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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, November 29, 2023

SPC Nov 29, 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
1100 PM CST Tue Nov 28 2023

Valid 291200Z - 301200Z


Scattered thunderstorm development is possible by this evening
across parts of the Colorado Plateau into the southern Rockies, and
across parts of the southern Great Plains overnight. The risk for
severe storms still appears negligible until after daybreak

While an initially deep and elongated mid-level low over Hudson Bay
may become more axisymmetric and deepen further through this period,
troughing to its southeast is forecast to continue to pivot away and
northeast of the Atlantic Seaboard. As it does, mid-level flow
appears likely trend more zonal across and east of the Mississippi
Valley, but cool to cold, dry and stable conditions across much of
the East will be slow to modify.

The center of the cold surface ridging is forecast to begin
redeveloping across and offshore of the southern Atlantic coast,
leading to a strengthening southerly return flow from the western
Gulf of Mexico into southern Great Plains. Models indicate that
this will be enhanced by deepening surface troughing to the lee of
the southern Rockies, as a short wave trough (within a branch of
westerlies emanating from the southern mid-latitude Pacific) digs
inland of the central/southern California coast, through the
Southwest by 12Z Thursday.

While the mid-level cold core is forecast to pivot inland of the
California coast during the day, low-level moistening and any
potential destabilization will remain confined to areas near and
offshore of southern California into northern Baja California
coastal areas. However, farther inland, across parts of the
Colorado Plateau into the southern Rockies, low-level warming and
steepening lapse rates aided by daytime heating, may contribute to
destabilization. As stronger forcing for ascent and mid-level
cooling overspreads this region, in the exit region of a 70-80 kt
500 mb jet streak nosing across northern Mexico, scattered weak
thunderstorm development is possible during the evening into the
overnight hours.

Farther downstream, models indicate that rapid low-level moisture
return from the southwestern Gulf of Mexico is possible,
particularly tonight as a southerly low-level jet (30-40+ kt around
850 mb) strengthens across the lower Rio Grande Valley into the
southern Great Plains. North and inland of the lower Texas coast,
associated destabilization will likely be rooted above at least a
shallow stable surface-based layer. Across the Hill Country into
northwest Texas, most unstable CAPE might increase to 500-1000 J/kg
by late tonight, beneath a generally capping plume of elevated
mixed-layer air. On the leading edge and northeast/east of this
plume, lift associated with warm advection may support increasing
thunderstorm development toward daybreak Thursday. However, weaker
and weakening lapse rates within this elevated convective regime
seems likely to minimize the risk for severe hail.

..Kerr/Weinman.. 11/29/2023

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)