Jul 9, 2021 0600 UTC Day 1 Convective Outlook
Updated: Fri Jul 9 05:07:14 UTC 2021 (20210709 1200Z Day 1 shapefile | 20210709 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20210709 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 43,111 4,075,011 St. Louis, MO...Springfield, IL...Columbia, MO...St. Charles, MO...St. Peters, MO...
SLIGHT 168,806 8,241,862 Kansas City, MO...Omaha, NE...Lincoln, NE...Des Moines, IA...Overland Park, KS...
MARGINAL 210,242 44,566,077 New York, NY...Philadelphia, PA...Boston, MA...Newark, NJ...Jersey City, NJ...
Probabilistic Tornado Graphic
20210709 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
5 % 36,014 1,721,196 Columbia, MO...St. Joseph, MO...Council Bluffs, IA...West Des Moines, IA...St. Peters, MO...
2 % 50,030 8,426,122 Kansas City, MO...Omaha, NE...St. Louis, MO...Lincoln, NE...Des Moines, IA...
Probabilistic Damaging Wind Graphic
20210709 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
SIG SEVERE 37,905 3,101,624 Columbia, MO...St. Joseph, MO...St. Charles, MO...St. Peters, MO...Florissant, MO...
30 % 43,111 4,075,011 St. Louis, MO...Springfield, IL...Columbia, MO...St. Charles, MO...St. Peters, MO...
15 % 168,614 8,191,187 Kansas City, MO...Omaha, NE...Lincoln, NE...Des Moines, IA...Overland Park, KS...
5 % 208,433 44,578,234 New York, NY...Philadelphia, PA...Boston, MA...Newark, NJ...Jersey City, NJ...
Probabilistic Large Hail Graphic
20210709 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
SIG SEVERE 38,405 477,996 St. Joseph, MO...Gillette, WY...Scottsbluff, NE...Maryville, MO...Torrington, WY...
15 % 177,804 9,851,142 Kansas City, MO...Omaha, NE...St. Louis, MO...Lincoln, NE...Des Moines, IA...
5 % 196,541 7,344,412 Sioux Falls, SD...Cedar Rapids, IA...Springfield, IL...Evansville, IN...Peoria, IL...
   SPC AC 090507

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1207 AM CDT Fri Jul 09 2021

   Valid 091200Z - 101200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LOWER MISSOURI
   VALLEY...

   ...SUMMARY...
   Thunderstorms, some with potentially significant severe weather, are
   expected this afternoon into tonight across parts of the lower
   Missouri Valley westward into the parts of the north-central High
   Plains.

   ...Lower Missouri Valley...
   A cluster of strong thunderstorms may be ongoing this morning near
   the nose of a LLJ over IA.  Warm air advection is forecast to weaken
   during the morning with thunderstorm outflow and differential
   heating providing a focus for additional thunderstorm development
   during the afternoon.  As a mid-level speed max moves from SD to the
   IA/MO border by late afternoon, initial storms will likely develop
   on the cool side of a warm frontal zone draped over the region. 
   Surface-based storms will likely develop farther west over southern
   IA/northern MO during the late afternoon/early evening within a very
   unstable airmass (3000+ J/kg MLCAPE).  A strongly veering and
   strengthening flow with height will favor supercells with the
   stronger and more discrete updrafts.  Upscale growth into a cluster
   of high-precipitation supercells and subsequently into a squall line
   will favor swaths of severe gusts over the lower MO Valley during
   the evening.  Some of the stronger gusts may be hurricane force in
   localized areas.  As this activity moves east into less-buoyant air
   over IL, a weakening and/or lessening in severe coverage is
   expected.  Storms may develop over southeast NE/northeast KS during
   the evening as a LLJ intensifies over the central Great Plains. 
   Hail/wind will be the primary severe hazards with this activity
   during the evening.

   ...Central Plains...
   Upslope flow regime is expected to evolve north of stalled front
   across the central plains.  Models are consistent in showing a
   corridor of mid 50s to near 60 F dewpoints beneath steep lapse rates
   and contributing to moderate instability with up to 2000 J/kg MLCAPE
   as the boundary layer destabilizes.  A mid-level shortwave trough
   initially over eastern ID will move into the north-central High
   Plains by late afternoon and contribute to 50+ kt effective shear. 
   Supercells will be the preferred storm type before one or more
   clusters evolves during the evening.  Large to very large hail and
   severe gusts will accompany the stronger storms.

   ...Southern New England to the Delmarva...
   T.C. Elsa will continue to progress northeast moving beyond the
   coast of southern New England by the early afternoon.  A conditional
   risk for a weak/brief tornado may exist near the immediate coast in
   association with an environment characterized as weak buoyancy and
   enlarging hodographs.  During the afternoon, isolated to scattered
   storms are likely to develop.  A few of the stronger storms may
   yield a localized wind-damage risk.

   ..Smith/Wendt.. 07/09/2021

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