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Source: US National Oceanic and Atmospheric Administration

SPC AC 151728

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1228 PM CDT Thu Aug 15 2019

Valid 161200Z – 171200Z

…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
THE CENTRAL HIGH PLAINS…CENTRAL PLAINS…AND MID MS VALLEY…

…SUMMARY…
Severe storms are possible from the central High Plains across
Kansas and Missouri and into western Illinois Friday.

…Synopsis…
A belt of enhanced westerly flow aloft will extend from the northern
Great Basin eastward into the middle MS Valley early Friday morning,
just ahead of a low-amplitude shortwave trough. This shortwave (and
associated cold temperatures aloft) is expected to continue eastward
across the central Plains with the attendant jet streak progressing
eastward just ahead of it. Farther north, a strong shortwave trough
is expected to move into the Canadian Prairie Provinces and northern
Rockies late Friday evening through early Saturday morning.

Early Friday morning surface pattern will likely feature a low
centered near the central MN/WI border with a cold front extending
southwestward into central KS and then back northwestward into
northeast CO. A moist air mass will be in place south of this
outflow-reinforced boundary, with afternoon dewpoints in the mid to
upper 60s. Low 70s dewpoints are possible in the immediate vicinity
of this composite boundary, which is expected to remain largely
stationary across central KS and central MO throughout the day. This
front is expected to be the focus for severe thunderstorms during
the late afternoon/early evening and continuing overnight. Severe
thunderstorms are also possible across southern portions of northern
High Plains and central High Plains during the afternoon and
evening.

…Central Plains into the Middle MS Valley…
Showers and thunderstorms (remnant from an overnight MCS across KS)
will likely be ongoing early Friday morning across central/southern
MO. Outflow from these storms (which will likely extend back into
central KS) will act as the effective front separating the warm and
moist conditions across southern KS/MO/IL and the southern Plains
from the cooler conditions across northern KS/MO and the remainder
of the central Plains and middle MS Valley. This front is expected
to act as the primary corridor for thunderstorm development,
although two different forcing mechanisms appear possible.

The first potential impetus for convective initiation is convergence
along the front amidst diurnal destabilization. However, given the
relatively warm layer between 850 and 700 mb and lack of stronger
large-scale forcing for ascent, there is some question whether
storms will be able to develop along the front during the late
afternoon/early evening. If storms do develop, very strong buoyancy
will contribute to strong updrafts capable of large hail and strong
wind gusts. The lack of stronger vertical shear suggest storms
should quickly become outflow dominant. Given the presence of a
surface boundary, a brief tornado or two is also possible.

The second impetus for convective initiation near the front is the
low-level jet, which is expected to strengthen across the TX
Panhandle, western OK, and southern KS Friday evening. Warm-air
advection into the frontal zone is expected to result in the
development of elevated thunderstorms from east-central KS, central
MO, and far west-central IL. Mid-level flow will be stronger here
and the potential exist for more organized storms capable of large
hail. Isolated very large hail (i.e. diameter greater than 2″) is
possible.

…Northern/Central High Plains…
Isolated thunderstorms will likely be ongoing across portions of the
NE Panhandle and vicinity as a subtle shortwave move through the
region. Higher thunderstorm coverage is anticipated during the
afternoon when storms are expected to develop amidst upslope flow
into the lee trough. The approaching shortwave trough will provide
additional support for vertical ascent. Most probable location for
initial storm development is across northeast/east-central CO and
vicinity, with storm motion then taking the storms into western KS.
Development a forward-propagating MCS is possible, with the frontal
zone acting a favored corridor for propagation and the strengthening
low-level jet providing additional moisture. Higher probabilities
may be needed is subsequent outlooks if this potential becomes more
probable.

…MAXIMUM RISK BY HAZARD…
Tornado: 5% – Slight
Wind: 15% SIG – Slight
Hail: 15% SIG – Slight

..Mosier.. 08/15/2019

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