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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.

Monday, April 3, 2023

SPC Apr 3, 2023 0600 UTC Day 2 Convective Outlook

LIVE MAP (ABOVE) ... SPC 0600Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1203 AM CDT Mon Apr 03 2023 Valid 041200Z - 051200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS LATE TUESDAY AFTERNOON AND EVENING ACROSS PARTS OF NORTHEASTERN MISSOURI INTO SOUTHEASTERN IOWA...NORTHWESTERN AND WEST CENTRAL ILLINOIS... ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SURROUNDING THE MODERATE RISK ACROSS MUCH OF NORTHERN MISSOURI....CENTRAL AND EASTERN IOWA...NORTHWESTERN AND CENTRAL ILLINOIS...AS WELL AS PARTS OF NORTHEASTERN TEXAS...SOUTHEASTERN OKLAHOMA...MUCH OF ARKANSAS...INTO SOUTHERN MISSOURI... ...SUMMARY... Severe thunderstorms appear likely to develop late Tuesday afternoon into Tuesday night across the lower Missouri Valley into southern portions of the Upper Midwest, and across parts of the southeastern Great Plains into portions of the Mid South. These could pose a risk for a few strong tornadoes, large hail and damaging wind gusts. ...Synopsis... As initially amplified mid-level ridging over the mid-latitude eastern Pacific gradually becomes suppressed, models indicate that downstream troughing will broaden from the Great Basin into the Mississippi Valley. This will be lead by a vigorous short wave trough, which is forecast to be accompanied by continuing strong surface cyclogenesis from the central Great Plains into the Upper Midwest, and building downstream mid-level ridging across the Upper Ohio Valley into Ontario, as well as across the northeastern Gulf of Mexico into Southeast. An intensifying southwesterly mid/upper jet streak (including speeds in excess of 100 kt at 500 mb) nosing across the central Great Plains through Upper Midwest will contribute to strong deep-layer shear within the warm sector of the cyclone. At the same time, intensification of southerly lower-level flow (to 50-70+ kt around 850 mb) likely will contribute to large clockwise-curved low-level hodographs. This could potentially contribute to an environment conducive to supercells and organizing lines or clusters capable of producing strong tornadoes and damaging winds, where large-scale forcing for ascent and thermodynamic profiles can become favorable. However, among a number of substantive lingering uncertainties, the quality of the boundary-layer moisture return from the Gulf of Mexico remains in question. Due to (at least initially) relatively shallow boundary-layer depth, downward mixing of drier air might impact sizable pockets of the potentially broad warm sector through the day, based on model output. Also, ahead of the mid/upper troughing, destabilization associated with large-scale ascent and an influx of high-level moisture from the subtropical Pacific may contribute to convective development which tends to saturate and stabilize lapse rates down into the mid-levels, across much of the Ozark Plateau into middle Mississippi Valley. While it appears that this will not completely erode the capping elevated mixed-layer air, thickening cloud cover aloft may inhibit surface heating and suppress potential thunderstorm development in the absence of lift to overcome the inhibition. ...Great Plains into the Mississippi Valley... Both the latest NAM and Rapid Refresh appear increasingly suggestive that the dryline could surge east-northeastward across southwestern Iowa and northwestern/west central Missouri, at least above the surface, by mid to late afternoon, in response to the progression of at least one speed maximum within the mid-level flow. Model output generally indicates that largest CAPE will become focused ahead of this feature, and south of the warm front advancing northward across central Iowa/northern Illinois during the late afternoon. And the dryline might provide a focus for sustained discrete supercell development with the potential to produce strong tornadoes while propagating northeastward across northeastern Missouri and southeastern Iowa into northwestern and west central Illinois through early evening. In the wake of this activity, as the cold front begins to overtake the dryline and advance southeastward, various model output continues to suggest that the evolution of an organizing line or cluster of storms is possible. This may pose a risk for large hail, damaging wind gusts, and perhaps a few tornadoes while propagating east-southeastward across the lower Missouri/middle Mississippi Valley vicinity into Tuesday night. Farther south, developments initially along the dryline and then ahead of the southeastward advancing cold front remain a bit more unclear. However, there has been a persistent signal within the model output that a narrow corridor of more substantive boundary-layer moistening could provide a focus for enhanced severe weather potential by Tuesday evening. It is possible that associated destabilization may become aligned with the strong deep-layer mean flow, possibly allowing for the evolution of one or two long track supercells, ahead of a developing squall line. ..Kerr.. 04/03/2023 Read more CHECK UPDATE ZOOM GRAPHIC