Temps | Gusts | WU KORD KPWK

CLICK for this month's BIG night sky ...




Cardinal SAT


MOBILE DEVICE? Turn sideways. Weather conditions directly above are near Lakefront. Top tabs refer to O'Hare (official).

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.


Sunday, September 12, 2021

SPC Sep 12, 2021 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0355 AM CDT Sun Sep 12 2021 Valid 151200Z - 201200Z ...DISCUSSION... A large-scale upper trough should continue to move eastward from Ontario and the Great Lakes region across eastern Canada and the Northeast on Day 4/Wednesday. Medium-range guidance continues to indicate that rich low-level moisture will be in place ahead of a surface cold front across the Northeast by Wednesday afternoon. Diurnal heating of this moist low-level airmass should foster at least moderate instability. Even though the strongest ascent and mid-level winds associated with the upper trough may be focused to the north in eastern Canada, there should be enough deep-layer shear and low-level convergence along the front to support isolated to scattered severe storms Wednesday afternoon and evening. If storms can congeal into one or more lines along/ahead of the front, then severe/damaging winds would probably be the main threat. There has been enough consistency in guidance to support the introduction of 15% severe probabilities for Day 4/Wednesday across parts of the Northeast, where the most favorable overlap of instability and shear is forecast ahead of the front. Some medium-range guidance suggests that another upper trough may develop eastward across central Canada and the north-central CONUS on Day 5/Thursday. There may be enough low-level moisture return ahead of this feature to support surface-based storms and perhaps an organized severe risk across parts of the northern/central Plains into the Upper Midwest ahead of a cold front. Regardless, there is still far too much uncertainty regarding the evolution of the upper trough, placement of the surface front, and overall storm coverage to include a 15% severe area for Thursday at this time. From Day 6/Friday through the end of the forecast period, differences in the synoptic-scale upper pattern across the CONUS become apparent in medium-range guidance, suggesting low predictability. Read more LIVE:
SUNRISE AND SUNSET TIMES IN UTC (if you're not logged in to Google)
CHICAGO UTC-6 during CST (Central Standard Time, e.g., winter)
CHICAGO UTC-5 during CDT (Daylight Savings Time, e.g., summer)