Dec 11, 2017 1300 UTC Day 1 Convective Outlook
Updated: Mon Dec 11 12:40:26 UTC 2017 (20171211 1300Z Day 1 shapefile | 20171211 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20171211 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
20171211 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
20171211 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
20171211 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 111240

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0640 AM CST Mon Dec 11 2017

   Valid 111300Z - 121200Z

   ...NO THUNDERSTORM AREAS FORECAST...

   ...SUMMARY...
   No thunderstorm areas are expected today or tonight.

   ...Synopsis...
   In mid/upper levels, a blocky upper-air pattern will continue
   through the period, dominated by mean troughing and related cyclonic
   flow over the East.  In the West, a Rex pattern has been taking
   shape gradually overnight, as a large but weak cyclone moves over
   Baja, south of a persistent high and ridge located over the Great
   Basin and interior Northwest.  In between:  a well-defined "clipper"
   perturbation in northwest flow was evident in moisture-channel
   imagery over parts of the Dakotas and MN.  This feature should
   proceed southeastward across the upper Mississippi Valley today,
   then pivot up the Ohio Valley overnight.  Its vorticity field should
   phase with a faster-moving, lower-amplitude perturbation now over
   SK, leading to a 12Z trough position positively tilted from PA to
   eastern TN to northern LA. 

   At the surface, a low associated with the northwest-flow trough
   aloft was located at 11Z over northern MN, with warm front
   southeastward across southern Lake Michigan, and cold front
   northwestward over eastern SK.  By 00Z, the low should move
   southeastward toward northern IN as another develops over the Lake
   Superior region.  Meanwhile, the cold front should move to the lower
   Ohio Valley, AR, southern OK and eastern NM.  By 12Z, the lows
   should consolidate over western NY, with cold front southwestward
   over the western Carolinas and southern LA. 

   ...Upper Mississippi Valley...
   Strong forcing for ascent, immediately preceding the shortwave
   trough, should steepen midlevel lapse rates across this region and
   weaken CINH, atop a high-RH layer located between 700-850 mb. 
   Forecast soundings through the forenoon hours indicate related
   development of around 50 J/kg MUCAPE is possible, astride the -20 C
   isotherm.  As such, very isolated/short-lived thunder cannot be
   ruled out.  However, an areal thunderstorm outline is precluded by
   the lack of greater values of both buoyancy and inflow-layer
   theta-e.

   ..Edwards.. 12/11/2017

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