SPC AC 201630
Day 1 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
1130 AM CDT Mon Aug 20 2018
Valid 201630Z - 211200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
SOUTHERN ILLINOIS...SOUTHEAST MISSOURI...NORTHEAST
ARKANSAS...WESTERN KENTUCKY...WESTERN TENNESSEE...AND NORTHWEST
CORRECTED FOR NDFD THUNDER GRID ERROR
Scattered severe storms are likely across the Mid-South from
mid-afternoon to early evening. Damaging winds should be the primary
hazard, but a couple tornadoes and large hail are possible.
...Mid MS Valley...
Only minor changes have been made to the ongoing forecast. An
unseasonably strong upper low is present today over MO, with a band
of moderately strong mid-level winds rotating cyclonically around
the base of the low into parts of MO/AR/IL/KY/TN. It appears that
initial convection will develop soon over south-central MO and
north-central AR, and track eastward across the ENH risk area
through the afternoon. Forecast soundings show favorable winds
aloft and sufficient CAPE for a risk of bowing line segment capable
of damaging wind gusts. Initial activity could also pose a threat
of hail and perhaps a tornado or two. Have expanded the risk areas
a little farther north into central/southern IL where
clearing/destabilization appears likely. Further details will be
available in an MCD that will be issued soon.
...Northern IL and vicinity...
Easterly surface winds over northern IL, will result in marginally
favorable hodographs for a few rotating storms later this afternoon
along and north of the warm front lifting across the region.
Widespread clouds will limit heating/destabilization, but morning
model guidance suggests the potential for a few isolated storms
capable of brief spin ups or damaging wind gusts.
Scattered thunderstorms are expected once again today over parts of
NC, where ample low level moisture remains. Winds in the lower
troposphere are weak, but the strongest cells will be capable of
locally gusty/damaging winds.
...Northern Great Basin...
A strong shortwave trough is moving across eastern OR and will
affect parts of ID/MT/UT/WY later today. Low level moisture is
limited, but forecast soundings suggest steep low-level lapse rates
and increasing risk of a few damaging wind gusts as the mid-level
wind max overspreads the region. Small hail will also be possible
in the higher elevations.
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