Nov 8, 2017 1300 UTC Day 1 Convective Outlook
Updated: Wed Nov 8 12:44:56 UTC 2017 (20171108 1300Z Day 1 shapefile | 20171108 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20171108 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
20171108 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
20171108 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
20171108 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 081244

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0644 AM CST Wed Nov 08 2017

   Valid 081300Z - 091200Z

   ...NO SEVERE THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   Severe storms are not expected across the contiguous United States
   today or tonight.

   ...Synopsis...
   An interesting upper-air pattern -- albeit unsuitable for severe
   local storms -- will characterize this period.  High-latitude
   blockiness will prevail, in the form of
   1.  Rex configuration over the northeastern Pacific and northwestern
   Canada, anchored by a synoptic-scale cyclone currently centered
   about 650 nm west of the Columbia River mouth.  This cyclone, with
   multiple/embedded vorticity lobes orbiting the common center, will
   pivot slowly eastward through the rest of the period.  Peripheral
   vorticity lobes will begin obliquely crossing the WA/OR coast, in
   southwest to south-southwest flow aloft, after 00Z.  Associated cold
   air aloft and steep lapse rates, atop a moist marine layer, will
   support the potential for isolated thunder near the coastline
   tonight.
   2.  A very large downstream cyclone centered over the northwestern
   Hudson Bay region at this time, but covering/influencing at least
   the northeastern 1/4 of North America.  A broadly curved shortwave
   trough -- now evident in moisture-channel imagery over AB/SK -- will
   move southeastward while gradually amplifying.  By 12Z the trough
   should extend from northwestern ON to portions of IA.

   Ahead of the latter feature's height falls, a three-lobed,
   positively tilted trough -- now with vorticity maxima over northern
   MO, southern CO and southern AZ -- will eject east-southeastward and
   weaken gradually.  By 00Z this trough should extend near a
   CRW-DYR-LIT-GGG-DRT axis.  By 12Z, only the middle vorticity lobe
   over MS should be pronounced, with the trough northeastward to
   Chesapeake Bay and southwestward to the LRD area.  A marginal
   potential for elevated thunder will exist in a broad precip plume
   preceding this trough across parts of southern NM and west to
   central TX.  This activity will be episodic and weak, supported by
   DCVA, weak warm advection and moisture transport in low/middle
   levels, atop a postfrontal, continental-polar air mass.

   Otherwise, isolated thunder will be possible with a plume of weak
   deep-layer lift and buoyancy over southeastern GA and extending
   northeastward, largely offshore from the Carolinas.  Brief/isolated
   lightning cannot be ruled out in the zone of elevated/low-level warm
   advection and isentropic lift between TX and GA; however, the
   potential appears too sparse and conditional for a general-thunder
   area.

   ..Edwards.. 11/08/2017

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