SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1221 AM CDT Tue Mar 29 2022
Valid 291200Z - 301200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHERN
AND CENTRAL PLAINS INTO THE LOWER MISSOURI VALLEY...
...SUMMARY...
Severe thunderstorms are expected across portions of the central and
southern Great Plains and Lower Missouri Valley Tuesday evening into
early Wednesday morning.
...Synopsis...
A closed upper-low over central California will start to move east
this morning and move into the central/southern Plains by late
tonight. A strong mid-upper level jet will overspread the southern
Plains into the Midwest. A deepening surface cyclone will develop
with a strong mass response and a large region of 50+ knot flow at
850mb from the western Gulf to the Upper Midwest after 00Z. A
dryline will extend from the surface low to west Texas for most of
the period before starting to advance eastward across the southern
Plains late tonight.
...Central/Southern Plains...
Moisture remains limited across the Plains this morning with 60
degree dewpoints barely north of I-10. As southerly low-level flow
strengthens through the day, this moisture will advect northward and
destabilize the warm sector ahead of a dryline which will extend
from West Texas to the I-35 corridor in Kansas. However, moisture
quality remains low and therefore, some mixing is anticipated with
dewpoints likely to stay in the upper 50s to low 60s. This dry
airmass, combined with a stout EML, should limit convective
potential during the day today despite persistent large-scale ascent
and height falls.
Expect storms to form along the dryline near 00Z as the upper-level
trough advances eastward and the low-level jet strengthens,
providing ample lift to overcome the large cap. Deep-layer shear
will support organized/rotating updrafts, however, storm motion will
remain mostly parallel to the dryline. Therefore, expect upscale
growth into a QLCS to occur rather quickly with a threat for
damaging winds and a few tornadoes. Most 00Z CAM guidance has a
somewhat disorganized line through 06Z with better organization
closer to 12Z. This seems to be associated with the arrival of
better quality moisture and a 60+ kt low-level jet. Expanded the 5
percent tornado probabilities from the prior Day 2 outlook eastward
across Oklahoma to account for this threat early Wednesday morning.
...Southeast Nebraska into Iowa...
The forecast is complicated across this region this evening/early
overnight as 00Z guidance shows considerable variability in moisture
quality across the region which has considerable impacts on storm
threats. Regardless of the low-level moisture, an elevated hail
threat is expected across eastern Nebraska and most of Iowa after
00Z along the cold front/dryline near the surface low. Forecast
soundings show very steep lapse rates (8 to 8.5 C/km), moderate to
strong instability (MUCAPE 1500 to 2000 J/kg) and effective shear in
excess of 50 knots. If sufficient low-level moistening can occur,
some of the storms on the southern extent of this activity could
become surface based. If this occurs, the low-level shear profile
would support a tornado threat. Given the low-quality nature of the
moisture and the northward distance it needs to travel, do not
expect much of a surface-based storm threat to materialize. However,
there is enough of a chance to warrant 2 percent tornado
probabilities.
..Bentley/Darrow.. 03/29/2022
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