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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.


Tuesday, April 12, 2022

SPC Apr 12, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0250 PM CDT Tue Apr 12 2022 Valid 122000Z - 131200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FAR EASTERN NEBRASKA INTO CENTRAL IOWA... ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS NORTHEAST KANSAS INTO SOUTHERN MINNESOTA AS WELL AS PORTIONS OF CENTRAL TO NORTHERN TEXAS... ...SUMMARY... Scattered severe thunderstorms capable of producing very large hail, damaging winds, and tornadoes are expected late this afternoon and tonight across a broad portion of the southern/central Plains into the Mississippi Valley. Some of the tornadoes could be strong across western and northern Iowa. ...Central to southern Texas... Deep convective initiation along the dryline is underway with one organized storm noted in regional radar imagery and additional attempts at deeper convection noted in GOES visible imagery. Isolated storms in the next 1-2 hours will likely increase in coverage through the late afternoon and evening hours. See mesoscale discussions #454 and #456 for additional details. ...Nebraska into Iowa... Latest surface observations and visible imagery show a consolidated low over central NE with a warm front lifting north across IA. Warming temperatures and increasing boundary-layer moisture (dewpoints in the low 60s) are augmenting instability within a somewhat narrow warm sector. Thunderstorm development remains likely heading into the late afternoon hours in the vicinity of the surface low and along the dryline/cold front. See MCD #457 for additional information. ..Moore/Mosier.. 04/12/2022 .PREV DISCUSSION... /ISSUED 1129 AM CDT Tue Apr 12 2022/ ...NE/IA/KS/MO later this afternoon into tonight... In advance of a deep midlevel trough over the central/northern Rockies, a 984 mb surface cyclone in northeast CO this morning will move to northeast NE this evening and northwest WI by 13/12z. Rapid low-level moisture advection will occur through the day in the cyclone warm sector into eastern NE and IA, as boundary-layer dewpoints in the low-mid 60s advect northward from eastern KS, and moisture also mixes downward as the low levels warm. Warm/moist advection beneath midlevel lapse rates greater than 8 C/km will result in MLCAPE of 2000-3000 J/kg with weakening convective inhibition in a narrow zone near the triple point, coincident with focused forcing for ascent. Thus, thunderstorm development is expected by about 22z near and immediately east of the triple point, across northeast NE into northwest IA, and storms will subsequently develop eastward near the warm front across northern IA. Long hodographs with substantial clockwise curvature in the low levels (effective SRH 300-400 m2/s2 and effective bulk shear of 50-65 kt), in combination with the strong buoyancy and sufficient low-level moisture, will favor supercells capable of producing strong, long-tracked tornadoes with a storm or two this evening, along with very large hail near the size of baseballs. Convection will likely grow upscale into a line overnight from western/central IA into eastern KS, as a cold front overtakes the dryline from north-to-south. The primary severe threat will transition to damaging winds with the overnight frontal squall line. ...TX/OK/AR/LA this afternoon through tonight... A southern stream shortwave trough near Del Rio this morning will move northeastward toward the Ark-La-Tex by this evening. Some elevated convection will be possible through the day across the eastern half of TX within the midlevel moisture plume atop the elevated mixed layer. There will be some potential for some of this convection to eventually root into the low levels, though any subsequent storm evolution is uncertain. Somewhat higher confidence exists in isolated-scattered severe storm development this afternoon/evening along the dryline in central/north TX, near the trailing influence of the southern stream midlevel trough. Aside from areas impacted by elevated convection, steep midlevel lapse rates, MLCAPE near 3000 J/kg, and effective bulk shear in excess of 40 kt will all favor supercells capable of producing very large hail, damaging winds, and a couple of tornadoes. One or more clusters of storms could evolve from the evening convection and persist into tonight while spreading toward LA/AR, with an attendant threat for damaging winds and large hail. Farther north into OK, there is substantial uncertainty regarding storm initiation along the dryline, with the more probable area being across southern OK in proximity to the southern stream trough moving over TX, and possible mesoscale influences of convective outflow. Immediately north-northwest of the TX midlevel trough, there is the potential for weak subsidence and disrupted hodograph structures related to a weakness in the midlevel flow. If storms do form along the dryline this afternoon/evening, there will be a conditional threat for isolated very large hail. Any tornado threat will depend on diurnal storms lingering into late evening as low-level shear increases, but convective inhibition also increases. Read more CHECK UPDATE ZOOM GRAPHIC
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