Jun 9, 2018 1300 UTC Day 1 Convective Outlook
Updated: Sat Jun 9 12:51:15 UTC 2018 (20180609 1300Z Day 1 shapefile | 20180609 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180609 1300 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 68,804 2,696,926 Cedar Rapids, IA...Davenport, IA...Waterloo, IA...Iowa City, IA...Dubuque, IA...
MARGINAL 344,182 53,221,269 Chicago, IL...Indianapolis, IN...Columbus, OH...Baltimore, MD...Washington, DC...
Probabilistic Tornado Graphic
20180609 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
5 % 14,749 649,727 Waterloo, IA...Cedar Falls, IA...Mason City, IA...Marshalltown, IA...Austin, MN...
2 % 17,517 1,108,468 Cedar Rapids, IA...Rochester, MN...Iowa City, IA...Mankato, MN...Marion, IA...
Probabilistic Damaging Wind Graphic
20180609 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
15 % 68,484 2,712,097 Cedar Rapids, IA...Davenport, IA...Waterloo, IA...Iowa City, IA...Dubuque, IA...
5 % 310,649 49,295,239 Chicago, IL...Indianapolis, IN...Columbus, OH...Baltimore, MD...Washington, DC...
Probabilistic Large Hail Graphic
20180609 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
15 % 32,636 1,897,934 Cedar Rapids, IA...Davenport, IA...Waterloo, IA...Iowa City, IA...Dubuque, IA...
5 % 227,974 22,617,733 Chicago, IL...Minneapolis, MN...St. Louis, MO...St. Paul, MN...Madison, WI...
   SPC AC 091251

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0751 AM CDT Sat Jun 09 2018

   Valid 091300Z - 101200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   INTO TONIGHT FROM SOUTHERN MN AND EASTERN IA TO NORTHWESTERN
   IL...AND ACROSS NORTH CENTRAL MT...

   ...SUMMARY...
   A cluster of severe storms, including some potential for a couple of
   tornadoes, is expected this afternoon across eastern Iowa and
   vicinity.  A few storms may produce damaging winds this
   afternoon/evening across north central Montana.

   ...Southern MN, eastern IA and northwestern IL this afternoon into
   tonight...
   The overnight MCS that moved from NE to western IA was
   faster/stronger and the outflow has likewise been more extensive
   than most model guidance from overnight.  The convection has
   weakened since 09z, and the lingering outflow introduces some
   uncertainty regarding the degree of destabilization this afternoon
   across IA.  However, cloud breaks will likely occur later this
   morning, and gradual recovery of low-level moisture will contribute
   to destabilization (MLCAPE values in the 2000-3000 J/kg range by mid
   afternoon).  Renewed thunderstorm development is expected this
   afternoon, primarily where the remnant MCV interacts with the warm
   front across north central and northeast IA and extreme southern MN.
   Vertical shear will be enhanced within the mesoscale corridor along
   the warm front, where a few supercells and tornadoes will be
   possible, though this threat will still depend on sufficient
   low-level moisture recovery by mid-later afternoon.  Otherwise,
   convection should subsequently evolve into another southeastward
   moving MCS across eastern IA into northwestern IL through early
   tonight, with an attendant threat for damaging winds and large hail.

   ...North central MT this afternoon/evening...
   A deep midlevel trough over the Pacific Northwest will progress
   eastward across the northern Rockies through tonight.  This trough,
   and a strong associated cold front, will begin to affect western and
   central MT this afternoon/evening.  Forcing for ascent will be
   focused along the front, and strong surface heating is expected
   within the warm sector.  Given the relatively limited moisture now
   present across MT, the expectation is for moderate buoyancy (MLCAPE
   of 1000-1500 J/kg) this afternoon as dewpoints mix into the 40s and
   lower 50s, and inverted-V thermodynamic profiles.  A few
   thunderstorms should form near the front by mid-late afternoon and
   then spread north-northeastward through this evening.  Damaging
   winds will be the main threat with the high-based storms, though an
   increase in vertical shear and steep lapse rates will also support
   some threat for isolated large hail for a few hours this
   afternoon/evening.

   ...OH Valley to Mid Atlantic this afternoon/evening...
   Moderate buoyancy is expected along and south of a slow-moving front
   from the Mid Atlantic westward into the OH Valley.  Storms will be
   focused this afternoon from northern VA into MD near the front, and
   in loose clusters IL/IN/OH in association with remnant MCVs in the
   vicinity of the front.  Isolated downburst winds will be the main
   threat.

   ..Thompson/Broyles.. 06/09/2018

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