Nov 18, 2021 1300 UTC Day 1 Convective Outlook
Updated: Thu Nov 18 12:52:37 UTC 2021 (20211118 1300Z Day 1 shapefile | 20211118 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20211118 1300 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Tornado Graphic
20211118 1300 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20211118 1300 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Large Hail Graphic
20211118 1300 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
No Risk Areas Forecast
   SPC AC 181252

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0652 AM CST Thu Nov 18 2021

   Valid 181300Z - 191200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   The risk of severe thunderstorms appears negligible across the U.S.
   today through tonight.

   ...Synopsis and Discussion...
   A positively tilted upper trough currently extends from central
   Ontario southeastward into Ozark Plateau. This upper trough is
   expected to progress eastward throughout the while assuming a more
   neutral tilt. By early Friday morning this upper trough will extend
   from the northern Quebec through the Mid-Atlantic States. During the
   same period, an occluded low associated with this trough will track
   across the James Bay and northern Quebec. 

   This low will be accompanied by an expansive cold front, which
   currently extends from the triple point over central Quebec
   southwestward into the Lower MS Valley. Steady
   eastward/southeastward progression of this front is anticipated,
   taking it through much of the Southeast as well as off the Northeast
   Coast by late tonight. By early tomorrow morning, the front should
   be through all of the eastern CONUS except southern FL. Isolated
   thunderstorms will likely continue near this front across the Lower
   MS Valley for the next few hours. Thunderstorm activity will likely
   continue across deep south TX through mid-day until after the front
   moves offshore as well. 

   Low-level moisture convergence to the north/northeast of a weak
   surface low is also contributing to thunderstorm development across
   south-central LA. This activity will likely persist throughout the
   day while moving eastward, although it is expected to stay primarily
   over the Gulf. 

   Lastly, a weak shortwave trough currently north of the Yucatan
   Channel is expected to continue northeastward, resulting in showers
   and thunderstorms across central and southern FL.

   ..Mosier.. 11/18/2021

   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z