Feb 22, 2017 0830 UTC Day 3 Severe Thunderstorm Outlook
Updated: Wed Feb 22 08:29:56 UTC 2017 (20170222 0830Z Day 3 shapefile | 20170222 0830Z Day 3 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
0830 UTC Day 3 Outlook Graphic
Day 3 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 33,502 6,112,469 Indianapolis, IN...Toledo, OH...Fort Wayne, IN...South Bend, IN...Bloomington, IN...
SLIGHT 100,738 28,800,937 Chicago, IL...Detroit, MI...Columbus, OH...Cleveland, OH...Cincinnati, OH...
MARGINAL 114,920 16,012,635 Nashville, TN...Pittsburgh, PA...Akron, OH...Grand Rapids, MI...Knoxville, TN...
Probabilistic Graphic
20170222 0830 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
30 % 33,502 6,112,469 Indianapolis, IN...Toledo, OH...Fort Wayne, IN...South Bend, IN...Bloomington, IN...
15 % 100,628 28,721,640 Chicago, IL...Detroit, MI...Columbus, OH...Cleveland, OH...Cincinnati, OH...
5 % 115,097 16,094,717 Nashville, TN...Pittsburgh, PA...Akron, OH...Grand Rapids, MI...Knoxville, TN...
   SPC AC 220829

   Day 3 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0229 AM CST Wed Feb 22 2017

   Valid 241200Z - 251200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR CENTRAL AND
   NORTHERN INDIANA INTO NORTHWESTERN OHIO AND FAR SOUTHERN LOWER
   MICHIGAN...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PORTIONS OF
   SOUTHERN LOWER MICHIGAN AND MUCH OF THE OHIO VALLEY...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   SLIGHT RISK...

   ...SUMMARY...
   One or more bands of strong to severe thunderstorms are forecast
   across the southern Great Lakes and Ohio Valley on Friday and Friday
   night.

   ...Synopsis...
   A mid-level trough/low is forecast to move from the middle MO Valley
   eastward to the western Great Lakes and OH Valley and assume a
   neutral to slightly negative tilt.  As this occurs, a belt of strong
   and cyclonically curved 500-mb flow is forecast to intensify in
   excess of 100-kt over the OH Valley late Friday night.  A surface
   low near the MO/IA border will develop northeastward into northern
   Lower Michigan as a warm front to its east advances northward.  A
   cold front near the MS River around midday Friday will sweep
   eastward across the OH and TN Valleys by daybreak Saturday.  

   ...southern Great Lakes and Ohio Valley...
   Low-level moisture is forecast to slowly increase on strong
   southerly flow with boundary-layer dewpoints forecast to range 52-58
   degrees F.  Although cloud cover will retard strong surface heating,
   cooling mid-level temperatures to around -19 degrees C will
   contribute to weak buoyancy (ranging from 250-1000 J/kg MUCAPE)
   within the northward expanding warm sector during the day.  As
   strong forcing for ascent (DCVA) approaches and overspreads the
   western parts of the area, a band of thunderstorms will likely
   develop and intensify.  Strong effective shear around 50 kt will act
   to organize updrafts and strengthening 700-mb flow to the 55-60 kt
   range will contribute to cold pool's organization and upscale
   growth. Downward momentum transport via damaging winds are the
   predominant severe risk.  However, some forecast soundings show
   relatively moist low levels with strong 0-1 km shear in excess of
   25-30 kt.  A tornado risk may develop with the maturing squall line
   and/or pre-frontal supercell(s) that eventually merges with the
   line.  A gradual weakening in buoyancy by the early to mid evening
   into the overnight will likely lead to a lessening in the
   damaging-wind risk as storms rapidly move east and northeastward
   after dark.

   ...TN and southern Appalachians...
   Storm development over this region will likely be inhibited by an 
   initially capped warm sector until stronger 500-mb height falls
   arrive towards evening.  Model guidance suggests a squall line will
   zipper southward into parts of TN as shear profiles strengthen. 
   Damaging winds will be the primary threat.

   ..Smith.. 02/22/2017

   NOTE: THE NEXT DAY 3 OUTLOOK IS SCHEDULED BY 0830Z