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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.

Tuesday, May 17, 2022

SPC May 17, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Tue May 17 2022 Valid 172000Z - 181200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF CENTRAL/EASTERN KANSAS INTO SOUTHEASTERN NEBRASKA...NORTHWESTERN MISSOURI...AND FAR SOUTHWESTERN IOWA... ...SUMMARY... Scattered severe thunderstorms are expected across a portion of the central states through tonight. The area to be most likely impacted, with potentially multiple rounds of severe weather, is focused on parts of Nebraska, Kansas, Iowa, and Missouri. A few tornadoes, significant damaging winds, and very large hail are possible. ...20Z Update... Primary change with this update was to expand 30% wind probabilities and the corresponding Enhanced Risk into more of north-central and central KS. It appears increasingly likely that a substantial reservoir of buoyancy will become established by early this evening to the south of ongoing convection across southeastern NE/western IA and east of a dryline becoming established in western KS. MLCAPE of 3000-4000+ J/kg will likely be in place by this evening across central/eastern KS as low-level moisture continues to gradually return northward and rather steep mid-level lapse rates remain present over the warm sector. Convection should increase in coverage later this evening from south-central NE into central KS as a southerly low-level jet strengthens. A rather quick transition to a mainly linear mode should occur within a couple of hours of convective initiation. Severe/damaging winds should become the main threat this evening and early tonight as thunderstorms spread eastward from central into eastern KS and southeastern NE. Some of these severe winds could be 75+ mph given the large instability forecast, although the loss of daytime heating and gradual stabilization of the boundary layer still lends some uncertainty to the overall magnitude of the severe wind threat. For more information on the near-term severe risk from far eastern NE into southwestern IA and northern MO, see Mesoscale Discussion 800. ..Gleason.. 05/17/2022 .PREV DISCUSSION... /ISSUED 1130 AM CDT Tue May 17 2022/ ...Central States... Low forecast confidence given potential for a variety of convective scenarios playing out through the period, as illustrated by marked spread among 12Z guidance. Given this uncertainty, have largely maintained the cat 3-ENH risk area, which remains more closely aligned with morning HRRR runs. A complex, largely zonal flow regime with subtle embedded speed maxima will affect the central CONUS. Primary feature of initial interest is a low-amplitude upper trough near the CO/KS/NE border area expected to move east to the IA/MO border area by early evening. Elevated convection within a persistent low-level warm theta-e advection regime has supported scattered storms mainly over eastern NE. While pronounced insolation is occurring to the south of this activity, surface dew points remain limited to the mid to upper 50s. Richer moisture characterized surface dew points greater than 65 F remains confined across south-central/southeast KS, given the impacts of overnight convection and subsequent MCV over the Ozark Plateau. But moisture recovery through both advection and evapotranspiration will occur farther north. Some CAMs suggest that just-in-time moisture return might support an emerging MCS emanating out of the midday elevated clusters in eastern NE with flanking southwest convective development near the NE/IA/MO/KS border vicinity later this afternoon. If this occurs, it would likely evolve southeast along the warm front. In the wake of the initial low-amplitude upper trough, weak lee cyclogenesis is expected over southwest KS with a dryline south, and a strengthening frontal zone extending north-northeast into central NE. Isolated to scattered thunderstorms will generally be confined to the post-frontal upslope regime over the central High Plains and along the dryline in western KS during the late afternoon. Into early evening, convection should increase along the frontal zone into central NE. Largest buoyancy will be most probable across eastern KS, initially displaced east-southeast of the expected surface front/dryline development corridors. In addition, most guidance indicates that belts of enhanced 500-250 mb westerlies will generally be prominent along the KS/OK border latitude in the southern stream and the NE/SD border latitude in the northern stream. This further suggests that convective mode will likely be quite messy, and within the exit region of a pronounced southern Great Plains low-level jet, the scenario should foster relatively quick upscale growth into multiple MCSs tonight. Primary threats will initially be dominated by large hail and transition to mostly a severe wind threat that gradually becomes more isolated overnight. Read more CHECK UPDATE ZOOM GRAPHIC
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