SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0259 PM CDT Tue May 31 2022
Valid 312000Z - 011200Z
...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON AND EVENING ACROSS THE SOUTHEASTERN TEXAS PANHANDLE
VICINITY AND NORTHERN/WESTERN OKLAHOMA...
...SUMMARY...
Scattered strong to severe thunderstorms are expected to develop in
a narrow corridor extending from the southern Great Plains into the
mid Mississippi Valley region later today through tonight. These
may become most numerous across parts of northwestern Oklahoma into
the southeastern Texas Panhandle vicinity, where large hail, a few
strong downbursts and a couple of tornadoes are possible.
...20Z Update...
No changes have been made to the Enhanced/Slight Risk areas across
the southern Plains into the mid MS Valley, where scattered
strong-to-severe storms are possible later this afternoon into this
evening.
The severe threat further east into parts of the Midwest and Great
Lakes appears more uncertain, due an expansive cirrus impacting
destabilization over parts of the region, and uncertainty regarding
storm coverage through the most favorable part of the day. Part of
eastern MI has been trimmed from the Slight, but no changes have
been made from western MI into the Midwest, due to some potential
for storms to increase early enough this evening to pose some
organized severe threat. The Marginal Risk across New England has
also been trimmed slightly from the east, based on the progress of
the back-door cold front.
..Dean.. 05/31/2022
.PREV DISCUSSION... /ISSUED 1111 AM CDT Tue May 31 2022/
...Synopsis...
The center of a fairly broad and deep, but occluding, surface
cyclone is now north of the Minnesota international border (near
Lake of the Woods), and forecast to gradually weaken while migrating
northward toward the southwestern shores of Hudson Bay by late
tonight. This will accompany an associated remnant mid-level
perturbation, which models continue to indicate will gradually
consolidate with another short wave trough digging southeast of the
Arctic latitudes, and contribute to a deepening, broader mid-level
low to the southwest of an increasingly prominent mid-level high to
the east of Hudson Bay. To the southeast of the mid-level high, an
already deep mid-level low is in the process of slow shifting
southward offshore of the northern New England coast and Canadian
Maritimes.
While a significant cold front associated with the eastern mid-level
low advances south of southern New England coastal areas, its
western flank is forecast to stall across the lower Great Lakes into
areas southwest of James and Hudson Bays, where it gradually will be
overtaken by the cold front associated with the weakening upstream
cyclone. This latter cold front is also forecast to continue
advancing southeastward across the interior U.S., through much of
the upper Great Lakes, upper half of the Mississippi Valley and
south central Great Plains by late tonight.
This front is preceded by a convectively generated and/or enhanced
boundary across the Upper Midwest into the lower Missouri Valley and
Texas/Oklahoma Panhandle vicinity, with substantive ongoing
lingering convection, associated precipitation and cloud cover
across much of the lower Missouri Valley into the Upper Midwest. As
the weakening deep-layer cyclone progresses away (north) of the
international border, this lead boundary may tend to become
displaced to the south of a seasonably strong west-southwesterly
mid/upper jet. This jet trails to the south and southwest of the
cyclone to another weaker, elongated low over the Great Basin, and
may tend to shift northward on the crest of building short wave
ridging across the central Great Plains, as the Great Basin
perturbation is gradually forced east-northeastward.
...Southern Texas Panhandle into southeastern Kansas...
While the lower/mid tropospheric flow tends to weaken through the
day, along and south of the convective boundary and cold front,
models continue to indicate that a seasonably moist boundary layer
and steep lower/mid tropospheric lapse rates will contribute to a
narrow corridor of large CAPE (2000-3000 J/kg) by late this
afternoon. Mid/upper support for thunderstorm initiation remains a
bit unclear, but models suggest that weakening inhibition with
daytime heating may be enough. Even to the south of the stronger
mid-level jet, deep-layer shear may still be marginally sufficient
to support supercell structures capable of producing large hail,
before convection becomes increasingly widespread. By this evening,
a few strong downbursts may be possible, but activity likely will be
generally slow moving and confined to a narrow corridor to the north
of stronger mid-level capping, with a tendency to be undercut by
conglomerating convective outflow.
...Lower Missouri Valley into Great Lakes...
It is not clear that one, well-defined MCV will emerge from the
weakening convection still ongoing across the lower Missouri Valley.
However, the latest Rapid Refresh suggests that a belt of 30-40+ kt
southwesterly flow in the 850-500 mb layer will nose northeastward
toward lower Michigan today through tonight. Near the southern
periphery of this jet, it is possible that deep-layer shear and
boundary-layer destabilization could become conducive to one or two
organizing thunderstorm clusters posing a risk for severe wind and
hail.
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