Dec 3, 2017 1730 UTC Day 2 Convective Outlook
Updated: Sun Dec 3 17:30:35 UTC 2017 (20171203 1730Z Day 2 shapefile | 20171203 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20171203 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
MARGINAL 78,241 6,466,539 St. Louis, MO...Springfield, MO...Springfield, IL...Columbia, MO...Fort Smith, AR...
Probabilistic Graphic
20171203 1730 UTC Day Probabilitic Graphic
Probability of severe weather within 25 miles of a point.
Hatched Area: 10% or greater probability of significant severe within 25 miles of a point.
Day 2 Prob. Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
5 % 77,352 6,448,767 St. Louis, MO...Springfield, MO...Springfield, IL...Columbia, MO...Fort Smith, AR...
   SPC AC 031730

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1130 AM CST Sun Dec 03 2017

   Valid 041200Z - 051200Z

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS EXTENDING FROM
   EASTERN OKLAHOMA AND WESTERN ARKANSAS TO THE MID MISSISSIPPI
   VALLEY...

   ...SUMMARY...
   A few thunderstorms may produce strong, gusty winds from parts of
   the southern Plains and western Arkansas to the mid Mississippi
   Valley Monday evening.

   ...Synopsis...
   A pattern change will continue to evolve across much of North
   America today into Monday, given the expectation for large-scale
   amplification of the mid- to upper-level flow.  Models are in good
   agreement with this pattern change and amplification, with a broad
   zone of cyclonic mid-level flow expanding eastward across the
   central U.S. Monday, as a potent impulse lifts from the central
   Plains northeastward to the upper Great Lakes, and another dives
   south into the Dakotas/Upper Midwest Monday night.  The resultant
   surface pattern will feature an intense deepening cyclone
   (especially Monday night), tracking northeast across the upper MS
   Valley toward northern Ontario.  Strengthening west/southwesterly
   500-mb winds across OK/KS through the mid MS/OH Valleys to the Great
   Lakes will support an attendant cold front sweeping eastward from
   the central and southern Plains.  By 12Z Tuesday, the cold front
   should extend from Lower MI and OH through the Mid South to East and
   south-central TX.

   The neutral orientation of the parent large-scale trough and the
   combination of stronger forcing for ascent, attendant to the
   progressive lead shortwave trough and track of the surface low,
   remaining north of much of the marginal severe risk will result in
   veering of low-level winds along and ahead of the cold front.  This
   suggests convective development should initially be along the front,
   with a tendency for forcing to become anafrontal Monday night,
   especially with southward extent.  

   Ahead of the cold front, modest low-level moisture (e.g., surface
   dew points in the upper 50s and lower 60s) will stream
   north/northeastward during the day.  This combined with limited
   surface heating (due to warm-sector cloudiness) and the presence of
   weak lapse rates suggests a narrow corridor of surface-based CAPE
   around 250-600 J/kg should materialize from eastern Oklahoma and the
   Ark-La-Tex to the mid Mississippi Valley.  A thin, low-topped band
   of thunderstorms is expected to develop by late afternoon or early
   evening hours and accelerate eastward with the front.  Despite the
   meager buoyancy, considerable low/mid-level flow upwards of 40-60 kt
   may support a few stronger gusts in the more robust convective
   elements. In addition, the strength of low-level shear suggests a
   tornado threat cannot be ruled out.  Marginal severe probabilities
   will be maintained given the weak overall instability.  Some
   expansion to the north and south with the marginal risk area may be
   needed in later outlooks.  Despite weaker instability into
   west-central IL, stronger forcing for ascent and some potential for
   surface-based parcels suggest a wind threat could occur, while
   farther south, greater buoyancy and sufficient low-level shear may
   support a severe storm prior to the convection becoming anafrontal.

   ..Peters.. 12/03/2017

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