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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.


Sunday, June 25, 2023

SPC Jun 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 1257 AM CDT Sun Jun 25 2023 Valid 251200Z - 261200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON INTO TONIGHT ACROSS PARTS OF CENTRAL AND EASTERN INDIANA INTO WESTERN OHIO...MUCH OF CENTRAL KENTUCKY...MIDDLE AND WESTERN TENNESSEE...MUCH OF CENTRAL AND SOUTHERN ARKANSAS...NORTHERN MISSISSIPPI AND ADJACENT PORTIONS OF NORTHWESTERN ALABAMA AND NORTHEASTERN LOUISIANA... ...SUMMARY... Strong to severe thunderstorms may become numerous late this afternoon into tonight across parts of the southeastern Great Plains and lower Mississippi Valley, into the lower Ohio Valley and adjacent portions of the Great Lakes. This may include supercells with a risk for tornadoes across parts of central and eastern Indiana into western Ohio and central Kentucky. ...Synopsis... Split flow across the eastern Pacific into western North America may amplify a bit further today through tonight. While ridging within the northern branch builds across the British Columbia vicinity, a significant perturbation within larger-scale southern branch troughing is forecast to progress inland across the central/southern California coast. As this occurs, short wave ridging, extending to the north of a prominent subtropical high centered over southwest Texas, appears likely to build across the Rockies into the Great Plains, while a significant downstream mid-level low digs southeast of the Upper Midwest through the Great Lakes region. This will be preceded by increasingly sheared mid-level troughing overspreading the Atlantic Seaboard, including the remnants of a cyclonic circulation turning northeastward across the northern Mid Atlantic toward southern New England. The prominent interior U.S mid-level low will be accompanied by a broadening, occluded surface cyclone, trailed by a cold front advancing southeast of the lower Missouri through lower Ohio Valleys, with a segment farther southwest stalling and weakening across the central into southern Great Plains. A corridor of seasonably high boundary-layer moisture content (with lower/mid 70s F dew points) along and southeast of this front likely will support large CAPE (on the order of 2000-4000 J/kg), beneath a plume of steep lapse rates associated with elevated mixed-layer air emanating from the southern Great Plains. This plume will gradually become suppressed southward and southwestward across the lower Ohio Valley and Mid South, beneath flow transitioning from west-northwesterly to northwesterly, to the southwest of the digging low. Closer to the center of the low, it appears that a belt of 50-70 kt flow around 500 mb will nose across the lower Missouri through lower Ohio Valleys. ...Southern Great Plains into Ohio Valley/Great Lakes... The coverage and intensity of the severe weather threat for today may be considerably impacted by sub-synoptic/mesoscale developments which has been a source of sizable model spread. However, it is appearing increasingly probable that forcing for ascent downstream of the digging mid-level low and associated troughing may be supporting an area of vigorous convection, mainly rooted in a lower/mid-tropospheric warm advection regime, across the western Kentucky/Tennessee vicinity at the outset of the period. Convection allowing model output suggests varying subsequent evolution. However, aided by rapid boundary-layer destabilization with insolation to the south and southwest of this activity, it is possible that associated outflow may gradually support increasing new boundary-layer based thunderstorm development. There appears sufficient shear to support an upscale growing cluster with potential to produce strong wind gusts, with a tendency to propagate south-southeastward then southward along the eastern periphery of the better low-level moisture and instability, in the wake of the Atlantic Seaboard mid-level trough. Stabilization in the wake of this initial convective cluster results in more uncertain convective potential across parts of the Tennessee into lower Ohio Valleys. However, a narrow corridor of moderate to strong pre-frontal destabilization across Indiana into southern Michigan may provide another focus for strong thunderstorm initiation by early this afternoon. Beneath increasingly difluent and strengthening west-northwesterly mid/upper flow on the nose of the digging jet, it appears that the environment could support scattered discrete supercells, at least initially. Preceded by an remnant effective warm frontal zone, associated with outflow from early convection, it appears that this activity may be accompanied by increasing tornadic potential potential, in addition to large hail, while spreading across Indiana into western Ohio, with additional storms perhaps developing southward into central Kentucky through this evening. Late this afternoon into this evening, if not a bit earlier, there are indications that one or two perturbations (likely of subtropical eastern Pacific origin) may contribute to thunderstorm initiation along and ahead of the cold front across parts of northern Arkansas into central Oklahoma. Beneath at least modest northwesterly mid-level flow, in the presence of strong instability, the environment appears conducive to consolidating and organizing clusters, with southeastward propagation focused along the northeastern periphery of the subtropical ridge. ...Northern Intermountain Region/Rockies... A corridor of weak destabilization, along the track of a northeastward migrating short wave perturbation may provide a focus for vigorous thunderstorm development this afternoon and evening. Deep-layer mean wind fields likely will be generally weak, but relatively steep low-level lapse rates may contribute to potential for small hail and perhaps brief, occasional gusts near severe limits. ..Kerr/Lyons.. 06/25/2023 Read more CHECK UPDATE ZOOM GRAPHIC
SUNRISE AND SUNSET TIMES IN UTC (if you're not logged in to Google)
CHICAGO UTC-6 during CST (Central Standard Time, e.g., winter)
CHICAGO UTC-5 during CDT (Daylight Savings Time, e.g., summer)