SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0256 PM CDT Tue Apr 19 2022
Valid 192000Z - 201200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
...SUMMARY...
General thunderstorms are expected across portions of the southern
Plains this evening and into the Ozarks and Midwest overnight.
...20z Update...
An ongoing cluster of thunderstorms along the Red River may continue
eastward this evening across portions of southern OK and eventually
western AR. However, meager low-level moisture within the dry
airmass (dewpoints in the 30s and 40s F) to the east suggests the
overall severe threat is decreasing owing to limited buoyancy.
Gradual redevelopment/expansion in general thunderstorm coverage
appears likely to emerge from the remnants of the cluster later this
evening across central/Eastern OK with an increase in warm advection
beneath the nocturnal low-level jet. Model soundings show moisture
continues to lag behind a subtle shortwave trough moving across the
southern Plains, resulting in only modest elevated buoyancy this
evening. Deeper moisture, slated to arrive after midnight, will miss
the deeper lift associated with the aforementioned shortwave as it
lifts off to the north and east. The lack of sizable buoyancy,
forcing for ascent and decreasing vertical shear suggests the
overall severe threat tonight will be low.
Across the Texas Big Bend, another cluster of storms may persist for
a few more hours along the US/Mexican Border. While low-level
moisture advection should continue to increase late this
afternoon/evening ahead of the cluster. Limited forcing for ascent
from the exiting shortwave, and increasing subsidence/capping in its
wake suggests little potential for additional
organization/strengthening of the ongoing storms through this
evening.
..Lyons/Jewell.. 04/19/2022
.PREV DISCUSSION... /ISSUED 1116 AM CDT Tue Apr 19 2022/
...Synopsis...
Broad height falls continue across the western CONUS this morning as
a mean longwave trough becomes established across the eastern
Pacific and West Coast. A pair of more progressive shortwave troughs
embedded within the mean flow across the Pacific Northwest and
northern Rockies will continue to eject towards the Canadian
Prairies through the day. The combination of the ejecting impulses
and increasing zonal flow over the central Rockies will help deepen
a lee trough through the day, which should consolidate into a lee
cyclone by early Wednesday. This low-level response will maintain
northward advection of a higher theta-e air mass from the TX Gulf
and Rio Grande valley into the Plains over the next 24 hours. Broad
isentropic ascent within this warm advection regime will support
isolated to scattered showers and thunderstorms across the southern
Plains this afternoon into the overnight hours.
...Northwest Texas into southwest Oklahoma...
Morning soundings show 7-8 C/km lapse rates across the southern
Plains atop of a cool, somewhat dry boundary layer. The combination
of adiabatic cooling via isentropic ascent and moistening from
poleward advection of richer Gulf moisture will support gradual
destabilization of the 850-700 mb layer across TX into OK today into
tonight. Early signs of this process are already evident with
isolated elevated convection noted across parts of northwest OK and
the Big Bend region of TX over the past few hours. Isolated
thunderstorms are possible where sufficient boundary-layer
moistening/warming and low to mid-level lift can overlap and
overcome lingering MUCIN. Confidence in exactly where this may occur
is low with considerable spread noted in recent CAM solutions.
Ensemble probabilities hint that this potential may be maximized
across portions of northwest TX into the Red River Valley this
afternoon and evening along the low/mid-level warm front. Despite
the elevated nature of convection, 50-60 knot flow near 6 km will
support 40-50 knots of effective bulk shear supportive of organized
storms with an attendant hail threat. Damaging winds are possible
with any stronger storm, but will likely be conditional on the
degree of daytime heating and the depth of boundary-layer mixing
(and hence will be maximized during the late afternoon).
Thunderstorms will likely persist well into the overnight hours
across southeastern OK into western AR, but the severe threat is
less certain across these regions as deep-layer shear weakens with
eastward extent.
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