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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, March 20, 2024

SPC Mar 20, 2024 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1238 AM CDT Wed Mar 20 2024

Valid 201200Z - 211200Z


A few clusters of thunderstorms should develop across parts of Texas
and western Oklahoma this afternoon through tonight. Some of this
activity may pose a marginal hail or gusty wind risk.

A southern-stream mid/upper-level jet will persist today over Mexico
and the Gulf, along with the southern Plains into the Southeast. A
weak mid-level shortwave trough will move eastward across NM and
into west TX by this evening, while a separate perturbation develops
across northern Mexico and south TX through late tonight. Surface
high pressure centered over the Gulf and Southeast will hamper the
northward advance of rich low-level moisture over much of TX through
this afternoon, although limited moisture should be able to reach
parts of the TX Panhandle and western OK along/east of a weak
surface trough. Somewhat greater low-level moisture should
eventually spread inland over portions of south/coastal TX late
tonight into early Thursday morning.

...Texas Panhandle into Western Oklahoma...
Even with weak surface cyclogenesis occurring over the southern High
Plains today, low-level moisture will likely remain quite modest
with surface dewpoints generally in the mid 40s to low 50s. Still,
cold temperatures aloft (around -16 to -20C at 500 mb) and steep
low/mid-level lapse rates should aid in the development of weak
MLCAPE this afternoon as modest daytime heating occurs. Sufficient
deep-layer shear owing to modestly enhanced mid-level winds should
be in place to support some updraft organization with any convection
that can form along/east of the surface trough. With lengthy
mid/upper-level hodographs, some of these thunderstorms could
produce small to marginally severe hail. A very well-mixed boundary
layer should also foster an isolated threat for strong to severe
downdraft winds. Limited moisture/instability are expected to keep
the overall severe threat fairly marginal/isolated across this area.

...South/Coastal Texas...
Low-level moisture will gradually increase this evening and
overnight across parts of south/coastal TX. While a stout cap will
likely suppress convection through much of the day, large-scale
ascent preceding a southern-stream shortwave trough may eventually
encourage isolated thunderstorms to develop late tonight. If this
occurs, convection should tend to remain elevated. But with moderate
MUCAPE and strong deep-layer shear, any thunderstorms that form and
persist could produce severe hail. This threat appears rather
conditional, with most high-resolution guidance suggesting that
robust convective development will be delayed until around 09-12Z
Thursday morning.

A strong mid/upper-level cyclone, with associated 70-90 kt mid-level
jet, will be in place over much of the Great Lakes and Northeast
today. A related surface low will develop eastward across southern
Quebec through the day, while a secondary surface low deepens and
quickly advances eastward in tandem with a cold front across coastal
parts of the Northeast and Mid-Atlantic. Most guidance shows minimal
instability ahead of the front, but cold mid-level temperatures and
modest diurnal heating may be enough to support the development of
very weak boundary-layer instability. It remains questionable if any
low-topped convection that develops will reach sufficient depths to
produce lightning. Regardless, occasional strong/gusty winds may
occur with this activity given the forecast strength of the
low/mid-level flow.

..Gleason/Flournoy.. 03/20/2024

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)