“Hottest” most humid MN day ever Tuesday! Severe risk today

And the weather hits just keep on comin'!

Call this one a "Humistorm" or "Torrid Tuesday."

The "Extreme Heat Wave of 2011" set numerous all time heat index & humidity records in Minnesota Tuesday.

3 consecutive days with 80 degree dew points at MSP Airport. (First time that has ever happened according to UM climate guru Dr. Mark Seeley)

82 degree dew point new all time record high dew point at MSP Airport. (May have been as high as 84 degrees in between hours!)

119 degree heat index (3:53pm) at MSP Airport ties all time record heat index at MSP!

88 degree dew point at Moorhead last night between 6pm and 8pm sets new all time record highest dew point reading in Minnesota! (Previous record was 86 degrees)

134 degree heat index reading at Moorhead sets new all time highest heat index reading for Minnesota! (Previous record was 124 degrees at Moorhead in 1966)

More records from Twin Cities NWS:

Temperature and Moisture Extremes During This Week's Heat Wave

The heat wave which has gripped the upper midwest since Sunday has broken records for temperature and dew point, and possibly even heat indices across the region.

In the Twin Cities:

-A record high minimum temperature was set on July 18th, when a low temperature of 80 degrees was recorded at Minneapolis - St. Paul International Airport. The previous record was 78 degrees which was set in 1986.

-The record high minimum temperature was tied on July 17th, with a low temperature of 79 degrees. The record was previously set in 1936 and 1942.

PUBLIC INFORMATION STATEMENT

NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN

400 PM CDT TUE JUL 19 2011

...UNOFFICIAL DEW POINT RECORD SET IN THE TWIN CITIES TODAY...

THE DEW POINT TEMPERATURE AT THE MINNEAPOLIS ST PAUL INTERNATIONAL

AIRPORT WAS 82 DEGREES ON THE 3 PM AND 4 PM OBSERVATION. THIS IS THE

HIGHEST DEW POINT TEMPERATURE REPORTED ON AN HOURLY OBSERVATION AT

THE MINNEAPOLIS ST PAUL INTERNATIONAL AIRPORT SINCE HOURLY DEW POINT

RECORDS BEGAN IN 1945.

THE PREVIOUS HOURLY DEW POINT RECORD WAS 81 DEGREES...WHICH WAS SET

ON JULY 30TH 1999. A DEW POINT OF 81 DEGREES WAS ALSO REPORTED AT

THE AIRPORT ON SUNDAY...MONDAY...AND EARLIER TODAY /JULY 17-19/.

THE MINNESOTA STATE CLIMATOLOGY OFFICE IS THE OFFICIAL SOURCE OF

DEW POINT RECORDS ACROSS THE STATE. THIS NEW RECORD WILL BE

CONSIDERED UNOFFICIAL UNTIL IT IS CONFIRMED BY THE STAFF AT THE

STATE CLIMATE OFFICE.

$$

MARGRAF

Uncharted Territory:

The torrid numbers in Minnesota Tuesday are simply unprecedented and astounding.

You can believe that many weather experts in Minnesota would have never imagined we'd smash heat and humidity records by such magnitude. The new (still unofficial) heat index record of 134 degrees at Moorhead Tuesday blew the previous record out of the water by a full 10 degrees!

With a heat index of 134 degrees, Moorhead was literally the hottest place on the planet Tuesday!

This truly was a "humidity storm" for Minnesota of epic proportions. Never before have Minnesotans felt such oppressive combined heat and humidity levels. While temperatures did not even come close to the state record of 114 degrees, dew point and heat index values were off the charts.

Why so hot & humid?

There's a simple explanation for why we're enduring record setting heat & humidity levels in Minnesota this week, and potentially more complicated reasons.

A huge intense ridge of high pressure in the upper atmosphere is acting like a "heat pump." Under the ridge the air is sinking and compressing, creating the heat wave. This is normal in a Midwest summer.

The more complicated factors may include the injection of additional low level moisture from the ocean of corn that lies in Iowa and southern Minnesota. Corn is an efficient "evapotranspirator." Studies have shown that massive corn fields can raise dew points in the environment as the corn "sweats" on hot summer days.

Take an already tropical air mass from the Gulf of Mexico and slide it over an ocean of corn in Iowa and Minnesota and you are truly modifying the air mass to become even more tropical. Call it an "uber-tropical" or "agriculturally modified" air mass.

Cool Front: Relief just 12 to 18 hours away!

A cool front cutting through Minnesota today will bring relief, but not before one more "excessively hot" day.

Highs will approach of exceed 100 in southern Minnesota today, including the Twin Cities metro. As drier air pushes in ahead of the front, dew points may actually fall into the lower 70s and 60s. The drier air will heat more efficiently, and as a result air temperatures may actually be hotter than Tuesday, even as heat index values are lower in some cases.

Either way you slice it, it's still going to be stinking hot today with temps & heat index values over 100 degrees until the front arrives.

More records today?

Details from Twin Cities NWS...

Another hot day is in store for the region today. High temperatures will be approaching record levels today, and the highest low temperature record in the Twin Cities is in jeopardy for July 20th. Here are the record highs and record highest minimum temperatures for the Twin Cities, St. Cloud, and Eau Claire:

Twin Cities:

Record High: 102 set in 1901

Record Highest Minimum: 76 set in 1901, 1935, and 1940 (low temperature so far today has been 83 degrees)

St. Cloud:

Record High: 105 set in 1901

Record Highest Minimum: 80 set in 1901 (low temperature so far today has been 78 degrees, so this record is safe)

Eau Claire:

Record High 102 set in 1932

Record Highest Minimum: 81 set in 1932 (low temperature so far today has been 72 degrees, so this record is safe)

Severe risk today:

As the cool front slices into the hot unstable air mass, a line of severe storms may expand from north to south.

SPC has most of Minnesota under a slight risk for severe weather today.

Storms will be common in northern Minnesota early, and may fire south into the Twin Cities and western Wisconsin by later afternoon and evening. High wind and hail appear to be the primary threats, but an isolated tornado or two can't be ruled out.

Keep an eye on the sky today for storms and possible warnings!

PH