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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, April 11, 2022

SPC Apr 11, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0243 PM CDT Mon Apr 11 2022 Valid 112000Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS EASTERN OKLAHOMA INTO ARKANSAS... ...SUMMARY... Isolated to scattered severe thunderstorms are expected later this afternoon into early tonight from parts of northeast Texas to the Ozarks and Mid-South, with the greatest threat expected over parts of far eastern Oklahoma and Arkansas. Very large hail, damaging winds, and a strong tornado or two all appear possible. ...Eastern Oklahoma/Arkansas... Latest GOES-16 imagery shows signs of decreasing inhibition across northeast TX into eastern OK. Deepening congestus, increasing echo tops, and a few lightning strikes are noted across eastern OK along the stationary boundary, possibly indicating the early signs of sustained, surface-based convective initiation. These trends are expected to continue through the late afternoon as inhibition continues to wane and instability increases to near 2500 J/kg MLCAPE amid increasing cloud breaks. This is in line with latest guidance, which shows thunderstorms increasing in coverage after 21 UTC across eastern OK into central AR (see MCD 447 for additional details). Small changes are made to the Enhanced risk area to better capture the northward extent of the developing thunderstorms along the stationary boundary, but the overall forecast remains on track. ..Moore/Mosier.. 04/11/2022 .PREV DISCUSSION... /ISSUED 1120 AM CDT Mon Apr 11 2022/ ...AR to southeast OK/north TX this afternoon into early tonight... Broadly cyclonic flow aloft will persist over the Plains and western CONUS, as a lead shortwave trough ejects east-northeastward over Lake Superior, and an upstream trough will amplify toward the Great Basin. An outflow boundary across AR and a surface front across east central and southeast OK have stalled and these boundaries will provide a focus for additional thunderstorm development later this afternoon into this evening, as a subtle mid-upper speed max progresses east-northeastward from the TX Panhandle. Late in the period, the front will begin to move northward as a warm front across OK, in response to strong lee cyclogenesis across the central High Plains (downstream from the Great Basin midlevel trough). Boundary-layer dewpoints in the mid-upper 60s continue to spread northward across TX/LA toward southeast OK and AR, to the south of the front and the outflow boundary across northern AR. Clouds will tend to slow surface heating in AR where the moist layer is relatively deep, but convective inhibition is not as strong compared to areas farther southwest in TX, based on the very warm elevated mixed layer noted in regional 12z soundings with convective temperatures at or above 90 F. However, surface heating will be stronger from southeast OK into northeast and north central TX where cloud breaks will be more pervasive. Though forcing for ascent and the prospects for surface-based storm development are uncertain across north TX along the front and dryline, storm development is more probable by mid-late afternoon along the front/outflow along the northeast edge of the stronger surface heating/deeper mixing in southeast OK. Any storms that form along or just south of the front/outflow from southeast OK into AR will likely become supercells, given MLCAPE of 2000-3000 J/kg and effective bulk shear near 50 kt. The large buoyancy, northeast extent of the midlevel lapse rates near or above 8 C/km, and supercell wind profiles will support the threat for isolated very large hail (potentially near the size of baseballs). Low-level moisture and hodograph length/clockwise curvature suggest that tornadoes will be possible with any persistent supercells, including a strong tornado or two. Otherwise, storms may persist into the early overnight hours and evolve into a cluster or two while spreading eastward across AR, before weakening late tonight as the subtle midlevel trough passes and background height rises commence over AR. Read more CHECK UPDATE ZOOM GRAPHIC
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