SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0101 AM CDT Fri Jun 11 2021 Valid 111200Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER EASTERN KANSAS AND NORTHEAST OKLAHOMA... ...SUMMARY... Scattered severe thunderstorms are expected Friday from southwest Iowa and southeast Nebraska south across much of eastern Kansas, western Missouri and into northern Oklahoma. Isolated severe storms are also possible across central and northern Wisconsin. Damaging winds and large hail will be the main severe hazards. ...Synopsis... A negatively-tilted upper-level trough will lift north from the northern Plains into Saskatchewan/Manitoba Friday, and a surface cold front will move southeast, extending from eastern MN into the TX Panhandle by 00z Saturday. An upper-level trough over the eastern U.S. will move slowly towards the coast, with an expansive ridge over the southwest/south-central states. A cold front will also extend from near the NC Outer Banks west/northwest into the upper Midwest late Friday afternoon. ...Central/Southern Plains... A very moist airmass will remain in place Friday south of the advancing cold front. Diurnal heating of widespread mid/upper 70s dew points combined with steep low- and mid-level lapse rates will contribute to strong/extreme instability, with MLCAPE of 3000-4500 J/kg. Although weak upper-level ridging will reside across much of the area, evening guidance remains reasonably consistent in depicting a re-strengthening of storms along the southern flank of the early morning portion of the line over NE during the day that moves south/southwest on the eastern periphery of the ridge. Although uncertainty remains regarding the exact evolution of early Friday storms and the strength of a capping inversion, the degree of instability and consistent signal in most model guidance warrants introduction of a categorical Slight Risk with this outlook for eastern KS and northeast OK. Considerable DCAPE in NAM forecast soundings (in excess of 1500 J/kg) suggests damaging winds will be the primary concern, with large hail also possible with the strongest updrafts. Spatial adjustments to the risk area are likely in subsequent outlooks as mesoscale details come into better focus. ...Central/northern Wisconsin... Thunderstorms are expected to develop along the front, aided by diurnal heating and glancing ascent with the upper trough as it lifts north. Moderate buoyancy and around 25 kts of effective shear, coupled with steep low-level lapse rates will result in a risk for isolated damaging gusts and large hail with multicell clusters during the afternoon/evening. ...OH Valley into the mid-Atlantic... A weak perturbation embedded within the eastern U.S. upper trough will move towards the mid-Atlantic coast Friday night. Ample moisture will contribute to widespread thunderstorm development during the day, with some potential for merging storms/outflows to result in a few reports of strong wind gusts. Weak shear will tend to limit storm organization and have opted not to introduce categorical Marginal risk areas with this outlook. ..Bunting/Moore.. 06/11/2021 Read more LIVE: spc.noaa.gov
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