SPC Jul 7, 2020 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
1228 AM CDT Tue Jul 07 2020

Valid 071200Z - 081200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF MONTANA INTO THE WESTERN DAKOTAS...

...SUMMARY...
Severe storms capable of intense damaging winds, large hail and a
few tornadoes are expected from central Montana eastward across the
northern Plains and into Minnesota Tuesday afternoon into the
nighttime hours.

...Montana to Minnesota...

Seasonally strong 12hr mid-level height falls (60-90m) will spread
across the northern Rockies later today ahead of a strong negatively
tilted short-wave trough. Latest model guidance suggests this
feature will approach the ID/MT border by 18z, MT/ND border by
08/06z, then into southern MB by sunrise Wednesday morning.
Favorable diffluent flow aloft, for storm-top venting, and a 60kt
500mb speed max, suggest thunderstorms should develop rather early
in the period. Forecast soundings favor convection organizing
quickly along a sharp cold front across western MT, possibly by 18z.
Wind profiles are quite strong and are more than adequate for
sustaining organized rotating updrafts. As a result, early in the
convective cycle, isolated supercells will likely be observed.
MLCAPE in excess of 2000 J/kg is expected across central MT into the
western Dakotas by mid afternoon as temperatures warm ahead of the
front.

Given the strong large-scale forcing for ascent, surging frontal
zone, and ample buoyancy, it appears convection should grow upscale
quickly along the wind shift. Late-evening CAMs support this
scenario with a pronounced squall line expected to mature and surge
across eastern MT by early evening. Large hail and a tornado threat
will be more common with supercell structures. Once the predominant
storm mode becomes a linear MCS, severe threat will transition to
damaging winds -- possibly with gusts in excess of 65kt in places.
Severe threat will progress across the northern Plains, ahead of the
aforementioned short wave, during the overnight hours.

..Darrow/Moore.. 07/07/2020

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from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html