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Scattered showers and t-storms late tonight/Tuesday; dry and cooler mid to late week

Scattered showers and thunderstorms are possible late tonight in far northern Minnesota. The risk for showers and thunderstorms will shift farther south/east during the day Tuesday. A few of the storms could become strong to severe late tonight into Tuesday with gusty winds and hail being the primary threats along with lightning and downpours.

Quite a large pool of strong potential instability in place late this Monday afternoon across portions of the Northern and Central Plains with 4PM Meso Analysis showing SBCAPE and MUCAPE of 4000 to around 7000 J/kg from southern North Dakota through most of South Dakota through central-eastern Nebraska. Also impressive is the large area of very steep mid level lapse rates of 7.0 to 9.0 C/km which covered much of the western High Plains, Northern and Central Plains today. Thunderstorm development is possible later tonight just north/east of where the greatest instability is located.

Source: https://www.spc.noaa.gov

A reservoir of strong potential instability will stick around through the night thanks to an Elevated Mixed Layer. Thunderstorm development is possible later tonight over portions of the northern Plains and upper Midwest, including in parts of northern Minnesota. Source: 18z NAM model; https://weather.cod.edu

As is often the case with convection the computer models disagree just a bit when it comes to storm intensity and whether or not storms will weaken.

First model image below is from the HRRR model (18z/1 PM run) valid from 1 AM Tuesday to 1 AM Wednesday.

This model shows a strong line of thunderstorms (possibly severe) moving quickly south/east out of northern Minnesota Tuesday morning. Note: Storms would impact the Duluth-Superior areas from roughly 9-11 AM Tuesday per HRRR model.

The second model image is from the NAM-WRF model (18z/1 PM run) valid from 1 AM to 7 PM Tuesday.

This model also shows a line of strong to possibly severe thunderstorms impacting far northern Minnesota early Tuesday morning, but then this line of storms dissipates as it moves farther south/east before Noon Tuesday with maybe a few showers affecting Duluth-Superior ~8 to 10 AM Tuesday. But this model unlike the HRRR model shows a few spotty storms redeveloping later Tuesday afternoon from the North Shore to Duluth, into northwest Wisconsin.

Low temperature forecast for Tuesday morning, Aug. 20 Source: https://graphical.weather.gov

High temperature forecast for Tuesday, Aug. 20

A pattern change takes place for mid to late week as an upper level low to our east amplifies the pattern. Will see a N/NW upper level flow setup across the upper Midwest and Great Lakes later this week while an upper level ridge over the southwest U.S. expands to the north.

Source: https://weather.cod.edu; 18z NAM model

Temperature and Precipitation report for Duluth, MN

August 11 through 17, 2019

High Temperatures/Departure from Normal

  • 8/11: 81F/+6 degrees above normal
  • 8/12: 75F/Normal
  • 8/13: 71F/-4 degrees below normal
  • 8/14: 72F/-3 degrees below normal
  • 8/15: 79F/+4 degrees above normal
  • 8/16: 79F/+4 degrees above normal
  • 8/17: 83F/+9 degrees above normal

Low Temperatures/Departure from Normal

  • 8/11: 61F/+6 degrees above normal
  • 8/12: 60F/+5 degrees above normal
  • 8/13: 55F/Normal
  • 8/14: 50F/-5 degrees below normal
  • 8/15: 58F/+3 degrees above normal
  • 8/16: 62F/+7 degrees above normal
  • 8/17: 58F/+3 degrees above normal

Note: Average temperature for the week of Aug. 11: 67.4 degrees (+2.5 degrees above normal) Source: https://www.dnr.state.mn.us

  • Total Precipitation: 0.24 inches
  • Normal: 0.84 inches
  • Departure: -0.60 inches below normal

State Average for Minnesota for the week of Aug. 11, 2019

  • Temperature: 67.3 degrees
  • Departure: -1.4 degrees below normal
  • Precipitation: 0.84 inches
  • Departure: 0.00 inches

Temperature departure map for the week of Aug. 11, 2019. Source: https://sercc.com

Precipitation departure map for the week of Aug. 11, 2019.

…Weather Summary…

A chance for showers and thunderstorms late tonight through the day Tuesday followed by a couple days of cooler and dry weather before rain chances return this weekend.

A cold front will move southeast out of far northern Minnesota through Tuesday afternoon while a warm front builds northeast out of Iowa, but this front won’t make it into the Northland as it gets pinched off by the southeastward advancing cold front.

Although the airmass won’t be quite as unstable in our neck of the woods compared to areas farther south, it still looks unstable enough for shower and thunderstorm development in scattered fashion or possibly a line of storms. Storms could develop late tonight, most likely after midnight or toward dawn in northern Minnesota, then we could see some storms farther south and east on Tuesday.

Lows tonight will range from the middle 50s to middle 60s with southerly winds 10 to 15 mph. Highs Tuesday will range from the lower 70s to lower 80s, warmest temps in parts of northwest Wisconsin. Winds will be out of the south-southwest or north at 10 to 20 mph.

Wednesday will be a day of transition as cold air advection occurs behind Tuesday’s cold front. 850mb temperatures will drop to around +5 to +10C with a breezy wind out of the northwest with gusts to 25 mph. Temperatures Wednesday afternoon will warm into the middle 60s to lower 70s. Dry weather is expected on Wednesday with partly cloudy skies.

Dry weather should continue Thursday and most of Friday as well, but rain chances return during the Friday night through Sunday time frame. It won’t rain continuously this weekend, but odds favor that most of the area if not the entire area will get some rain at some point between Saturday and Sunday. High temps mainly in the 60s and 70s Friday through Sunday (near to below normal for late August)

Note: Far West Days 2019 take place Friday through Sunday, August 23-25 in the Gary neighborhood in Duluth, Minnesota. The weather for this event includes a chance for rain Saturday and Sunday, with Sunday looking like the wetter day of the weekend. Friday looks dry at the moment. High temperatures Friday, Saturday and Sunday are forecast to be right around 70 degrees. More information about Far West Days at this link https://www.perfectduluthday.com/the-event/far-west-days-2019/2019-08-23/

Note: Also taking place Friday and Saturday, August 23-24 is the Harvest Cup stock car race at the Ogilvie Raceway in Ogilvie, Minnesota. Unfortunately rain could be a factor for this big race, but timing of when it rains is still a bit uncertain. As of Monday afternoon the best chance for rain looks to be from late Friday night into Saturday morning, and possibly again late Saturday night, so if this is the case, then there shouldn’t be much of an issue to get both shows in before the rain hits.

Forecast for Duluth and Superior

.Tonight… Clear to partly cloudy. Low 60 to 65. Wind southwest 10 to 15 mph.

.Tuesday… Scattered showers or thunderstorms. Partly to mostly cloudy. High 73 to 78. Wind southwest 10 to 20 mph, becoming northwest.

.Wednesday… Partly cloudy. High 70 to 75. Wind northwest 10 to 20 mph.

Normal temperatures for August 20

  • High 74
  • Low 54
  • Sunrise Tuesday 6:13 AM CDT
  • Sunset Tuesday 8:11 PM CDT
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