Valid 092000Z – 101200Z
…THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS
AFTERNOON/EVENING FOR SOUTHWEST OK AND NORTHWEST TX…
…SUMMARY…
Supercells with large hail and isolated damaging winds will be
possible this evening across southwest Oklahoma and northwest Texas.
More isolated large hail may occur overnight into the middle
Missouri Valley.
…Discussion…
No substantial change was made to the previous convective outlook.
..Smith.. 10/09/2019
.PREV DISCUSSION… /ISSUED 1120 AM CDT Wed Oct 09 2019/
…Southern Plains to the middle MO Valley through tonight…
A deep midlevel trough over the northern Rockies will dig
southeastward over the Great Basin toward the central Rockies, as a
downstream shortwave trough ejects northeastward from KS/OK to the
upper MS Valley. Lee cyclogenesis is expected across eastern CO in
advance of the Great Basin midlevel trough, as an early season cold
air mass surges southward from WY into CO this afternoon through
tonight. The lee cyclone will induce low-level moisture return
northward from TX across OK/KS, where boundary-layer dewpoints will
increase into the low-mid 60s by this evening.
Weak subsidence aloft is possible this afternoon over western OK in
the wake of the ejecting trough this morning, as suggested by the
stable layer and 5-6 C warming at 500 mb from 00 to 12z at ABQ.
Though large-scale forcing for ascent should remain neutral/weak, a
few thunderstorms should form by late afternoon/evening along the
sharpening dryline near the southeast TX Panhandle/northwest TX,
where mixing and moisture advection will result in MLCAPE near 1500
J/kg and weakening convective inhibition. Despite the midlevel
stable layer, the moderate buoyancy and westerly effective bulk
shear in excess of 40 kt with long hodographs aloft will favor
supercells capable of producing isolated large hail and damaging
gusts into early tonight across southwest OK and extreme northwest
TX. There will be a small window of opportunity for an isolated
tornado this evening as low-level shear increases, prior to surface
cooling/stabilization.
Farther north, destabilization is expected above the surface in
conjunction with a strengthening low-level jet. Warm advection
overnight could support a few storms capable of producing isolated
large hail into the middle MO Valley.
…Southeast FL coast this afternoon…
A slow-moving front will remain across central FL this afternoon,
while surface heating will drive a weak east coast sea breeze to the
south of the front. MLCAPE will increase to 1500-2000 J/kg as
surface temperatures warm into the mid-upper 80s with mid 70s
dewpoints, and there will be just enough deep-layer vertical shear
for semi-organized storm clusters. However, very moist profiles
suggest that downdraft potential will be largely limited to
precipitation loading with cell mergers, and the potential for
damaging outflow winds appears too low for an outlook area.
$$