Areas affected…Portions of eastern Montana…far western North
Dakota
Concerning…Severe potential…Watch unlikely
Valid 222328Z – 230130Z
Probability of Watch Issuance…20 percent
SUMMARY…Isolated to scattered thunderstorms are likely this
evening with latest observational/model trends suggesting
development by 7-8 PM MDT. Large hail and strong/severe wind gusts
will be possible with these storms. Overall lack of storm
organization will likely preclude WW issuance.
DISCUSSION…Visible satellite imagery shows an increase in agitated
cumulus from the northern Big Horn vicinity and points northward
into eastern Montana. Convergence within the central/eastern Montana
surface trough coupled with increasing mid-level ascent will lead to
isolated to scattered storm development by early evening. Deep-layer
shear is currently relatively weak across eastern Montana and is not
expected to increase significantly this evening as the mid-level jet
is expected to be displaced south/southwestward of the discussion
area. Still, marginal effective shear (20-30 kts) and steep
mid-level lapse rates of 7.5-8 C/km will support semi-organized
storms capable of large hail. Strong/severe wind gusts will also be
possible as low-level lapse rates have become very steep with strong
heating/mixing this afternoon in eastern Montana. A WW is not
anticipated given the overall lack of storm organization expected.
..Wendt/Grams.. 08/22/2019
…Please see www.spc.noaa.gov for graphic product…
ATTN…WFO…BIS…UNR…BYZ…GGW…
LAT…LON 45390645 47230734 48740738 48970636 48900432 48660401
46390362 45430382 45110469 45130575 45390645