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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.

Monday, July 3, 2023

SPC Jul 3, 2023 1300 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0747 AM CDT Mon Jul 03 2023 Valid 031300Z - 041200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON THROUGH EARLY TONIGHT FROM NORTHEAST WY INTO SD...AND THIS AFTERNOON/EVENING ACROSS THE MID-ATLANTIC AND CAROLINAS... ...SUMMARY... Scattered damaging winds and large hail are expected across the Mid-Atlantic Region and portions of the northern Great Plains this afternoon into tonight. ...Northern Plains to northern Rockies/Great Basin... A surface cold front across MN/SD and gradual height falls with an approaching midlevel trough will support scattered thunderstorm development, mainly this afternoon into early tonight from northern UT/WY to SD and vicinity. The environment centered on western/central SD will be the most favorable for severe storms based on steep lapse rates, MLCAPE of 1500-2500 J/kg and effective bulk shear of 30-40 kt. The initial storms will likely be supercells this afternoon in SD, and another cluster or two could spread into western SD from WY late this evening into tonight. The primary threats will be isolated very large hail (up to 2.5 inches in diameter) with the initial supercells, and severe outflow gusts of 60-75 mph with both the supercells and later storm clusters. Low-level shear will not be particularly strong and temperature-dewpoint spreads will be relatively large, though an isolated tornado or two could occur with supercells along the front. Farther west into western WY and northern UT/southeast ID, high-based thunderstorm development is expected this afternoon. Inverted-V profiles with modest CAPE and large DCAPE, in combination with 25-40 kt midlevel flow, will support the potential for at least isolated strong-severe outflow gusts of 55-70 mph. ...Mid-Atlantic into the Southeast this afternoon/evening... A slowly weakening midlevel trough and associated surface cyclone/cold front will move eastward over the Appalachians to the Mid-Atlantic and southern New England by tonight. A moist boundary layer with dewpoints in the lower 70s precedes the front, and surface heating in cloud breaks will boost MLCAPE to 1500-2000 J/kg prior to convective initiation around early-mid afternoon. The moderate buoyancy and effective bulk shear of 25-35 kt will favor a mix of multicell clusters and some supercells capable of producing damaging outflow gusts and isolated large hail. Flow will weaken gradually with southward extent, though this will be offset some by hotter surface temperatures and a deeper layer of steep low-level lapse rates into the Carolinas. Moderate-large buoyancy (MLCAPE 2000-3000 J/kg) will extend farther west along/south of the cold front into MS/AL/GA, and as far west as a remnant MCV in OK. Despite weak vertical shear, water-loaded downdrafts in an environment with DCAPE near 1000 J/kg will support the potential for isolated damaging winds this afternoon/evening. ..Thompson/Gleason.. 07/03/2023 Read more CHECK UPDATE ZOOM GRAPHIC