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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.


Thursday, April 20, 2023

SPC Apr 20, 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 1256 AM CDT Thu Apr 20 2023 Valid 201200Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM CENTRAL TX INTO THE MID MS VALLEY... ...SUMMARY... Scattered severe thunderstorms capable of hail and severe gusts are possible from parts of mid Mississippi Valley southwestward into the Ark-La-Tex and central Texas this afternoon and tonight. ...Synopsis... A longwave upper trough will deepen over the central CONUS today. Within the larger-scale trough, one shortwave will move from the central Plains toward the upper Great Lakes, while another will move into the southern Plains tonight. A surface low will propagate east-northeastward toward the upper Midwest, as a cold front sweeps through the Plains and eventually the Ozarks. ...Southern Plains into the ArkLaTex... Widely scattered thunderstorm development is expected this afternoon along a southeastward-moving cold front from parts of Texas toward the Ozark Plateau. Moderate to locally strong buoyancy will support intense updrafts, especially along the Texas portion of the front, though deep-layer shear may be somewhat marginal for much of the day. Very large hail will be the initial threat, with some potential for upscale growth this evening and a corresponding risk of severe/damaging gusts. Low-level flow/shear across TX is expected to remain rather modest, but may be sufficient for a threat of a tornado or two with any sustained supercells. Prefrontal diurnal development will be possible from east-central into southeast TX within a weakly capped environment, with the strongest cells in this region capable of hail, locally damaging gusts, and possibly a tornado. Later tonight, one or more thunderstorm clusters may move toward the upper TX Gulf Coast, with a risk of damaging gusts, isolated hail, and possibly a brief tornado or two. Uncertainty remains regarding the timing of the cold front across Texas, and the magnitude of the severe threat late tonight with any upscale growth toward the Gulf Coast. Depending on shorter-term observational and guidance trends, higher hail and/or wind probabilities may eventually be needed. ...Upper Midwest into the Ozarks... Substantial early-day convection is expected across parts of IA/MO/WI/IL. Some threat of isolated hail and/or strong/damaging gusts may accompany the morning storms. In the wake of the early storms, renewed development is expected along the front from the mid MS Valley into the Ozark Plateau. Front-parallel flow from AR into MO will likely result in a messy convective mode, but instability and deep-layer shear will be sufficient for a hail and wind threat with the strongest storms. Farther north into eastern IA and northern IL, there is greater uncertainty regarding the recovery of instability in the wake of morning storms, and guidance is generally more muted regarding the intensity of frontal convection in this area. However, wind profiles will be favorable for supercells in this region, and a conditional all-hazard risk will develop if any supercells can be sustained during the afternoon/early evening. ..Dean/Bentley.. 04/20/2023 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)