ACUS01 KWNS 150554
SWODY1
SPC AC 150552
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1252 AM CDT Sun Mar 15 2026
Valid 151200Z - 161200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON THROUGH TONIGHT ACROSS PARTS OF THE MID SOUTH INTO LOWER
OHIO VALLEY AND ACROSS PARTS OF THE EASTERN GULF COAST STATES...
...SUMMARY...
Widespread strong to severe wind gusts may accompany a developing
squall line across and east of the middle into lower Mississippi
Valley late this afternoon into this evening. A couple of strong
tornadoes are also possible within and just ahead of this line
across parts of the lower Ohio Valley into Mid South, with a couple
of strong tornadic supercells also possible across parts of the
Florida Panhandle and southeastern Alabama into adjacent Georgia
late tonight.
...Discussion...
To the north of an expanding blocking mid-level high, centered off
the southern California coast, models indicate that large-scale
ridging will continue to build inland of the British Columbia/U.S.
Pacific coast, through the Canadian Rockies and U.S. Intermountain
West during this period. Downstream, a significant short wave
trough is forecast to continue amplifying southeastward across the
Great Plains and Mississippi Valley, preceded by building ridging
near and east of the Atlantic Seaboard.
Downstream of the digging short wave trough, a broad and deep
cyclone has already formed to the east of the Colorado Rockies, with
a plume of warm elevated mixed-layer air overspreading the central
and southern Great Plains toward the lower Mississippi Valley. The
center of the cyclone is forecast to redevelop east-northeast into
the St. Joseph MO vicinity by daybreak, before continuing to deepen
while migrating northeastward toward lower Michigan today through
tonight. It appears that the northeastern periphery of the elevated mixed-layer plume will spread across the lower Missouri Valley
before becoming suppressed southeastward.
In the wake of a preceding surface cyclone and associated cold
frontal passage, Gulf boundary-layer moistening and inland return
flow remain limited at this time. Although it should improve some,
aside from a narrow corridor of better boundary-layer moisture
return across the southeastern Great Plains toward the lower Ohio
Valley, and broader corridors across the southern through middle
Atlantic Seaboard, as well as across the eastern Gulf Coast vicinity
by late tonight, warm sector dew points may not exceed lower/mid 50s
F. This may prove a limiting factor to the overall severe threat.
Nevertheless, guidance continues to indicate the development of a
fairly extensive squall line along much of the length of a cold
front advancing across and east of the Mississippi Valley toward the Appalachians late this afternoon through tonight.
...Lower Mississippi Valley into Great Lakes...
Latest model output suggests that the stronger 850 mb jet core may
tend to shift ahead of the deepening surface cyclone, north of the
Ohio Valley into and through the lower Great Lakes region during the
afternoon. However, 40-50+ kt southerly flow may tend to trail back
ahead of the cold front to the southwest, at least as far as the Mid
South vicinity through late afternoon, as a narrow corridor of
better boundary-layer moisture return (characterized by lower 60s F
surface dew points) surges across northeastern Arkansas and
southeastern Missouri into southern Illinois, western Kentucky and
Tennessee.
North-northeast and east of this vicinity, toward the Great Lakes
and upper Ohio Valley, the narrow corridor of better pre-frontal
moisture is likely to be more modest and supportive of rather modest
to weak CAPE. And there is concern that deeper boundary-layer
warming and mixing in the drier pre-convective environment may
actually be more efficient at mixing down stronger momentum to the
surface than the thunderstorm activity.
However, based on the latest forecast soundings, there does still
appear potential for widespread potentially damaging wind gusts at
least approaching or exceeding 50 kts, with an evolving pre-frontal
squall line as it spreads across and east of the middle to lower
Mississippi Valley vicinity. Gusts exceeding 65 kts, and potential
for tornadoes, may tend to be confined to meso-vortices evolving
along the leading edge of the convective outflow, particularly
within the more moist environment across the lower Ohio Valley into
Mid South.
There may also be a late afternoon into early evening window of
opportunity, across this same corridor, for either initially
discrete supercell development or discrete supercell development
just ahead of the evolving eastward advancing line. If this occurs,
there will probably be at least somewhat greater potential for
strong tornadoes. However, this remains unclear, particularly given
the limited breadth of the moist sector, and the tendency for it to
be rather quickly overtaken by the cold front.
...Eastern Gulf Coast States...
Models continue to indicate a separate area of better low-level
moisture return across the eastern Gulf coast, which may include
surface dew points increasing through the lower/mid 60s across the
western Florida Panhandle, southeastern Alabama and adjacent Georgia
by late tonight. It appears that this will support a corridor of boundary-layer destabilization characterized by CAPE in excess of
1000 J/kg. Coincident with enlarging, clockwise curved low-level
hodographs beneath 40-45 kt southwesterly 850 mb flow overspreading
the region, and in the presence of sufficient deep-layer shear,
there appears potential for the evolution of longer-lived supercells
which could become capable of producing strong tornadoes.
..Kerr/Thornton.. 03/15/2026
$$
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