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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.

Saturday, May 22, 2021

SPC May 22, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0257 PM CDT Sat May 22 2021 Valid 222000Z - 231200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR PARTS OF THE CENTRAL AND SOUTHERN HIGH PLAINS... ...SUMMARY... Scattered large hail and severe winds along with a few tornadoes remain possible this afternoon into evening from the Colorado/New Mexico Front Range into the adjacent central and southern High Plains including eastern Colorado, eastern New Mexico, and southwest Nebraska. ...20Z Update... The previous forecast remains on track, with minor adjustments made to severe probabilities based on current observations and the latest high resolution model guidance consensus. Scattered strong to severe thunderstorms have recently developed in close proximity to the Rockies across the central and southern High Plains. These storms are expected to maintain a discrete/semi-discrete storm mode over the next few hours with primarily a large hail/isolated tornado threat, with damaging gusts gradually becoming a greater concern as storms merge into linear segments. Please refer to MCDs 0702, and 0703 for more details. Convection continues to gradually intensify within an MCV across central TX, where adequate 0-3km CAPE and low-level vertical vorticity may still support a brief tornado or two over the next few hours. Convection may still gradually intensify along the International border across northeast MN. Large hail will be the primary threat with any storms that manage to sustain themselves and intensify. Please see MCD 0701 for more information. ..Squitieri/Gleason.. 05/22/2021 .PREV DISCUSSION... /ISSUED 1130 AM CDT Sat May 22 2021/ ...Colorado/New Mexico I-25 and central/southern High Plains... The region will be increasingly influenced by a prominent upper trough centered over the Great Basin, with a strong/cyclonically curved polar jet extending from the Lower Colorado River Valley through the Four Corners vicinity. Under the influence of this meridional regime, a relatively moist air mass (50s and some lower 60s F surface dewpoints) extends as far west as east-central/northeast New Mexico and the Raton Mesa/Colorado Front Range at late morning. Although cloud cover remains prevalent at late morning, the degree of moisture in conjunction with cyclogenesis-aided increasing low-level upslope flow is expected to contribute to a relatively early increase in thunderstorm development/intensification by early/mid-afternoon, initially near the Front Range/foothills/Raton Mesa vicinity of Colorado and New Mexico. Ample effective shear will exist for initial supercells, essentially across all of eastern New Mexico, as well as the Colorado Front Range vicinity and Colorado/western Nebraska areas near and north of the synoptic front. Low-level hodographs initially may remain modest, but should enlarge with time by late afternoon/early evening. A mixed mode of supercells evolving into broader clusters is anticipated, particularly in two regimes, one focused on east-central/northeast New Mexico, and the other in east-central/northeast Colorado to west/southwest Nebraska in vicinity of the surface low and northeastward-extending front. Large hail and a few tornadoes will be possible, along with some increase in severe-caliber wind potential by early evening as storms cluster across the adjacent Plains. ...Central Texas... An MCV centered between San Antonio and Austin this morning will continue to drift north-northwestward across central Texas through the afternoon. Limited cloud breaks and some diurnal warming may allow for a modest increase in updraft depth/intensity and thunderstorm potential this afternoon. A belt of enhanced 0-1 km shear within the eastern quadrant of the MCV coupled with limited boundary-layer heating may be sufficient for the threat of brief/weak tornadoes, particularly for areas generally near/west of I-35. ...Northern Minnesota... Isolated thunderstorms may develop during the late afternoon to early evening along the trailing portion of a modest warm conveyor belt along/just ahead of a slow-moving cold front. The presence of an upstream mid-level ridge over the Dakotas within a pronounced gradient of mid-level westerlies suggest the corridor of severe potential should remain spatially confined. Isolated severe hail and locally damaging winds are possible. Read more LIVE: