A strong trough of low pressure is lifting slowly NE across the central-northern Rockies today. We’ve seen clusters of strong to severe thunderstorms erupt out ahead of this trough today from parts of North Dakota into far northwest Minnesota.
Source: Goes-16 Lower Level Water Vapor imagery; https://weather.cod.edu
Radar loop from Friday, September 20, 2019 showing the waves of thunderstorms which have moved through portions of the Dakotas and northwest Minnesota today. Source:
There is a marginal risk of severe thunderstorms tonight in much of north-central and east-central Minnesota into portions of northeast Minnesota and far northwest Wisconsin. Note: The greatest risk of severe thunderstorms tonight is over northwestern Minnesota.
The risk for strong to severe thunderstorms continues in the Northland on Saturday with a slight risk of severe thunderstorms covering portions of north-central Minnesota and a marginal risk of severe thunderstorms in place for the rest of the Northland.
Note: Primary hazards with the storms tonight and Saturday will be hail, strong winds, torrential downpours and lightning. Stay Weather Aware!
18z HRRR model radar forecast valid through 1 AM Sunday. Source: https://weathermodels.com
Scattered showers and thunderstorms expected through Saturday in the Northland.
Northern Minnesota has the greatest chance to get the highest rainfall totals through Saturday with potential for half to one inch plus totals. Lesser amounts of rain are expected farther south and east.
Winter is coming! Over a foot of snow is possible by Saturday afternoon above 8000 feet with winter storm warnings and advisories in effect in parts of Montana and Wyoming. Source: https://www.pivotalweather.com/
It’s been a foggy day around Lake Superior thanks to the cool/humid easterly flow coming off the lake per Goes-16 visible satellite imagery. Source: https://weather.cod.edu
Low temperature forecast for Saturday morning, September 21. Source: https://graphical.weather.gov
High temperature forecast for Saturday, September 21.
Very little change in the upper level pattern through early October based on long range model projections. Here’s the 500mb forecast valid through October 5 per European ensemble model.
Overall a west coast trough – east coast ridge type of pattern into early October. At times will see this pattern amplify with a stronger trough and ridge, one amplification period is during the middle of next week, with another one possible next weekend.
Source: 12z European ensemble model 9.20.19; https://weathermodels.com
Humid weather continues through Saturday with occasional showers and thunderstorms along with areas of dense fog and drizzle especially near Lake Superior. Mild tonight with lows in the 60s, but in the 50s near Lake Superior. Highs Saturday in the 70s, cooler along the North Shore. South to southeast winds tonight and Saturday at 10 to 20 mph with higher gusts.
A potent upper level trough will head northeast out of the Rockies through Saturday while an area of low pressure moves northeast through the Dakotas on Saturday, this low will then pass north of Lake Superior on Sunday.
Humid southerly flow will be in place out ahead of this system with PWATS ranging from around 1.20-1.90″ along with dew points of 60 to near 70 degrees.
A strong low level jet of 30-50 knots will continue through Saturday which will lead to warm air and moisture advection, and this low level jet will also help maintain an unstable atmosphere over the Northland through Saturday with CAPE of 1000 to around 3000 J/kg while mid level lapse rates steepen to 7.0-8.0 C/km during the day Saturday.
Mid and upper level winds will increase Saturday as the low and trough approach the area, this will help produce stronger wind shear across the area.
The above mentioned ingredients are favorable for severe weather development in our area on Saturday, but warm temperatures aloft or a cap means that we may see very little in the way of thunderstorm activity Saturday afternoon/evening. 700mb temperatures look toasty, hanging out at around +10 to +12C, and with the best forcing passing NW of us, it will be difficult to break this cap.
The way it looks now is that will see some showers and thunderstorms Saturday morning in a warm air/moisture advection regime, then Saturday afternoon-evening looks more like a patchy drizzle with a few showers type of scenario, but if thunderstorms were to develop Saturday afternoon-evening they would most likely be confined to northern Minnesota closer to the strongest forcing.
Note: The severe weather parameters are quite high later Saturday afternoon over much of the Northland with high values of significant tornado probabilities and supercells, but the chances of this actually verifying are quite low due to the cap, still something to keep an eye on though.
Breezy and cooler on Sunday with west to northwest winds 15 to 30 mph. A few showers are possible on the backside of low pressure which heads E-NE across Ontario. Highs on Sunday ranging from the 50s in the Arrowhead to the 60s elsewhere.
Looks like will have a dry and pleasant day on Monday, but rain chances return at times starting next Tuesday, carrying over into next weekend the way it looks now.
Forecast for Duluth and Superior
.Tonight… Dense fog and drizzle. Low 55 to 60, cooler near Lake Superior. Wind east to southeast 10 to 20 mph.
.Saturday… Humid. Areas of dense fog and drizzle. Scattered showers. A few thunderstorms also possible. High 69 to 74, cooler near Lake Superior. Wind east to southeast 10 to 20 mph becoming south in the afternoon.
.Sunday… Breezy. Partly to mostly cloudy. A few showers possible. High 62 to 67. Wind west 15 to 25 mph.
Normal temperatures for Saturday
- High 63
- Low 44
- Sunrise Saturday 6:54 AM CDT
- Sunset Saturday 7:09 PM CDT
Thanks for reading!