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Weather conditions on bar directly above are near Lakefront. Tabs under Moon Phases refer to O'Hare (official).

Archives for SPC Convective outlook are updated daily with a live map a the beginning of the article. Touch or click map to get possible update, and follow link at end of article for referral to NOAA/NWS Storm Prediction Center. Archives for Chicago's hourly weather data were updated 24-48 hours after end of each day prior to Dec. 2020.

Monday, May 9, 2022

SPC May 9, 2022 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1250 AM CDT Mon May 09 2022 Valid 091200Z - 101200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE UPPER MISSISSIPPI VALLEY... ...SUMMARY... A complex and conditional severe risk will accompany multiple rounds of thunderstorms through the period across the Upper Mississippi Valley this morning through tonight. Large hail, damaging gusts, and a few tornadoes are all possible. ...Synopsis... A broad cyclonic upper flow regime will be in place across the western half of the CONUS today, with an embedded mid-level impulse ejecting into the Upper Mississippi Valley this afternoon and evening. A 990 mb surface low should be established across central SD this morning, and is poised to deepen considerably through the day while tracking north-northeast towards Manitoba. Near and ahead of the surface low, rapid northward advection of deep low-level moisture should foster increasing buoyancy across the warm sector given the presence of steep mid-level lapse rates. Scattered thunderstorms (some strong to severe) are expected to be in progress across the northern Plains at the start of the period, which will complicate later afternoon/evening severe potential ahead of an approaching cold front across the Upper Mississippi Valley. However, modest convergence along the cold front, preceded by some airmass recovery during the day, suggests that a conditional risk for more widespread strong to severe thunderstorms will exist later in the period. ...Upper Mississippi Valley - Early to Mid Morning... The leading edge of an 80+ kt southwesterly 500 mb jet streak will be overspreading the nose of a 50-60 kt 850 mb jet over the eastern Dakotas at the start of the period (12Z), where robust elevated convection will already be in place. While most guidance indicates that these storms will be rooted around 850 mb, 50-60 kts of effective bulk shear and well over 2000 J/kg MUCAPE should foster the continued eastward progression of these elevated storms. Given 8+ C/km mid-level lapse rates, some severe hail will be possible with the strongest storms moving from northeast SD into central MN. Modest damaging-gust potential may also accompany storms where mid-morning boundary-layer mixing may foster more efficient downward momentum transport. ...Minnesota into far northwest Wisconsin - Afternoon... A conditional severe risk may accompany any storms that manage to intensify ahead of the cold front later into the afternoon/early evening hours if airmass recovery can occur behind initial elevated storms along the nose of the low-level jet. Guidance consensus depicts strong tropospheric wind fields across MN by afternoon as the breadth of the mid-level jet streak overspreads the Upper Mississippi Valley and contributes to further intensification of the surface low (centered over east ND by 18Z) and associated low-level flow fields. Several guidance members depict long, curved hodographs ahead of the cold front during the afternoon, which would support organized storm structures (including supercells) capable of all hazards. Despite strong low-level warm/moist-air advection anticipated through the day, significant airmass modification would be required to generate appreciable instability to support a more substantial severe threat. Given uncertainties in airmass recovery, higher severe probabilities have been withheld for now, but may need to be introduced in future outlooks if greater recovery becomes apparent. ...Southern Minnesota into Iowa and western Wisconsin - Evening... Greater upper support will glance the Midwest along with the core of the mid-level jet streak. As such, the greatest source of lift for convection will be from low-level convergence associated with the cold front, which will sweep across the Mississippi Valley during the afternoon and evening hours. Convective inhibition is expected to erode within a narrow corridor of the warm sector ahead of the cold front by 00Z, from central and eastern IA into southern MN/western WI. Mid to upper 60s F surface dewpoints overspread by a mixed boundary layer and 8 C/km mid-level lapse rates will support 2000-3000 J/kg MLCAPE. Some veering with height through the tropopause will yield modestly curved/elongated hodographs. With convection expected to be relatively isolated ahead of the cold front, small linear segments/semi-discrete supercells are expected by late afternoon and will progress eastward through the evening. Large hail, damaging gusts, and a few tornadoes may accompany the more dominant, longer-lived storms. ..Squitieri/Darrow.. 05/09/2022 Read more CHECK UPDATE ZOOM GRAPHIC