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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 4, 2023

SPC Apr 4, 2023 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0104 AM CDT Tue Apr 04 2023 Valid 041200Z - 051200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM EASTERN IOWA INTO NORTHWEST ILLINOIS AND NORTHEAST MISSOURI...AND FROM SOUTHERN MISSOURI SOUTHWESTWARD TOWARD THE ARKLATEX... ...SUMMARY... A large area of severe potential will develop today into tonight, from eastern portions of the Plains into the Missouri and mid/upper Mississippi Valleys. Strong, potentially long track tornadoes are possible, in addition to large hail and damaging winds. Both afternoon and overnight potential is expected across various regions, including the risk of dangerous nighttime tornadoes. ...Synopsis... A deep upper trough will move from the Intermountain West/Rockies toward the Great Plains today. Within the large-scale trough, an upper cyclone will deepen as it moves northeastward toward the Dakotas. An 80-100 kt midlevel jet will overspread the central Plains during the afternoon/evening, while a secondary jet maximum intensifies through the day from the southern Plains into parts of the Midwest. At the surface, a broad cyclone will gradually consolidate and deepen as it propagates from the central High Plains toward western IA by early evening. A warm front will move northward into central/northern IA and northern IL by late afternoon, and into parts of WI/lower MI late tonight. A dryline will extend southward across eastern portions of the central/southern Plains, with a cold front expected to sweep through the Plains/Midwest this evening into the overnight. ...Iowa into parts of the Great Lakes states... Short-term guidance continues to vary greatly regarding the extent of mixing across the warm sector over parts of the Midwest later today. The typically overmixed RAP/HRRR drop surface dewpoints to near 60F south of the warm front as temperatures warm to near 90F, while the generally undermixed NAM maintains cooler temperatures and upper 60s F dewpoints across the warm sector, and is slower to advance the warm front northward. The current expectation is for the magnitude of mixing to be somewhere between these two extremes, with dewpoints remaining in the mid 60s in closer proximity to the warm front, with somewhat stronger mixing possible farther south. Considerable spread remains regarding convective evolution among regional/global guidance and CAMs. However, two areas of possible storm initiation this afternoon are evident. The first is near the MO/IA/IL border region, where substantial warming/moistening beneath steep midlevel lapse rates will result in rapid destabilization near/south of the warm front. Any supercell that develops in this region during the afternoon will pose a threat of very large to giant hail. Very favorable low-level and deep-layer shear will support a threat of strong tornadoes as well for as long as any supercell traverses the warm sector along/south of the warm front. The second area of potential initiation will be farther west across west-central IA, closer to the surface low. Some uncertainty remains regarding the moisture quality this far west, but moderate buoyancy and very favorable wind profiles will support a threat of supercells capable of all severe hazards, including the potential for a strong tornado or two with any cell that can persist in the warm sector. Additional convection may develop later tonight in association with the cold front and move into the region, posing a threat of hail and damaging gusts. A conditional tornado threat will also persist overnight with any sustained supercells. Finally, storms capable of hail will be possible north of the warm front, where MUCAPE in excess of 1000 J/kg, steep midlevel lapse rates, and sufficient deep-layer shear will support elevated supercell potential, despite rather cold surface temperatures. ...Southern Plains into the Ozark Plateau... A very favorable severe thunderstorm environment will also reside across the southern Plains into the Ozark Plateau, beginning this afternoon and persisting overnight east of the dryline/cold front. Diurnal storm development along the dryline is expected to be isolated at best, with large-scale ascent remaining weak for much of the day. However, convection is expected to increase this evening and especially overnight from northeast TX into AR and southern MO, within a persistent low-level moist plume associated with a strong low-level jet. Moderate buoyancy and very favorable wind profiles will support supercells, both with diurnal storms (if any develop) and nocturnal convection. Some nocturnal storms may be somewhat elevated (at least initially) and the mode may be a mix of discrete cells and clusters, but weak MLCINH will not prohibit surface-based convection, and the current expectation is for supercell potential to increase overnight. Any nocturnal supercells will be capable of all severe hazards, and the concern remains regarding the potential for nocturnal strong tornadoes from near the ArkLaTex region into parts of southern MO. ..Dean/Thornton.. 04/04/2023 Read more CHECK UPDATE ZOOM GRAPHIC
SUNRISE AND SUNSET TIMES IN UTC (if you're not logged in to Google)
CHICAGO UTC-6 during CST (Central Standard Time, e.g., winter)
CHICAGO UTC-5 during CDT (Daylight Savings Time, e.g., summer)