Storm Prediction Center Mesoscale Discussion 1621

   Mesoscale Discussion 1621
   NWS Storm Prediction Center Norman OK
   1144 PM CDT Tue Jul 14 2026

   Areas affected...portions of northern New York into Vermont and New
   Hampshire.

   Concerning...Severe Thunderstorm Watch 489...

   Valid 150444Z - 150615Z

   The severe weather threat for Severe Thunderstorm Watch 489
   continues.

   SUMMARY...Strong to severe storms are expected to persist across the
   western portions of WW489 into the overnight hours. Hail and
   damaging winds are the most likely hazards.

   DISCUSSION...As of 0440 UTC, a cluster of severe storms, including a
   robust supercell over St Lawrence County NY, are ongoing across
   western portions of WW489. Moderate buoyancy and strong deep-layer
   shear remain in place ahead of this convection, and new storm
   development just across the ON border. Hail is the most likely
   threat tonight, especially with the aforementioned supercell showing
   peak MRMS MESH of 2+ inches and a persistent cellular storm mode.
   Damaging winds are also possible with the stronger cells, though
   upscale growth appears limited given the very strong deep-layer
   shear. A tornado also cannot be ruled out given the ongoing
   supercells and strong vertical shear.

   With the favorable parameter space likely to persist tonight, severe
   potential should be maximized across parts of northern NY, into VT
   and southern NH. Storm should begin to weaken late tonight as they
   approach a more stable air mass into southern New England.

   ..Lyons.. 07/15/2026

   ...Please see www.spc.noaa.gov for graphic product...

   ATTN...WFO...GYX...BTV...ALY...

   LAT...LON   44537274 44167218 43637149 43287141 42997161 42977210
               43277331 44137519 44527574 45027513 45177451 44997374
               44537274 

   MOST PROBABLE PEAK TORNADO INTENSITY...85-110 MPH
   MOST PROBABLE PEAK WIND GUST...55-70 MPH
   MOST PROBABLE PEAK HAIL SIZE...1.00-1.75 IN