SPC AC 071255
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0755 AM CDT Thu Jul 07 2022
Valid 071300Z - 081200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS MAINLY ACROSS
PARTS OF MONTANA...AND FROM THE LOWER MISSOURI VALLEY INTO THE
CAROLINAS...
...SUMMARY...
Scattered thunderstorms, some severe, will be possible today mainly
across parts of Montana, and from the lower Missouri Valley into the
Carolinas. Damaging winds are possible over all areas, with large
hail also expected over Montana.
...Synopsis...
The large-scale pattern in mid/upper levels will continue to feature
troughing off the West Coast, mean ridging across the south-central
CONUS and Rockies, and west-northwest to northwest flow across much
of the Upper Midwest, Great Lakes and Appalachians. The Rockies
ridging is expected to amplify through the period, leading to a net
westward displacement of the main/anchoring 500-mb high across the
southern Plains and toward NM. An embedded shortwave trough -- now
evident in moisture-channel imagery over eastern portions of CO/WY
and central NM -- should pivot eastward over the central Plains,
closely following a smaller, MCV-reinforced shortwave trough now
over north-central/west-central KS. Downstream, a series of mostly
low-amplitude/mesoscale perturbations will cross the Ohio Valley and
Southeast.
At the surface 11Z analysis showed a wavy/quasistationary front from
a low over the Delmarva Peninsula, across west-central VA, WV,
southern IN, and northern MO, with a diffuse segment northwestward
to a low over central SD. A cold front was drawn from a low over
west-central KS across the TX Panhandle and northeastern NM. The
main foci for convection this period should be boundaries south of
the front over the eastern outlook area, and north of the front
across the northern Rockies/northern High Plains regions.
...MT and vicinity...
Isolated to scattered thunderstorms are expected to develop this
afternoon -- mainly over higher terrain of southern/western MT --
and move northeastward while offering the potential for sporadic
severe gusts and large hail. Any supercells that survive into the
more-suitable moisture profiles of central/northern MT will be
capable of significant hail, and depending on storm-scale processes
and boundary interactions, a marginal/conditional tornado threat.
Large-scale support will be more nebulous today compared to previous
days, with net height rises forecast across the region. Convection
will be focused largely by heating of elevated terrain,
preferentially weakening MLCINH sooner compared to lower elevations
in the northern/eastern areas, and secondarily along boundaries left
from prior activity. A drier and more deeply mixed boundary layer
is expected with southwestward extent (and increasing elevation)
across MT, away from a low-level moist/theta-e axis extending from
central SD to north-central/northeastern MT. This should contribute
to MLCAPE ranging from around 2000-2500 J/kg near that axis to 1000
J/kg over southern/western MT near the main, orographically aided
convective initiation zones. Forecast soundings also suggest strong
veering of winds with height, though modest low-level wind speeds
will keep hodographs and SRH marginal in magnitude. Some of the
diurnal activity may aggregate upscale into an evening cluster
across eastern MT into the western Dakotas, nearer to the moist
axis, with severe gusts being the main concern until convection
encounters progressively more-stable boundary layer and stronger
MLCINH tonight in the Dakotas.
...KY/TN to Carolinas...
Again today, a large swath of the area from the Ohio Valley to
Southeast will have thunderstorm potential, with the greatest
concentration likely in and near the "slight"/15%-wind outlook area.
Multicell clusters and pulse storms will be common and locally
numerous, offering the threat of damaging gusts, with a few
severe/50+ kt gusts possible.
Development should be focused mainly along higher terrain, a surface
trough east of the mountains, and especially any number of outflow
boundaries south of the synoptic front -- both from prior convection
and generated throughout today's event. Strong surface heating in a
richly moist air mass (dewpoints commonly in the upper 60s to mid
70s F), along with a deep troposphere, will offset modest midlevel
lapse rates enough to yield MLCAPE in the 1500-2500 J/kg (locally
higher) over much of the outlook area. Deep-tropospheric flow and
vertical shear each will be weak, but oriented such that
southeastward-propagating clusters will be favored. Potential
should wane after dark as the boundary layer stabilizes from a
combination of outflows and nocturnal/diabatic cooling.
...Central Plains to mid Mississippi Valley...
Scattered thunderstorms are possible today over parts of IL as an
eastward extension of ongoing activity in northeastern MO, as well
as near a diurnally heated/modified version of the trailing outflow
boundary across parts of northern MO to eastern KS. Damaging gusts
and isolated large hail will be the main concerns, and at least a
marginal tornado threat may develop with any supercell that can take
advantage of favorable low-level vorticity/SRH along the boundary.
In addition to the northern KS MCV, others are evident in
west-central to central NE and over northeastern KS/southeastern NE.
Mesoscale enhancements to both large-scale lift aloft, and vertical
shear, are possible east and south of these features as they move
eastward today, while the outflow boundary moves/diffuses somewhat
northward. Relatively undisturbed, richly moist boundary-layer air
over the mid Mississippi Valley, central/southern MO and eastern KS
will be available as inflow to convection developing today, and over
IL for convection moving in from MO. By midafternoon, 2500-3500
J/kg MLCAPE and negligible CINH are expected. Weak mid/upper flow
over most areas suggests modes could become clustered and messy, but
favorable low-level shear may persist along or north of the outflow
boundary for support of at least transient supercellular
characteristics. Overall coverage/intensity should diminish from
late evening into tonight.
