Spotty T-showers overnight into Thursday
Deep Blue
Talk about a deep blue Minnesota summer sky.
Our first full day of astronomical summer gives way to nagging T-Storm chances overnight and Thursday.
Severe thunderstorm watch west
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A severe T-Storm watch is in effect until 10 pm for the Red River Valley and much of western Minnesota.
URGENT - IMMEDIATE BROADCAST REQUESTED
Severe Thunderstorm Watch Number 361
NWS Storm Prediction Center Norman OK
505 PM CDT Wed Jun 21 2017
The NWS Storm Prediction Center has issued a
* Severe Thunderstorm Watch for portions of
Western Minnesota
Eastern North Dakota
Northeast South Dakota
* Effective this Wednesday afternoon and evening from 505 PM
until 1000 PM CDT.
* Primary threats include...
Scattered large hail and isolated very large hail events to 2
inches in diameter possible
Scattered damaging wind gusts to 70 mph possible
SUMMARY...Thunderstorms will intensify over eastern ND/SD and track
eastward across the watch this afternoon and evening. Locally
damaging winds and hail will be possible in the stronger cells.
Thunder threat
Synoptic meteorology in summer often means more subtle weather features. Weaker fronts and subtle differences in air masses can make it harder to forecast precise T-storm locations. That's a welcome challenge for us as meteorologists. But still a challenge.
A weak low pressure trof crosses Minnesota overnight. A broken line of storms may accompany that low pressure wave overnight. New storms may fire along a developing warm front south of the Twin Cities. The two features may bump into one another close to the Twin Cities around midnight. Keep an eye out for lightning after dark, and an ear out for thunder in the hours surrounding midnight.
NOAA's NAM 3 km model shows scattered coverage on storms tonight. But if one develops overhead, expect a light show, thunder, downpours, and possible hail.
Slight severe risk
I agree with NOAA's discussion that there are limiting factors for severe weather tonight. Still, a slight risk for a big chunk of Minnesota.
Farther north into southeast South Dakota/southwest
Minnesota/northwest Iowa area, there is increased uncertainty about
storm development during the late afternoon/evening over this area,
as some model guidance maintain a cap during peak heating in the
wake of morning convection. However, convergence associated with a
surface low and an associated warm front and an approaching cold
front/trough line suggest some potential for storm development.
Given large CAPE values over this region and sufficient deep layer
shear for organized storms, a conditional severe risk will be
maintained over this region.
Guidance is more supportive of storms developing along a cold front
moving into northwest Minnesota and northeast South Dakota and
spreading eastward during the evening hours. Strong vertical shear
will support a few severe storms. This activity is expected to
spread eastward and develop southeastward as a strengthening warm
advection pattern develops from Minnesota into Wisconsin during the
overnight hours.
Another cool front
We managed 80 degrees in the twin Cities Wednesday. Another cool front means we enjoy another few days with highs in the 70s. Temps struggle to climb to the 70 degree mark this weekend.
Cool start to July?
I'm still searching for the usually inevitable July heat wave. Not finding it yet. Upper air trends continue to suggest a potentially cool pattern for the Upper Midwest through late June into early July.
NOAA's GFS 16-day temperature output continues to advertise cooler than average weather into the 4th of July.
Stay tuned.