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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.

Friday, August 20, 2021

SPC Aug 20, 2021 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1259 AM CDT Fri Aug 20 2021 Valid 211200Z - 221200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Severe-weather risk appears low for Saturday across the CONUS. ...Synopsis... As mid-/upper-level trough moves across the Intermountain West on Saturday, a second feature -- initially crossing the north-central U.S. -- will move quickly northeastward into/across Ontario. Meanwhile, in the East, a weak upper low -- centered over the Mid-Atlantic States -- and surrounding cyclonic flow will linger east of the Mississippi. At the surface, a cold front will move slowly eastward across the Upper Great Lakes as the parent low deepens northward across Ontario, while trailing portions of the boundary stall across the central Plains. Meanwhile, a weak cold front is forecast to advance across the Intermountain West. In the east, a rather nondescript low-level pattern is progged, as Tropical Storm Henri -- likely to have become a hurricane by Day 2 per NHC forecasts -- remains offshore over the western Atlantic. ...Northern Utah/western Wyoming and vicinity... As the upper trough shifts slowly eastward into the Intermountain region, slight cooling aloft accompanying the trough will facilitate weak destabilization as diurnal heating maximizes by late afternoon. This will support scattered thunderstorm development across a rather broad zone from Idaho/western Montana to Utah/Colorado. Moderately strong mid-level southwesterlies are expected atop much of this area, which should support a few locally stronger storms/convective bands. Aided by evaporative effects within the well-mixed boundary layer, winds may reach or exceed severe levels in a few areas. At this time, coverage of severe wind is expected to be sparse, and thus a risk area will not be introduced. ...Central Gulf Coast states and vicinity... Thunderstorms are forecast to be ongoing at the start of the period, from the Mid Mississippi Valley area southeastward into parts of Mississippi and Alabama. As a weak mid-level disturbance embedded within a belt of moderate northwesterly flow aloft shifts southeastward across Mississippi and Alabama, a few semi-organized bands of storms may evolve within the broader area of disorganized convection. Aided by a moist/amply unstable environment and the moderate northwesterlies aloft, any bands that can evolve along the leading edge of small cold pools, could become capable of locally strong/gusty winds. At this time, uncertainty regarding this scenario, and coverage of any possibly stronger gusts, precludes introduction of a risk area at this time. ..Goss.. 08/20/2021 Read more LIVE: