SPC AC 180537
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1237 AM CDT Wed Jul 18 2018
Valid 191200Z - 201200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ...
A marginal severe threat will be possible on Thursday across parts
of the upper Mississippi Valley.
...Upper Mississippi Valley...
An upper-level trough will move into the upper Mississippi Valley on
Thursday as a 45 to 55 kt mid-level jet moves across northeastern
sections of the central Plains. At the surface, a low is forecast to
move into the upper Mississippi Valley as a cold front advances
eastward across the mid Missouri Valley. A moist airmass should be
in place ahead of the front with surface dewpoints in the mid to
upper 60s F. As a result, a corridor of moderate instability appears
possible ahead of the front by Thursday afternoon. Elevated
convection may ongoing Thursday morning ahead of the front near the
axis of the low-level jet. This convection is forecast to weaken by
early afternoon with new surface-based thunderstorms developing
along the front. These storms are forecast to move eastward across
the Upper Mississippi Valley during the mid to late afternoon and
early evening. Moderate deep-layer shear along the front, evident on
forecast soundings, should enable the stronger cells to have
marginally severe wind gusts and hail. The magnitude of the severe
threat will likely depend upon how much instability materializes
across the moist sector. At this time, forecast instability appears
low enough to keep the threat at marginal.
...MAXIMUM RISK BY HAZARD...
Tornado: 2% - Marginal
Wind: 5% - Marginal
Hail: 5% - Marginal
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z