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Mesoscale Discussion 1349
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   Mesoscale Discussion 1349
   NWS Storm Prediction Center Norman OK
   0205 PM CDT Wed Jul 19 2017

   Areas affected...Portions of Arizona

   Concerning...Severe potential...Watch unlikely 

   Valid 191905Z - 192130Z

   Probability of Watch Issuance...5 percent

   SUMMARY...The risk for a few strong thunderstorms will exist into
   the evening hours. A couple of marginally severe storms cannot be
   ruled out, though Watch issuance will not be necessary.

   DISCUSSION...Low-level lapse rates are steepening in response to
   widespread insolation from southeast and south-central AZ through
   central and into northwest AZ, behind scattered to widespread
   convective debris clouds from the lower Colorado River Valley arcing
   into southwest AZ. Rich deep moisture is in place across the area,
   with 12Z soundings at Phoenix AZ, Tucson AZ, and Las Vegas NV
   indicating 1.5-2.0-inch PW -- i.e., near record values per the SPC
   Sounding Climatology. Visible satellite images indicate increasingly
   agitated cumulus development over the higher terrain, with initial
   thunderstorm development ongoing from this activity. Thunderstorms
   will experience an increase in coverage and a modest increase in
   intensity during the next few hours, while drifting westward and
   northwestward into the evening hours. A slight enhancement to the
   mid-level flow peripheral to an MCV moving across southern AZ may
   support loose organization for convective structures in
   south-central and west-central AZ -- spreading off the Mogollon Rim
   to the lower deserts. Across the entire region, sufficiently steep
   low-level lapse rates and small-scale merging outflows may support
   locally strong wind gusts -- perhaps reaching marginally severe
   levels on a very isolated basis. Small hail may also occur over the
   mountains. The lack of stronger deep shear, and modest magnitude of
   mid-level lapse rates, will mitigate the overall severe risk.

   ..Cohen/Coniglio/Hart.. 07/19/2017

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

   ATTN...WFO...TWC...FGZ...PSR...VEF...

   LAT...LON   31511124 32941255 34331343 35671366 36431286 36411199
               35311105 33620963 32780925 31550955 31511124 

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Page last modified: July 19, 2017
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