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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.


Monday, September 25, 2023

SPC Sep 25, 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 1234 AM CDT Mon Sep 25 2023 Valid 251200Z - 261200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS PORTIONS OF SOUTHERN TEXAS AND CENTRAL FLORIDA... ...SUMMARY... Isolated strong to severe thunderstorms will be possible across parts of Texas and Florida today. ...Synopsis... Strong to severe thunderstorm potential is expected to remain confined to southern portions of Texas and the Florida Peninsula for today. An occluding low over the upper MS River Valley will continue to weaken as an attendant mid-level impulse shifts east through the day. In its wake, upper-level ridging will become established across the Intermountain West. This synoptic regime will favor a gradually building surface high over the Plains (as evidenced by steady pressure rises over the past 12 hours). As a result, the diffuse cold front draped across the southern Plains will continue to migrate south through the day, and will be a focus for thunderstorm development later this afternoon and evening. ...Texas... Latest forecast guidance shows reasonably good agreement in the southward progression of the cold front across southern TX today. This boundary may be convectively reinforced by ongoing thunderstorm clusters across eastern TX at the start of the period. This early-morning convection may re-intensify and pose a severe wind threat for the TX coastal plain during the afternoon hours amid diurnal warming of a moist air mass downstream. To the west, closer to the Edwards Plateau and the Big Bend region, thunderstorm develop along the cold front is expected by mid/late afternoon. MLCAPE values are forecast to reach near 2000 J/kg as temperatures warm into the low to mid 90s. Although mid-level winds will be somewhat modest (20-30 knots), southeasterly low-level flow will support elongated hodographs with effective bulk shear values near 30-40 knots. Such wind profiles and weak ascent along the front may support initially discrete modes, including the potential for a supercell or two with an attendant large-hail threat. However, deep-layer shear and storm-motion vectors largely along the frontal boundary may favor a tendency for storm clustering through the late afternoon/evening. Thunderstorm development off the higher terrain of the Davis and Serranias del Burro mountains may also support discrete supercells, but confidence in storm coverage via orographic ascent is limited. ...Florida... A weak tropical low north of the Yucatan Peninsula is establishing a plume of rich moisture into FL (as sampled by 00z soundings). Moderate heating of this air mass through the day should support a modestly buoyant, but uncapped environment (MLCAPE upwards of 1000 J/kg) by mid afternoon over central FL. Glancing ascent from the passing mid-level trough to the north will support scattered to widespread thunderstorms, and may sufficiently strengthen mid-level flow to support effective bulk shear values between 20-25 knots. Although the kinematic environment will be meager, a few instances of hail approaching severe criteria are possible. Additionally, steepening low-level lapse rates and PWAT values approaching 2 inches will be conducive for wet downbursts capable of strong to severe winds. ..Moore/Leitman.. 09/25/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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