Wednesday, August 3, 2016

August 3, 2016: Showers and thunderstorms possible through Thursday; Risk for a few strong to severe storms and heavy rain. Muggy Thursday, dew points around 70.

/Issued 6:10 PM CDT, Wednesday, August 3, 2016/

Tornado watch until 11 PM CDT tonight in the red shaded area on the map.  This watch includes much of North Dakota and far northwest Minnesota.  Source, Storm Prediction Center.


Source, Storm Prediction Center.

Source, Storm Prediction Center.

Surface map forecasts from the Weather Prediction Center.

Excessive Rainfall Outlook valid for Thursday, August 4, 2016.  Source, Weather Prediction Center.

Forecast for Duluth and Superior

Normal temperatures for Thursday

High:  76
Low:   56

Sunrise Thursday:  5:53 AM CDT
Sunset Thursday:   8:35 PM CDT

Tonight's low temperature forecast.  Source, National Weather Service Duluth, Minnesota.

Thursday's high temperature forecast.  Source, National Weather Service Duluth, Minnesota.

Weather Summary for NE Minnesota and NW Wisconsin
Date:  August 3, 2016

A warm day but not quite as humid as it was on Tuesday.  Highs today were mainly in the 80s with late afternoon dew points in the 50s and 60s.  Winds shifted to the south, southwest or southeast at 5 to 15 mph.  Weather map at 5 PM had high pressure averaging 1014mb over the eastern Great Lakes and Ohio Valley with low pressure of 1001mb over southeast Saskatchewan Province -- A warm front attached to this low extended from northern North Dakota through central Minnesota to central Wisconsin with a cold front moving into the western Dakotas.

Forecast Discussion for NE Minnesota and NW Wisconsin

Tonight (August 3)

Partly to mostly cloudy skies with mild low temperatures in the 60s to around 70 degrees.  Winds out of the south at 10 to 15 mph.  Low pressure will move into southern Manitoba Province tonight while a warm front lifts northeast into the Northland while a cold front moves toward western Minnesota by daybreak -- Moisture and instability will be on the increase tonight as a S-SW low level jet of 30-40 knots develops later in the night.  We should see showers and thunderstorms increase in coverage from west to east across the Northland later this evening and through the overnight hours.  A few of these storms could be strong to severe with damaging winds and possibly some hail.  Locally heavy rain is also expected in any thunderstorm as PWATS continue to climb to around 1.30-1.60".

Thursday (August 4)

Occasional showers and thunderstorms under mostly cloudy to partially sunny skies.  Muggy with dew points in the 60s to lower 70s although it will turn less humid by Thursday afternoon across northern Minnesota, and then over the remainder of the Northland by Thursday night.  Highs on Thursday are expected to be in the 70s and 80s with winds from the south or west at 10 to 20 mph.

A strong area of low pressure will move from southeast Manitoba Province to central Ontario Province on Thursday with a cold front sweeping through the Northland from west to east.  Strong winds aloft; 50-65 knots in the mid levels and 70-90 knots in the upper levels will spread into the Upper Midwest, this combined with forcing associated with the approaching cold front and upper level system should result in potentially a few rounds of thunderstorms passing through parts of the Northland.

Its unclear how much clearing will occur on Thursday and this may impact the potential for severe storms, also the timing of the cold front could play a role...An earlier frontal passage would likely mean that most of the storms Thursday afternoon-early evening would be confined to central and northern Wisconsin.  A later frontal passage which the 18z NAM is showing could lead to more storms affecting northeast and east central Minnesota and northwest Wisconsin from Thursday afternoon-early evening.

There's also a chance that even without much clearing for CAPE to remain at around 1000-1500 j/kg which combined with the amount of shear and forcing could be enough to trigger some severe thunderstorms through the day on Thursday despite the lack of sun/warming near the surface.

Severe thunderstorms on Thursday could contain damaging winds and large hail, and this could be one of those situations where storms persist most of the day.

Quieter weather returns Thursday night under partly cloudy skies with lows in the 50s and 60s.  Winds will be out of the west or northwest at 10 to 20 mph.

Extended Forecast

Friday and Saturday:  Pleasant! Cooler and less humid weather on the way with a few showers possible mainly over the Arrowhead of Minnesota, dry elsewhere in the Northland.  Highs are forecast to be in the 70s with lows Friday night and Saturday night mostly in the 50s.