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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, July 12, 2023

SPC Jul 12, 2023 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1251 AM CDT Wed Jul 12 2023 Valid 121200Z - 131200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE CENTRAL PLAINS INTO THE MIDWEST... ...SUMMARY... Severe thunderstorms will be possible across much of Missouri, Illinois, and adjacent portions of the central Plains and Midwest on Wednesday. Damaging winds and large hail should be the main threats, with some potential for significant (75+ mph) severe winds across parts of Missouri and vicinity. ...Synopsis... A strong shortwave trough will continue across the northern Plains through this morning. Strong mid-level winds will be present across parts of the central Plains into the Midwest. At the surface, a boundary will be situated from Nebraska/Iowa becoming more diffuse farther eastward into New England. ...Kansas/Missouri... Convection is expected to be ongoing this morning in parts of Nebraska and Iowa. Outflow from this convection will delimit the northern edge of greater severe risk during the afternoon. To the southwest, a frontal-wave cyclone will move east along the northern baroclinic zone and push a cold front into central/western Kansas. The convective outflow and cold front will serve as foci for additional development during the afternoon. Strong heating of a moist (upper 60s/low 70s dewpoints) airmass will promote strong buoyancy (3000-3500 J/kg MLCAPE). Mid-level lapse rates and low-level moisture will be less favorable with eastward extent to some degree. Shear across the region will be relatively strong given the strength of mid/upper-level winds for this time of year. Initial storms will likely be supercellular and be capable of large to very large hail. As upscale growth occurs, intense winds will be possible, some in excess of 75 mph. A more organized wind threat may occur wherever the buoyancy gradient is located. Enough uncertainty still exists that an increase in unconditional severe wind probabilities is not warranted. ...Midwest... Greater forecast complexity exists for parts of Iowa into Illinois. Convection will likely be ongoing in Iowa early this morning. The overall strength of that activity is somewhat uncertain given a likely more stabilized boundary layer by that time. Remnants of this activity are expected to generally move eastward. Some reintensification is possible from northeast Missouri into central Illinois. However, more modest lapse rates aloft and slightly lower low-level moisture (particularly farther east) should limit the spatial extent of the severe risk with time. Strong/damaging winds will be the primary risk, though isolated large hail is also possible. ...Lower Great Lakes into New England... Storms will be possible along the weak surface boundary during the afternoon. Broad cyclonic flow aloft will provide sufficient shear for marginally organized convection. Damaging winds will be the main hazard from locally strong downbursts. ..Wendt/Thornton.. 07/12/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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CHICAGO UTC-6 during CST (Central Standard Time, e.g., winter)
CHICAGO UTC-5 during CDT (Daylight Savings Time, e.g., summer)