SPC AC 270059
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0759 PM CDT Fri Jul 26 2024
Valid 270100Z - 271200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
DAKOTAS AND NORTHWEST MN...NORTHEAST NV INTO WESTERN
UT...SOUTH-CENTRAL/SOUTHEAST AZ...
...SUMMARY...
Isolated severe storms remain possible this evening across parts of
the Dakotas into northwest Minnesota, Great Basin, and Arizona.
...Northern High Plains into eastern ND and northwest MN...
A few strong storms have developed from eastern ND into northwest
MN, in the vicinity of a weak cold front. MLCAPE of 2000-3000 J/kg
and effective shear of 30-40 kt could support a supercell or two
through the evening, with a threat of hail, isolated damaging gusts,
and possibly a tornado. See MCD 1714 for more information.
Farther southwest, high-based convection is ongoing across parts of
the northern High Plains, which could pose a threat of isolated
strong to severe gusts through the evening. Elevated convection may
increase later tonight and spread northeastward along/north of the
cold front from northern SD into eastern ND and northwest MN, which
could pose a threat of gusty winds and some hail.
...Central into southeast AZ...
Occasional strong storms have been noted from central into southeast
AZ through the afternoon, mainly in closer proximity to the higher
terrain. Multiple areas of outflow are spreading southward, though
with rather strong MLCINH in place, potential for substantial
development into the lower elevations is uncertain. Some threat for
strong to isolated severe gusts cannot be ruled out through the
evening, though confidence is low.
...Great Basin...
Isolated strong storms remain possible this evening across parts of
west-central/northwest UT. MLCAPE of around 500 J/kg and effective
shear around 30 kt were noted on the 00Z SLC sounding, and briefly
organized storms could pose a threat of isolated strong/severe gusts
and small to near-severe hail. Another round of convection is
possible later tonight from northeast NV into western UT, in advance
of an approaching shortwave trough. A residual well-mixed boundary
layer could support locally gusty winds with this later convection.
..Dean.. 07/27/2024
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z
SPC AC 261730
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Fri Jul 26 2024
Valid 271200Z - 281200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS
CENTRAL/EASTERN ND INTO FAR NORTHWEST MN...
...SUMMARY...
Scattered severe thunderstorms are likely across portions of the
northern Plains vicinity on Saturday.
...Synopsis...
Upper troughing is expected to extend from the northern/central
Canadian Prairie Provinces southwestward into northern/central CA
early Saturday morning. Two primary shortwave troughs will be
embedded within this troughing, one over the northern/central
Canadian Prairies and the other over northern CA. Both shortwaves
are expected to progresses east-northeastward throughout the day
while losing amplitude. Eastward progress of this systems will be
slowed by the Rex block downstream, with the southern cyclone
initially over northeast OK/southeast KS and the northern
anticyclone over Lake Michigan. This Rex block is forecast to break
down under the influence of the western troughing, with the upper
low drifting northeastward into southern MO and the upper ridge
shifting eastward over the Lower Great Lakes by early Sunday.
Surface pattern is forecast to feature an eastern CONUS ridge,
initially centered over the Lower Great Lakes but extending
southward into the Southeast. This ridging is expected to remain
largely in place, while lee surface troughing sharpens across the
High Plains and a cold front associated with the Canadian Prairie
shortwave trough moves into the northern Plains. Thunderstorm
development is anticipated along the cold front across ND Saturday
evening. Storm development is also anticipated farther southwest
across the central Rockies, with the resulting storms then tracking
eastward into the central High Plains.
...Northern Plains..
Showers and thunderstorms will likely be ongoing early Saturday
morning from the eastern Dakotas int northwest MN, remnant from
overnight development across the western/central Dakotas. This
activity will likely be weak, but cloud cover and associated outflow
could act to provide the surface boundaries needed to provide the
impetus for additional storms during the afternoon/evening.
Large-scale forcing will be weak, but low-level convergence and
ample low-level moisture could still result in thunderstorm
initiation. Given the steep low-level lapse rates and high cloud
bases, damaging gust will be the primary threat. Even so, some hail
is possible with the early, more cellular storms. A tornado or two
is possible as well if the boundary is sharp, with surface winds
backing in its vicinity. Mesoscale factors will play a large role in
determining the storm coverage and associated severe potential,
which merits keeping low severe probabilities with this outlook
given the forecast range.
Farther east, thunderstorm development appears likely along the
southeastward-progressing cold front expected to move across the
western Dakotas during the late afternoon. Ample low-level moisture
will support airmass destabilization despite strong mixing, and
robust updrafts are likely within the initial development. Hail is
possible early, with a quick transition to outflow-dominant
structures anticipated. Highest coverage is expected across ND,
which corresponds to the greatest severe thunderstorm potential as
well. Storm longevity will be limited by the onset of nocturnal
cooling, which should lead to relatively quick low-level airmass
stabilization.
...Northern Great Basin into the central Rockies and central High
Plains...
A belt of enhanced mid-level flow is forecast to stretch from the
base of the northern/central CA shortwave trough mentioned in the
synopsis into the northern Plains. The CA shortwave is expected to
progress northeastward throughout the period, with a subtle,
convectively enhanced lead shortwave trough likely proceeding it
across the central Rockies. Large-scale ascent attendant to these
shortwaves coupled with increased mid-level moisture and deep
boundary-layer mixing will support thunderstorms across much of the
region, beginning over the higher terrain and then eventually
spreading into the High Plains. Gusty outflow winds could accompany
of any of the stronger, more persistent storms. Coverage of these
strong storms may be high enough to merit greater severe
probabilities in later outlooks.
..Mosier.. 07/26/2024
WUUS02 PTSDY2
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
SPC AC 260712
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0212 AM CDT Fri Jul 26 2024
Valid 281200Z - 291200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE CENTRAL/NORTHERN PLAINS AND UPPER MIDWEST....
...SUMMARY...
Strong to severe thunderstorms are possible across portions of the
central/northern Plains and the Upper Midwest.
...Synopsis...
As mid-level flow strengthens across the central Rockies on Sunday,
lee cyclogenesis is expected to intensify during the day. This will
result in strengthening southerly flow and moisture advection across
the central Plains ahead of the surface low and cold front.
Thunderstorms are expected during the afternoon and evening hours
along and ahead of the surface front from northern Kansas to
northwest South Dakota. Shear should remain somewhat weak during the
day with only around 20 to 25 knots of mid-level flow emerging over
the Plains. Therefore, storms will likely remain somewhat loosely
organized with marginal severe weather threat in a moderately
unstable environment.
The GFS, ECMWF, and NAM all show some version of a mid-level
shortwave trough amplifying somewhat across the Plains Sunday
evening and into the overnight hours with some differences in
timing/amplitude. The arrival of this shortwave trough will result
in strengthening deep-layer shear and a low-level jet response which
should aid in storm development and intensity after sunset. The most
likely period for a greater severe weather threat will be in this
time period, likely across southeast South Dakota and eastern
Nebraska when shear and instability will be maximized. Higher
probabilities may need to be added in this region in later outlooks
as timing and location of the overnight shortwave trough becomes
more clear.
..Bentley.. 07/26/2024
WUUS03 PTSDY3
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
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