Aug 14, 2018 1730 UTC Day 2 Convective Outlook
Updated: Tue Aug 14 17:31:32 UTC 2018 (20180814 1730Z Day 2 shapefile | 20180814 1730Z Day 2 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20180814 1730 UTC Day 2 Outlook Graphic
Day 2 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 24,824 85,506 North Platte, NE...Scottsbluff, NE...
MARGINAL 289,609 15,427,343 Indianapolis, IN...Colorado Springs, CO...St. Louis, MO...Aurora, CO...Louisville, KY...
Probabilistic Graphic
20180814 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
15 % 24,824 85,506 North Platte, NE...Scottsbluff, NE...
5 % 289,609 15,427,343 Indianapolis, IN...Colorado Springs, CO...St. Louis, MO...Aurora, CO...Louisville, KY...
   SPC AC 141731

   Day 2 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1231 PM CDT Tue Aug 14 2018

   Valid 151200Z - 161200Z


   A few severe storms will be possible mainly over the central High
   Plains Wednesday afternoon and evening. Isolated strong to severe
   storms will also be possible over the middle Mississippi Valley
   region and parts of New England.

   A closed mid/upper-level low over NY/PA today will develop into a
   open shortwave trough as it moves eastward off the East Coast
   Wednesday morning. A separate shortwave trough over Ontario is
   likewise forecast to move eastward across southern Quebec by
   Wednesday evening. An upper trough/low initially over IA/MO will
   continue east-northeastward across the mid MS Valley and Lower Great
   Lakes as it slowly de-amplifies through the period. Another upper
   low with a 40-50 kt embedded west-northwesterly mid-level jet should
   develop eastward across SD/NE as upper ridging remains over much of
   the western CONUS. At the surface, a cold front will slowly advance
   southeastward across parts of New England, while a weak low develops
   northeastward across the mid MS Valley/Lower Great Lakes in tandem
   with the previously mentioned devolving upper trough/low. An
   ill-defined cold front attendant to this surface low should stall
   over parts of the southern/central Plains by Wednesday afternoon.

   ...Southern/Central Plains...
   Modest east-northeasterly low-level winds should reside to the north
   of a weak cold front across western SD/NE Wednesday afternoon. As
   large-scale ascent associated with an upper low overspreads this
   region, isolated to scattered thunderstorms should form along
   along/south of this boundary across western/central NE. With MLCAPE
   up to 1500-2000 J/kg expected owing to diurnal heating and at least
   modestly steepened mid-level lapse rates, and effective bulk shear
   of 40-50 kt, supercells will probably be the predominant initial
   storm mode. Isolated large hail and damaging winds should be the
   main severe threats, although a tornado or two may be possible along
   the weak boundary where surface winds are backed to an
   easterly/northeasterly direction, locally enhancing 0-1 km SRH. A
   southerly low-level jet may strengthen by early Wednesday evening
   across NE, and some potential for upscale growth into a small bowing
   line segment may exist.

   Farther south across eastern CO/western KS and parts of the southern
   High Plains, additional thunderstorms should develop over the higher
   terrain and then spread eastward through the early evening.
   Mid-level flow will be weaker across these areas, and resultant
   effective bulk shear will be limited to mainly the 25-35 kt range.
   Still, multicells will probably pose an isolated strong/damaging
   wind threat, along with some potential for large hail. The severe
   threat will likely wane with eastward extent Wednesday evening as
   convective inhibition increases.

   ...Eastern OK into the Mid MS Valley and Lower OH Valley...
   Mid-level lapse rates will be very poor across much of the mid MS
   Valley into the lower OH Valley and vicinity on Wednesday as a
   subtropical airmass characterized by precipitable water values of
   1.75-2+ inches remains in place. Thunderstorms will also likely be
   ongoing at the start of the period over parts of these regions,
   which coupled with substantial cloudiness and the poor lapse rates
   should generally limit surface heating and related instability. Even
   so, a belt of 30-40 kt flow in the 850-500 mb layer may allow for
   some transient storm organization. Isolated strong/gusty winds may
   occur with any thunderstorms that can redevelop Wednesday afternoon
   and spread east-northeastward in one or more small line segments.

   ...New England...
   Isolated to perhaps widely scattered thunderstorms should develop
   along/ahead of a cold front by Wednesday afternoon across southern
   Ontario/Quebec, and subsequently spread eastward into parts of
   northern NY/VT/NH and ME. Although surface temperatures may not
   become overly warm as mid-level cloudiness somewhat limits surface
   heating, a moist low-level airmass is expected to remain in place
   across this area, with surface dewpoints in the mid to upper 60s
   common. Even though mid-level lapse rates should remain weak,
   sufficient diurnal heating coupled with the moist low levels should
   result in MLCAPE up to  1500 J/kg by peak heating. The strongest
   mid-level winds associated with a shortwave trough may lag the cold
   front slightly, but around 30-35 kt of effective bulk shear should
   prove enough to support at least modest storm organization, with
   multicells capable of producing isolated strong to locally damaging
   winds probably the main severe threat.

   Tornado:   2%     - Marginal
   Wind:     15%     - Slight
   Hail:     15%     - Slight

   ..Gleason.. 08/14/2018