SPC 0100Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0800 PM CDT Wed Jun 11 2025 Valid 120100Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS EVENING ACROSS PARTS OF NORTHEASTERN IOWA INTO ADJACENT SOUTHWESTERN WISCONSIN AND NORTHWESTERN ILLINOIS... ...SUMMARY... Thunderstorm activity may still increase across parts of central Texas, toward the upper Texas coastal plain, tonight accompanied by at least some risk for severe weather. Otherwise, ongoing thunderstorm development elsewhere is expected to generally wane by mid to late evening. ...01Z Update... ...Midwest... Convection with small cluster which has evolved along a stalled frontal zone across northeastern Iowa remains strong. However, it appears that forcing associated with a supporting mid-level perturbation is beginning to shift east of the Upper Midwest into Great Lakes, where the environment along the frontal zone becomes less unstable and will trend more stable with the loss of daytime heating. As this occurs, storms are expected to generally diminish in intensity this evening across northeastern Iowa through southern Wisconsin/northern Illinois. ...Northern Intermountain Region and Rockies... Downstream of a weak mid-level trough progressing eastward into the northern Rockies, stronger convection is now spreading in a swath across south central Montana and northern Wyoming. Instability is weak due to limited low-level moisture, but steep lower/mid-tropospheric lapse rates, including a modestly heated and deeply mixed boundary layer, are contributing to the generation of strong to severe gusts with the most vigorous storms. This should begin to wane as low-level lapse rates stabilize with the onset of boundary-layer cooling. ...Texas... Within slow moving, weak mid-level troughing, a digging smaller-scale perturbation is supporting increasing thunderstorm development near/west of the I-35 corridor of central Texas. In the presence of 10-20 kt westerly to southwesterly deep-layer mean flow, it appears that instability and large-scale forcing for ascent will be sufficient to support a further increase in convection through 04-06Z, which probably will tend to slowly advect across and east of the I-35 corridor. It appears that low-level warm advection/convergence focused along a remnant frontal zone near/north of the San Antonio/Austin area could support an upscale growing cluster, perhaps aided by inflow of seasonably moist air becoming characterized by CAPE in excess of 2000 J/kg. This may be accompanied by at least some increase in potential for strong to severe gusts associated with a developing cold pool while spreading toward the upper Texas coast overnight. However, given the initial weakness of the ambient mean flow/shear and lack of steeper lower/mid-tropospheric lapse rates, the severe threat appears conditioned on strong convective augmentation of the wind fields, which seems relatively low in probability. ..Kerr.. 06/12/2025