Oct 2, 2017 0600 UTC Day 1 Convective Outlook
Updated: Mon Oct 2 05:46:39 UTC 2017 (20171002 1200Z Day 1 shapefile | 20171002 1200Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20171002 1200 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 138,644 5,537,080 Minneapolis, MN...St. Paul, MN...Sioux Falls, SD...Sioux City, IA...Bloomington, MN...
Probabilistic Tornado Graphic
20171002 1200 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
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
20171002 1200 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
5 % 60,801 4,305,050 Minneapolis, MN...St. Paul, MN...Sioux City, IA...Bloomington, MN...Plymouth, MN...
Probabilistic Large Hail Graphic
20171002 1200 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
5 % 86,081 1,473,170 Sioux Falls, SD...Sioux City, IA...Grand Island, NE...Kearney, NE...North Platte, NE...
   SPC AC 020546

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1246 AM CDT Mon Oct 02 2017

   Valid 021200Z - 031200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS
   AFTERNOON INTO TONIGHT ACROSS PARTS OF THE CENTRAL PLAINS INTO THE
   MIDDLE MISSOURI AND UPPER MISSISSIPPI VALLEYS...

   ...SUMMARY...
   Strong thunderstorms may impact a corridor from the central Plains
   through the middle Missouri and upper Mississippi Valleys late today
   into tonight, accompanied by at least some risk for severe weather.

   ...Synopsis...
   Mid/upper flow will remain amplified, but it appears that
   large-scale upper troughing now present across much of western
   Canada and the U.S. will undergo considerable deformation during
   this period.  Models suggest that this will occur as seasonably
   strong large-scale ridging builds across much of the Gulf of Mexico
   and Gulf Coast states northward through the Ohio Valley, Great Lakes
   and Atlantic Seaboard, while the crest of sharp ridging off the
   Pacific coast also noses inland across the Canadian Rockies and
   Prairies.

   Within the residual cyclonic regime, mid-level height falls
   associated with one short wave impulse are forecast to spread across
   and northeast of the North Dakota/Manitoba border by late this
   afternoon.  Another short wave trough emerging from the Great Basin
   is forecast to accelerate northeastward across the Colorado Rockies
   into the northern Plains late today into tonight, but models
   indicate that this will occur in the presence of larger-scale
   mid-level height rises, which may commence across the central Plains
   and mid/lower Missouri Valley into the northern Plains and upper
   Mississippi Valley by late this afternoon.

   In lower levels, a surface front reaching the Upper Midwest, mid
   Missouri Valley and central Plains appears likely to stall with some
   erosion of its shallower leading edge due to at least some
   combination of insolation and strong low-level warm advection.  Most
   guidance indicates a deepening surface low within lee troughing
   across southeastern Colorado during the day, before a modest wave
   eventually develops and migrates northeastward along the front
   across the middle Missouri into upper Mississippi Valleys tonight. 
   This may be accompanied by some further moistening along the front,
   from the central Plains into the upper Mississippi Valley, but it
   appears that higher moisture content air emanating from the Gulf of
   Mexico may only reach southeastern portions of the Plains and Ozark
   Plateau/lower Missouri Valley by late tonight. 

   ...Central Plains into middle Missouri and upper Mississippi
   Valleys...
   The evolving large-scale pattern, particularly at mid/upper levels,
   suggests that forcing for ascent supportive of convective
   development will be generally focused to the cool side of the
   surface frontal zone through this period.  However, a plume of
   relatively warm elevated mixed-layer air may contribute to at least
   modestly steep mid-level lapse rates within a narrow post-frontal
   corridor, where vertical shear and CAPE within the elevated
   potential convective layer could support supercells.  It may also be
   capping and suppressive of thunderstorm development until mid/upper
   forcing associated with the perturbation emerging from the Great
   Basin begins impacting the region.  This may not be until this
   evening, but initial elevated thunderstorm development probably will
   be accompanied by some risk for severe hail, before storms increase
   in coverage and tend to train along the frontal zone by late this
   evening.

   Any sustained thunderstorm development near or just to the warm side
   of the surface front may be accompanied by more appreciable severe
   weather potential, including the risk for potentially damaging wind
   gusts, and perhaps a risk for tornadoes.  However, guidance
   continues to suggest that the probabilities for this are still low
   to negligible (particularly with regard to tornadoes).

   ..Kerr/Karstens.. 10/02/2017

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