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Weather conditions directly above are near Lakefront. Top tabs refer to O'Hare (official).

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.

Thursday, September 22, 2022

SPC Sep 22, 2022 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1221 AM CDT Thu Sep 22 2022 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE MID-ATLANTIC AND NEW ENGLAND COASTS AND OVER PORTIONS OF THE NORTHERN HIGH PLAINS... ...SUMMARY... Thunderstorms with damaging winds will be possible this morning into the early afternoon hours from the Mid-Atlantic to the New England coasts. Strong to severe winds are also possible across portions of the northern High Plains this afternoon. ...Synopsis... Early-morning water-vapor imagery reveals an upper-level wave continuing to slowly amplify over the Great Lakes region as it migrates east. At the surface, an associated surface low over eastern Canada will undergo some deepening over the next 12-24 hours as it lifts northeast. A trailing surface cold front is noted in surface observations stretching from the Lower Great Lakes into the central Plains. Thunderstorm coverage has increased along this front across portions of PA and NY during the 04-05 UTC period with additional development likely through the late morning hours. To the west, an upper low over the northern Great Basin/northern Rockies will meander to the east/northeast, supporting ascent and thunderstorm chances across portions of the northern High Plains this afternoon. ...New England and Mid-Atlantic Coasts.... Elevated thunderstorms will likely be ongoing at the start of the period across the New England region due to a combination of focused ascent along the front and 500-1000 J/kg MUCAPE. Mean flow along the boundary will maintain a linear mode with winds in the 925-850 mb layer strengthening to 35-45 knots between 12-16 UTC. Limited diurnal heating will modulate low-level lapse rates and the potential for convection to become rooted in the boundary layer. However, more robust downdrafts may mix the stronger low-level winds to the surface and support isolated damaging winds. The wind threat may increase for locations that can see temperatures climb into the low 70s via daytime heating by late morning, but this scenario appears limited and will likely be confined closer to the coast. To the south across the Mid-Atlantic/Carolinas, thunderstorm development is expected along the front by early to mid afternoon. While mid-level lapse rates will be modest, steepening 0-3 km lapse rates and gradually increasing deep-layer shear will support a few strong cells capable of isolated damaging winds. Isolated to scattered thunderstorms are likely along the front into the Southern states, but weak deep-layer flow will limit the potential for organized severe convection. ...Southeast Montana and Northeast Wyoming... Increasing mid-level flow and upper-level difluence ahead of the Great Basin upper low will support lee troughing along the northern High Plains through the day. 7-8 C/km mid-level lapse rates, sampled in upstream 00 UTC soundings, are expected to advect into the region by mid afternoon amid the west/southwest flow regime. Modest moisture in the 850-700 mb layer should support adequate buoyancy for convection within the left-exit region of the upper-level speed max. Storms maturing in a deep, well-mixed boundary layer to the west of the sharpening surface trough will be capable of a few strong to severe wind gusts. ..Moore/Jewell/Weinman.. 09/22/2022 Read more CHECK UPDATE ZOOM GRAPHIC
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