SPC AC 211730
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Sat Jul 21 2018
Valid 221200Z - 231200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SUNDAY AFTERNOON
AND EVENING FROM THE FL PANHANDLE INTO SOUTHEAST GA AND OVER PARTS
OF THE NORTHERN PLAINS...
A few severe thunderstorms are possible Sunday afternoon and evening
across parts of the FL Panhandle and southern GA, and across parts
of the northern Plains.
Overall upper pattern across the CONUS, characterized by ridging
center over the southern Rockies and troughing center over the
middle OH valley, is expected to change little throughout the period
Sunday. Enhanced northwesterly flow aloft will extend southeastward
from the MO Valley to the central Gulf Coast between these two
primary features. Farther north, a more progressive shortwave trough
will move from southern Saskatchewan eastward/northeastward into
central Manitoba while moderate westerly flow aloft extents through
its southern periphery from the northern Rockies through the
At the surface, an occluded low will slowly drift southward from the
middle OH Valley into the TN Valley while another low pivots
northwestward across the Lower Great Lakes. A weak frontal zone is
expected along the base of the upper ridge, extending roughly from a
lee low over the Carolina Piedmont southwestward to southern AL/MS
and then back northwestward to a lee low over the central High
Plains. Farther north, a cold front attendant to the
Saskatchewan/Manitoba shortwave trough will move through the
northern and central Plains Sunday afternoon and evening.
Expectation is for the previously mentioned cold front to extend
from central ND southward through the NE Panhandle at 18Z with
gradual eastward progress anticipated thereafter. By 12Z Monday, the
cold front will likely extend from north-central MN southwestward
into southwest NE. Modest moisture return is anticipated across the
northern Plains ahead of the approaching cold front, which when
combined with strong insolation, will result in airmass
destabilization. The strongest forcing for ascent will occur across
southern Saskatchewan/Manitoba and adjacent portions of ND.
Consequently, the highest likelihood for thunderstorms exists here.
Modest instability coupled with seasonally strong westerly flow
aloft is expected to support a few strong to severe storms in this
area. Gradually decreasing thunderstorm coverage is expected
southward through SD, largely due to further displacement from the
stronger forcing for ascent. A secondary increase in thunderstorm
coverage is possible across northeast CO as storms come off the
higher terrain. Decreasing shear with southern extent is expected to
keep the severe threat more isolated that areas farther north.
...Central Gulf Coast...FL Panhandle/Northern
Some potential exist for storms to be ongoing across the region at
the beginning of the period but an overall scouring of the airmass
is not currently anticipated. As such, strong instability is
expected to develop from the central Gulf Coast eastward to the
southeast GA coast amidst favorable low-level moisture (i.e.
dewpoints in the mid 70s), seasonally cool mid-level temperatures,
and strong daytime heating. Enhanced northerly/northwesterly flow
aloft is also anticipated across the region, leading to a higher
chance of storm organization than typically experienced this time of
year. Primary severe threat will be damaging wind gusts.
...MAXIMUM RISK BY HAZARD...
Tornado: 2% - Marginal
Wind: 15% - Slight
Hail: 15% - Slight
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z