Jul 19, 2018 1630 UTC Day 1 Convective Outlook
Updated: Thu Jul 19 16:58:23 UTC 2018 (20180719 1630Z Day 1 shapefile | 20180719 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180719 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 173,172 13,633,548 Kansas City, MO...Wichita, KS...St. Louis, MO...Des Moines, IA...Little Rock, AR...
MARGINAL 363,581 18,812,476 Phoenix, AZ...Memphis, TN...Tucson, AZ...Mesa, AZ...Tulsa, OK...
Probabilistic Tornado Graphic
20180719 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 % 78,974 5,197,461 Des Moines, IA...Springfield, MO...Cedar Rapids, IA...Davenport, IA...Columbia, MO...
Probabilistic Damaging Wind Graphic
20180719 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 % 163,536 13,284,333 Kansas City, MO...Wichita, KS...St. Louis, MO...Des Moines, IA...Little Rock, AR...
5 % 336,874 19,042,925 Phoenix, AZ...Memphis, TN...Tucson, AZ...Mesa, AZ...Tulsa, OK...
Probabilistic Large Hail Graphic
20180719 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
SIG SEVERE 21,754 1,105,665 Independence, MO...Blue Springs, MO...Marshalltown, IA...Ottumwa, IA...Sedalia, MO...
15 % 115,839 8,698,149 Kansas City, MO...Wichita, KS...Des Moines, IA...Overland Park, KS...Springfield, MO...
5 % 220,689 10,409,504 Minneapolis, MN...St. Louis, MO...St. Paul, MN...Springfield, IL...Peoria, IL...
   SPC AC 191658

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1158 AM CDT Thu Jul 19 2018

   Valid 191630Z - 201200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF
   THE MIDWEST...LOWER MO VALLEY/OZARKS...AND SOUTH-CENTRAL PLAINS...

   ...SUMMARY...
   Scattered severe thunderstorms are expected through the afternoon
   and evening across portions of Iowa, Missouri, Kansas, western
   Illinois, and Arkansas.

   ...Central/southern MO to Mid-South...
   Have expanded the Slight Risk southward across the region to account
   for increasing concerns that an increasingly well-organized complex
   of storms in central MO will continue southward across the region
   through the afternoon and evening. Additional storms should occur
   along outflow on the western flank of the early-day storm complex,
   while additional storms may move into MO late in the afternoon or
   evening out of KS. Ample moisture and buoyancy (2000+ J/kg MLCAPE)
   along with seasonably strong mid/high-level northwesterly winds will
   contribute to the potential for corridors of wind damage and large
   hail. 

   ...KS into northern OK...
   Storms continue to develop/intensify across northern KS at late
   morning. It seems likely that this trend will continue
   east/southeastward through the afternoon/early evening with the
   strongest storms being capable of large hail/damaging winds.
   Reference Mesoscale Discussion 1083 for early-day details.

   ...IA/northern MO into western IL...
   While multi-level clouds have persisted much of the morning to the
   north of storms across north-central MO, gradual clearing from the
   west/southwest should occur through the afternoon. The main
   potential for surface-based severe storms (including some
   supercells) later today should be focused near the surface triple
   point across east-central/southeast IA. Large hail, damaging winds,
   and a couple of tornadoes will all be possible where sufficient
   destabilization occurs this afternoon.

   ...Northern Plains...
   Widely scattered thunderstorms are possible primarily this
   afternoon, in a broad zone of favorable residual moisture (surface
   dew points 50s to 60s F) characterizing the air mass ahead of a
   weak/secondary cold front. Destabilization will arise largely from
   the juxtaposition of 
   1.  Seasonally cool midlevel temps under northwest flow aloft, with 

   2.  Boundary-layer lapse rates steepened by insolation, following
   the breakup of most of the morning clouds/precip, as the mid/upper
   cyclone moves away from the area.  

   Although low-level forcing will be weak, so will capping,
   contributing to MLCAPE generally 1000-1500 J/kg in modified forecast
   soundings.  This buoyancy, atop a well-mixed subcloud layer, should
   support sporadic strong pulse/multicell convection with isolated,
   marginally severe hail and/or gusts.  Convective density should be
   greatest near the front, and activity should diminish considerably
   after about 03Z, in the absence of more robust deep lift.

   ...AZ/Southwest States...
   Widely scattered to scattered thunderstorms are expected to form
   again this afternoon, this process being primarily tied to areas of
   strong heating of higher terrain. Damaging, isolated severe gusts
   appear to be the primary concern. Related weakening of CINH and
   steepening of low-level lapse rates, amidst high moisture content,
   will offset relatively warm midlevel temperatures.  This should
   yield deep buoyancy (MLCAPE 500-1500 J/kg), atop well-mixed subcloud
   layers that will deepen with underlying dropoffs in elevation. A
   deeper layer of mid/upper easterlies is expected with southward
   extent, and distance from the ridge aloft, likely leading to greater
   potential for propagation into lower deserts over southeastern AZ,
   where greater buoyancy (MLCAPE 1500-2500 J/kg) may be encountered.

   ..Guyer/Wednt.. 07/19/2018

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