Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Sep 13 2025 20:04:33 ACUS01 KWNS 132004 SWODY1 SPC AC 132003 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0303 PM CDT Sat Sep 13 2025 Valid 132000Z - 141200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF NEW MEXICO... ....SUMMARY... Isolated severe wind and hail will be possible from the Southwest/southern Rockies, particularly over parts of New Mexico, into the northern Great Plains and a portion of the Midwest, mainly this afternoon and early evening. ....20Z Update... A few stronger elevated thunderstorms have persisted across northwest Indiana through early afternoon. These storms appear to be maintaining themselves as they move across western Indiana. Storms are currently on the eastern periphery of the instability which could limit longevity. However, strong mid-level flow is in place (45-50 knots around 4 km per LOT VWP) which will continue to support supercells and may help maintain storms even with limited instability. Only a slight southeast expansion was made to the Marginal Risk to account for areas downstream of the recently warned storms. Will maintain the Marginal risk farther west across eastern Illinois, but confidence is not that high that storms will form across this area. However, if they do, the environment would support strong to severe storms capable of large hail and wind gusts. Farther west, scattered thunderstorms have developed across New Mexico and are starting to move east. Weak to moderate instability and moderate to strong shear will support some severe weather potential with large hail and wind gusts as the primary threats. See MCD 2071 for additional information about the threat in this area. Across southeast Utah and southwest Colorado, several storms have developed with some apparent supercell structures. Increased ambient vorticity beneath the upper-level low has provided an environment apparently favorable for tornadoes. At least one well-developed tornado/landspout has been observed thus far. Added 2% tornado probabilities to this region as an additional threat could be possible from the same storm or a few other stronger cells in the region. ...Bentley.. 09/13/2025 ..PREV DISCUSSION... /ISSUED 1136 AM CDT Sat Sep 13 2025/ ....New Mexico and southern Rockies/High Plains... A prominent upper trough will continue to shift east-northeastward today and tonight over the Four Corners area and south-central Rockies. DPVA/cooling aloft and plentiful moisture preceding the trough will contribute to a relatively high coverage, and potentially multiple rounds, of thunderstorms regionally. The 12z observed sounding from El Paso featured Precipitable Water values in the upper 5-10 percent of daily climatological values. Ongoing thunderstorms/cloud cover will tend to mute diurnal destabilization in areas, but portions of southern/eastern New Mexico may see somewhat more aggressive destabilization pending cloud breaks. Will defer to the ample moisture/coverage of storms and rather favorable deep-layer flow field (40+ kt effective shear) and introduce a categorical Slight Risk for portions of New Mexico, where hail/wind risks, including some supercells, are most probable this afternoon through early evening. ....Northern Plains including NE/SD/ND... It still seems that residual cloud cover/outflow from last night's multiple rounds of thunderstorms will tend to temper destabilization later today within a modestly-sheared environment. Nevertheless, some isolated severe wind/hail potential will exist as storms redevelop across the High Plains later today. ....Midwest including portions of Illinois/Indiana... Overall severe potential should remain relatively limited (or at least highly uncertain), however some redevelopment and/or reintensification could occur across downstate portion of Illinois/Indiana, and/or farther north along the instability gradient across northeast Illinois/Chicagoland vicinity into northwest Indiana, where some air mass recovery is plausible. Will maintain low hail/wind probabilities regionally given some lingering severe potential, on a more conditional/uncertain basis with north-northwestward extent under the increasing influence of the upper ridge. $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .