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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, April 20, 2022

SPC Apr 20, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Wed Apr 20 2022 Valid 202000Z - 211200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF EASTERN OKLAHOMA AND FAR SOUTHEASTERN KANSAS... ...SUMMARY... The greatest severe-weather threat for today and this evening appears to be over portions of central/eastern Oklahoma into the western Ozarks region, where up to a few supercells with hail, isolated severe gusts and a tornado are possible. ...20z update Central/Southern Plains... Considerable uncertainty still remains on the potential for discrete convective initiation along the dryline across portions of central/eastern OK into southeastern KS this afternoon/evening. Regional water vapor imagery shows a well-defined, compact vort max moving across the southern Plains. Lift from this feature along with strong heating along the dryline may support a few supercells late this afternoon into this evening. Deeper mixing has allowed the dryline to move slightly farther eastward than depicted by most morning hi-res guidance. Visible imagery trends and veering surface flow around the OKC metro suggest the greater severe threat may develop across eastern OK. Area RAP/HRRR soundings continue to show a favorable environment for supercells, particularly along the triple point/warm front stretching from far southeastern KS to eastern OK. Mid-level lapse rates of 7-8 C/km and large hodographs will support a risk for large to very large hail with any supercells able to become established. Backed surface flow sheltered from stronger mixing beneath the lingering stratus deck slowly eroding across eastern OK may also support low-level mesocyclones capable of a tornado or two with the more dominant storms should they develop this evening. Th previous forecast remains valid with no changes for portions of the Pacific Northwest. ..Lyons/Mosier.. 04/20/2022 .PREV DISCUSSION... /ISSUED 1117 AM CDT Wed Apr 20 2022/ ...Eastern OK and Vicinity... Water vapor imagery shows a shortwave trough moving into western KS. Ahead of this trough, strong heating is occurring west of the surface dryline over OK, helping to mix it eastward. By mid/late afternoon, the dryline will extend from a low in southeast KS into east-central OK, with a very moist/unstable air mass present in the warm sector. A capping inversion is also evident in forecast soundings and in the numerous wave clouds present in visible satellite imagery. The confidence/coverage of convective initiation remains the main forecast problem today. 12z model guidance continues to show a diversity of solutions, ranging from several storms along the dryline from southeast KS into southern OK, to virtually no storms. Forecast soundings along the dryline show considerable low-level and deep-layer shear that would be favorable for discrete supercell development capable of very large hail, damaging winds, and a tornado or two. Soundings also show a persistent but weak cap. Therefore, will maintain the ongoing MRGL/SLGT areas with no changes. However, will add a 5% tornado risk area given the conditional risk if a storm or two can form. The primary risk should be in the 22-03z window, before diurnal cooling strengthens inhibition again. ...Western OR... A shortwave trough off the coast of southwest OR will rotate northeastward later today and affect the Cascades and coastal areas. 12z CAM solutions suggest a rather compact system with a focused low-level jet tracking northward across the region late this afternoon and evening. Enhanced low-level shear/forcing may be sufficient for a few rotating showers or thunderstorms capable of gusty winds or a brief tornado spin-up. Instability will be quite weak, and it is uncertain whether updrafts will be strong enough to take advantage of the low-level wind fields. Read more CHECK UPDATE ZOOM GRAPHIC