May 29, 2018 1300 UTC Day 1 Convective Outlook
Updated: Tue May 29 12:57:13 UTC 2018 (20180529 1300Z Day 1 shapefile | 20180529 1300Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180529 1300 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
ENHANCED 29,276 523,668 Salina, KS...Hutchinson, KS...Newton, KS...Great Bend, KS...Woodward, OK...
SLIGHT 142,175 9,793,391 Oklahoma City, OK...Omaha, NE...Minneapolis, MN...Wichita, KS...St. Paul, MN...
MARGINAL 356,182 23,648,432 Nashville, TN...Kansas City, MO...Atlanta, GA...Tulsa, OK...Des Moines, IA...
Probabilistic Tornado Graphic
20180529 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 % 14,850 114,395 Great Bend, KS...Woodward, OK...
2 % 168,185 17,458,624 Oklahoma City, OK...Nashville, TN...Atlanta, GA...Wichita, KS...Lincoln, NE...
Probabilistic Damaging Wind Graphic
20180529 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 % 22,616 534,757 Salina, KS...Hutchinson, KS...Newton, KS...Great Bend, KS...Woodward, OK...
15 % 148,583 9,782,579 Oklahoma City, OK...Omaha, NE...Minneapolis, MN...Wichita, KS...St. Paul, MN...
5 % 356,711 23,622,250 Nashville, TN...Kansas City, MO...Atlanta, GA...Tulsa, OK...Des Moines, IA...
Probabilistic Large Hail Graphic
20180529 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 25,767 225,920 Dodge City, KS...Great Bend, KS...Woodward, OK...
30 % 23,747 229,671 Hutchinson, KS...Great Bend, KS...Woodward, OK...
15 % 141,796 9,284,162 Omaha, NE...Minneapolis, MN...Wichita, KS...St. Paul, MN...Lincoln, NE...
5 % 276,810 10,062,850 Oklahoma City, OK...Kansas City, MO...Tulsa, OK...Des Moines, IA...Overland Park, KS...
   SPC AC 291257

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0757 AM CDT Tue May 29 2018

   Valid 291300Z - 301200Z

   ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
   CENTRAL KANSAS TO NORTHWESTERN OKLAHOMA...

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER MUCH OF
   MINNESOTA AND SURROUNDING THE ENHANCED RISK...

   ...SUMMARY...
   Severe thunderstorms are expected over parts of the central and
   southern Plains and upper Midwest.  Greatest concentration and
   intensity of threat appears to be from central Kansas into
   northwestern Oklahoma during the afternoon and evening.

   ...Synopsis...
   In mid/upper levels, a trough now located from the northern High
   Plains across the central Rockies to west-central NM will eject
   northeastward and weaken through the period, but still remain
   defined enough to contribute to northward ejection of the remains of
   Alberto on day-2.  In the meantime, the primary shortwave trough
   associated with the Rockies system -- now apparent in moisture-
   channel imagery from eastern WY to central CO -- will reach the
   Black Hills and central High Plains by 00Z, then the lower/mid
   Missouri Valley (from ND to the MKC area) by the end of the period. 

   At the surface, a wavy frontal zone was drawn at 11Z from the St.
   Lawrence Valley across central Lower MI to central MN, to a weak low
   over northwestern SD.  This boundary should move northward across ND
   and MN through this evening.  Farther south, a composite boundary,
   reinforced by multiple convective-outflow episodes, was evident
   across northeastern, central and western OK, bending back
   northwestward to a lee low over southeastern CO.  This boundary
   should retreat northward somewhat across the Panhandles and
   northwestern OK today.  A dryline, initially analyzed from the lee
   low southward near the TX/NM line to the Big Bend region, will mix
   eastward over the southern High Plains today.  

   ...Central/southern Plains...
   Scattered thunderstorms should develop along/ahead of the dryline
   this afternoon, with the greatest concentration still expected in
   the enhanced-risk area.  Early, relatively discrete storm modes
   should become supercellular amidst favorable deep shear and at least
   marginal low-level shear, with surface dew points upper 50s to 60s F
   and strong heating away from pre-existing cloud areas contributing
   to 2500-3500 J/kg MLCAPE.  Southern storms will have the most
   unimpeded access to relatively undisturbed boundary-layer air for
   the longest time, as well as residual vorticity related to the
   outflow boundary.  

   Magnitude and duration of air-mass recovery become more uncertain
   (but likely weaker) with northward extent from the outflow boundary
   across KS and NE, and multiple recent runs of convection-allowing
   guidance have been very poor at depicting the large area of precip
   and convection now present over much of western/central KS.  As
   such, unconditional probabilities for severe have diminished enough
   to pull the 30%/enhanced lines southward across the region, though
   lesser probabilities will be maintained for the time being. 
   Sufficient buoyancy should remain in at least a narrow north/south
   corridor to support scattered severe thunderstorms into much of
   central KS.  

   A relatively sharp southern delimiter to convection is likely this
   afternoon/evening, reflected in the tighter probability gradient
   compared to the previous outlook, although some uncertainty remains
   about whether isolated supercell development can occur near the
   dryline south of about I-40.  Regardless, warm air aloft and related
   capping will substantially limit convective/severe potential with
   southward extent across southwestern OK and northwest TX.  Some
   persistence and at least loose nocturnal organization is possible
   with thunderstorm clusters evolving from the afternoon/early evening
   activity, with damaging gusts and occasional hail possible. 

   ...Upper Midwest...
   Scattered thunderstorms are expected to develop this afternoon in a
   zone of relatively minimized MLCINH, as well as confluence/
   convergence with steepening lapse rates and warm advection in low
   levels.  Sporadic hail and damaging gusts are possible.  Forecast
   soundings suggest that sufficient heating will occur, amidst
   generally 60s F surface dew points, to yield MLCAPE 1500-2000 J/kg
   (locally higher), atop a reasonably well-mixed boundary layer.  The
   largely unidirectional/south-southeasterly character of the deep-
   layer flow and lack of speed shear will result in weak vertical bulk
   shear by most measures.  As such, convective mode should be a blend
   of pulse and multicellular in character, with a general decline in
   coverage and intensity likely soon after sunset.
    
   ...KY to GA...
   The remnants of Alberto will retain a well-defined deep-layer
   circulation, but diminishing in strength, as its core region
   proceeds north-northwestward across AL to western middle TN.  IR and
   early VIS imagery indicate that a broad area east through at least
   north-northeast of center will experience cloud breaks today
   sufficient for sustained diabatic heating, amidst rich boundary-
   layer moisture, with surface dew points commonly mid-60s to low-70s
   F.  This should offset modest midlevel lapse rates enough to enable
   MLCAPE to reach near 1000 J/kg through much of the afternoon, away
   from thicker clouds and convection.  

   Kinematically, forecast soundings reasonably suggest 150-250 J/kg
   effective SRH in an arc north through east-southeast of center from
   mid TN over parts of GA, and also, that low-level hodograph size and
   bulk-shear vector magnitudes each generally diminish with northward
   extent over KY and eastward extent from the northern GA/western SC
   area.  Damaging gusts, approaching severe limits, also cannot be
   ruled out from water-loaded downdrafts virtually anywhere in and
   near the circulation envelope containing persistent thunderstorms. 

   Remaining advisories for this system have been assumed by WPC, and
   those (along with local forecast updates) should be followed for
   other hazards related to Alberto.

   ..Edwards/Dial.. 05/29/2018

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