SPC 2000Z Day 1 Outlook

Day 1 Outlook Image

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0243 PM CDT Mon Oct 12 2020

Valid 122000Z - 131200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Organized severe thunderstorms are not expected through tonight.

...20Z Update...
A strongly forced band of convection continues to move eastward just
ahead of the leading edge of the cold front northern and central
portions of Lower MI. Regional surface observations have yet to
measure any substantial gusts within this band, evidence of its
elevated character, which will continue to limit any severe
potential across the Upper Great Lakes.

Farther south and east, less stable low levels may result in a few,
convectively enhanced gusts at the surface. However, the stronger
flow and forcing for ascent will remain displaced north of the
modest instability across the OH Valley, keeping the overall
potential for wind gusts over 50 kt low.

..Mosier.. 10/12/2020

.PREV DISCUSSION... /ISSUED 1101 AM CDT Mon Oct 12 2020/

...Great Lakes and OH Valley through this evening...
Within a largely zonal flow regime, a midlevel shortwave trough will
move eastward from the upper MS Valley to the Great Lakes/OH Valley
while gradually losing amplitude, as an upstream speed max
progresses eastward from the northern Rockies to the northern
Plains.  Elevated convection is ongoing across WI in the zone of
ascent along a surface cold front and immediately downstream from
the midlevel trough, where lingering midlevel lapse rates near 8
C/km and MUCAPE of 500-1000 J/kg will support isolated, sub-severe
hail through midday.  This regime will shift eastward over MI this
afternoon, though diminishing buoyancy aloft with eastward extent
suggests that the severe threat is minimal.  

Farther south, low-level moisture advection in advance of the cold
front, as well as modest surface heating in cloud breaks beneath a
narrow plume of 7-8 C/km midlevel lapse rates, will support MLCAPE
of 250-500 J/kg this afternoon/evening across the OH Valley. 
However, low-level flow will not be particularly strong (30 kt or
less), and the potential for strong/damaging gusts with shallow
frontal convection appears too low to warrant an outlook area.

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