Rain north; 70s by Friday? NASA: 97% of Greenland’s ice sheets “thawing”

82F high temp at MSP Tuesday

Coolest day in nearly a month for metro (Since 82 on June 26th)

String of 80s 6 of past 7 days in the 80s at MSP Airport

90s return for a 1 day cameo Wednesday

70s dew points - It's going to feel like a sauna Wednesday in the metro and southern Minnesota

78F Forecast high for the metro area Friday!

Heavy rain up north - 2" to 3"+ possible in a zone from Fargo-Brainerd-Duluth

(most of the storms may miss the metro to the north)

Source: Twin Cities NWS

97% of Greenland's ice sheets in "thaw mode" this month -a record

1.74" rainfall at MSP Airport Tuesday (New daily rainfall record at MSP)

1.44" previous daily record for July 24th set in 1985

1.82" rainfall in Rochester Tuesday

Scattered T-Storms again Tuesday night & Wednesday AM

Storms shifting north overnight - focus on north metro into central & N MN

Source: Twin Cities NWS

Up North Forecast: Loud & Wet

If you didn't get much sleep last night, you may be sleepy eyed again Wednesday.

Another round of overnight "nocturnal" thunderstorms will rumble across MN tonight.

The difference?

The storms early Tuesday AM focused on the south & west metro. The troubled front spawning the storms will gradually lift north tonight, and that means central and northern Minnesota will get to play the nocturnal T-Storm lottery overnight tonight.

Brainerd and Duluth should get in on the action overnight. Drought stricken towns in northwest Minnesota like Thief River Falls, Bemidji and Roseau should also pick up some much needed rainfall in the next 48 hours.

Source: NOAA/http://wxcaster.com/gis-radar-overlays.php3?STATIONID=DLH

SPC has a slight risk for much of MN overnight.

Dual low pressure systems linger Wednesday & Thursday:

There are two separate low centers swirling over Minnesota this week. The first will slide through Wednesday with scattered storms & much needed rainfall.

A second low will drop south from Canada Thursday. This should bring another shot of showers to Minnesota, and even more welcome rain.

The two systems could dump a bunch of rain up north. An arc of 2" to 3"+ may fall from Bemidji to Ely and Grand Marais by Thursday night.

Worst of summer heat & humidity over? 70s by Friday

It's too early to say that brutal summer heat is done in Minnesota, but looking out at the medium range models the next two weeks the trend is encouraging.

I'm pretty sure we'll log a few more 90+ degree days this summer, but I really think the worst of the brutal summer heat and humidity is now behind us. It's going to be tough to get a sustained stretch of 95 to 100+ degree heat again this summer like we saw in early July.

We're sitting at 23 days of 90 degree heat so far in 2012. Looking ahead, I think it's quite possible we may add another 5 or so. That would put us at 25-30 days of 90 degree heat for the season, and we could rival the 27 days at or above 90 we sweated through in 2007.

Drought 2012: Low water on Old Man River

The persistent drought of 2012 in the nation's midsection is having an imopct on water levels on the lower Mississippi River. CNN has the details on the near record low water on the usually "Mighty Mississippi."

The "mighty Mississippi" has lost some of its might with the season's epic drought taking its toll on river levels, which are falling to near historic lows.

The U.S. Army Corps of Engineers will spend nearly $7 million dredging in an attempt to keep ports operational and keep the river open for barge traffic in the coming weeks. River levels in Memphis have dropped to within three feet of their historic lows from the 1988 drought.

In just one year, the river has gone through extreme fluctuation. Last May, it was within a foot of its record-high crest because of massive flooding, and today it's 55 feet lower and experiencing historic lows due to drought.

Dramatic images taken from NASA's Terra satellite show the swollen river in late April of last year compared with images from early July this year. The expanse of the water was over 3 miles wide in parts of Missouri and Arkansas as levees were blown up in order to help protect the town of Cairo, Illinois from flood waters. The image taken July 2012 this year shows a much different story with the river less than a half mile wide in spots.

NASA: up to 97% of Greenland's ice sheet show some melting this month

This is an eye opener. According to NASA, multiple satellites are showing a record 97% of Greenland's ice sheet went into thaw mode this month, a new record.

Source: NASA Earth Observatory

The amount of runoff has been huge this summer, Here's an excerpt from NASA.

Nearly the entire ice sheet covering Greenland--from its thin coastal edges to its two-mile-thick center--experienced some degree of melting for several days in July 2012. According to measurements from three satellites and an analysis by NASA and university scientists, an estimated 97 percent of the top layer of the ice sheet had thawed at some point in mid-July, the largest extent of surface melting observed in three decades of satellite observations.

The data visualization above shows the extent of surface melting in Greenland on July 8 (left) and July 12, 2012 (right). The maps are based on observations from the Special Sensor Microwave Imager/Sounder (SSMI/S) on the U.S. Air Force's DMSP satellite, from India's OceanSat-2, and from the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra and Aqua satellites. The satellites measure different physical properties at different scales, and they pass over Greenland at different times. Taken together, they provide a picture of an extreme melt event.

On July 8, satellites showed that about 40 percent of the ice sheet had undergone thawing at or near the surface. By July 12, the extent of melting spread dramatically beyond the norm. In the images above, areas classified as "probable melt" (light pink) correspond to sites where at least one satellite detected surface melting. Areas classified as "melt" (dark pink) correspond to sites where two or three satellites detected melting.

The extreme melting coincided with an unusually strong ridge of warm air--a "heat dome"--over Greenland. The ridge was one in a series that dominated Greenland's weather between May and July 2012.

Even the area around Summit Station in central Greenland, which at two miles above sea level is near the highest point of the ice sheet, showed signs of melting. A National Oceanic and Atmospheric Administration weather station at Summit confirmed that air temperatures hovered above or within a degree of freezing for several hours from July 11 to July 12.

Such pronounced melting at Summit and across the ice sheet has not occurred since 1889, according to ice cores analyzed by Kaitlin Keegan at Dartmouth College. "Ice cores from Summit show that melting events of this type occur about once every 150 years," said Lora Koenig, a NASA scientist and member of the team analyzing the satellite data. "With the last one happening in 1889, this event is right on time. But if we continue to observe melting events like this in upcoming years, it will be worrisome."

PH