Severe threat Saturday

Posted at 3:41 PM on July 16, 2010 by Paul Huttner
Filed under: Severe weather

Update 4:45pm

SPC issues severe thunderstorm watch until 11pm tonight the southeast tip of Minnesota, southwest Wisconsin and much of Iowa. The watch does not include the Twin Cities area but does include Rochester and La Crosse.

Storms will stay south of the metro tonight, but those of you in southern Minnesota along the I-90 corridor should expect severe storms packing the potential for 60mph winds and large hail.

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Get the latest warnings here.

PH

Just in time for the weekend, get ready for another round of severe storms Saturday.

Several parameters are coming together over Minnesota Saturday that will likely produce another round of severe and possibly tornadic storms Saturday afternoon and evening. If you are going to be out and about Saturday, here's an early heads up to keep an eye out for severe storms, watches and warnings.

NOAA's Storm Prediction Center is so impressed with the potential for severe weather in Minnesota Saturday that they have placed Minnesota under a moderate risk for severe storms.

When SPC places an area under moderate risk, it anticipates a higher probability of severe weather than the common "slight risk" they lay out in convective outlooks. As a percentage, SPC is anticipating a 45% chance of severe weather within 25 miles of any location in the risk area. So that's about a 50/50 shot that wind damage, large hail or tornadoes could strike close to home Saturday.

Check out the strong wording in Saturday's convective outlook from SPC below.

TSTMS SHOULD INCREASE IN EARNEST BY
LATE AFTERNOON/EARLY EVENING WITHIN THE AFOREMENTIONED CORRIDOR.
CONSIDERABLY VEERING WIND PROFILES AND A VERY MOIST AIRMASS/STRONG
POTENTIAL INSTABILITY WILL SUPPORT EARLY MODAL SEMI-DISCRETE
SUPERCELLS WITH LARGE HAIL/SOME TORNADOES POSSIBLE. AIDED BY A
NOCTURNALLY STRENGTHENING LOW LEVEL JET/INCREASING MOISTURE
TRANSPORT REGIME...IT SEEMS PROBABLE THAT STORMS WILL GROW
UPSCALE/ORGANIZE INTO ONE OR MORE SOUTHEASTWARD MOVING SEVERE MCS/S
DURING THE EVENING...WITH THE POTENTIAL FOR DAMAGING WINDS TO
MARKEDLY INCREASE ACROSS PORTIONS OF MN INTO WI/NORTHERN IA.

Heavy rain too?

There should be plenty of low level moisture for the storms to feed on as they develop Saturday afternoon. Tropical moisture is surging back into Minnesota, with dew points in the upper 60s and low 70s expected Saturday. That means some of the storms can dump torrential rain.

Some of the forecast models are hinting at bands of convective rainfall in excess of 1" to 2" with localized 3" amounts possible.

The nicer parts of the weekend for outdoor activities should be Saturday morning and most of Sunday. Heat will be a factor Saturday as temperatures soar into the lower 90s before the storms arrive. Sunday should feature a cooler and less humid air mass.

The bottom line for Saturday is keep your head up for developing severe storms in the afternoon and evening in Minnesota, western Wisconsin and northern Iowa.

We will have coverage as storms brew on MPR news stations Saturday.

PH

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