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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.


Wednesday, May 19, 2021

SPC May 19, 2021 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1258 AM CDT Wed May 19 2021 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND NORTHERN HIGH PLAINS... ...SUMMARY... Severe thunderstorms with large hail and wind damage will be possible on Thursday across parts of the central and northern High Plains. Marginally severe thunderstorms may occur outside of the slight risk area in parts of the High Plains and in the Upper Midwest. ...Central and Northern High Plains... An upper-level low will move south-southeastward across the Intermountain West on Thursday as south to south-southwesterly mid-level flow remains over the Rockies and northern High Plains. At the surface, a lee trough will deepen across eastern Wyoming and eastern Colorado as a cold front moves across southeast Montana. Surface dewpoints in the lower to mid 50s F are forecast to the east of the lee trough where a corridor of moderate instability will likely develop by afternoon. Convection is expected to initiate in the higher terrain of eastern Wyoming by mid afternoon, with thunderstorms developing and moving northeastward into the central and northern High Plains. Forecast soundings from Scottsbluff to Rapid City by 00Z/Friday have MLCAPE near 2000 J/kg with 700 to 500 mb lapse rates near 8.0 C/km. This combined with 0-6 km shear in the 30 to 35 kt range will likely support supercells with large hail. Wind damage will also be possible as the storms mature during the early evening. The most likely area for a severe threat would be in northeast Wyoming and southwestern South Dakota where initiation appears more certain. Further south into southwestern Nebraska and far northeast Colorado, initiation will be more conditional. But will maintain a slight risk in this area for now due to a favorable environment that is forecast. ...Upper Midwest... Southwest mid-level flow will be in place across the north-central U.S. as a shortwave trough moves into the western Great Lakes. At the surface, southerly flow will result in moisture advection across the Upper Midwest on Thursday. Surface dewpoints should reach the lower to mid 60s F across parts of upper Mississippi Valley, where weak instability should be in place by late afternoon. A 30 to 40 kt low-level jet is forecast to strengthen and move into the region from the southwest during the afternoon. This will provide the lift necessary for thunderstorm development. Scattered thunderstorms are expected to move northeastward across the upper Mississippi Valley during the late afternoon and early evening. Deep-layer shear is forecast to be adequate for an isolated severe threat, with potential for strong wind gusts and hail. The severe threat should be the greatest in areas that destabilize the most, but instability is expected to remain too weak for organized convection. ..Broyles.. 05/19/2021 Read more LIVE:
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