Feb 21, 2017 2000 UTC Day 1 Convective Outlook
Updated: Tue Feb 21 19:44:18 UTC 2017 (20170221 2000Z Day 1 shapefile | 20170221 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170221 2000 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
20170221 2000 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
20170221 2000 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
20170221 2000 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 211944

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0144 PM CST Tue Feb 21 2017

   Valid 212000Z - 221200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   The risk for severe thunderstorms appears negligible across the
   U.S., today through tonight. Isolated thunderstorms are possible
   from the lower Mississippi Valley region eastward along the Gulf
   Coastal Plain, and from northern California to parts of Wyoming and
   the northern High Plains.

   ...Gulf Coast...
   Isolated to scattered thunderstorms will continue in two distinct
   regimes -- one in the warm conveyor crossing the Florida panhandle
   and another associated with the cold core mid-level circulation over
   the lower Mississippi Valley. The only change with this outlook is
   the removal of thunder for locations to the north/west of the
   forcing for ascent associated with the mid-level low.

   ..Picca/Broyles.. 02/21/2017

   .PREV DISCUSSION... /ISSUED 1027 AM CST Tue Feb 21 2017/

   ...Lower Mississippi Valley and Eastern Gulf Coast...
   Scattered thunderstorms are expected along with and in advance of an
   upper low that will move eastward along the Gulf Coast this
   afternoon and tonight. Cold temperatures aloft will support some
   small hail across portions of southern LA this afternoon as modest
   heating/destabilization occurs, though low tropopause heights in the
   vicinity of the upper cyclone will limit the depth of convection and
   preclude any substantial severe hail risk. 

   ...Northern CA/Southern OR into the Great Basin/Northern Rockies...
   As an upper trough approaches the Pacific Coast, generally weak
   convection is expected across a broad area from the northern
   CA/southern OR coast eastward into the Great Basin and Northern
   Rockies, with isolated thunderstorms possible where convection
   becomes sufficiently deep. Somewhat greater instability across
   portions of the northern CA coast into the northern Sacramento
   Valley may support some thunderstorms capable of small hail and
   locally gusty winds, though generally weak effective shear
   magnitudes should limit storm organization. 

   ...Portions of the Northern High Plains...
   A shortwave trough over portions of the Northwest will move quickly
   into the northern High Plains this afternoon and evening. Ahead of
   this feature, weak but sufficient instability will support
   fast-moving clusters of convection later this afternoon and tonight
   from central/eastern MT into ND. Relatively strong low/midlevel flow
   and effective shear may support locally gusty winds and perhaps some
   small hail with the strongest of these clusters.

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z