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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.

Tuesday, April 19, 2022

SPC Apr 19, 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 Apr 19 2022 Valid 192000Z - 201200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... General thunderstorms are expected across portions of the southern Plains this evening and into the Ozarks and Midwest overnight. ...20z Update... An ongoing cluster of thunderstorms along the Red River may continue eastward this evening across portions of southern OK and eventually western AR. However, meager low-level moisture within the dry airmass (dewpoints in the 30s and 40s F) to the east suggests the overall severe threat is decreasing owing to limited buoyancy. Gradual redevelopment/expansion in general thunderstorm coverage appears likely to emerge from the remnants of the cluster later this evening across central/Eastern OK with an increase in warm advection beneath the nocturnal low-level jet. Model soundings show moisture continues to lag behind a subtle shortwave trough moving across the southern Plains, resulting in only modest elevated buoyancy this evening. Deeper moisture, slated to arrive after midnight, will miss the deeper lift associated with the aforementioned shortwave as it lifts off to the north and east. The lack of sizable buoyancy, forcing for ascent and decreasing vertical shear suggests the overall severe threat tonight will be low. Across the Texas Big Bend, another cluster of storms may persist for a few more hours along the US/Mexican Border. While low-level moisture advection should continue to increase late this afternoon/evening ahead of the cluster. Limited forcing for ascent from the exiting shortwave, and increasing subsidence/capping in its wake suggests little potential for additional organization/strengthening of the ongoing storms through this evening. ..Lyons/Jewell.. 04/19/2022 .PREV DISCUSSION... /ISSUED 1116 AM CDT Tue Apr 19 2022/ ...Synopsis... Broad height falls continue across the western CONUS this morning as a mean longwave trough becomes established across the eastern Pacific and West Coast. A pair of more progressive shortwave troughs embedded within the mean flow across the Pacific Northwest and northern Rockies will continue to eject towards the Canadian Prairies through the day. The combination of the ejecting impulses and increasing zonal flow over the central Rockies will help deepen a lee trough through the day, which should consolidate into a lee cyclone by early Wednesday. This low-level response will maintain northward advection of a higher theta-e air mass from the TX Gulf and Rio Grande valley into the Plains over the next 24 hours. Broad isentropic ascent within this warm advection regime will support isolated to scattered showers and thunderstorms across the southern Plains this afternoon into the overnight hours. ...Northwest Texas into southwest Oklahoma... Morning soundings show 7-8 C/km lapse rates across the southern Plains atop of a cool, somewhat dry boundary layer. The combination of adiabatic cooling via isentropic ascent and moistening from poleward advection of richer Gulf moisture will support gradual destabilization of the 850-700 mb layer across TX into OK today into tonight. Early signs of this process are already evident with isolated elevated convection noted across parts of northwest OK and the Big Bend region of TX over the past few hours. Isolated thunderstorms are possible where sufficient boundary-layer moistening/warming and low to mid-level lift can overlap and overcome lingering MUCIN. Confidence in exactly where this may occur is low with considerable spread noted in recent CAM solutions. Ensemble probabilities hint that this potential may be maximized across portions of northwest TX into the Red River Valley this afternoon and evening along the low/mid-level warm front. Despite the elevated nature of convection, 50-60 knot flow near 6 km will support 40-50 knots of effective bulk shear supportive of organized storms with an attendant hail threat. Damaging winds are possible with any stronger storm, but will likely be conditional on the degree of daytime heating and the depth of boundary-layer mixing (and hence will be maximized during the late afternoon). Thunderstorms will likely persist well into the overnight hours across southeastern OK into western AR, but the severe threat is less certain across these regions as deep-layer shear weakens with eastward extent. Read more CHECK UPDATE ZOOM GRAPHIC
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