Augtober: Humid with slight severe risk on October 17th?

Ah, October in Minnesota. Crisp frosty mornings. Brisk northwest breezes.

Not this year.

Welcome to Minnesota’s new climate. Mild and tropically humid with a slight risk for severe weather on October 17th? Somebody pinch me.

Our atmospheric Time Warp continues today with a mild and humid air mass overhead. Temperatures soar into the 70s. Dew points hit the tropical 70 degree mark this morning in Decorah just over the Iowa border. Our morning fog mixes into the lower atmosphere today, fuel for scattered afternoon T-Storms. The Doppler should light up between 4 pm and 8 pm. There is a slight risk for severe storms from the Twin Cities southeast. And yes, it’s October 17th.

Just. Plain. Weird.

  • +3.7 degrees – temps vs. average so far in October at MSP Airport
  • 13th consecutive warmer than average month at MSP
  • 7.27″ – rainfall total at MSP Since September 1st (+2.77″ vs. average)
  • 33.59″  – precipitation at MSP so far in 2016 (+6.92″ vs average)

August humidity levels – in October

Yes it felt like late summer when you walked outside this morning. Tropical humidity levels slid into southeast Minnesota overnight. Dew points in the 60s to near 70 degrees degrees blanket the region. That’s unusual for mid-October in Minnesota.

NOAA

Low pressure wave this evening

The next low pressure wave arrives by evening across southern Minnesota. With ample moisture in place, look for scattered T-Storms to break out. It could be a thundery evening commute for southern Minnesota and northern Wisconsin.

NOAA

Stormy Monday (evening)

T-Storms should fire along the frontal boundary late this afternoon through this evening. A few showers linger overnight. Here’s NOAA’s NAM 4 km model solution.

NOAA

Slight risk

There is a marginal risk a few storms could reach severe limits in the Twin Cities. A narrow higher probability ‘slight’ risk zone starts at about Lakeville and continues south and east including Eau Claire and Red Wing.

NOAA

Here’s the convective outlook discussion for southern Minnesota from NOAA’s Storm Prediction Center. I’ve italicized the most pertinent passages.

Feed your inner weather geek.

…PORTIONS SD/SRN MN…
ISOLATED TO WIDELY SCATTERED TSTMS NOW APPEAR MORE PROBABLE LATE AFTN INTO EARLY EVENING OVER PORTIONS CENTRAL/ERN SD…MOVING EWD TO SRN MN LATER THIS EVENING. OVER THIS CORRIDOR…STRONGEST DCVA/COOLING ALOFT OVERLIES POST-FRONTAL…BUT STILL POTENTIALLY/BRIEFLY SFC-BASED…INFLOW PARCELS W OF SFC LOW. PROGS INDICATE FAIRLY WELL-DEVELOPED LOW-LEVEL TROUGH EXTENDING W OF SFC LOW…ACCOMPANIED BY SUFFICIENT/RESIDUAL LOW-LEVEL MOISTURE TO SUPPORT TSTMS. NLY AND ELY COMPONENTS OF BOUNDARY-LAYER FLOW NEAR THAT TROUGH WILL COMBINE WITH STG MID/UPPER-LEVEL FLOW TO YIELD FAVORABLE SPEED SHEAR.
MEANWHILE…LAPSE RATES SHOULD STEEPEN ENOUGH TO SUPPORT MLCAPE IN 400-800 J/KG RANGE EVEN WITH SFC TEMPS LOW-MID 60S F…BASED ON MODIFIED MODEL SOUNDINGS. SMALL BOWS AND/OR TRANSIENT SUPERCELL STRUCTURES MAY DEVELOP…AUGMENTING WIND/HAIL POTENTIAL BEYOND WHAT MAY BE EXPECTED WITH SUCH MODEST CAPE OTHERWISE. GIVEN THIS SCENARIO…BOTH GEN-TSTM AND MRGL-SVR PROBABILITIES HAVE BEEN EXTENDED WWD IN THIS FCST.

Cooler week ahead

After today’s late summer rewind, cooler breezes and fronts drop south from Canada this week as October returns to form.

NOAA

Sunny skies and crisp days return. The average high for MSP this week? 57 degrees.

Graphic: Twin Cities NWS

Keep an eye on the Doppler late today.