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Mesoscale Discussion 1565
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   Mesoscale Discussion 1565
   NWS Storm Prediction Center Norman OK
   1148 PM CDT Mon Aug 24 2020

   Areas affected...Lower Great Lakes region/St. Lawrence Valley and
   adjacent New York state

   Concerning...Severe potential...Watch unlikely 

   Valid 250448Z - 250645Z

   Probability of Watch Issuance...20 percent

   SUMMARY...A line of thunderstorms may continue to develop and
   strengthen while spreading across the lower Great Lakes region and
   adjacent portions of the upper St. Lawrence Valley.  While this
   activity may pose a risk for hail and gusty winds as it spreads into
   portions of western and northern New York state by 4-6 AM, it may
   remain generally below severe limits.  A severe weather watch
   currently appears unlikely, but trends will continue to be
   monitored.

   DISCUSSION...In advance of a significant, digging short wave trough,
   scattered thunderstorms have recently initiated over southern
   Ontario.  Activity is in the process of increasing, near or just
   ahead of an initial southeastward advancing cold front.  A narrow
   corridor of seasonably high boundary-layer moisture (upper 60s to
   around 70 F surface dew points) appears to be contributing to
   mixed-layer CAPE up to around 1500 J/kg, despite somewhat modest
   initial mid-level cooling.  This air mass is forecast to advect
   southeastward across the lower Great Lakes region and adjacent St.
   Lawrence Valley vicinity, into portions of western and northern New
   York state through 08-10Z.  Coupled with ongoing modest
   strengthening of cyclonic deep-layer west-northwesterly mean flow
   (to around 30-35 kt), the environment may be conducive to further
   upscale growth and organization of convection, with the potential to
   produce small to marginally severe hail, and at least locally strong
   surface gusts which may approach severe limits.

   ..Kerr/Grams.. 08/25/2020

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

   ATTN...WFO...BTV...ALY...BGM...BUF...

   LAT...LON   45147702 45537503 44557399 42887687 42647898 42798040
               43917976 45147702 

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Page last modified: August 25, 2020
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