SPC Forecast Products

SPC - No watches are valid as of Wed Sep 20 13:24:02 UTC 2017

No watches are valid as of Wed Sep 20 13:24:02 UTC 2017.

SPC - No MDs are in effect as of Wed Sep 20 13:24:02 UTC 2017

No Mesoscale Discussions are in effect as of Wed Sep 20 13:24:02 UTC 2017.

SPC Sep 20, 2017 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook
Day 1 Outlook Image
Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0738 AM CDT Wed Sep 20 2017

Valid 201300Z - 211200Z


Isolated severe hail and damaging winds are possible from the Upper
Peninsula of Michigan to northern Missouri between about 4 to 11 pm

...Upper MI to northern MO...
A potent shortwave trough over the southern Canadian Prairies to Red
River Valley will move northeast towards Hudson Bay. Attendant cold
front will push east into central WI with trailing portion about to
stall over the Lower MO Valley. Middle 60s to lower 70s surface dew
points will be maintained ahead of this boundary with mean mixing
ratios of 12-16 g/kg common in area 12Z observed soundings. The 06Z
NAM appears overdone with depictions of mean mixing ratios reaching
17-19 g/kg and extreme MLCAPE of 3500-5000 J/kg. A plume of
2000-3500 J/kg appears more probable from central WI southwestward
at peak heating.

Capping will inhibit surface-based storm development until after 21Z
amid weak mid-level height rises. Convergence near the front, aided
by modest low-level warm advection, may eventually yield widely
scattered storms during the evening. Hodographs will remain small
west of the MS River. The WI vicinity will lie on the fringe of
moderate mid-level southwesterlies, marginally favorable for a
couple transient supercell structures. The predominant mode should
be multicells offering a risk of isolated severe hail and damaging
winds. Storms should weaken by late evening owing to the modest
shear and forcing for ascent.

..Grams/Kerr.. 09/20/2017

Read more