash flood warnings). The storms moved quickly, less than 45 minutes of rain for most neighborhoods, under .25 to .50" of rain.


Paul's Conservation MN Outlook for the Twin Cities and all of Minnesota

Today: Partly sunny, breezy, less humid. Winds: NW 10-20, afternoon gusts to 25. High: 82

Wednesday night: Clearing and comfortably cool. Low: 61

Thursday: Plenty of sunshine, still pleasant with less wind. High: 83

Thursday night: Clouds increase, a good chance of T-storms late at night. Low: 65

Friday: Storms early, then partly sunny - drying out during the day. High: 78

Saturday: Lot's of sun - reasonable humidity, light winds (probably the nicer day). High: 85

Sunday: Hazy sun, a little more humidity creeping back into town. T-storms far western MN late in the day (but probably dry from the northern lakes into the metro area). High: 87

Monday: Less sun, good chance of a few T-storms. High: 83

Tuesday: Unsettled, another T-storm or two. High: 86

Did you wander outside Tuesday? 94 in the Twin Cities by late afternoon, a dew point in the mid 70s - the result: a heat index up around 102 to 104 F. It was just a fleeting taste of the baking, sauna-like heat gripping much of America (and much of the northern hemisphere, for that matter). Heat advisories were issued for southern Minnesota - it was an uncomfortable 8-12 hours, but from Kansas City to Nashville, Atlanta and Washington D.C this has been an almost daily occurrence since early June.

We've been lucky: crazy-heat has stayed just south of Minnesota, the northern fringe of this massive heat wave sparking wave after wave of severe thunderstorms across Iowa and Illinois, resulting in historic rainfall amounts. There's been just enough cooler, drier, Canadian air leaking south of the border to take the edge off the heat from North Dakota into Minnesota, Wisconsin and Michigan.

Good Looking Saturday. This is the GFS model valid around dinnertime on Saturday, showing expected rainfall between noon and 6 pm. A weak bubble of high pressure should keep us partly to mostly sunny with dew points in the 50s to near 60, relatively light winds - probably the nicer day of the weekend.

48 tornadoes so far in Minnesota this year, according to the National Weather Service. We won't be adding to that number (twice normal, btw) anytime soon - although heavy thunderstorms may return as early as Thursday night and Friday morning. Skies clear in time for a pretty nice weekend, sunshine the rule Saturday and most of Sunday. A few Dakota storms may drift into far western MN late Sunday, but the weekend weather looks better than average - 80s, generous amounts of sun, a relatively comfortable Saturday giving way to a little more humidity on Sunday.

Nothing to gripe about in the weather department. No boiling heat, no Guam-like humidity, no sirens cutting through the evening air. All is right with the world. For a now.

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