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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.

Sunday, June 19, 2022

SPC Jun 19, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0241 PM CDT Sun Jun 19 2022 Valid 192000Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS SOUTHEAST MT AND WESTERN ND... ...SUMMARY... A couple long-tracked supercells, potentially producing significant severe hail and wind, will most likely occur centered on southeast Montana into western North Dakota through this evening. ...20z Update... Only minor adjustments have been made to the ongoing outlook with the 20z update. Marginal probabilities have been removed from much of UT as storms have shift north/northeast and instability is diminishing. Otherwise, only some minor changes to the 10 percent general thunderstorm line have been made across the central Gulf Coast and FL vicinity. The airmass across eastern MT into western ND continues to recover after morning convection. Instability is increasing and inhibition weakening. Severe storms are still expected through this evening. Thunderstorm clusters across FL are drifting south/southwest across portions of the Peninsula. This activity will continue to pose a threat for isolated strong/locally damaging gusts the next few hours. For additional details in short term severe potential, reference MCDs 1224 and 1225. ..Leitman.. 06/19/2022 .PREV DISCUSSION... /ISSUED 1129 AM CDT Sun Jun 19 2022/ ...Southeast MT/northeast WY/western ND... Basal shortwave impulse embedded within the amplified western mid-upper trough should eject from the Great Basin north-northeast towards the northern Rockies. Large-scale ascent tied to this wave has supported scattered thunderstorms ongoing from eastern UT into western WY, and will reach the Big Horns later this afternoon. Primary severe potential will emanate out of this latter development as post-frontal low-level upslope flow persists and cloud breaks aid in weak surface-based buoyancy. 12Z guidance does differ appreciably with the degree of destabilization, as well as the degree of effective bulk shear with the NAM appearing less environmentally favorable than the RAP. Ongoing cloud coverage and lack of wind profiler data in the genesis corridor for supercells further lowers confidence. Nevertheless, ARW-based HREF guidance remains insistent on simulating at least a couple long-track supercells spreading northeast off the Big Horns. MLCAPE in western ND will be comparatively larger in this portion of the post-frontal regime owing to 60s surface dew points west of the surface cyclone drifting east into central ND. This suggests that any established supercells should be sustained into western ND before eventually becoming undercut with time later tonight as the front accelerates southeast. Significant severe hail and wind still appears possible. ...Eastern Great Basin to western/central SD... Eastward progress of the Great Basin trough will bring stronger mid-level flow farther east compared to previous days. Despite widespread clouds to slow surface heating over most of the Rockies, long/straight hodographs could support some organized storm structures within the monsoonal moisture plume from the Four Corners Area north into WY. A few strong-severe outflow gusts and isolated marginally severe hail are the main hazards. Farther northeast into central SD, mid-level flow will be weaker, but greater boundary-layer heating and much deeper inverted-v profiles will favor a few strong-severe outflow gusts with high-based storm clusters late this afternoon into the evening along a surface trough. ...FL Peninsula... Another day of largely diurnal convection is expected, with scattered thunderstorm development focused by a weak surface front drifting south in north FL, and sea breeze circulations farther south. Weak northeasterly mid-level flow suggests that pulse to loosely organized multicell clusters will spread southwestward this afternoon. Slightly weaker mid-level lapse rates relative to yesterday should hold MLCAPE to around 2500-3000 J/kg. Localized damaging winds from wet microbursts and small to marginally severe hail will be possible. Read more CHECK UPDATE ZOOM GRAPHIC