July 5th through July 7th--SEVERE WEATHER RISK IN MN

Special Forecast 7/5 through 7/7:

Hello Everyone:


Welcome to Minnesota Weather Plus--A Division of US Weather Plus.
Forecaster: Bohdan Cole 

Posting through various channels, and forecaster for multiple sources.

Here are my thoughts below on a possible severe weather event for MN this weekend, particularly on Saturday 7/6.  


The Jet Stream and winds thru various levels of atmosphere:  It is flowing overhead, but tends to split off into two branches...one which rides to the north, and another which will spin down into a mini-trough through the central US, and then shoot back north over the East coast.  This will help provide the upper air level winds that we need.  The Jet Stream generally rides at the 300mb level.  Anything with a lower number than that is higher above, and anything with a larger number than that, is coming down towards the surface.  Surface winds, you will see are generally coming from the south.  Halfway up into the atmosphere, they start changing directions with height.  This is referred to as Wind Shear.  See the maps below, in order from Surface Winds, to Aloft.

SURFACE WINDS

925 MB Level

850 MB Level

700 MB Level

500 MB Level

300 MB Level

250 MB Level

200 MB Level

The image below from NCSU--indicated the various pressure levels in the atmosphere, according to height, to give you a better idea of what these maps mean, and where the winds are flowing, according to the level.  Keep in mind that most of our weather happens below that 90% threshold, just above Mount Everest in the picture. 

Pressure Change w/Height

Temperatures:  Temps in the area will certainly be warm enough, up near 90. 

TEMPERATURES

DEWPOINT (Measure of moisture in the air for these storms): 

DEWPOINT

CAPE:  It is looking fairly high, with some spikes to the north of MSP. 

CAPE

Lifted Index Values:

LIFTED INDEX

TWO WIND SHEAR PARAMETER MAPS:

WIND SHEAR 1

WIND SHEAR 2

One thing that could get in the way, is a slight capping inversion.  It looks a bit better to the north, but down here, the temps begin to warm with height.  They don't warm above the surface temp and not as drastic, but it could have an impact in how these storms decide to form. 

GFS_3_2013070512_F33_45.0000N_93.0000W

In summary, I am thinking Northern/Western MN, back through the Dakotas is looking good.  Also, there is a risk here in southern MN.  Wind shear appears to be greater just north of us as well, so any isolated cells could likely turn tornadic up there.  I am thinking later in the day, the cells will merge into one of the MCS's that had been giving us trouble with bow echo's and wind damage the last few weeks, here in MN.

Here is your extended forecast for the next 7 days, and basic precip maps for tomorrow.

Stay safe! 
Bo