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Sep 21, 2019 0730 UTC Day 3 Severe Thunderstorm Outlook
Updated: Sat Sep 21 07:23:12 UTC 2019 (Print Version | 20190921 0730Z Day 3 shapefile | 20190921 0730Z Day 3 KML)
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 Forecast Discussion
   SPC AC 210723

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0223 AM CDT Sat Sep 21 2019

   Valid 231200Z - 241200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER CENTRAL
   ARIZONA...

   ...SUMMARY...
   Scattered storms, some severe with damaging wind and hail, are
   expected over much of Arizona Monday.

   ...Synopsis...
   An upper low will drop south across the Great Basin and into AZ,
   providing large-scale lift and increasing shear from the CO Valley
   across much of AZ. A surface low and wind shift will exist over
   southwest AZ, with a cold front pushing through the state overnight.
   Ahead of the upper low, gulf moisture will be in place, with 60s F
   dewpoints over much of southern and central AZ fueling storms. To
   the east, a potent shortwave trough will move across the
   northeastern states, along with a weak cold front. Shear will be
   strong in this region, but instability will be weak.

   ...Arizona...
   Models have been consistent for several days now showing a favorable
   combination of lift, instability and shear over AZ with the approach
   of the upper low. Low-level winds are expected to be weak, but mid
   to high level flow will be strong, which will result in elongated
   hodographs favorable for discrete storms or small bows capable of
   hail and wind. Strong heating will lead to 1000-1500 J/kg MUCAPE
   with storms forming over western AZ near the moisture gradient, and
   along the Rim where weak upslope flow will aid lift. Given continued
   cooling aloft, a long duration of thunderstorm activity is possible,
   with heavy rain, locally damaging wind gusts and hail. Isolated
   strong storms may also persist overnight, spreading into parts of
   southwest NM.

   ...Northeastern states...
   A strong shortwave trough will progress across the Northeast on
   Monday, providing large-scale lift and strong deep-layer wind
   fields. A cold front will move across NY and PA during the day, and
   will clear all but Maine by 12Z Tuesday. Despite the favorable
   synoptic setup, forecast soundings indicate instability will be very
   weak, with only a few hundred J/kg MUCAPE possible. By the time the
   more significant cooling aloft arrives, low-level winds will be
   veered to westerly. While a strong wind gust cannot be ruled out,
   severe potential appears low at this time. Instability trends will
   continue to be monitored in subsequent outlooks.

   ..Jewell.. 09/21/2019

   CLICK TO GET WUUS03 PTSDY3 PRODUCT

   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0730Z

        
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Page last modified: September 21, 2019
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