SPC AC 200045
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0745 PM CDT Thu Sep 19 2024
Valid 200100Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF THE
UPPER MISSISSIPPI VALLEY INTO PARTS OF NORTHEAST OKLAHOMA...
...SUMMARY...
Scattered strong to severe storms remain possible through this
evening from the upper Mississippi Valley southward into northeast
Oklahoma.
A shortwave trough will shift northeastward out over the Dakotas and
MN this evening, as an upper low moves northeastward across MB.
Winds aloft will weaken over the area, though cooling aloft will
continue spreading into the upper Great Lakes.
At the surface, a weak front/wind shift extends from the main
surface low over MB southward across MN and into IA, and from
southeast KS into northwest OK.
The strongest cells currently stretch from the MN Arrowhead
southward into north central IA, with primarily discrete storm mode
along the front. Farther south, a secondary area of storms persist
over southeast KS into northeast OK.
Tornado watch #678 continues over northwest WI this evening, where
low-level shear is a bit stronger. Storms across this area may
persist for several more hours before dissipating, as temperatures
aloft are cooling.
Farther south, Severe Thunderstorm watches #677 and #679 continue
along the boundary, where storms remain within the diurnal
instability axis. Temperatures aloft are quite warm here, and storms
should dissipate sooner than points north. Until then, locally
severe gusts or hail will be possible.
For more information see mesoscale discussion #2089.
..Jewell.. 09/20/2024
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z
SPC AC 191730
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1230 PM CDT Thu Sep 19 2024
Valid 201200Z - 211200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE
MIDWEST AND ALSO THE SOUTH-CENTRAL PLAINS...
...SUMMARY...
Isolated strong to severe thunderstorms are possible in the late
afternoon Friday in parts of Illinois, Indiana, and southwest Lower
Michigan. Isolated strong to severe storms are also possible across
parts of the south-central Plains.
...Midwest...
A low-amplitude shortwave trough will pass across the Upper to
central Great Lakes during the first half of the period. This will
outpace a cold front that trails from a cyclone shifting northeast
in MB, yielding a largely weakening to stalling front by Friday
evening. Most guidance suggests at least isolated thunderstorms
should form within a low-level warm conveyor ahead of the front,
generally focused on a moderate buoyancy plume emanating northeast
from parts of MO/AR. A fast westerly upper jet will further impinge
on this portion of the front as well, favorably timed with peak
boundary-layer heating. A few marginally severe storms may develop
within this regime. Despite weak mid-level lapse rates, elongation
of the mid to upper hodograph should support a threat for 1-1.5 inch
hail, along with strong to marginally severe gusts from 45-60 mph.
These threats should diminish quickly after sunset.
...Southern KS/northern OK vicinity...
A mid/upper-level shortwave trough is forecast to move slowly
eastward across the Southwest on Friday. Farther east, a surface
boundary initially draped from the lower MO Valley into southern
KS/northern OK is forecast to lift northward as a warm front.
Large-scale ascent across much of the Plains may remain relatively
limited, outside of low-level warm advection near/north of the
front. However, relatively strong heating along the western/northern
periphery of returning low-level moisture could support thunderstorm
development during the afternoon somewhere in the vicinity of
southwest KS/northwest OK. Effective shear of 30-40 kt will support
potential for somewhat organized convection. Strong to localized
severe gusts may be the most likely hazard, but hail cannot be ruled
out if any more discrete storms can move into an environment of
greater moisture/instability.
...New Mexicco...
Scattered thunderstorms will be possible across much of NM on
Friday, in closer proximity to the approaching shortwave trough.
While deep-layer shear will be rather strong, generally weak
midlevel lapse rates and buoyancy may tend to limit the potential
for more robust storms. If confidence increases regarding sufficient
heating/destabilization, then severe probabilities may eventually be
needed for parts of the region.
...Central Plains into the lower MO Valley...
Guidance continues to vary regarding the potential for robust
elevated convection Friday night into Saturday morning, within a
low-level warm advection regime. Increasing elevated buoyancy and
sufficient mid/upper-level flow could support a few stronger storms
with hail potential, but confidence in sufficient coverage and a
favored region for this potential is too low for probabilities at
this time.
..Dean.. 09/19/2024
WUUS02 PTSDY2
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0600Z
SPC AC 191940
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0240 PM CDT Thu Sep 19 2024
Valid 211200Z - 221200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PARTS OF NM INTO
THE SOUTHERN HIGH PLAINS...PARTS OF THE UPPER MIDWEST INTO THE
CENTRAL PLAINS...CENTRAL APPALACHIANS VICINITY...
...SUMMARY...
Isolated severe thunderstorms are possible on Saturday afternoon to
early evening in New Mexicco and the southern High Plains, mid
Missouri Valley to upper Mississippi Valley, and central
Appalachians region.
...Southern High Plains...
In advance of a southern-stream shortwave trough reaching the Four
Corners, a strong midlevel jet is forecast to eject over NM by early
evening Saturday. This will yield favorable deep-layer shear for
organized storms across NM into parts of northwest TX. Strengthening
large-scale ascent within a low-level warm/moist conveyor should
overspread this region by Saturday morning. This should yield
early-period convection and renders moderate uncertainty over the
degree of destabilization by afternoon.
Still, with ample boundary-layer heating to the south of early-day
activity, a plume of at least weak-surface based buoyancy should
develop. Renewed afternoon to early evening thunderstorms could
become severe. Steep mid-level lapse rates should be confined along
and west of the Sangre de Cristo Mountains, rendering further
uncertainty over the intensity and coverage of the severe threat.
The eastern extent of the threat should be limited by the confined
buoyancy plume and decreasing instability deeper into TX/OK.
...Central Plains and Lower/Mid-MO Valley to the Upper MS Valley...
A relatively complex and uncertain evolution to convective potential
remains evident on Saturday afternoon/evening. This region will
largely remain within a low-amplitude mid-level ridge. This may
flatten somewhat in between a southern-stream shortwave trough in
the Southwest and a northern-stream trough over the southern Prairie
Provinces to along the ND/MN international border. In association
with the latter wave, a surface cold front should push southeast in
the north-central states. Guidance varies with the degree of
destabilization ahead of it, and especially with the spatial extent
of afternoon/evening convection. There is sufficient confidence in
destabilization and storm coverage to introduce a 5% area from the
mid MO Valley to the upper MS Valley, though uncertainty remains
rather high.
...Parts of the Northeast/Mid Atlantic...
A low-amplitude midlevel shortwave trough is forecast to move
through northwesterly flow aloft across parts of the upper Ohio
Valley into the Mid Atlantic on Saturday. Isolated to scattered
thunderstorm development will be possible across the region during
the afternoon. Veering wind profiles within the northwesterly flow
regime will support effective shear for some storm organization,
though it remains somewhat uncertain if instability will become
sufficient to support an organized severe threat. Guidance has
trended toward somewhat greater instability and storm coverage, and
a small Marginal Risk has been included where confidence is
currently highest in some severe threat.
..Dean.. 09/19/2024
WUUS03 PTSDY3
NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z
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