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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 2000 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0253 PM CDT Thu Jul 13 2023 Valid 132000Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF NORTHERN NEW YORK AND WESTERN VERMONT... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER MUCH OF THE PLAINS...PARTS OF THE OHIO VALLEY...AND NORTHEAST... ...SUMMARY... Numerous severe thunderstorms are likely today across eastern New York and western Vermont, with scattered severe thunderstorms possible across parts of the Ohio Valley and portions of the southern/central Plains. Damaging winds, large hail, and perhaps a couple of tornadoes are possible in these areas. Isolated very large hail may occur across parts of the central Plains. ...Northeast... A line of storms continues to push rapidly east across NY, with strong wind gusts measured recently. Instability remains favorable ahead of the line, and heating continues as well. While the primary threat is for damaging winds, effective SRH over 150 m2/s2 and deep-layer shear over 30 kt will also favor a few supercells with hail or brief/weak tornado risk. For more information see mesoscale discussion 1523. Farther south, a relative minimum in thunderstorm coverage is expected over southern PA into MD, and the Slight Risk has been modified in these areas as the severe risk should remain isolated. The primary risk farther south is expected to remain over the OH Valley, WV and western VA. ...Plains... Extreme moisture and instability is noted into eastern CO where dewpoints are in the 68-72 F range. The backed/easterly low-level flow beneath moderate high level flow is resulting in long hodographs with around 50 kt effective shear. The result should be very large hail, as well as developing damaging wind threat as storms increase in coverage and blend outflows through the OK/TX Panhandles and into western OK. For more information see mesoscale discussion 1519. ..Jewell.. 07/13/2023 .PREV DISCUSSION... /ISSUED 1119 AM CDT Thu Jul 13 2023/ ...NY into New England... Water vapor loop shows a strong mid-level shortwave trough moving across southern Ontario, with a surface cold extending extending from Lake Erie into central/eastern OH. A warm front extends east from a surface low over southeast Ontario Province to the coast near Portland, ME. The cold front will move steadily east this afternoon into NY where thunderstorm development is underway, with an increase in coverage likely over the next few hours. Surface dewpoints in the mid 60s and substantial heating will yield pockets of MLCAPE over 2000 J/kg, along with moderately steep low and mid-level lapse rates. Shear profiles are also rather strong, conducive for organized/supercell structures. Thunderstorms are expected to intensify over eastern NY in the Hudson Valley vicinity before spreading into western New England. A mixture of discrete supercell storms and bowing structures is expected, capable of large hail and damaging wind gusts, and perhaps a tornado or two. Storms should weaken during the evening while moving into a more stable environment with time. See recently issued Mesoscale Discussion 1517 for additional details on short-term thinking in this area. ...KY/WV/OH... As the cold front sags southward into the upper OH Valley by mid-afternoon, scattered thunderstorms are expected to develop. Sufficient westerly flow aloft and MLCAPE of 1500 to locally 2000 J/kg will promote supercells and organized clusters capable of damaging winds and severe hail. ...High Plains from SD to TX... A broad upper-level ridge is present today over the southwest states, with the southern fringe of stronger westerlies extending across CO/KS. A surface dryline will become established by late afternoon extending from the Black Hills vicinity across eastern CO. Forcing will be subtle, however minimal CINH and ample moisture/instability will result in widely scattered intense storms along the dryline, spreading southeastward through the evening. Supercells capable of very large hail appear possible. Storms over western SD/NE, and also over southwest KS and adjacent TX/OK panhandles may persist well into the night and spread eastward across those states. Read more CHECK UPDATE ZOOM GRAPHIC
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