While we’re talking fall-like temps in the 50s and 60s over the Northern Plains, we’re talking record 90s and 100s for the Pacific Northwest.
The extremity of the ridge and 10-15 above normal is contributing to the 10-20 below normal east of the Rockies.
Credit: weather.com
Severe Weather Returns to the Plains, Midwest and Great Lakes Through Saturday
Published:
Story Highlights
Severe weather returns to the northern Plains Thursday, then moves eastward.
The tornado threat is low, but some large hail and damaging winds are possible.
Cooler air comes in for the weekend.
After a break from severe weather, conditions are coming together to produce severe storms over parts of the Plains, Midwest and Great Lakes through Saturday. Although the tornado threat will be low, wind damage and large hail will likely be the main impacts.
NOAA’s Storm Prediction Center has issued the following severe weather watches:
- A severe thunderstorm watch valid until 9 p.m. CDT for extreme northeast Iowa and south-central and southeast Minnesota. This includes Rochester, Minnesota.
- A severe thunderstorm watch valid until 12 a.m. CDT for southwestern Wisconsin. This includes Madison and La Crosse, Wisconsin.
In the wake of this severe weather, some much cooler air will be ushered in behind a cold front for the upcoming weekend.
(MORE: Pattern Change To Bring A Taste Of September This Weekend)
Below is an outline of when and where severe thunderstorms may develop.
Severe Weather Forecast
Thursday Evening
- Forecast: Showers and thunderstorms are expected to develop late in the day and into the evening from parts of the Dakotas to Minnesota and west-central Wisconsin as a cold front approaches the region.
- Threats: Damaging winds gusts and large hail are the main threats, though the chance of a tornado cannot be ruled out.
- Cities: Pierre, South Dakota | Minneapolis | La Crosse, Wisconsin
Thursday Evening’s Thunderstorm Forecast
Areas shaded red have the greatest chance of seeing severe weather.
Friday
- Forecast: Thunderstorms – some severe – will become more numerous and widespread, mainly during the afternoon and evening hours from the Upper Midwest to the central Plains.
- Impacts: Damaging winds gusts and large hail are the main threats, though the chance of a tornado cannot be ruled out.
- Cities: Omaha, Nebraska | Rochester, Minnesota
Friday’s Thunderstorm Forecast
Areas shaded red have the greatest chance of seeing severe weather.
Saturday
- Forecast: The severe threat becomes a bit more spotty as the weather system weakens, but some thunderstorms remain possible, mainly from Michigan to Missouri and western Kentucky.
- Impacts: Widely scattered damaging wind gusts possible.
- Cities: Chicago | Indianapolis | St. Louis
Saturday’s Thunderstorm Forecast
Areas shaded red have the greatest chance of seeing severe weather.
(MORE: Louisiana’s Historic Flood Likely the State’s Second Billion-Dollar Disaster of 2016)
Setup For Severe Weather
Late Week Surface Features Across The Central U.S.
A trough of low pressure (dip in the jet stream) will move from the northern Rockies to the northern Plains as a ridge of high pressure aloft (bulge in the jet stream) weakens to the east.
Meanwhile, an area of low pressure and its associated cold front will develop at the surface, and they will slide slowly eastward through Saturday.
Most of this activity will occur from the Plains into the Midwest.
Late Week Jet Stream Forecast
Warm, moist air will be pulled up from the south ahead of the cold front. The front will lift this warm, moist air, and thunderstorms will erupt late Thursday and again on Friday.
The system will weaken on Saturday, but there could be widely scattered severe weather from the Great Lakes to parts of the Midwest.
Tropical Storm Fiona Faces a Rough Road Ahead in the Central Atlantic
Story Highlights
Tropical Storm Fiona formed Wednesday evening in the central Atlantic Ocean.
Fiona faces two main obstacles that could spell its eventual demise.
The tropical storm is no threat to land.
Tropical Storm Fiona, the sixth named storm of the Atlantic hurricane season, is a bit more organized today, but faces a more hostile atmosphere in the days ahead in the central Atlantic Ocean.
As of Thursday morning, Fiona’s convective presentation on infrared satellite imagery looked the part of a tropical storm, with a central area of thunderstorms and some banding evident especially north of the center, which was about halfway between the Lesser Antilles and the coast of western Africa.
Infrared Satellite Image
The highest cloud tops, corresponding to the most vigorous convection, are shown in the orange and red colors.
Here is the latest status from the National Hurricane Center:
- Tropical Storm Fiona was located around 1,150 miles west of the Cabo Verde Islands.
- Fiona is moving toward the northwest around 10 mph.
(MORE: Hurricane Central)
Current Storm Status
Forecast: Hostile Environment Ahead
As our forecast path shows, Fiona will continue heading northwest into the central Atlantic Ocean during the next five days and is no threat to land.
Projected Path
The red-shaded area denotes the potential path of the center of the tropical cyclone. Note that impacts (particularly heavy rain, high surf, coastal flooding) with any tropical cyclone may spread beyond its forecast path.
Although some short-term strengthening is expected, it faces a familiar pair of nemeses headed into the weekend.
First, Fiona is expected to face increased wind shear, namely, differing winds aloft compared to near the surface.
Current Satellite, Wind Shear in the Atlantic
White colors denote higher cloud tops in infrared satellite. Stronger wind shear is denoted by purple contours. Upper-level winds are in light blue. Location of the current system shown by the white circle.
Wind shear tends to displace a tropical cyclone’s convection from its center of circulation and can also tilt that circulation. While some intense hurricanes can fend off some light to moderate wind shear, weaker systems can be ripped apart if the shear is too strong.
(MORE: Hurricane Season Outlook Update)
The increased southwest winds aloft responsible for the anticipated wind shear, along with a fairly weak Bermuda-Azores high will also cause Fiona to gain too much latitude to ever be a threat to the Lesser Antilles.
Dry air in the central Atlantic is also expected to wrap into Fiona’s circulation, encouraging stronger thunderstorm downdrafts and dispersing the convection from the system’s center.
Satellite Image: Where the Dry and Moist Air Is
This satellite image shows the amount of water vapor in the atmosphere’s middle levels. Dry air shows up as dark orange and red. The location of the current system is shown by a white circle.
Therefore, it is possible Fiona, weakened by wind shear and dry air, could degenerate into a remnant low or tropical wave.
Fiona is not a threat to either the Lesser Antilles or the U.S., at this time.
It’s not entirely out of the question Fiona, or what’s left of it after the hostile environment, could end up somewhere near Bermuda around the middle of next week.
We’re now headed into the climatologically most active time of the Atlantic hurricane season.
(MORE: When Atlantic Season Peak Arrives)
This time of year, you can see tropical waves, also known as African easterly waves, lined up over Africa south of the Sahara Desert, ready to emerge into the eastern Atlantic Ocean.
A fraction of these tropical waves serve as the seed for an Atlantic basin tropical storm or hurricane each season.
Africa Infrared Satellite
The highest cloud tops, corresponding to the most vigorous convection, are shown in the orange and red colors, roughly highlighting the African easterly waves.
So, while this latest Atlantic system may not pose a significant threat to land, that may not be the case with subsequent tropical waves in the heart of the hurricane season.
Check back with us at weather.com for the latest on this system and any other systems during the hurricane season.
See today’s video.
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