..Edwards/Goss.. 07/07/2022
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
SPC AC 070559
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Thu Jul 07 2022
Valid 081200Z - 091200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN ROCKIES/PLAINS...
...SUMMARY...
Isolated to scattered severe thunderstorms may occur Friday across
parts of the northern Rockies/Plains. Large hail and severe/damaging
wind gusts should be the main threats.
...Northern Rockies/Plains...
An upper ridge will remain prominent across much of the Southwest,
Rockies, Plains and central Canada on Friday. Around 35-45 kt of
mid-level southwesterly flow preceding an upper trough over the West
Coast is forecast to overspread parts of the northern Rockies and
adjacent northern Plains of MT through the period. A moist low-level
airmass will likely be present along/east of a surface trough
extending across the northern High Plains. At least moderate
instability should once again develop across much of MT and vicinity
as daytime heating occurs. Steep mid-level lapse rates should also
be present over the warm sector.
Initially high-based convection that forms over the northern Rockies
Friday afternoon will spread generally east-northeastward across MT
through Friday night. Deep-layer shear should be strong enough for
some supercell structures. Both large hail and severe wind gusts may
occur with this convection. Some upscale growth into one or more
bowing clusters may also occur Friday evening/night with eastward
extent into MT as a low-level jet modestly strengthens. Overall
coverage of thunderstorms becomes more uncertain with eastward
extent into ND. But, an isolated severe threat should exist owing to
a favorable thermodynamic and kinematic environment.
...Mid Mississippi Valley into the Midwest, Ohio Valley,
Central/Southern Appalachians, and Southeast...
Modest enhancement to the mid-level west-northwesterly flow should
be present Friday from parts of the mid MS Valley/Midwest into the
OH Valley, central Appalachians, and Carolinas. A moist low-level
airmass, with dewpoints generally in the low to mid 70s, will likely
be present across these regions along/south of a weak front. Diurnal
heating of this airmass should aid the development of moderate to
locally strong instability by Friday afternoon. The fairly modest
deep-layer shear should limit updraft organization to some extent.
Still, some clustering of convection should occur, and multicells
capable of producing mainly isolated damaging winds should spread
east-southeastward across these regions through Friday evening.
Some guidance suggests that an MCV and remnant convection will be
present across parts of the mid MS Valley at the start of the period
Friday morning. If it holds together, this activity may pose an
isolated severe threat through the morning hours as it spreads
eastward into the Midwest and lower OH Valley. High-resolution
guidance suggests varying solutions regarding the track/evolution of
this MCV and related potential for the redevelopment of strong to
severe thunderstorms across these areas Friday afternoon. Have
expanded the Marginal Risk to account for this uncertainty, and
greater severe wind probabilities may be needed if a more focused
corridor of MCS damaging wind potential becomes apparent.
...Central High Plains...
High-based convection that forms Friday afternoon over parts of the
central Rockies should spread into the adjacent High Plains by early
Friday evening. Modest low-level upslope flow should also occur
through the day. Even with mid-level winds and related deep-layer
shear remaining modest, weak to moderate instability and steepened
low-level lapse rates should aid in robust updrafts being maintained
as convection spreads generally east-southeastward. Isolated severe
wind gusts and hail may occur with the strongest updrafts.
...Maine...
Strong mid-level westerly flow associated with an upper trough over
eastern Canada will be present across ME on Friday. Although
low-level moisture is forecast to remain fairly limited, modest
heating and weak instability may develop in a narrow corridor by
Friday afternoon. A couple of strong to marginally severe
thunderstorms capable of producing occasional hail/wind may develop
in this regime.
..Gleason.. 07/07/2022
WUUS02 PTSDY2
SPC AC 070729
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0229 AM CDT Thu Jul 07 2022
Valid 091200Z - 101200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
THE NORTHERN PLAINS...
...SUMMARY...
Isolated to scattered severe thunderstorms may occur Saturday into
Saturday night across parts of the northern Plains.
...Northern Plains...
An upper trough over the Pacific Northwest is forecast to move
eastward across the northern Rockies/Plains and western Canada on
Saturday. This trough will act to suppress large-scale upper ridging
over the northern Plains. Warm low/mid-level temperatures associated
with a strong cap should tend to suppress convection through much of
the day. However, some guidance does show robust thunderstorms
developing across the open warm sector in ND during the day. If this
convection forms, it would be on the northeastern extent of the cap
and EML plume emanating from the higher terrain of the
northern/central Rockies. Additional thunderstorms are expected to
form Saturday evening/night across MT into ND as ascent associated
with the upper trough overspreads this region, and as a cold front
sweeps eastward. Even though details in convective evolution remain
somewhat unclear, the strong forecast instability and deep-layer
shear will be more than sufficient for severe thunderstorms posing a
threat for all hazards through Saturday night.
...Southeast...
Modest west-northwesterly mid-level flow will overspread much of the
Southeast on Saturday. A weak front is also forecast to sag slowly
southward across this region through the period. A very moist
low-level airmass should be in place across the warm sector. Diurnal
heating will contribute to moderate/strong instability and steepened
low-level lapse rates by Saturday afternoon. Even though deep-layer
shear should remain modest, multiple loosely organized clusters
capable of producing mainly wind damage should spread
south-southeastward across much of the Southeast through Saturday
afternoon. A broad Marginal Risk has been included to account for
the damaging-wind potential, and greater severe probabilities may
eventually be needed if corridors of greater mesoscale severe
potential become evident.
..Gleason.. 07/07/2022
WUUS03 PTSDY3
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
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