SPC AC 031236
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0736 AM CDT Tue Oct 03 2023
Valid 031300Z - 041200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
INTO EARLY TONIGHT FROM WESTERN/CENTRAL KS INTO SOUTH CENTRAL NE...
...SUMMARY...
Isolated very large hail, occasional severe gusts and a few
tornadoes will be possible this afternoon through early tonight
across parts of the Great Plains.
...Synopsis...
A surface cyclone in ND will develop northeastward today toward
southeast SK/western ON as an associated/lead shortwave trough
ejects northeastward over the northern Plains. A trailing shortwave
trough near the Four Corners will progress east-northeastward over
the central Plains later this afternoon through early tonight, with
weak lee cyclogenesis is expected near the CO/KS border today. A
surface cold front will move eastward/southeastward across the
Dakotas, western NE and northeast CO this afternoon, in the wake of
the ND cyclone (and north of the weak lee cyclone). South of the
weak lee cyclone, a dryline will mix eastward into southwest KS and
the western TX Panhandle by mid afternoon. The front and the
dryline will help focus severe thunderstorm development, primarily
this afternoon/evening from NE/KS into west TX.
...Central/southern Plains through tonight...
A narrow corridor of low-mid 60s boundary-layer dewpoints will
spread northward today to the east of a sharpening dryline, and in
the wake of scattered morning convection that is ongoing from
western KS to the TX South Plains. Surface heating along the moist
axis, beneath midlevel lapse rates greater than 7 C/km, will result
in afternoon MLCAPE values of 1500-2500 J/kg with weakening
convective inhibition. Initial severe storm development may occur
by about 20z across KS/NE, with subsequent expansion of the storms
northeastward across NE toward southeast SD, with more scattered
development southward along the dryline toward TX. Long hodographs
(effective bulk shear ranging from 45 kt across west TX to 65 kt
closer to the KS/NE border) with the moderate buoyancy will favor
supercells initially, with the potential to produce isolated very
large hail up to 2.5 inches in diameter. Some upscale growth into
line segments is anticipated from northern KS into NE as storms
align along the cold front. The tornado threat will be modulated by
rather modest hodograph curvature/SRH through much of the afternoon
where the more discrete supercells are expected, and any evening
increase in low-level shear will be somewhat countered by the
tendency for more linear convective modes with northward extent.
Farther south into west TX, weaker forcing for ascent suggests that
storm coverage will be widely scattered along the dryline. Still,
there will be sufficient vertical shear/buoyancy for splitting
supercells capable of producing large hail/isolated wind damage late
this afternoon through late evening.
..Thompson.. 10/03/2023
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