Clearpost.online It's your post, so post it!

Day 1 Convective Outlook  
NWS Storm Prediction Center Norman OK
0750 AM CDT Sun May 08 2022

Valid 081300Z - 091200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE NORTHERN PLAINS AND NORTH TX...

...SUMMARY...
Isolated severe hail and/or gusts may occur this afternoon over
portions of the north-central Plains and north Texas, with the
potential persisting into tonight over the northern Plains.

...Synopsis...
A high-amplitude mid-upper-level pattern is forecast to persist
through the period.  A leading cyclone -- initially located over the
Delmarva peninsula -- is forecast to move slowly out to sea through
12Z tomorrow.  An upstream ridge -- analyzed from central MX across
the Mid-South region to the lower Ohio Valley and southwestern QC --
will amplify but exhibit little lateral movement.

A longwave trough over western North America will be anchored by a
large, co*plex cyclonic gyre, orbited by numerous vorticity maxima
and smaller-scale circulations, and covering most of western Canada
and the northwestern CONUS.  One of those circulations -- evident in
moisture-channel imagery west of the OR coastline -- should move
inland around 18Z today then devolve into an open-wave trough across
the northern Great Basin and ID by 12Z.  Ahead of it, several
smaller-scale perturbations will eject northeastward over the
central/northern Rockies and northern Plains.

The 11Z surface analysis showed a low over west-central KS, with
warm front arching across north-central KS then southeastward over
eastern OK and northwestern to southeastern LA.  A weak cold front
was drawn from the low over the northern TX Panhandle and
northeastern NM.  A separate cold-frontal zone, with weak attached
low(s), was evident from eastern ND across east-central SD, the
southwestern NE Panhandle, and southeastern WY.

Surface cyclogenesis is expected this afternoon over central to
northeastern CO, rendering the southern boundary a warm front by 00Z
east-southeastward across parts of KS, as the northern frontal zone
beco*es quasistationary and more diffuse.  By 12Z, the low should
eject across the central Plains to near the VTN-9V9 corridor, with
cold front southwestward over east-central/southeastern CO and warm
front across western IA to central MO.  A dryline -- now over the
eastern TX Panhandle, northwest TX, and the lowest parts of the
Pecos River, should shift eastward this afternoon as far as
west-central/central OK, western north TX, to near SJT and north-
central Coahuila, before retreating northwestward overnight.

...North-central Plains States...
Isolated to widely scattered thunderstorms are possible this
afternoon into the overnight hours near the low-level frontal zone,
with some supercell evolution possible.  Occasional potential will
exist for severe gusts/hail.  A more-uncertain but non-negligible
threat also is apparent, in some guidance, for the development of a
loosely organized cluster or co*plex of elevated thunderstorms with
severe hail potential tonight, particularly over the eastern
SD/southwestern MN area.

Surface dewpoints in the 50s F and lack of a substantial EML
influence at these latitudes will render minimal MLCINH, amidst
pockets of 500-1000 J/kg peak/afternoon MLCAPE.  Surface-based
effective-inflow parcels may remain essentially uncapped well into
the evening, given some low-level theta-e advection to offset slow
nocturnal cooling.  Weak low-level flow is forecast before sundown
(generally 10 kt or less below the 700-mb level before sunset), but
around 90-100 kt anvil-level flow, and 50 kt at 500 mb, should
render strong cloud-layer shear and aid in storm organization. 
After about 02Z, a strengthening northwestern branch of the LLJ,
featuring southeast flow, will serve several favorable purposes,
including:
* Increased low-level shear with enlarging hodographs, even for
elevated storms,
* Stronger storm-relative winds in at least part of the
effective-inflow layer, and
* Increasing low-level moisture above the surface, with warming/
saturating parcels in the 8000-850-mb layer, beneath slightly
cooling midlevel conditions preceding ejecting vorticity maxima. 
This may support elevated MUCAPE of more than 2000 J/kg, with
50-70-kt effective-shear vectors.

Confidence in timing and breadth of any nocturnal co*plex(es)
remains too low to introduce an unconditional upgrade at this
still-early hour.  However, one may be needed if better mesoscale
foci and/or greater guidance consistency beco*e apparent.

...North TX...
Another strongly conditional setting for severe-thunderstorm
potential is evident for just 2-3 hours late this afternoon --
slightly northward from yesterday, and along/ahead of the dryline. 
Any sustained convection that develops through the diurnally
weakened EML inversion in this area will pose a threat for severe
downdrafts and large hail.  Slightly greater confidence exists in
this scenario co*pared to yesterday's, given the more-cyclonic
nature of the flow aloft, height falls, rich low-level moisture, and
near-record surface temperatures near the dryline to eliminate
MLCINH, potentially for long enough to sustain deep convection to
maturity.  Still, a stout EML inversion, sampled by the 12Z FWD
RAOB, renders highly uncertain (but likely isolated) coverage and
duration of potential, in turn keeping the unconditional
probabilities at marginal levels for now.

Upper 60s to low 70s F surface dewpoints should remain over the
region ahead of the dryline, underlying steep low/middle-level lapse
rates.  This contributes to projected peak/preconvective MLCAPE in
the 3000-4000 J/kg range (locally/briefly larger), atop a well-mixed
subcloud layer with DCAPE exceeding 1500 J/kg.  Modest mid/upper
flow is expected, substantially restricting deep shear, with
effective-shear magnitudes struggling to exceed 30 kt in forecast
soundings.  However, strong veering of winds with height is forecast
in low levels, along with enlarging hodographs from late afternoon
into early evening, as the southwestern rim of a broad LLJ develops
over the area.  This, amidst the very strong and deep buoyancy,
indicates transient/messy supercell structures and organized
multicells are favored.  Any severe threat should diminish rapidly
after sunset in the absence of appreciable large-scale forcing, and
as the layer of near-surface static stability strengthens/deepens.

..Edwards/Gleason.. 05/08/2022