Jun 8, 2018 0600 UTC Day 1 Convective Outlook
Updated: Fri Jun 8 05:31:04 UTC 2018 (20180608 1200Z Day 1 shapefile | 20180608 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180608 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 30,862 103,773 Pierre, SD...
SLIGHT 38,865 326,567 Rapid City, SD...Mitchell, SD...Yankton, SD...Huron, SD...Spearfish, SD...
MARGINAL 364,484 33,731,675 Chicago, IL...Indianapolis, IN...Columbus, OH...Omaha, NE...Cincinnati, OH...
Probabilistic Tornado Graphic
20180608 1200 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 % 56,011 841,746 Rapid City, SD...Mason City, IA...Fort Dodge, IA...Watertown, SD...Ledyard, IA...
Probabilistic Damaging Wind Graphic
20180608 1200 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
30 % 31,164 101,995 Pierre, SD...
15 % 39,035 331,766 Rapid City, SD...Mitchell, SD...Yankton, SD...Huron, SD...Spearfish, SD...
5 % 366,663 33,979,975 Chicago, IL...Indianapolis, IN...Columbus, OH...Omaha, NE...Cincinnati, OH...
Probabilistic Large Hail Graphic
20180608 1200 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 % 67,499 429,352 Rapid City, SD...Mitchell, SD...Pierre, SD...Yankton, SD...Huron, SD...
5 % 365,655 33,299,837 Chicago, IL...Indianapolis, IN...Columbus, OH...Omaha, NE...Cincinnati, OH...
   SPC AC 080531

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1231 AM CDT Fri Jun 08 2018

   Valid 081200Z - 091200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
   SOUTH DAKOTA INTO NORTHERN NEBRASKA...

   ...SUMMARY...
   Severe hail and wind is likely across parts of the northern Plains
   during the late afternoon and evening. Sporadic hail or wind is also
   possible across the central and southern High Plains, over parts of
   the Midwest, and over central Florida.

   ...Synopsis...
   An upper ridge will stretch from the Plains into the Canadian
   prairies, with large upper troughs across the Pacific Northwest and
   New England. Beneath the upper ridge, minor disturbances will exist
   in association with areas of convection, from the Dakotas into MN
   during the day also developing across the central and northern High
   Plains during the afternoon. At the surface, a lee trough will also
   develop across the High Plains, with southeasterly surface winds
   maintaining widespread 60s F dewpoints from the Dakotas south. To
   the east, a stationary front will extend roughly from the upper MS
   Valley southeastward across northern IL, IN, and OH, with mid to
   upper 60s F dewpoints common there. Western portions of this
   boundary will return north as a warm front, with a narrow corridor
   of enhanced low-level shear over MN and IA. Elsewhere, a weak upper
   low will affect the eastern Gulf of Mexico and FL, providing a
   pocket of cool air aloft and a small increase in winds aloft.

   ...Northern Plains...
   Early-day storms across parts of SD may produce outflow, but this
   should modify with heating as the storms diminish. Widespread mid
   60s F dewpoints are expected across much of SD, with low 60s F
   extending westward toward the Black Hills. This, along with cool
   temperatures aloft will support strong instability with large LI's.
   While shear profiles will be weak, robust updrafts should lead to
   scattered severe storms initiating near the Black Hills and
   southward along the WY/NE border near the lee trough. Damaging winds
   and large hail, perhaps briefly very large, are expected. Given the
   amount of instability, another MCS is likely late in the day, and a
   relatively concentrated area of wind potential may materialize
   across south central SD into northern NE.

   Farther east into northern IA and western MN, storm coverage is
   expected to be isolated. However, hodographs along the warm front
   will conditionally support supercells should storms form there. A
   brief tornado and/or hail would be possible.

   ...Central and southern High Plains...
   Strong heating will occur near the lee trough, with an uncapped air
   mass by late afternoon. Hail is likely with widely-spaced storms
   from eastern CO into the TX Panhandle, with storms diminishing
   around 03Z. A deeply mixed boundary layer with hot temperatures will
   also favor the production of strong outflow winds, with localized
   damage possible.

   ...IA...IL...IN...OH...
   Daytime heating and convergence near the front will lead to widely
   scattered afternoon storms, most likely from IL into OH. Cool
   temperatures aloft may support hail in the stronger cores, with
   localized damaging wind gusts. Shear will be weak, but modest
   westerlies aloft may support a few multicell clusters.

   ...Central FL Peninsula...
   Heating along with surface convergence will lead to scattered
   daytime storms, while the presence of relatively cool air aloft with
   the weak upper low support vigorous updrafts. Shear will remain
   weak, but 20-40 kt mid to upper flow may result in a few storm
   clusters capable of marginally severe hail or strong wind gusts.

   ..Jewell/Wendt.. 06/08/2018

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