Jul 15, 2017 1630 UTC Day 1 Convective Outlook
Updated: Sat Jul 15 16:30:44 UTC 2017 (20170715 1630Z Day 1 shapefile | 20170715 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170715 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 59,216 6,768,288 Milwaukee, WI...Madison, WI...Rockford, IL...Green Bay, WI...Rochester, MN...
MARGINAL 280,608 37,478,001 Chicago, IL...Phoenix, AZ...Charlotte, NC...Tucson, AZ...Mesa, AZ...
Probabilistic Tornado Graphic
20170715 1630 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
2 % 26,128 2,059,941 Green Bay, WI...Appleton, WI...Oshkosh, WI...La Crosse, WI...Fond du Lac, WI...
Probabilistic Damaging Wind Graphic
20170715 1630 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
15 % 58,902 6,758,850 Milwaukee, WI...Madison, WI...Rockford, IL...Green Bay, WI...Rochester, MN...
5 % 274,487 37,067,935 Chicago, IL...Phoenix, AZ...Charlotte, NC...Tucson, AZ...Mesa, AZ...
Probabilistic Large Hail Graphic
20170715 1630 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
15 % 54,057 5,645,824 Milwaukee, WI...Madison, WI...Green Bay, WI...Rochester, MN...Racine, WI...
5 % 271,368 31,340,705 Phoenix, AZ...Charlotte, NC...Tucson, AZ...Mesa, AZ...Atlanta, GA...
   SPC AC 151630

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1130 AM CDT Sat Jul 15 2017

   Valid 151630Z - 161200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS WESTERN GREAT
   LAKES...

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

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PORTIONS OF THE
   SOUTHEAST...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS CENTRAL/SOUTHERN
   ARIZONA...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS NORTHEAST IDAHO
   AND WESTERN MONTANA...

   ...SUMMARY...
   Severe thunderstorms with damaging winds and large hail will be
   possible this afternoon and evening across portions of the upper
   Mississippi Valley and western Great Lakes region, with sporadic
   strong storms across the Southeast states, southern Arizona and
   western Montana.

   ...Western Great Lakes Region...
   Morning water vapor imagery depicts a weak mid-level shortwave
   trough moving southeast across the northern Plains and
   upper-Midwest. Associated with this trough, a weak surface cold
   front will move southeast across the same areas. Ahead of this cold
   front, low-level moistening should allow for surface dewpoints to
   reach the low-to-mid 70s beneath mid-level lapse rates of 7-8 C/km,
   resulting in a strongly unstable environment. 

   Ascent from the shortwave trough and increasing low-level
   convergence along the front should help initiate thunderstorms
   across central Wisconsin by mid-to-late afternoon. Although the best
   deep-layer shear should remain north of the area, deep-layer shear
   should be sufficient to support a mix of supercells and organized
   multicells, before a likely transition to one or two small
   linear/bowing segments with time. Large hail and isolated damaging
   thunderstorm winds will be primary threats as these storms move
   southeast.

   ...Southeast...
   A weak surface front moving east from the Appalachians should
   provide a focus for thunderstorm development this afternoon within a
   weakly capped and unstable atmosphere. Most-unstable CAPE values in
   excess of 1500 J/kg, weak vertical wind shear, and precipitable
   water values approaching 2 inches should support an isolated wet
   downbursts/microbursts potential with the strongest thunderstorm
   cores along with thunderstorm mergers and outflow boundary
   collisions.

   ...Southern/Central Arizona...
   Thunderstorms should develop once again this afternoon within the
   North American monsoon. These thunderstorms should slowly move
   southwest, eventually merging/growing upscale with time. Strong
   thunderstorm outflows will support the potential for a marginal
   damaging wind threat.

   ...Northeast Idaho and Western Montana...
   Modest ascent from an upstream short-wave trough over the Pacific
   Northwest will combine with diurnal heating/mixing to support
   thunderstorm developing of locally favored terrain. These
   thunderstorms should develop east of the greater deep-layer flow,
   which should act to limit the overall severe threat. However, deep
   inverted-V soundings would support isolated damaging winds with some
   storms.

   ..Marsh/Cook.. 07/15/2017

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