Apr 28, 2017 1630 UTC Day 1 Convective Outlook
Updated: Fri Apr 28 16:35:12 UTC 2017 (20170428 1630Z Day 1 shapefile | 20170428 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170428 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 123,598 10,171,640 Oklahoma City, OK...Tulsa, OK...Lexington-Fayette, KY...Louisville, KY...Springfield, MO...
SLIGHT 116,054 14,410,350 Indianapolis, IN...Columbus, OH...Nashville, TN...St. Louis, MO...Cincinnati, OH...
MARGINAL 129,646 10,504,465 Memphis, TN...Fort Wayne, IN...Little Rock, AR...Springfield, IL...Columbia, MO...
Probabilistic Tornado Graphic
20170428 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
10 % 24,192 3,053,200 Lexington-Fayette, KY...Louisville, KY...Clarksville, TN...Owensboro, KY...Bowling Green, KY...
5 % 93,441 7,084,508 Oklahoma City, OK...Cincinnati, OH...Evansville, IN...Norman, OK...Lawton, OK...
2 % 102,681 10,091,539 Memphis, TN...Nashville, TN...Tulsa, OK...Little Rock, AR...Dayton, OH...
Probabilistic Damaging Wind Graphic
20170428 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 % 168,890 14,444,537 Oklahoma City, OK...Tulsa, OK...Cincinnati, OH...Lexington-Fayette, KY...Louisville, KY...
5 % 137,350 15,383,216 Indianapolis, IN...Columbus, OH...Memphis, TN...Nashville, TN...St. Louis, MO...
Probabilistic Large Hail Graphic
20170428 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 113,673 9,192,149 Oklahoma City, OK...Tulsa, OK...Lexington-Fayette, KY...Louisville, KY...Evansville, IN...
30 % 122,862 10,120,270 Oklahoma City, OK...Tulsa, OK...Lexington-Fayette, KY...Louisville, KY...Springfield, MO...
15 % 111,577 14,124,261 Indianapolis, IN...Columbus, OH...Nashville, TN...St. Louis, MO...Cincinnati, OH...
5 % 126,506 10,011,757 Memphis, TN...Fort Wayne, IN...Little Rock, AR...Springfield, IL...Columbia, MO...
   SPC AC 281635

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1135 AM CDT Fri Apr 28 2017

   Valid 281630Z - 291200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OK TO TN
   VALLEY...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
   ENHANCED RISK...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SOUTHERN GREAT
   PLAINS TO CENTRAL APPALACHIANS...

   ...SUMMARY...
   Numerous severe storms are expected today, initially across parts of
   the Ohio and Tennessee Valleys this afternoon, and across the
   southern Great Plains and Ozarks by tonight. Very large hail,
   tornadoes, and damaging winds are anticipated.

   ...Synopsis...
   Potential exists for multiple severe episodes this afternoon into
   tonight across the Enhanced Risk characterized by increasing
   moisture, moderate to strong buoyancy, and ample vertical shear.
   However, some of this risk is conditional and confidence is below
   average in mesoscale details regarding severe coverage.

   ...TN/OH Valleys...
   A mid-level impulse over eastern NE should decay during the period
   as an upstream shortwave trough pivots over the Four Corners into
   AZ/NM. This will effectively yield rising heights over a large
   portion of a poleward-advecting warm sector emanating from the Gulf.
   This warm sector will remain characterized by rather rich mean
   mixing ratios with upper 60s to middle 70s surface dew points
   becoming established from the OH Valley on south as a warm front
   passes north through this evening. 

   Within the low-level warm-advection regime, elevated convection is
   ongoing from NE/IA into MO/IL. Additional activity may develop
   farther south/east closer to the advancing warm front towards late
   afternoon. Low-level hodographs will be comparatively large within
   this corridor in conjunction with 40-50 kt 850-mb flow. This setup
   could support mixed modes of discrete supercells and upscale-growing
   bows capable of tornadoes, large hail, and damaging winds. These
   threats will probably remain along and north of the warm front, with
   capping increasingly pronounced with southern extent in the warm
   sector.

   ...Southern Great Plains to the Ozarks...
   Similar to areas farther east, an increasingly rich low-level air
   mass is steadily returning, but beneath a more substantial 700-mb
   cap. This should inhibit sustained storm development until about
   03Z. Along the northwest periphery of the warm sector, a
   consolidating surface cyclone over northwest TX amid near-neutral
   mid-level height change should result in strengthening frontal
   convergence and yield storm development over OK into far northwest
   OK. Storm coverage should become widespread overnight along and
   north of the quasi-stationary front eastward across the Ozarks.

   Supercell-favorable wind profiles and steep mid-level lapse rates
   should support several rotating storms with large hail (some
   significant) as the primary hazard. Damaging winds and a couple
   tornadoes will also be possible, particularly with cells that can be
   sustained along the quasi-stationary front. The overall evolution
   into a broad clustering band with embedded line segments amid an
   anafrontal setup should yield a predominant hail and some wind risk,
   continuing on an increasingly isolated basis into the overnight.

   ..Grams/Mosier.. 04/28/2017

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 2000Z