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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.

Tuesday, August 31, 2021

SPC Aug 31, 2021 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook Day 1 Convective Outlook CORR 2 NWS Storm Prediction Center Norman OK 0838 AM CDT Tue Aug 31 2021 Valid 311300Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING FOR PARTS EASTERN AL/GA/FL PANHANDLE AND THE MID-ATLANTIC... CORRECTED AGAIN FOR TSTM LINE IN THE CAROLINAS ...SUMMARY... A couple of tornadoes will be possible today from eastern Alabama into Georgia with the remnants of tropical cyclone Ida. A few storms with damaging winds may also occur across parts of the Mid-Atlantic. ...AL/GA today with remnants of tropical cyclone Ida... The remnants of Ida will move east-northeastward from northwest AL this morning to southeast TN by this evening, as a trailing confluence zone likewise translates eastward from AL to GA. The belt of strongest low-level flow (near 50 kt) and low-level shear (effective SRH up to 300 m2/s2) is coincident with this confluence band. Some modest diurnal destabilization is expected the first half of the day in cloud breaks along and east of the confluence zone, which suggests that some increase in the threat for supercells with a couple of tornadoes is probable by late morning into early afternoon. The threat may persist through the afternoon, but then should decrease by late evening as the remaining belt of stronger flow/shear is no longer in phase with sufficient surface-based buoyancy. ...Northern VA to the Delmarva this afternoon/evening... Surface heating will be strongest the first half of the day, prior to the arrival of the thicker high clouds from the remnants of Ida. At the surface, a weak front sagging southward from PA toward northern VA will provide a focus for thunderstorm development this afternoon into this evening. Moderate buoyancy (MLCAPE of 1500-2000 J/kg) is expected in the warm sector as surface temperatures warm into the 80s with dewpoints at or above 70 F. Though midlevel lapse rates will be poor in the moisture plume aloft emanating from Ida, low-level lapse rates will be relatively steep with daytime heating, and there will be an increase in the 700-500 mb flow into the 40-50 kt range this afternoon. These factors will support a threat for damaging winds with the stronger cells/clusters this afternoon into this evening. ...Northeast KS into western/central MO later today... The remnants of overnight convection are moving southeastward across northwest MO and southeast NE, with the composite outflow a little to the south and west of the ongoing storms. Isolated strong-severe outflow gusts may occur this morning with the southeast NE storms prior to weakening, and then any additional storm development will tend to focus along the remnant outflow and any lingering MCVs from the morning storms. On the larger scale, forcing for ascent will be rather nebulous today beyond the mesoscale influences of the morning convection, so confidence is somewhat low in later storm development/evolution. Thus, will maintain low wind/hail probabilities to reflect the conditional threats in an environment with moderately large buoyancy and effective bulk shear near 25 kt. ..Thompson/Broyles.. 08/31/2021 Read more LIVE: spc.noaa.gov