SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0241 PM CDT Sun Jun 19 2022
Valid 192000Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST
MT AND WESTERN ND...
...SUMMARY...
A couple long-tracked supercells, potentially producing significant
severe hail and wind, will most likely occur centered on southeast
Montana into western North Dakota through this evening.
...20z Update...
Only minor adjustments have been made to the ongoing outlook with
the 20z update. Marginal probabilities have been removed from much
of UT as storms have shift north/northeast and instability is
diminishing. Otherwise, only some minor changes to the 10 percent
general thunderstorm line have been made across the central Gulf
Coast and FL vicinity.
The airmass across eastern MT into western ND continues to recover
after morning convection. Instability is increasing and inhibition
weakening. Severe storms are still expected through this evening.
Thunderstorm clusters across FL are drifting south/southwest across
portions of the Peninsula. This activity will continue to pose a
threat for isolated strong/locally damaging gusts the next few
hours. For additional details in short term severe potential,
reference MCDs 1224 and 1225.
..Leitman.. 06/19/2022
.PREV DISCUSSION... /ISSUED 1129 AM CDT Sun Jun 19 2022/
...Southeast MT/northeast WY/western ND...
Basal shortwave impulse embedded within the amplified western
mid-upper trough should eject from the Great Basin north-northeast
towards the northern Rockies. Large-scale ascent tied to this wave
has supported scattered thunderstorms ongoing from eastern UT into
western WY, and will reach the Big Horns later this afternoon.
Primary severe potential will emanate out of this latter development
as post-frontal low-level upslope flow persists and cloud breaks aid
in weak surface-based buoyancy. 12Z guidance does differ appreciably
with the degree of destabilization, as well as the degree of
effective bulk shear with the NAM appearing less environmentally
favorable than the RAP. Ongoing cloud coverage and lack of wind
profiler data in the genesis corridor for supercells further lowers
confidence. Nevertheless, ARW-based HREF guidance remains insistent
on simulating at least a couple long-track supercells spreading
northeast off the Big Horns. MLCAPE in western ND will be
comparatively larger in this portion of the post-frontal regime
owing to 60s surface dew points west of the surface cyclone drifting
east into central ND. This suggests that any established supercells
should be sustained into western ND before eventually becoming
undercut with time later tonight as the front accelerates southeast.
Significant severe hail and wind still appears possible.
...Eastern Great Basin to western/central SD...
Eastward progress of the Great Basin trough will bring stronger
mid-level flow farther east compared to previous days. Despite
widespread clouds to slow surface heating over most of the Rockies,
long/straight hodographs could support some organized storm
structures within the monsoonal moisture plume from the Four Corners
Area north into WY. A few strong-severe outflow gusts and isolated
marginally severe hail are the main hazards.
Farther northeast into central SD, mid-level flow will be weaker,
but greater boundary-layer heating and much deeper inverted-v
profiles will favor a few strong-severe outflow gusts with
high-based storm clusters late this afternoon into the evening along
a surface trough.
...FL Peninsula...
Another day of largely diurnal convection is expected, with
scattered thunderstorm development focused by a weak surface front
drifting south in north FL, and sea breeze circulations farther
south. Weak northeasterly mid-level flow suggests that pulse to
loosely organized multicell clusters will spread southwestward this
afternoon. Slightly weaker mid-level lapse rates relative to
yesterday should hold MLCAPE to around 2500-3000 J/kg. Localized
damaging winds from wet microbursts and small to marginally severe
hail will be possible.
Read more CHECK UPDATE ZOOM GRAPHIC
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