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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.


Thursday, July 13, 2023

SPC Jul 13, 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 0125 AM CDT Thu Jul 13 2023 Valid 131200Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE OHIO VALLEY INTO THE NORTHEAST AND PARTS OF THE CENTRAL/SOUTHERN HIGH PLAINS... ...SUMMARY... Scattered severe thunderstorms capable of producing damaging winds, large hail, and perhaps a couple of tornadoes are possible Thursday across parts of the Ohio Valley into the Northeast, and portions of the southern/central Plains. Isolated very large hail may occur across parts of the central Plains. ...Synopsis... A shortwave trough continues through the Lower Great Lakes region. This feature will reach the Northeast by early afternoon. Moderate mid-level winds will exist across parts of the northern Mid-Atlantic into New England. Stronger northwesterly flow aloft will be present across much of the northern and central Plains. At the surface, a low pressure system will deepen along the Canadian border in the Northeast through the day. A cold front will extend southwestward to near the Mid-South. Convective outflow is likely to be situated from northern Arkansas into parts of northern Oklahoma. ...Northeast... While some cloud cover may be present during early portions of the day ahead of the approaching shortwave, these clouds should not be overly prohibitive with regard to surface heating by the afternoon. Ahead of the trough and surface front, 850 mb winds are forecast to reach around 35 kts. Shear will be sufficient for some storm organization, but a majority of that shear will exist in the lowest 3 km or so. Wind profiles above that level are unidirectional and fairly uniform in speed as well. The very moist airmass in place (likely upper 60s F dewpoints) will support 1500-2000 J/kg MLCAPE. A line of storms is expected to form along the cold front in central New York and progress eastward during mid/late afternoon. Wind damage is expected to be the primary threat. Given the low-level shear, a few tornadoes occur could as circulations develop within the line or a discrete storm or two forms ahead of the line. The most intense updrafts may also produce large hail. Given line-parallel upper level winds, the eastward progress of the line may only be modest. This decreases confidence in higher potential for wind damage. ...Parts of Ohio Valley... Stronger mid-level flow will extend southwestward into the Ohio Valley. The airmass will be similarly moist in this region as well. With the upper-level jet moving into the region, deep-layer shear will approach 40-50 kts. Scattered storms will be capable of damaging winds and large hail. Low-level shear will be relatively weak, though a brief tornado could occur with the strongest supercell structures. ...Central/southern Plains... Moderate mid-level flow across the Divide will allow storms initiating within the higher terrain to organize into supercells. As storms move into the moist airmass to the east, large to very large hail and severe/damaging winds will be possible. Some clustering may occur with time and lead to corridors of greater wind damage potential. With an outflow boundary expected to be situated in northern/central Oklahoma, it is possible that some activity from the High Plains will track eastward during the evening. The Slight risk has been extended east to account for this possibility, but may need adjustment as observations and newer guidance warrants. ...Northern Plains into parts of Upper Midwest.. At least isolated to widely scattered storms are expected from north-central Montana into the Dakotas and Minnesota. Northwest flow aloft will be strong enough to promote 25-35 kts of effective shear to the west with values increasing to 35-45 kts farther east. Lack of greater surface moisture should limit the overall severe threat. Greater moisture is possible near the Nebraska/South Dakota border into southern Minnesota, but model guidance may be too high with dewpoints. Large hail and damaging winds are the expected hazards. If an area of higher storm concentration becomes apparent, an increase in wind/hail probabilities may be warranted. ..Wendt/Thornton.. 07/13/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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CHICAGO UTC-6 during CST (Central Standard Time, e.g., winter)
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