Mixed clouds & sun today; Severe risk Friday; “Loud thunder?”

Get set for a mixed weather bag again today across Minnesota.

They say all weather is local, and today will be one of those days. Even across the metro there may be big differences in sky cover today. It could be cloudy in Cambridge and sunny in Shakopee this afternoon.

Surface weather maps and the morning 1km GOES visible satellite image make 2 things clear this Thursday.

1) The center of low pressure is spinning near Hibbing & the Iron Range today.

2) The back edge of the cloud line is hanging right near the metro.

GOES 1km visible image shows low clouds. They should gradually burn off in southern Minnesota today.

Expect mostly sunny skies in southwest Minnesota...right up to the southwest edge of the metro. Cloudy skies will prevail much of the day from the metro north and east until the system slowly pulls away to the northeast, and drier air should mix in to help gradually burn off some of the low clouds near the metro.

Temperatures will recover nicely into to near 80 in the southwest, with 70s elsewhere this afternoon.

Next wave Friday:

It's hard to string together two dry days in a row this spring it seems. Our next wave of showers and T-Storms may roll in with a warm front late Friday PM & evening.

NAM model paints scattered rain & T-Storms late Friday PM & evening.

The system could generate a narrow line of convection Friday, and there may be just enough oomph to spawn a few severe storms.

Summer like weekend?

After the warm front pushes through Friday night, this weekend may finally feel a bit more like summer.

Saturday and Sunday should both bring ample sunshine and temps near 80 in southern Minnesota.

There will be a threat of a passing thunderstorm or two this weekend, but the bigger more organized storm threat appears to hold off until late Monday or Monday night.

A mostly dry weekend with occasional rain chances?

Loud Thunder?

We got several reports of "loud thunder" Tuesday night and early Wednesday in Minnesota...including in St. Paul.

That got us thinking, is thunder sometimes louder than other times?

The answer it seems is, yes!

There are a few factors that affect the volume and duration of thunder at nay location.

1) The distance from the lighting bolt. Simply put, the closer you are to the actual lighting bolt the louder and more immediate the thunder.

Nearby bolts may cause a sharp "clap" of thunder, while more distant (or horizontal) bolts may produce less intense or rolling thunder as the sound waves form different parts of the lighting bolt's thunder reach your ear.

2) Temperature inversions can make thunder louder, often at night. When there is colder air near the surface and a warm layer aloft (warm front) you get a temperature inversion...where temperatures increase with height above ground.

The inversion creates a discontinuity or "sound barrier" in the atmosphere which can "bounce" sound waves back to the ground. The result can be louder and more "rolling thunder" as the waves are more focused and reflected back to the ground level.

Temperature inversions can also be the reason distant trains or highways seem louder on some nights.

Gulf of Mexico Dead Zone: Biggest ever in 2011?

Sad news from NOAA. It looks like all that record spring flooding will create the largest "hypoxic dead zone" on record in the Gulf of Mexico this year.

The massive floodwaters in 2011 swept huge amounts fo "nitrogen runoff" into the Gulf, and the subsequent algal blooms may suck the oxygen out of the Gulf Waters.

Major flooding on the Mississippi river predicted to cause largest Gulf of Mexico dead zone ever recorded

June 14, 2011

"The Gulf of Mexico's hypoxic zone is predicted to be the largest ever recorded due to extreme flooding of the Mississippi River this spring, according to an annual forecast by a team of NOAA-supported scientists from the Louisiana Universities Marine Consortium, Louisiana State University and the University of Michigan. The forecast is based on Mississippi River nutrient inputs compiled annually by the U.S. Geological Survey (USGS).

Scientists are predicting the area could measure between 8,500 and 9,421 square miles, or an area roughly the size of New Hampshire. If it does reach those levels it will be the largest since mapping of the Gulf "dead zone" began in 1985. The largest hypoxic zone measured to date occurred in 2002 and encompassed more than 8,400 square miles."

On a brighter note, enjoy the quieter weather pattern most of today and early Friday!

PH