Mesoscale Discussion 1467
NWS Storm Prediction Center Norman OK
0659 PM CDT Tue Aug 11 2020
Areas affected...southwestern North Dakota...western South
Dakota...and far southeast Montana
Concerning...Severe potential...Watch possible
Valid 112359Z - 120200Z
Probability of Watch Issuance...60 percent
SUMMARY...Storms developing over southeastern Montana/southwestern
North Dakota vicinity may increase in coverage -- and possibly grow
upscale -- over the next few hours. Resulting severe potential --
mainly in the form of damaging winds -- could warrant WW issuance.
DISCUSSION...Latest radar loop shows isolated thunderstorms
continuing to develop in the southeastern Montana vicinity, near the
northwestern fringe of an axis of moderate instability (1500 to 3000
J/kg mixed-layer CAPE) lying northwest to southeast across South
Dakota. The storms appear to be initiating in the vicinity of a
northern High Plains lee trough, and with ample instability but
dewpoint depressions of 40 to 50 degrees F indicative of the deep
mixed layer that exists, locally damaging wind gusts will likely
accompany the stronger storms (along with large hail potential).
With time, as a low-level jet develops this evening, the resulting
increase in warm advection -- combined with the aforementioned axis
of favorable instability -- may support some degree of upscale
growth, into an east-southeastward-moving MCS. Such evolution would
result in greater/more widespread potential for wind damage -- which
warrants WW consideration across this area.
..Goss/Thompson.. 08/11/2020
...Please see www.spc.noaa.gov for graphic product...
ATTN...WFO...ABR...BIS...UNR...BYZ...
LAT...LON 45780491 46230449 46530321 45500054 44060111 43720254
44550409 45780491
Read morefrom SPC Forecast Products http://www.spc.noaa.gov/products/md/md1467.html
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