Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1237 AM CDT Tue Jul 14 2020 Valid 141200Z - 151200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE SOUTH-CENTRAL HIGH PLAINS TO THE UPPER MIDWEST... ...SUMMARY... Strong to severe storms are expected Tuesday from the south-central High Plains to the Upper Midwest. ...Upper Midwest... Weak height falls will spread across the upper MS Valley region during the day ahead of a short-wave trough that should extend from the MB/ON border into the eastern Dakotas by 15/00z. Models are in general agreement that a surface front should precede the short wave, advancing into northwestern WI - southeast MN - western IA by early afternoon. This boundary should serve as the focus for strong to severe thunderstorm development during the afternoon/evening hours. Prior to this development, substantial convection may be ongoing across portions of eastern SD into southern MN. This activity will likely be the remnants of ongoing convection currently observed over western SD. Extensive cloud debris and decaying precip shield should limit boundary layer heating across much of this region. Even so, a narrow corridor of somewhat steeper low-level lapse rates should evolve within the near-frontal warm sector from southwest IA into west-central WI. This is expected to aid buoyancy for potentially more robust convection. With a 60kt 500mb speed max forecast to approach western WI by late afternoon, wind profiles should support organized rotating updrafts and isolated supercells are expected. While a few tornadoes can not be ruled out, the primary severe risks will be wind/hail. ...South-central High Plains... Surface pressures will rise across the northern/central High Plains early in the period in the wake of ejecting short wave. Extensive precipitation within the post-frontal environment across SD should enhance the frontal surge which should advance into central KS, arcing into southeast CO by mid afternoon. Intense surface heating south of the wind shift will result in surface temperatures soaring well above 100F across the OK/TX Panhandle region. Convective temperatures will be easily breached in these areas. Frontal/upslope convergence is expected to aid thunderstorm development across southeast CO into the northern TX Panhandle. CAMs are reasonably consistent in this scenario and one or more thunderstorm clusters should spread east-southeast into the evening hours. There is some concern that severe wind probs may need to be increased across this region to account for high-based convection maturing downstream into an environment that will be quite moist/unstable. This will be considered in future updates. ...Southern New England... Seasonally cool upper trough will shift east across New England during the day. Latest guidance suggests low-level lapse rates will steepen quickly beneath this trough from CT into southern VT/NH. Forecast soundings suggest convection will develop early then drift southeast within a weak-flow regime. While marginally severe hail could be noted, the primary risk with this diurnally driven activity will be locally gusty winds. ..Darrow/Lyons.. 07/14/2020Read more
from SPC Forecast Products http://www.spc.noaa.gov/products/outlook/day1otlk_1200.html
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