Sunday, September 4, 2016

Showers/t-storms tonight (Heavy rain possible) Risk for strong to severe t'storms Monday evening/overnight otherwise mild and muggy

/Issued 2:45 PM CDT, Sunday, September 4, 2016/

Monday, September 5, 2016 - Severe Weather Outlook.  Source, Storm Prediction Center.

Last week's temperature departure map -- Most of the Northland had above average to near average temperatures for the week of August 28th, but an area around the head of Lake Superior had the greatest departure from average with much warmer than normal temperatures last week.

Last week's precipitation departure map -- Parts of the Northland had above average rain totals last week while most of northwest Wisconsin had below normal to average rain totals.

Tonight's low temperature forecast.

Monday's high temperature forecast.

Temperature and precipitation report for Duluth, Minnesota (Airport location)

August 28-September 3, 2016

High temperatures:

8/28:  74 F/+2 degrees above normal
8/29:  83 F/+11 degrees above normal
8/30:  76 F/+5 degrees above normal
8/31:  75 F/+4 degrees above normal
9/1:  68 F/-3 degrees below normal
9/2:  73 F/+3 degrees above normal
9/3:  74 F/+4 degrees above normal

Low temperatures:

8/28:  55 F/+2 degrees above normal
8/29:  62 F/+10 degrees above normal
8/30:  56 F/+4 degrees above normal
8/31:  51 F/-1 degree below normal
9/1:  54 F/+2 degrees above normal
9/2:  51 F/Normal
9/3:  56 F/+5 degrees above normal

Total precipitation:  1.72"
Normal:  0.90"
Departure:  +0.82" above normal

-Showers and thunderstorms should become more numerous across northeast Minnesota and northwest Wisconsin tonight thanks in part to a strengthening low level jet out of the SW with speeds increasing to 35-50 knots during the night, this combined with a frontal boundary moving toward northwest Minnesota and disturbances lifting northeast along that boundary should provide the necessary lift in the atmosphere to kick off showers and thunderstorms in our area tonight.

-I don't think there's much of a severe potential with the storms tonight but elevated CAPE is forecast to increase to around 500-1000 j/kg over parts of the area so there will be a chance for gusty winds or small hail in the strongest storms.

-Heavy rain will be a bigger threat for tonight as PWATS range from 1.50" to nearly 2.00".  Lightning will also be a hazard from any thunderstorm tonight.

Labor Day (Monday)

Showers or thunderstorms could linger into the morning hours in portions of northeast Minnesota and northwest Wisconsin but a break in the rain should take place from late morning through most of the afternoon hours with some clearing possible during the afternoon.  If skies do clear soon enough, then high temperatures could top out in the 80s but if skies remain fairly overcast, then highs will likely stay in the 70s.  It will also be quite muggy on Monday with dew points in the 60s to lower 70s.

A cold front should be over northwest Minnesota Monday morning, this front will move slowly south/east and should reach northeast Minnesota and northwest Wisconsin early Tuesday morning.

Showers and thunderstorms are forecast to redevelop across the Northland Monday evening or late Monday night -- Prior to this, the atmosphere could become quite unstable with CAPE possibly building to >2000 j/kg with Lifted Indices of -3 to -8 degrees C.  Strong winds aloft ~80 knots over the Upper Midwest and over 100 knots over the northern Plains combined with 30-40 knots of deep layer wind shear and a 30-40 knot S-SW low level jet Monday night could result in a severe thunderstorm risk especially for areas along and south of Highway 2 in northeast Minnesota into far northwest Wisconsin.

Large hail and damaging wind gusts look like the main hazards if thunderstorms develop Monday night, but there is a risk for a couple of tornadoes mainly along and north of I94 running from Alexandria to the Brainerd Lakes area toward Hinckley and Princeton between the hours of 7 PM-Midnight Monday evening.  Warm temperatures aloft or the CAP will need to break in order for surface-based supercells (tornado risk) to occur Monday evening -- There is a chance that storms won't develop until closer to Midnight, if that is the case then that would likely result in little or no chance for a tornado in central Minnesota.