SPC AC 311611

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1111 AM CDT Tue May 31 2022

   Valid 311630Z - 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
   Great Lakes 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.

   ...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.

   ..Kerr.. 05/31/2022

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