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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.


Friday, July 21, 2023

SPC Jul 21, 2023 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1116 AM CDT Fri Jul 21 2023 Valid 211630Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE MID-SOUTH/TENNESSEE VALLEY/SOUTHEAST...NORTHEAST STATES...AND SOUTHERN HIGH PLAINS... ...SUMMARY... Severe thunderstorms capable of wind damage and some hail are expected across the Mid-South and Tennessee Valley to the Southeast States, while additional severe storms will be possible across the Northeast and High Plains. ...AR into the Southeast States... A large MCS that tracked across southern OK last night is now over northern/central AR. This system and its attendant MCV will move into western TN this afternoon, where sufficient heating and a very moist air mass will support the potential for re-intensification. If this scenario occurs, locally damaging wind gusts would be the main concern. To the southeast of the MCS, a weak surface boundary extends across southeast AR into portions of MS/AL/GA. A very unstable air mass will become established this afternoon along this axis, where scattered thunderstorm development is expected. MLCAPE values around 3000 J/kg will combine with winds in the 5-7km layer around 30 knots to pose some risk of damaging wind gusts in the stronger cells. The risk of wind damage will increase later this afternoon if sufficient thunderstorm coverage can result in more organized outflows. ...New England... An upper trough is moving across the northeast states today, with an associated cold front currently extending across parts of eastern NY/PA. Clouds have been clearing ahead of the front across western New England, where temperatures will rapidly warm into the 80s. Ample low-level moisture is present from southern VT/NH southward, where upper 60s/lower 70s dewpoints will yield afternoon MLCAPE values of 1500-2000 J/kg. Forecast soundings show sufficient deep layer shear for a few organized/rotating storms capable of strong/damaging wind gusts and perhaps hail for a few hours this afternoon. ...Northeast NM... Weak easterly low-level upslope flow is present today over northeast NM, helping to transport 60s dewpoints westward toward the higher terrain. Thunderstorms are expected to form in the mountains near Raton and drift southeastward through the afternoon. Steep low-level lapse rates and 30-40 knots of effective shear will promote the development of a few supercells capable of large hail and damaging wind gusts. ..Hart/Thornton.. 07/21/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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