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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.


Wednesday, August 23, 2023

SPC Aug 23, 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 1231 AM CDT Wed Aug 23 2023 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE GREAT LAKES AND UPPER OHIO VALLEY... ...SUMMARY... Thunderstorms associated with damaging wind gusts and hail are expected to develop tonight across parts of the lower Great Lakes region and upper Ohio Valley. Marginally severe wind gusts and hail will also be possible in parts of the northern Plains late this afternoon and evening. ...Great Lakes/Upper Ohio Valley... A mid-level anticyclone will be located across the central U.S. today. On the northeastern periphery of this feature, mid-level flow will be from the west and northwest across the Great Lakes region. Thunderstorms will likely be ongoing across parts of Lower Michigan at the start of the period. This activity is expected to weaken by late morning. A moist airmass will advect eastward across Lower Michigan today, with surface dewpoints increasing into the lower to mid 70s F. Within northwest mid-level flow, a shortwave trough is forecast to move southeast across the eastern Great Lakes. Ahead of this feature, model forecasts consistently develop scattered thunderstorms late this evening. This activity is forecast to organize into an MCS and move southeastward across eastern Lower Michigan, and into northern Ohio and northwest Pennsylvania during the overnight period. RAP forecast soundings near the track of the MCS around midnight suggest that the storms will be surface-based with strong instability (MUCAPE above 4000 J/kg), and moderate deep-layer shear. This should support a wind-damage threat as the MCS develops into a bowing line segment. The MCS could impact areas as far south as southeast Ohio and western Pennsylvania later in the period. ...Northern Plains... Mid-level flow is forecast to be from the west-southwest across the north-central U.S. today, over the top of a mid-level anticyclone in the central U.S. At the surface, a quasi-stationary front will remain from central South Dakota into southern Minnesota. Low-level moisture will be maximized to the north of this boundary from northeastern South Dakota into central and eastern North Dakota, where an axis of instability will likely develop. Isolated thunderstorms may form across parts of North Dakota near this axis of instability from late afternoon into evening. The storms will most likely develop along the leading edge of a band of large-scale ascent ahead of an approaching shortwave trough, with most of the convection remaining elevated. In spite of this, effective shear near 40 knots and somewhat steep lapse rates above 700 mb may be enough for a marginal hail threat. A few strong wind gusts will also be possible. ..Broyles/Weinman.. 08/23/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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