Not as hot this weekend; best thunderstorm chances shift south on Saturday

It was way too hot Friday afternoon.

The official Twin Cities temperature at Minneapolis-St. Paul International Airport hit 99 degrees Friday:

We were just one degree from a triple-digit high temperature. The dew point temperature was 72 degrees, so our heat index was 108 degrees.

It was a good afternoon to take it easy.

Here are some peak heat index values reported by the NWS through mid afternoon:

PUBLIC INFORMATION STATEMENT

NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN

318 PM CDT FRI JUN 29 2018

...HIGHEST HEAT INDICES AS OF 3:15 PM...

LOCATION                     TEMP      TIME/DATE       PROVIDER

SOUTH ST. PAUL 1WSW          112 F     0231 PM 06/29   MNDOT

LAKE ELMO AP                 110 F     0243 PM 06/29   AWOS

FARIBAULT 1SSW               110 F     0114 PM 06/29   AWS

ALBERTVILLE 2ESE             110 F     0239 PM 06/29   AWS

CAMBRIDGE AP                 109 F     0255 PM 06/29   AWOS

LAKEVILLE AP                 109 F     0255 PM 06/29   AWOS

SILVER LAKE 3E               109 F     0235 PM 06/29   MNDOT

FOLEY 6WSW                   109 F     0210 PM 06/29   MNDOT

RED WING 4W                  109 F     0235 PM 06/29   MNDOT

PRINCETON AP                 109 F     0216 PM 06/29   AWOS

RED WING AP                  109 F     0255 PM 06/29   AWOS

AUGUSTA 1NW                  108 F     0305 PM 06/29   RAWS

ISLE 1WSW                    108 F     0220 PM 06/29   AWS

WYOMING 6WSW                 107 F     1206 PM 06/29   RAWS

EAU CLAIRIE 2NE              107 F     0244 PM 06/29   AWS

ST. LOUIS PARK 2ESE          107 F     0209 PM 06/29   AWS

FARIBAULT AP                 107 F     0235 PM 06/29   AWOS

GRANITE FALLS AP             107 F     0255 PM 06/29   AWOS

LADYSMITH 2SW                107 F     0305 PM 06/29   RAWS

LINO LAKES 2W                107 F     0244 PM 06/29   AWS

MAPLE LAKE AP                107 F     0255 PM 06/29   AWOS

NEW GERMANY 1NW              107 F     0230 PM 06/29   MNDOT

MORTON                       107 F     0235 PM 06/29   MNDOT

MADELIA 3ENE                 107 F     0240 PM 06/29   MNDOT

SKYLINE                      107 F     0145 PM 06/29   MNDOT

ST. PAUL 1NNE                107 F     0245 PM 06/29   MNDOT

MINNEAPOLIS-ST. PAUL AP      107 F     0253 PM 06/29   ASOS

STANTON AP                   107 F     0215 PM 06/29   AWOS

WACONIA 1WSW                 107 F     0214 PM 06/29   AWS

BLAINE AP                    106 F     0255 PM 06/29   AWOS

APPLE VALLEY 2WSW            106 F     0210 PM 06/29   AWS

CHAMPLIN 2ESE                106 F     0239 PM 06/29   AWS

SANTIAGO 3E                  106 F     0220 PM 06/29   RAWS

EAU CLAIRE AP                106 F     0256 PM 06/29   ASOS

EDEN PRAIRIE AP              106 F     0253 PM 06/29   ASOS

FARMINGTON 2ESE              106 F     0249 PM 06/29   AWS

HUTCHINSON AP                106 F     0235 PM 06/29   AWOS

MORA 1ENE                    106 F     0308 PM 06/29   RAWS

LE CENTER                    106 F     0240 PM 06/29   AWS

BLUE EARTH 2NW               106 F     0245 PM 06/29   MNDOT

CLEARWATER 1SE               106 F     0215 PM 06/29   MNDOT

MAYER 1NE                    106 F     0240 PM 06/29   MNDOT

OSCEOLA AP                   106 F     0255 PM 06/29   AWOS

OSCEOLA 1NNE                 106 F     0240 PM 06/29   AWS

ST. PAUL DWTN AP             106 F     0253 PM 06/29   ASOS

Slightly higher heat index values were reached in many spots before the afternoon was over.

Excessive heat warnings expire at 10 p.m. this Friday evening for the Twin Cities metro area and much of the southern half of Minnesota, plus portions of western Wisconsin.

Parts of southeastern Minnesota will be in a  heat advisory overnight Friday night through Saturday afternoon.

Cooler weekend temps

Saturday highs will drop back to the upper 80s in the Twin Cities metro area.  The northwestern half of Minnesota will see highs in the upper 70s, with mostly 80s in the southeastern half of our favorite state. Parts of far southeastern Minnesota could reach the lower 90s.

On Sunday, most of northern Minnesota will top out in the upper 70s, with lower 80s in the central and south:

Twin Cities metro are highs are expected to reach the mid 80s Monday, followed by upper 80s Tuesday and around 90 on the 4th of July.

Thunderstorm chances

Northern and central Minnesota have the best chance of thunderstorms overnight Friday night and early Saturday morning. A few severe thunderstorms will be possible.

Updated weather information can be heard on the Minnesota Public Radio Network, and updates are also posted on the MPR News live weather blog.

The Twin Cities metro area could see an isolated strong thunderstorm late in the overnight hours and early Saturday.

The best chance of some periods of thunderstorms in the Twin Cities metro area and southern Minnesota will be Saturday afternoon and Saturday night.

Some of those thunderstorms could be severe.

The Storm Prediction Center of the National Weather Service shows a marginal risk of severe weather in the metro area Saturday and Saturday night, with a slight risk in southeastern Minnesota:

Marginal risk means that an isolated severe thunderstorm is possible, slight risk means that scattered severe storms are possible:

The metro area and southern Minnesota could also see some scattered showers and thunderstorms on Sunday. 

Friday morning severe thunderstorms

The Minnesota State Climatology Office has a nice recap of the severe thunderstorms that downed trees and power lines in parts of northern Minnesota early on Friday.

Their summary includes the following:

... by early morning on the 29th, a long-lived thunderstorm complex with damaging winds raced into northwestern Minnesota at speeds of up to 70 mph. The accelerating storms produced 55-70 mph winds and a long swath of tree, power line, and even minor structural damage. The hardest hit areas were near Bemidji and Kelliher. Area radars showed that the system had a classical “bow echo” appearance, with the storms oriented along a curved or bulging line. This is a common appearance for severe thunderstorms that produce damaging winds.

Another interesting feature of this second storm system was its longevity, and especially the amount of time it spent producing strong winds. The complex of storms had originated in east-central Montana Thursday evening, and then tracked across North Dakota before getting to Minnesota. Sensors from west to east across North Dakota indicate the storms produced winds of 50-80 mph for several consecutive hours before entering Minnesota. Long-lasting, wind damage-producing thunderstorm complexes of this type are called “derechos” (pronounced “deh-RAY-cho”), and are considered to be a rare class of severe thunderstorms.

Their post includes an impressive radar replay of the severe thunderstorms that raced across northern Minnesota, as well as numerous detailed severe storm reports.

You can hear my live weather updates on Minnesota Public Radio at 7:35 a.m., 9:35 a.m. and 4:35 p.m. this weekend.