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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, August 9, 2023

SPC Aug 9, 2023 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1229 AM CDT Wed Aug 09 2023 Valid 091200Z - 101200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE OZARKS INTO THE MID-MISSISSIPPI RIVER VALLEY... ...SUMMARY... Severe thunderstorms are expected today from eastern Oklahoma/Kansas eastward to the Lower Ohio and Tennessee Valley vicinity. ...Synopsis... Overnight surface analysis reveals a surface low slowly deepening over the High Plains ahead of an approaching upper wave. Further deepening of the low is expected as it migrates east into the Ozarks by early evening. A broad warm advection regime ahead of the synoptic wave will support scattered elevated convection across portions of the Ozarks to the mid-MS River Valley by late afternoon. A second round of storms is expected during the early evening hours across the Ozarks along a trailing cold front, and should pose a risk for all hazards before spreading east during the overnight hours. ...Ozarks into the Mid-MS River Valley... Thunderstorm clusters developing over northwest KS as of 05 UTC are expected to propagate to the southeast in tandem with the deepening surface low. While it remains unclear how much of this initial activity will persist into MO, convective re-development appears probable by mid-afternoon with additional development within a warm advection regime across northern MS/AL and western TN. 40-50 knot mid-level flow over the region will support adequate shear for organized cells with an attendant large hail risk prior to gradual upscale growth into clusters. Low-level shear is expected to gradually improve through the day with the approach of the synoptic wave with forecast soundings across the mid-MS Valley showing ESRH values between 100-200 m2/s2. This should support a tornado threat with initially discrete cells, though this may be conditional on the degree of destabilization that can occur prior to convective initiation (most forecast soundings suggest temperatures in the low to mid-80s are required). A second round storms will likely develop across southwest MO into northwest AR/northeast OK along a trailing cold front closer to 00 UTC. Although a residual cold pool may be in place from prior convection, southwesterly low-level flow should aid in air mass recovery, and steep lapse-rate advection aloft will compensate for any weakness in low-level thermodynamics. Deep-layer shear vectors orthogonal to the front should support initially discrete cells. The longevity of discrete storm modes is uncertain with spread noted in latest CAM guidance, but more south/southwesterly flow in the vicinity of the surface low should support effective SRH values on the order of 150-250 m2/s2 at the time of initiation. Consequently, a tornado or two is possible across northern AR into southwest MO. Further southwest into OK, a hotter, more deeply mixed air mass may limit the tornado potential, but will support severe downburst winds. Storms along the front are expected to gradually spread east overnight into TN and northern MS/AL as one or more organized lines. The potential for severe/damaging winds may be modulated by cold pools from prior convection and background nocturnal stabilization to some degree. ...Dakotas into the Upper Peninsula of Michigan... Thunderstorms developing along a diffuse cold front will mature in an environment with only modest buoyancy (MLCAPE between 500-1000 J/kg), but effective shear values between 30-35 knots. Given storm motions and deep-layer shear vectors largely off the front, discrete to semi-discrete storms appear probable. A similar environment Tuesday supported isolated severe storms, and this should be the case again today from the eastern Dakotas into MN, WI, and the Upper Peninsula of MI. ..Moore/Jewell.. 08/09/2023 Read more CHECK UPDATE ZOOM GRAPHIC