Apr 17, 2019 1300 UTC Day 1 Convective Outlook
Updated: Wed Apr 17 12:51:26 UTC 2019 (20190417 1300Z Day 1 shapefile | 20190417 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20190417 1300 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 97,134 12,381,962 Dallas, TX...Austin, TX...Fort Worth, TX...Arlington, TX...Wichita, KS...
SLIGHT 283,146 20,830,205 San Antonio, TX...Oklahoma City, OK...Tulsa, OK...St. Louis, MO...Madison, WI...
MARGINAL 191,161 29,630,834 Chicago, IL...Houston, TX...Indianapolis, IN...Memphis, TN...Kansas City, MO...
Probabilistic Tornado Graphic
20190417 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 % 153,257 15,771,006 Dallas, TX...Fort Worth, TX...Oklahoma City, OK...Tulsa, OK...Arlington, TX...
2 % 257,048 21,561,385 San Antonio, TX...Austin, TX...Kansas City, MO...St. Louis, MO...Madison, WI...
Probabilistic Damaging Wind Graphic
20190417 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
30 % 82,665 11,369,561 Dallas, TX...Austin, TX...Fort Worth, TX...Arlington, TX...Wichita, KS...
15 % 291,422 21,277,268 San Antonio, TX...Oklahoma City, OK...Tulsa, OK...St. Louis, MO...Shreveport, LA...
5 % 169,463 26,278,313 Chicago, IL...Houston, TX...Indianapolis, IN...Memphis, TN...Kansas City, MO...
Probabilistic Large Hail Graphic
20190417 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
SIG SEVERE 81,456 11,915,269 San Antonio, TX...Dallas, TX...Austin, TX...Fort Worth, TX...Arlington, TX...
30 % 97,138 12,426,739 Dallas, TX...Austin, TX...Fort Worth, TX...Arlington, TX...Wichita, KS...
15 % 257,539 19,240,952 San Antonio, TX...Oklahoma City, OK...Tulsa, OK...St. Louis, MO...Madison, WI...
5 % 216,230 31,164,308 Chicago, IL...Houston, TX...Indianapolis, IN...Memphis, TN...Kansas City, MO...
   SPC AC 171251

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0751 AM CDT Wed Apr 17 2019

   Valid 171300Z - 181200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM CENTRAL
   TEXAS TO SOUTHERN OKLAHOMA...AND FROM SOUTHERN KANSAS TO THE
   NORTHERN TEXAS PANHANDLE....

   ...SUMMARY...
   The greatest threat for severe storms this afternoon and evening is
   from central Texas across the Dallas/Fort Worth Metroplex to
   southern Oklahoma, and from southern Kansas to the northern Texas
   Panhandle.  Expect damaging hail, and a few severe gusts and
   tornadoes also are possible.

   ...Synopsis...
   A mid/upper-level synoptic trough, containing split flow, is evident
   over the central/northern Rockies and Desert Southwest, with an
   embedded cyclone centered over AZ.  The associated 500-mb low is
   forecast to the TX/NM border near HOB by 00Z, with a trough
   southwestward across far west TX, Chihuahua and southern Sonora.  An
   intermediary shortwave trough, with some antecedent convective
   vorticity enhancement, is evident in moisture-channel imagery over
   west-central/southwestern NE.  This feature will eject northeastward
   to northern IA/southern MN by 00Z.  By 12Z, the mid/upper cyclone
   will have ejected east-northeastward to OK and deteriorated to an
   open wave, in response to a speed max digging southeastward over the
   northern/central High Plains.  At that time the synoptic trough
   should extend from an amplifying northern-stream shortwave
   perturbation over MN, southwestward over the central Plains to
   central OK, west-central TX, and north-central MX.

   At the surface, the 11Z analysis showed a broad area of low
   pressure, attached to a wavy frontal zone across eastern/south-
   central NE and north-central/southwestern KS.  A cold front extended
   from there over northeastern NM.  A warm front was drawn over
   western/southeastern IA and north-central portions of IL/IN.  The
   low-pressure area should consolidate into a discrete cyclone today,
   deepen,  and move northeastward to the northeastern IA/southeastern
   MN area by 00Z, ahead of the northern-stream perturbation.  The cold
   front should extend from there southwestward over northwestern MO,
   southeastern KS, northwestern OK, and parts of the TX Panhandle.  A
   warm front will extend from the low east-southeastward across OH. 
   By 12Z, the low should reach eastern Upper MI, with cold front
   across central IL, the MO/AR Ozarks, and north-central to southwest
   TX.  The dryline should assume an arc shape by 00Z from western to
   south-central OK and north-central TX, and across the Hill Country
   to near DRT.  The front will overtake the dryline from north-south
   the remainder of the period.

   ...Southern Plains to southern KS...
   Two relatively dense corridors of convective coverage -- and
   associated large-hail potential -- are evident:  near the frontal
   zone from the TX Panhandle to southern KS, and ahead of the dryline
   from portions of southern OK through south-central TX.  Significant/
   2-inch or greater hailstones are possible in each area from
   supercells in early stages of the convective evolution.  The threat
   will transition unevenly more toward wind with time, and a few
   tornadoes also are possible in both supercellular and quasi-linear
   modes.

   Supercells in the northern area will be relatively short-lived
   before convective mode becomes messier and the wind threat more
   prominent, amidst well-mixed preconvective sub cloud layers in the
   warm sector, and mean/deep-layer flow nearly parallel to the
   boundary.  Over the TX/southern OK corridor, including the
   Metroplex, supercells with very large and destructive hail are
   possible, in a regime of very steep lapse rates and high
   inflow-layer water content.  This will support large buoyancy
   (MLCAPE 3000-4000 J/kg), with much of that CAPE distributed into
   ideal icing layers for hail production.

   The bifurcation of the enhanced-level probabilities for this outlook
   package does not mean that severe weather won't occur in between --
   indeed, isolated supercells conditionally are possible, despite the
   relatively weak deep-layer forcing compared to farther north and
   south.  Instead, the severe/convective potential simply appears more
   densely concentrated over the remaining, more-precise 30%/enhanced
   areas.  As modes transition to more clustered and linear with time
   overnight and activity shifts/develops eastward toward the areas
   from IL to AR and central/east TX, pockets of locally maximized
   damaging/severe wind and/or brief tornadoes may occur with embedded
   bows/LEWPs and mesocirculations.

   ...Lower Missouri Valley to mid/upper Mississippi Valley...
   Isolated to scattered thunderstorms are possible near the surface
   low and nearby segments of the warm, and cold fronts this afternoon
   into this evening, where low-level convergence will be maximized,
   along with large-scale ascent preceding the ejecting intermediary
   shortwave trough.

   Activity initially should form over portions of IA/southern
   MN/southwestern WI, moving northeastward.  Some backbuilding down
   the front is possible with time into the evening.  Large hail and
   sporadic damaging winds are possible.  A tornado threat may develop
   near the low and warm front, where near-surface flow will be most
   strongly backed, helping to maximize low-level shear/SRH and
   storm-relative winds in the inflow layer.  However, convective
   coverage and duration of any relatively discrete supercellular modes
   still are uncertain. Sufficient moisture advection and diurnal
   heating are expected to support a pre-cold-frontal corridor of
   around 1000-1500 J/kg MLCAPE amidst 40-50 kt effective-shear
   magnitudes, with effective SRH potentially exceeding 300 J/kg along
   and immediately adjoining the warm front.

   ..Edwards/Goss.. 04/17/2019

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