SPC AC 200544
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1244 AM CDT Wed Jun 20 2018
Valid 211200Z - 221200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE
MIDDLE AND LOWER MISSISSIPPI VALLEY...ACROSS CENTRAL MONTANA...AND
OVER PARTS OF THE SOUTHERN HIGH PLAINS...
Scattered severe hail and wind is possible Thursday across parts of
the middle and lower Mississippi Valley. Isolated hail is also
possible across parts of the southern High Plains and northern
An upper low will travel southeastward across MO, with a belt of
50-60 kt midlevel northwesterly winds moving from the central Plains
into the lower MS Valley. At the surface, low pressure will develop
toward the middle MS Valley. A cold front will extend southwestward
toward the Arklatex by 00Z, with a warm front extending east across
the OH Valley. To the west, an upper high will be centered over AZ,
with a low-amplitude shortwave flattening the ridge over the
northern Rockies where a cold front moving into MT and WY.
...Mid to lower MS Valley...
Cool air aloft with the upper trough and ample low-level moisture
will lead to areas of 1000-2000 J/kg MUCAPE from TX to IL.
Complicating this forecast scenario will be widespread precipitation
and clouds early in the day. However, a plume of heating and
steepening low-level lapse rates is expected to develop mainly along
and west of the MS river. Given cool temperatures aloft, an arc of
diurnal re-development is expected. Hail and wind will be possible,
and portions of the area may eventually be upgraded to a Slight Risk
once predictability issues decrease in later outlooks.
...Central and southwest MT and vicinity...
Lift associated with the upper trough and cold front will lead to
scattered storms during the afternoon. Steep lapse rates and
lengthening hodographs will favor cells and/or small bows capable of
large hail or damaging winds.
...Southern High Plains...
Strong heating along with 50s F dewpoints will lead to a pocket of
1500 J/kg MUCAPE by late afternoon. Weak southeasterly surface winds
will lead to sufficient convergence for isolated afternoon storms
mainly over northeast NM. Straight hodographs and northwest flow
aloft will favor slow, southeastward-moving cells capable of
marginally severe hail.
...MAXIMUM RISK BY HAZARD...
Tornado: 2% - Marginal
Wind: 5% - Marginal
Hail: 5% - Marginal
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NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 1730Z