Monday, September 12, 2016

Scattered thunderstorms this evening to frost early Wednesday morning in north central Minnesota; Pleasant midweek; Rain chances return late this week

/Issued 4:52 PM CDT, Monday, September 12, 2016/

Source, 18z NAM --

Dew point forecast at 7 AM Wednesday.  The best chance for frost should remain west of Duluth and away from Lake Superior the way it looks now.

Tonight's low temperature forecast.

Tuesday's high temperature forecast.

Weather Summary for northeast Minnesota and northwest Wisconsin
Date:  September 12, 2016

A cold front has been moving through the Northland today -- At 3 PM this front extended from the Arrowhead of Minnesota down into far northwest Wisconsin into southern Minnesota.  There's a decent amount of convergence taking place this afternoon near this boundary and the atmosphere has become quite unstable this afternoon thanks to some sunshine this morning and early this afternoon .  Mesoanalysis shows CAPE of around 1000-1500 j/kg over northeast Minnesota and northwest Wisconsin with mid level lapse rates of 7.5-8.5 c/km.  A corridor of upper 50s to lower 60s dew points were found along and ahead of the cold front with PWATS around 1.50".  Mid level winds of 40 knots with upper level winds from 60-80 knots across northern Minnesota and around 100 knots from northern North Dakota to western Ontario Province with around 40 knots of deep layer wind shear over the area.  We have seen an area of thunderstorms erupt late this afternoon along the North Shore of Lake Superior generally from near Silver Bay up toward Grand Marais and Grand Portage.  Other showers have been trying to develop late this afternoon farther south across east central Minnesota into far northwest Wisconsin.

High temperatures today ranged from the 70s in northwest Wisconsin and eastern Minnesota with 60s over northern Minnesota southwest to the Brainerd Lakes area.  Winds today were out of the south, southwest or north at 10 to 20 mph.

Forecast Discussion for northeast Minnesota and northwest Wisconsin

...Short Term Forecast...

Tonight (September 12)

Scattered showers and thunderstorms in northwest Wisconsin with a threat for small hail and gusty winds in the strongest storms.

Scattered showers across northeast Minnesota with isolated thunderstorms possible mainly this evening.

Mostly cloudy skies and turning cooler tonight as a cold front moves east of the Northland.  Lows will fall into the 40s and 50s while 850mb temperatures which ranged from +8 to +14 degrees Celsius early this evening drop to around +4 degrees C in northern Minnesota to around +12 degrees C in northwest Wisconsin by daybreak.

Winds tonight will shift to the north or west at 10 to 20 mph.

Tuesday (September 13)

Cooler with a chance for frost late Tuesday night mainly over north central areas of Minnesota.  Mostly cloudy skies are expected tomorrow with a few showers possible.  Cold air advection continues through the day with 850mb temperatures bottoming out in the 0 to +6 degree C range which is certainly the chilliest airmass we've seen around here since last spring.  High temperatures on Tuesday will be in the 50s to lower 60s with lows Tuesday night in the 30s and 40s.  Winds will be out of the north or northwest at 10 to 20 mph.

...Extended Forecast...

Wednesday (September 14)

Dry and pleasant on Wednesday with highs generally in the 60s which is where they should be for mid September.  Lows Wednesday night will once again bottom out in the 30s and 40s with another chance for frost in parts of the Northland especially away from Lake Superior.

Note:  The dominant weather feature that will affect us Tuesday and Wednesday will be high pressure which moves east out of the northern Plains and into the Upper Midwest/western Great Lakes region by midweek.

Thursday (September 15)

A return flow develops later this week as high pressure moves off to the east allowing a southerly flow to develop starting on Thursday -- Should remain dry in our area during the day but rain showers could move in late Thursday night as an upper level trough and area of low pressure move east out of the northern Rockies and western High Plains.  Highs on Thursday are forecast to be in the 60s to around 70 degrees.

Note:  Occasional showers and possibly a few thunderstorms are expected in northeast Minnesota and northwest Wisconsin on Friday, September 16.

Forecast for Duluth and Superior

.Tonight...  Mostly cloudy.  Scattered showers and thunderstorms mainly this evening.  Low 47 to 52.  Wind becoming north to northwest at 10 to 20 mph.

.Tuesday...  Cooler.  Considerable cloudiness.  High 57 to 62.  Wind northwest at 10 to 20 mph.

Normal temperatures for Tuesday

High:  66
Low:  47

Sunrise Tuesday:  6:45 AM CDT
Sunset Tuesday:   7:23 PM CDT