Paul Douglas Weather Column: Growing Severe Risk Wednesday

Wednesday Weather Oulook

"A low pressure system will move across the area on Wednesday and Thursday, and bring the chance for strong to severe thunderstorms across much of the area. Warm temperatures on Thursday will be reduced into the 60s and 70s for highs on Friday in the wake of the cold front. Cool and dry, autumn-like weather will then prevail for the upcoming weekend."

Growing Severe Risk
By Todd Nelson

As daylight continues to dwindle in the Northern Hemisphere, a cold pool of air begins to grow and intensify. This expanding blob tightens the temperature gradient from north to south, which stimulates the upper level winds. This energetic wind field tends to whip up more fequent and volatile storms and that's something we may be seeing more of in the future.

One of these said storms will meander into our neck of the woods today. Humidity values will spike to stickier levels and ignite strong to severe storms this afternoon. Watches/warnings may be issued later Wednesday, so stay tuned.

Lingering storms shake out some of the humidity by late Thursday. You'll notice a much more refreshing breeze by Friday... in fact, there will be a hint of Fall in the air by the weekend!

Apple picking season has commenced in some locations, so it might not be a bad idea to check out your local orchard this weekend. You can stock up on your favorite pie apples and start baking away! Just make sure you invite me over for a large slice, though I'll be busy on Sunday watching the Vikes lock horns with the Rams in the first regular season game. Yes, it's Fall! -Todd Nelson

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TUESDAY NIGHT: Partly cloudy, still quiet. Low: 61.
WEDNESDAY: Warmer and stickier, fading sunshine with PM Storms. Dew point: 70. High: 84. Winds: SSE 10.15
WEDNESDAY NIGHT: Thunderstorms likely, some strong to severe. Low: 72
THURSDAY: Breezy and unsettled with spotty storms. Dew point: 68. High: 84.
FRIDAY: Cooling trend, refreshing breeze. Wake-up: 55. High: 70
SATURDAY: Sunny, hints of Fall in the air. Dew point: 47. Wake-up: 53. High: 71
SUNDAY: AM light jackets, midday couch/football patrol. Wake-up: 52. High: 72
MONDAY: Gray skies return. Spotty thunder potential. Wake-up: 55. High: 74.
TUESDAY: Unsettled. More humid. Wake-up: 56. High: 77.

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This Day in Weather History
September 3rd

1989: An early afternoon thunderstorm dropped 1 3/4 inch hail in Stearns and Morrison Counties.

1980: An F2 tornado resulted in $2.5 million in property damage later an F3 touched down causing $25 million in damages in Stearns County.

1970: The record-setting hailstone fell that made Coffeyville, KS famous. It had a circumference of 17.5 inches and weighed 1.67 pounds.

1917: Earthquake felt from Staples to Brainerd.

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Average High/Low for MSP
September 3rd

Average High: 77F (Record 97F set in 1925)
Average Low: 58F (Record 32F set in 1974)

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Sunrise/Sunset Times for MSP
September 3rd

Sunrise: 6:37am
Sunset: 7:46pm

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Moon Phase for September 3rd at Midnight
1.8 Days Since First Quarter

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Minneapolis Temperature Trend

It'll be warm and sticky into mid week as a storm system approaches. Thunderstorm potential becomes more interesting on Wednesday as indices point to strong to severe potential! Post front, temperatures drop to more 'fall-like' readings into the weekend.

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Wednesday Weather Outlook

We haven't had many hot days this summer and it doesn't appear any hot days are in order for the first half of September. We do warm up a bit on Wednesday. Temperatures will slide into the low/mid 80s across the southern half of the state, while folks in the northern part of the state warm into the mid 70s. Dew points will also be on the rise and hover in the upper 60s to near 70 by the afternoon, which will be nearly tropical feeling. With the heat and humidity builiding out ahead of a cool front, showers and thunderstorms could turn strong to severe later in the day. The image on the right suggests severe potential by the afternoon/evening hours.

Simulated Radar/Accumulated Precipitation Potential

The simulated radar reflectivity from AM Tuesday through PM Thursday suggests strong to severe storm potential by PM Wednesday. Hail and high wind potential could certainly be a big concern along with isolated pockets of heavy rain/flash flood concerns.

The accumulated rainfall potential from AM Tuesday through PM Thursday suggests heavier rain in central Minnesota and into west-central Wisconsin.

Severe Threat Wednesday

According to NOAA's SPC, the severe threat on Wednesday is greatest over the Upper Mississippi Valley. A front splashing out of Canada will promote thunderstorm development in the PM hours with hail and high winds being the primary threat.

