Dec 4, 2017 2000 UTC Day 1 Convective Outlook
Updated: Mon Dec 4 19:37:16 UTC 2017 (20171204 2000Z Day 1 shapefile | 20171204 2000Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20171204 2000 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 82,364 4,806,976 Springfield, MO...Cedar Rapids, IA...Davenport, IA...Columbia, MO...Fort Smith, AR...
MARGINAL 127,195 10,208,222 Memphis, TN...Tulsa, OK...St. Louis, MO...Little Rock, AR...Rockford, IL...
Probabilistic Tornado Graphic
20171204 2000 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
2 % 104,958 6,065,435 Little Rock, AR...Springfield, MO...Cedar Rapids, IA...Davenport, IA...Columbia, MO...
Probabilistic Damaging Wind Graphic
20171204 2000 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
15 % 82,232 4,802,584 Springfield, MO...Cedar Rapids, IA...Davenport, IA...Columbia, MO...Fort Smith, AR...
5 % 126,844 10,178,385 Memphis, TN...Tulsa, OK...St. Louis, MO...Little Rock, AR...Rockford, IL...
Probabilistic Large Hail Graphic
20171204 2000 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 % 70,938 4,474,734 Tulsa, OK...Springfield, MO...Independence, MO...Broken Arrow, OK...Fort Smith, AR...
   SPC AC 041937

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   0137 PM CST Mon Dec 04 2017

   Valid 042000Z - 051200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS
   AFTERNOON AND EVENING ACROSS PARTS OF EASTERN OKLAHOMA AND NORTHWEST
   ARKANSAS THROUGH MISSOURI...EASTERN IOWA...NORTHWESTERN ILLINOIS AND
   SOUTHWESTERN WISCONSIN...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS
   SURROUNDING AREAS OF THE PLAINS AND OZARK PLATEAU INTO THE UPPER
   MIDWEST...

   ...SUMMARY...
   Isolated strong to severe thunderstorms are expected across eastern
   Oklahoma and the Ark-La-Tex region, northward across Missouri into
   portions of the Upper Midwest, late this afternoon into tonight.

   ...20Z Outlook Update...
   Severe weather categorical and probabilistic areas have been
   expanded westward some to account for the current frontal position,
   and some lingering uncertainty concerning exact timing of storm
   initiation late this afternoon.  The axis of strongest pre-frontal
   surface heating currently extends northward near/east of
   Bartlesville, OK through the Chillicothe, MO area, and seems likely
   to provide the focus for strongest storm development through early
   evening.  Modest boundary layer destabilization is also ongoing
   within a narrow pre-frontal corridor as far north as the deepening
   surface low center, now near Minneapolis, and severe categorical/
   probabilistic lines have been expanded northward through the Upper
   Midwest to account for this.

   ..Kerr.. 12/04/2017

   .PREV DISCUSSION... /ISSUED 1027 AM CST Mon Dec 04 2017/

   ...Synopsis...
   A surface cyclone in southwest MN this morning will move toward Lake
   Superior by tonight, with rapid deepening expected in response to
   strong deep-layer forcing for ascent within the left exit region of
   a 130 kt upper jet streak.  An associated surface cold front will
   surge southeastward in the wake of the cyclone and cross the mid MS
   Valley and southern Plains by the end of this forecast period.  In
   advance of the cold front, a narrow moist sector with boundary-layer
   dewpoints in the mid 50s into IA and mid-upper 60s in TX, will
   continue to spread northeastward through the day.  Though surface
   heating will be tempered by widespread clouds, the low-level
   moisture and remnant steep midlevel lapse rates will support at
   least weak surface-based buoyancy as far northeast as parts of
   IA/IL.

   ...Mid MS Valley to the Ozarks through tonight...
   Thunderstorm development is expected in a band along the cold front
   from mid-late afternoon (21-23z).  It appears there will be a 2-4
   hour window of opportunity for damaging winds (and perhaps an
   isolated tornado) this evening as far northeast as southeast IA and
   northwest IL, given buoyancy rooted at the surface and 50-60 kt flow
   just above the surface.  Strong deep-layer shear may support
   embedded supercells within the line for a few hours this evening. 
   The frontal convection will maintain intensity longer from eastern
   OK into AR, where mid 60s dewpoints will drive at least weak
   buoyancy into tonight.  However, the convection will become more
   anafrontal with time and low-level flow will veer/weaken, which will
   limit the southwestward extent of any severe-storm threat.

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z