May 2, 2018 1630 UTC Day 1 Convective Outlook
Updated: Wed May 2 16:30:54 UTC 2018 (20180502 1630Z Day 1 shapefile | 20180502 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Public Severe Weather Outlook

The SPC is forecasting ...Severe thunderstorms expected over parts of the central Plains this afternoon and tonight....   Please read the latest public statement about this event.  View What is a Watch? clip.

Categorical Graphic
20180502 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MODERATE 41,563 3,082,123 Kansas City, MO...Overland Park, KS...Kansas City, KS...Topeka, KS...Olathe, KS...
ENHANCED 80,030 3,586,389 Oklahoma City, OK...Wichita, KS...Lawton, OK...Columbia, MO...Edmond, OK...
SLIGHT 180,504 19,568,294 Chicago, IL...Tulsa, OK...St. Louis, MO...Lincoln, NE...Des Moines, IA...
MARGINAL 158,951 25,026,153 Dallas, TX...Detroit, MI...Fort Worth, TX...Milwaukee, WI...Omaha, NE...
Probabilistic Tornado Graphic
20180502 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
SIG SEVERE 47,797 2,717,347 Oklahoma City, OK...Wichita, KS...Topeka, KS...Lawton, OK...Lawrence, KS...
10 % 62,614 4,394,306 Oklahoma City, OK...Kansas City, MO...Wichita, KS...Overland Park, KS...Kansas City, KS...
5 % 80,701 3,306,795 Peoria, IL...Independence, MO...Norman, OK...Wichita Falls, TX...Davenport, IA...
2 % 168,322 21,495,470 Chicago, IL...Fort Worth, TX...Tulsa, OK...Des Moines, IA...Aurora, IL...
Probabilistic Damaging Wind Graphic
20180502 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
SIG SEVERE 27,976 2,973,356 Kansas City, MO...Overland Park, KS...Kansas City, KS...Topeka, KS...Olathe, KS...
45 % 47,731 3,864,155 Kansas City, MO...Wichita, KS...Overland Park, KS...Kansas City, KS...Topeka, KS...
30 % 62,501 1,672,097 Lawton, OK...Columbia, MO...Enid, OK...Quincy, IL...Jefferson City, MO...
15 % 153,381 14,725,841 Oklahoma City, OK...Tulsa, OK...St. Louis, MO...Des Moines, IA...Aurora, IL...
5 % 123,975 21,553,587 Chicago, IL...Dallas, TX...Fort Worth, TX...Milwaukee, WI...Omaha, NE...
Probabilistic Large Hail Graphic
20180502 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 96,405 3,411,189 Oklahoma City, OK...Wichita, KS...Topeka, KS...Lawton, OK...San Angelo, TX...
45 % 18,795 319,511 Salina, KS...Hutchinson, KS...Great Bend, KS...Woodward, OK...
30 % 52,699 2,675,739 Kansas City, MO...Wichita, KS...Kansas City, KS...Topeka, KS...Lawton, OK...
15 % 196,569 18,638,620 Chicago, IL...Oklahoma City, OK...Tulsa, OK...Lincoln, NE...Des Moines, IA...
5 % 177,146 28,433,307 Dallas, TX...Detroit, MI...Fort Worth, TX...Milwaukee, WI...Omaha, NE...
   SPC AC 021630

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1130 AM CDT Wed May 02 2018

   Valid 021630Z - 031200Z


   Severe thunderstorms are expected across parts of the southern and
   central Plains into the middle Mississippi Valley this afternoon
   into tonight. Swaths of damaging winds, large to very large hail,
   and several tornadoes are anticipated, especially from
   western/central Oklahoma across southern to eastern KS and northern
   to central MO.

   A complex overall forecast with significant severe potential for all
   hazards evident across a large swath of the central/southern Great
   Plains this afternoon and evening. As such, have expanded Enhanced
   and Moderate risks with this update.

   The surface front is stalling from southwest KS to southern IA. A
   lead mid-upper speed max will eject northeast from NM/far west TX to
   central KS by this evening.  This speed max will interact with the
   front and warm sector starting by early afternoon in southwest KS,
   where convective initiation is expected. Surface dewpoints in the
   mid to upper 60s, beneath mid-level lapse rates in excess of 8 C/km,
   will combine with daytime heating to support MLCAPE of 2500-3500
   J/kg along and south of the stalled front. Effective bulk shear
   around 50 kt will be sufficient for supercells, though low-level
   shear/hodograph curvature will not be particularly large for most of
   the afternoon. The expectation is for initial supercells with very
   large hail to grow upscale into clusters and potentially bowing
   segments through the afternoon and evening while surging northeast
   along the front, with an increasing threat for widespread damaging
   winds by late afternoon, persisting into the evening across MO. The
   tornado threat is uncertain given the expected messy convective
   modes and relatively weak low-level shear through most of the
   afternoon. However, towards 00Z, increasing low-level shear in
   conjunction with the strongly unstable air mass may support
   semi-discrete tornadic supercells just ahead of/southeast of the
   emerging clusters/bows, where a couple strong tornadoes are

   ...Western/central OK...
   A strongly unstable warm sector is expected into western OK this
   afternoon, with upper 60s surface dew points beneath very steep
   mid-level lapse rates. The dryline will mix east of the thicker high
   cloud band in west TX as surface temperatures warm into the mid 90s.
   Convergence along the dryline should strengthen beneath the
   mid-level speed max ejecting towards KS. This scenario should
   support discrete supercell development at least as far south as the
   Red River near the southwest OK/northwest TX border. MLCAPE of
   3000-4000 J/kg and 50-60 kt effective shear will support at least
   very large hail. Forecast wind profiles will have some weakness near
   700 mb this afternoon, though low-level shear will increase and
   become more favorable for tornadic supercells in the evening. The
   main uncertainty is whether discrete storm mode will persist into
   this time frame with most CAMs suggesting it will not. While this
   volatile setup has some potential to yield long-track supercells
   with a few strong tornadoes, will only expand but not upgrade
   probabilities with this outlook.

   ...West to central and north TX...
   Guidance appears to be trending faster with convection forming near
   the Permian Basin this evening along the retreating portion of the
   dryline. Very large hail will be the main initial threat with these
   storms given a highly favorable CAPE/shear combination. Upscale
   growth into clusters with both severe wind gusts and large hail will
   be possible tonight, with this activity eventually weakening

   ...Southern IA to northern/central IL...
   Clusters of strong to severe storms will probably develop this
   afternoon along the stalling to slow-moving cold front. While the
   overall intensity/coverage is not anticipated to be as large as
   farther southwest, all hazards appear possible with clusters/bows
   and a few embedded supercells. The late evening/overnight portion of
   the MO MCS may also affect parts of central IL with a wind threat as

   ..Grams/Wendt/Marsh.. 05/02/2018