Here's the latest from the SPC:

A CLUSTER OF ELEVATED TSTMS SHOULD BE ONGOING AT 12Z/WED ACROSS PARTS OF THE SIOUXLAND DRIVEN BY LOW-LEVEL WAA WELL N OF THE SURFACE FRONT. THIS CONVECTION MAY BE SUSTAINED THROUGH THE MORNING ACROSS PARTS OF CNTRL/SRN MN WITH A MARGINAL HAIL RISK ON THE FRINGE OF LARGER BUOYANCY. THIS ACTIVITY SHOULD YIELD A PRONOUNCED DIFFERENTIAL HEATING CORRIDOR AS STRONG POTENTIAL INSTABILITY DEVELOPS WITHIN THE WARM SECTOR CHARACTERIZED BY UPPER 60S TO LOWER 70S SURFACE DEW POINTS BENEATH AN EXPANDING EML. NEUTRAL TO WEAK MID-LEVEL HEIGHT RISES ARE ANTICIPATED WELL DOWNSTREAM OF THE SHORTWAVE TROUGH OVER THE NORTHWEST. HOWEVER...DIFFLUENT UPPER-LEVEL FLOW IN CONJUNCTION WITH PERSISTENT LOW-LEVEL WAA SHOULD FOSTER SUFFICIENT ASCENT FOR STORMS DURING THE AFTERNOON/EVENING ON THE PERIPHERY OF THE EML/CAPPING INVERSION. DEEP-LAYER SHEAR WILL BE QUITE FAVORABLE FOR ROTATING UPDRAFTS...WITH ENLARGED LOW-LEVEL HODOGRAPHS TOWARDS THE MS RIVER VALLEY. SEVERE THREAT WILL BE GREATEST WITH STORMS THAT MANAGE TO ROOT INTO THE MOIST BOUNDARY LAYER NEAR THE WARM FRONT. LARGE HAIL /SOME SIGNIFICANT/ AND A FEW TORNADOES ALONG WITH ISOLATED DAMAGING WINDS APPEAR PROBABLE. HOWEVER...THE SRN EXTENT AND OVERALL AMPLITUDE OF THE RISK WILL LIKELY BE MODULATED BY STRONGER CAPPING THAN IS DEPICTED IN MODEL FORECAST SOUNDINGS.

Sunrise Over Tropical Storm Dolly

Dolly became the 4th named storm of the 2014 Atlantic Hurricane Season earlier this week. The loop below shows the sunrise from Tuesday over Tropical Storm Dolly in the Bay of Campeche/western Gulf of Mexico. As Dolly drifts northwest, heavy rain will be one of the main concerns for northeast Mexico and the southern tip of Texas.

Heavy Rain in Mexico

According to NOAA's HPC, the 5 day rainfall forecast in northeast Mexico suggests as much as 4" of rain or more through the upcoming weekend. Some of this heavy rain will slide into southern Texas

Norbert Develops

Tropical Storm Norbert developed early Tuesday morning in the Eastern Pacific. The loop below was sunrise over Norbet just off the west coast of Mexico.

Tracking Norbert

Norbert is the 14th named storm of the East Pacific Hurricane Season and follows Hurricane Marie, which was a category 4 hurricane early last week. According to NOAA's HPC, the forecast keeps Norbert a tropical storm through the end of the week, however, we could certainly see hurricane strength at some point this week.

Snowy Labor Day Weekend in the Mountains

While this may be a shocking view for some, it isn't all that strange to see snow in the mountains in early September, especially in the peaks. Thanks to the Togwotee Mountain Lodge for the picture below!

Winter Weather Advisory

...WINTER WEATHER ADVISORY IN EFFECT FROM 3 AM TO 9 PM MDT WEDNESDAY FOR GLACIER NATIONAL PARK WEST OF THE CONTINENTAL DIVIDE...

THE NATIONAL WEATHER SERVICE IN MISSOULA HAS ISSUED A WINTER WEATHER ADVISORY FOR SNOW FOR GLACIER NATIONAL PARK WEST OF THE CONTINENTAL DIVIDE...WHICH IS IN EFFECT FROM 3 AM TO 9 PM MDT WEDNESDAY.

* IMPACTS: RAIN WILL START THIS EVENING, AND SNOW LEVELS WILL DROP AROUND 6,000 FEET OVERNIGHT CAUSING SNOW ACCUMULATIONS OVERNIGHT AND WEDNESDAY MORNING. COLD, WET, AND WINDY CONDITIONS WILL BE DANGEROUS FOR THOSE UNPREPARED IN THE BACK COUNTRY.

* TIMING: THE HEAVIEST PRECIPITATION IS EXPECTED FROM MIDNIGHT THROUGH 9 AM, WITH THE TRANSITION TO ACCUMULATING SNOW OCCURING AFTER 3 AM MDT.

Weather Outlook

The same storm responsible for snow in the northern Rockies will be responsible for some strong to severe storm potential in the Upper Midwest Wednesday and Thursday.