Sep 20, 2020 0730 UTC Day 3 Severe Thunderstorm Outlook
Updated: Sun Sep 20 07:26:52 UTC 2020 (20200920 0730Z Day 3 shapefile | 20200920 0730Z Day 3 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
0730 UTC Day 3 Outlook Graphic
Day 3 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Graphic
20200920 0730 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 3 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
   SPC AC 200726

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0226 AM CDT Sun Sep 20 2020

   Valid 221200Z - 231200Z


   The severe potential associated with Tropical Cyclone Beta appears
   too limited on Tuesday to include any severe probabilities across
   southeastern Texas or Louisiana at this time.

   ...Southeastern Texas into Louisiana...
   Tropical Storm Beta should be located along/near some portion of the
   middle TX Coast Tuesday morning per latest NHC forecast. Most 00Z
   guidance indicates that Beta will remain over land while slowly
   weakening through the period. The low-level wind field associated
   with Beta should likewise slowly diminish through Tuesday afternoon,
   with southeasterly 850-mb winds around 15-25 kt across southeastern
   TX and LA. The flow field should further weaken through mid levels.
   The forecast vertical wind profile across this region appears quite
   marginal to support organized storms. Dry low/mid-level air is also
   forecast to wrap around the eastern half of Beta's circulation,
   which may further hinder already weak forecast instability. At this
   point, there appear to be too many limiting factors to include any
   severe probabilities across southeastern TX and LA for Tuesday, but
   this potential will be reevaluated in subsequent outlooks.

   ...Northern Plains...
   Farther north, a shortwave trough embedded within mid-level westerly
   flow is forecast to move eastward along the U.S./Canada border from
   the Pacific Northwest to the northern Plains through the period.
   Low-level moisture is forecast to remain quite meager ahead of this
   feature until it reaches the vicinity of ND late Tuesday night,
   where low to mid 50s surface dewpoints may be present. A modest
   southerly low-level jet along with a southeastward-surging cold
   front may aid convective initiation late Tuesday across northern ND
   into south-central Canada. Steep mid-level lapse rates should also
   be present over this region, and potential exists for mainly
   elevated storms to produce some hail given the forecast combination
   of weak to locally moderate instability with strong deep-layer
   shear. Regardless, will defer inclusion of any severe probabilities
   across northern ND for now, as guidance differs on both the degree
   of low-level moisture present and overall storm coverage.

   ..Gleason.. 09/20/2020