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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, August 1, 2022

SPC Aug 1, 2022 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0734 AM CDT Mon Aug 01 2022 Valid 011300Z - 021200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH LATE EVENING FOR THE OH VALLEY...AND FROM THIS EVENING INTO EARLY TONIGHT ACROSS NORTH/NORTHEAST NE... ...SUMMARY... Scattered severe thunderstorms, mainly capable of damaging gusts, are possible today across parts of Ohio, Indiana and Kentucky. Isolated strong to severe storms also are possible across the broader Midwest vicinity as well as parts of Nebraska. ...OH Valley area later this afternoon through late evening... A midlevel shortwave trough now from northern IL to Lake MI will continue east-southeastward over the OH Valley and lower Great Lakes by tonight, accompanied by a weak surface cold front. Some slightly elevated convection has persisted overnight in the zone of ascent and low-level warm advection immediately preceding the midlevel trough and surface front. This convection may persist through at least midday/early afternoon with an isolated strong-severe gusts threat given the somewhat organized cold pool and weak-moderate buoyancy with only small convective inhibition ahead of the storms across IN. In the wake of this morning convection, strong surface heating and warm/moist advection from the mid MS Valley eastward to the OH Valley will contributed to destabilization, with MLCAPE increasing into the 2000-3500 J/kg range with minimal convective inhibition by mid-late afternoon. Additional thunderstorm development is anticipated after 21z along the surface wind shift. The individual storms will move toward the southeast, though there will be a tendency for upstream development toward the west through the evening. Forecast hodographs show sufficient vertical shear for clusters and some supercell structures, given effective bulk shear near 35 kt with the moderate-strong buoyancy. Supercell longevity will tend to be limited somewhat by forecast weaknesses in the midlevel flow by evening. Damaging winds and marginally severe hail will be the main threats, though an isolated tornado or two could occur with embedded supercells based on sufficient low-level moisture (boundary-layer dewpoints in the low 70s) and hodograph curvature (effective SRH near 200 m2/s2). ...North/northeast NE late this afternoon into early tonight... A surface cold front is in the process of stalling across east central and central NE, and this boundary is expected to move some to the north as a warm front this afternoon. Strong surface heating and deep mixing could support thunderstorm development by this evening across north central NE, where low-level ascent will be strongest at the intersection of the warm front and a more north-south lee trough. Steep low-midlevel lapse rates and boundary-layer dewpoints in the 60s will support large MLCAPE near 3000 J/kg, and deep-layer vertical shear will be sufficient for supercells. The steep lapse rates and large buoyancy with DCAPE in excess of 1200 J/kg will favor occasional severe outflow gusts, whereas any supercells will be capable of producing isolated large hail from this evening into early tonight as storms spread generally eastward. ...ND this afternoon into tonight... The richer low-level moisture is confined to along and south of a front across NE/southern IA, but residual boundary-layer dewpoints of 55-60 F remain across ND this morning. Strong surface heating beneath steep midlevel lapse rates will result in destabilization during the day, but some convective inhibition is likely to remain through the afternoon. There will be some chance for deep convection to form on the north/northeast edge of the deepest mixing near a weak surface lee cyclone in southwest ND by mid-late afternoon. If storms do form, thermodynamic and wind profiles will support high-based supercells capable of producing isolated strong-severe outflow gusts and some hail. Otherwise, some elevated convection may form tonight across northeast ND in a zone of 850-700 mb warm advection, though the magnitude of buoyancy and the threat for large hail are unclear. Given the conditionality and/or uncertainty in both scenarios, will not add any severe wind/hail probabilities. ..Thompson/Kerr.. 08/01/2022 Read more CHECK UPDATE ZOOM GRAPHIC
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