Subj : DAY48SVR: Nws Storm Prediction Center Norman Ok
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Dec 08 2022 10:08:18

ACUS48 KWNS 081008
SWOD48
SPC AC 081006

Day 4-8 Convective Outlook
NWS Storm Prediction Center Norman OK
0406 AM CST Thu Dec 08 2022

Valid 111200Z - 161200Z

....DISCUSSION...
Medium-range models appear to remain solidly consistent -- both in
terms of similarity with each other in the most recent run, and also
with other, previous runs over the prior 48 hours -- through Day
6/Tuesday Dec. 13.  Days 7-8, differences in evolution of the large
upper cyclone over the central U.S. lead to differences in timing of
surface frontal advance/evolution across the Southeast, with
uncertainty thus precluding assessment severe risk beyond Day 6.

During the first half of the period, when models are in remarkable
agreement, severe risk is expected to gradually increase, from
negligible at best (Day 4/Sunday), to increasing over the Oklahoma
vicinity Day 5/Monday, and through what is expected to be
substantial potential Day 6 from eastern portions of the southern
Plains to the Lower Mississippi Valley.

The event should begin overnight Monday and into early Tuesday,
focused on the Oklahoma vicinity, as a deep upper low crosses the
Rockies through the day, and then the central/southern High Plains
overnight.  This upper low progression will be accompanied by a
mature surface low that should shift out of the central High Plains,
while a trailing cold front crosses Texas/Oklahoma overnight.
Strong southerly winds ahead of the front will result in an increase
in low-level moisture -- and thus modest destabilization.  Despite
the unfavorable time of day, very strong/favorable flow aloft
accompanying this system suggests an increase in all-hazards severe
weather through the latter stages of the period.

Later on into the day on Tuesday (Day 6), continued eastward advance
of the deep upper cyclone, and an occluding surface low over the
Nebraska vicinity, is expected.  As the cold front continues
eastward across the southern Plains and into the Ozarks/Arklatex,
high theta-e low-level air and modest heating should yield ample
CAPE -- particularly across Louisiana and into Arkansas during the
afternoon.  With a very strong/veering flow field with height that
should prove quite supportive of severe/supercell storms, risk for
tornadoes is apparent, along with damaging winds and hail.  This
risk will shift gradually eastward in tandem with frontal advance,
likely crossing into the Mississippi and western Tennessee vicinity
into the overnight hours.

While convection, and some severe potential, should continue
spreading eastward/southeastward, increasing uncertainty precludes
delineation of a Day 7 area at this time.

...Goss.. 12/08/2022

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