SPC AC 071925

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0225 PM CDT Fri Aug 07 2026

   Valid 072000Z - 081200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
   IOWA...NORTHERN WISCONSIN INTO THE UPPER PENINSULA OF MICHIGAN...AND
   THE MID-ATLANTIC...

   ...SUMMARY...
   Isolated to scattered severe thunderstorms are possible across parts
   of the Upper Midwest/Great Lakes this afternoon and evening, with
   large to very large hail and severe winds the main threats.
   Thunderstorms capable of scattered damaging winds may also occur
   over portions of the Mid-Atlantic.

   ...20z Update...
   Adjustments were made to the D1 Convective Outlook to trim
   probabilities behind the cold front across Minnesota/Iowa and behind
   morning/early afternoon convection across Kansas/Oklahoma. The
   Marginal Risk was shifted southward across Oklahoma/Arkansas to
   account for recent trends in storm/outflow evolution and resulting
   increasing potential for damaging wind downstream. 

   A Marginal Risk was added across portions of southwestern New Mexico
   into far western Texas. Across this region, a very deeply mixed and
   hot boundary layer will support outflow dominant storms. Hi-res
   guidance suggests that storms may produce strong to severe outflow
   winds across this region later this afternoon. 

   See previous discussion below for more information.

   ..Thornton.. 08/07/2026

   .PREV DISCUSSION... /ISSUED 1106 AM CDT Fri Aug 07 2026/

   ...Upper Midwest/Great Lakes...
   Thunderstorms are ongoing along/ahead of a cold front late this
   morning from the MN Arrowhead southwestward into southern
   MN/northern IA. While there are still uncertainties regarding
   convective evolution this afternoon and evening, it appears
   increasingly probable that two mesoscale corridors of greater severe
   potential will exist: one across southern MN into IA, and another
   across northern WI into the U.P of MI. In general, the severe risk
   today will be aided by a mid/upper-level trough advancing
   east-southeastward across these regions in tandem with a 35-50 kt
   west-northwesterly mid-level jet.

   Thunderstorms are expected to further increase in coverage and
   intensity along the eastward-advancing cold front this afternoon
   across parts of northern WI into the western U.P of MI. While latest
   NAM/RAP forecast soundings across this area suggest low-level
   moisture remains fairly shallow/limited, mostly clear conditions are
   noted on recent visible satellite imagery. Resultant moderate
   instability and gradually strengthening deep-layer shear with the
   approach of the mid/upper-level trough will aid in thunderstorm
   organization. Small clusters/bowing line segments will probably be
   the dominant mode given the linear forcing of the cold front, with
   enhanced low/mid-level flow aiding the risk for scattered
   severe/damaging winds. A Slight Risk has been added for parts of
   northern WI into the U.P of MI given increased confidence in this
   scenario occurring.

   Farther south, generally elevated convection is ongoing across
   southern MN into northern IA. The 12Z observed sounding from MPX
   showed fairly steep low/mid-level lapse rates in the 850-530 mb
   layer, which along with 35-40 kt of effective bulk shear and around
   2000 J/kg of MUCAPE may continue to support a threat for severe hail
   with this activity in the short term. Even though cloud cover
   remains prevalent across these areas late this morning, a corridor
   of moderate to locally strong instability is still forecast to
   develop this afternoon across parts of eastern NE into IA ahead of
   the cold front. Current expectations are for multiple surface-based
   supercells and/or bowing clusters to develop along/ahead of the
   front in southern MN, and then spread southeastward across IA
   through the late afternoon/early evening. A threat for both large
   hail and damaging winds should exist with this activity, and a
   Slight Risk has been introduced where confidence is greater that
   robust convection will occur. 2+ inch diameter hail and perhaps a
   tornado also appear possible with any surface-based supercell, even
   though low-level flow will not be overly strong.

   ...Ohio Valley into the Mid-Atlantic...
   Between upper troughing over central Canada/the Upper Midwest and
   upper ridging over the western Atlantic, around 20-30 kt of
   southwesterly mid-level flow will exist today from the OH Valley
   into the Mid-Atlantic and Northeast. Greater destabilization and
   steepening of low-level lapse rates are anticipated this afternoon
   across the Mid-Atlantic, where recent visible satellite imagery
   shows generally clear skies. Loosely organized cells/clusters that
   initially develop across the higher terrain of the central
   Appalachians should spread into the Mid-Atlantic coastal plain
   through the afternoon/evening, while posing a threat for scattered
   damaging winds up to 50-60 mph and perhaps marginally severe hail.
   Across the OH Valley, somewhat weaker mid-level flow may tend to
   limit updraft organization. Still, some potential for clustering and
   isolated damaging winds may exist downstream of ongoing convection
   where greater destabilization can ocur. Have therefore expanded the
   Marginal Risk across much of the OH Valley to account for this
   possibility.

   ...Southern/Central Plains into the Ozarks...
   Elevated thunderstorms posing an isolated hail threat in southeast
   KS late this morning should further diminish into the early
   afternoon as a southwesterly low-level jet gradually weakens. To the
   south and east of this activity, a hot and unstable airmass will
   exist this afternoon across OK into parts of southern MO and AR.
   Although details regarding convective evolution remain unclear, it
   is possible that robust thunderstorms develop/continue on the
   outflow from this morning's activity, or near multiple MCVs present
   from earlier convection. Isolated strong to severe winds appear
   possible, even though deep-layer shear should remain weak. The
   Marginal Risk has been expanded eastward and connected to the risk
   area in the OH Valley. Other isolated thunderstorms posing some
   severe wind threat may develop this afternoon farther west across
   eastern NM into the OK/TX Panhandles.

   ...Arizona...
   Modest east-southeasterly mid-level flow will persist today over AZ
   to the south of a mid/upper-level anticyclone centered over the Four
   Corners. Widely scattered convection should develop over the
   Mogollon Rim and the higher terrain in southeast AZ this afternoon,
   and gradually spread into the lower deserts this evening. Given the
   very well-mixed boundary layer and weak to locally moderate
   instability expected to be in place ahead of these thunderstorms,
   have maintained low severe wind probabilities.

   ...Northern Nebraska/Southern South Dakota...
   Elevated thunderstorms may develop across parts of northern NE and
   southern SD late tonight/early Saturday morning as isentropic ascent
   increases in tandem with modest strengthening of a southerly
   low-level jet. Low-level moistening beneath steepening mid-level
   lapse rates should support sufficient MUCAPE for robust updrafts, 
   although confidence in overall coverage remains low due to
   weak/nebulous large-scale ascent. Regardless, strong shear in the
   cloud-bearing layer across this area should promote organized
   convection capable of producing isolated severe hail.

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