SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1255 PM CDT Mon Apr 03 2023
Valid 041200Z - 051200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM EASTERN
IOWA INTO NORTHWEST ILLINOIS...AND FROM SOUTHERN MISSOURI
SOUTHWESTWARD TOWARD THE ARKLATEX....
...SUMMARY...
A large area of severe potential will exist from Tuesday afternoon
into Wednesday morning, from eastern portions of the Plains into the
Missouri and mid/upper Mississippi Valleys. Strong tornadoes and
particularly damaging winds are expected. Both afternoon and
overnight potential will exist across various regions, including the
risk of dangerous nighttime tornadoes.
...Synopsis...
A large upper trough will move from the Rockies into the Plains on
Tuesday, with an upper low tracking from WY to northern MN by
Wednesday morning, deepening after 00Z. Meanwhile, upper ridging
will occur over the eastern states. A strong 100 kt midlevel jet max
will be positioned from NM into western KS during the day, with an
intensifying jet core Tuesday night from KS into IA. Just ahead of
the primary upper trough/jet, a leading speed max will strengthen
from OK into KS and MO during the day, perhaps with a subtle lobe of
cooling aloft.
At the surface, low pressure will exist over eastern CO Tuesday
morning, and will shift eastward across KS during the day,
translating east/northeast along a cold front. This low will shift
into IA by evening, and into WI by 12Z Wednesday. Ahead of the low,
a prominent warm front will move rapidly north, beginning the day
from northeast KS into central IL, and reaching near I-80 from IA
into northern IL by 00Z. This boundary will continue north into
southern WI and western Lower MI overnight, ahead of the surface
low. Behind the low, a cold front will make an eastward push during
the late evening and overnight across IA, northwest MO and eastern
KS.
South of the low, a dryline will stretch from eastern KS into
central OK and north TX at 00Z, and may become stationary or even
back westward over the southern Plains during the late evening and
prior to the cold front arriving from the north.
Given relatively high heights over the eastern CONUS preceding the
upper trough, a very wide warm sector will develop from the surface
low and dryline eastward well east of the MS River, with upper 60s F
dewpoints common from eastern OK and AR southward. The combination
of an expansive warm sector and strong shear, for long duration and
in various forcing regimes, suggests that significant severe weather
is likely. However, subtleties regarding timing with regard to the
diurnal cycle, capping, and conflicting model output will make this
prediction challenging, especially when weighing potential impacts
to life and property.
...IA...northern MO...IL...southern WI - DAYTIME...
The area near the warm front and later in late into the overnight
hours ahead of the surface low will be a favored area for supercells
and tornadoes. Storms are expected to form from northern MO into IA
during the late afternoon, shifting northeastward with the warm.
Low-level shear will be extremely favorable for tornadoes, as with
over 300 m2/s2 SRH and MUCAPE perhaps up to 3000 J/kg. The steep
lapse rates aloft will maximize updraft strength as well, resulting
in strong tornadoes. This threat may persist farther northeast into
southern WI and northern IL into the night as the warm and unstable
air with the warm front continues to move north with this strong
system.
...Northeast TX into AR and into MO - OVERNIGHT...
Confidence is increasing in the potential for rare and dangerous
overnight tornadoes and damaging winds, and a Moderate Risk has been
introduced for this region. The air mass will remain capped during
the day, as boundary-layer moisture builds. Steep lapse rates will
exist above the capping layer, which will not be particularly strong
overnight due to robust moisture. As the cold front approaches from
the west, the low-level jet will remain strong providing theta-e
advection through the night. Nocturnal storms are forecast to erupt
after 06Z, and perhaps closer to 08Z from southwest MO into western
AR and into northeast TX. Hodographs will strongly favor tornadic
supercells with effective SRH near 400 m2/s2. Further, steep lapse
rates aloft and ample instability will favor strong tornadoes, and a
long tracked tornado cannot be ruled out. This appears to be a rare
case where the front may act more like a dryline during the
overnight hours, with veering at 850 mb being more gradual. Capping
is most likely to limit the eastward extent of the threat for
southern areas near LA.
..Jewell.. 04/03/2023
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