LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1128 AM CDT Tue Aug 29 2023
Valid 291630Z - 301200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS THROUGH TONIGHT
ALONG THE WEST COAST OF FL...AND THIS AFTERNOON/EVENING ACROSS PARTS
OF THE NORTHERN ROCKIES...
...SUMMARY...
A few tornadoes will be possible this afternoon through tonight,
mainly from the west central Florida into the Florida Big Bend in
the northeast quadrant of strengthening Hurricane Idalia.
Occasional damaging wind gusts will be possible across the northern
Rockies.
...FL Gulf coast through tonight...
Hurricane Idalia is strengthening as of midday over the southeast
Gulf of Mexico and is forecast to make landfall Wednesday morning
near the FL Big Bend as a major hurricane (please see latest NHC
advisories for additional information). Storm motion will be
largely parallel to the FL west coast into early tonight, so
eastward expansion of the stronger wind field and more favorable
low-level hodograph structures will be a gradual process (per the
trends in the VWPs from Key West and Tampa). Surface observations
show 77-80 F dewpoints across almost all of central/south FL, which
will help maintain surface-based buoyancy into this evening and
overnight. Thus, the primary increase in supercell/tornado threat
is expected late this afternoon into tonight from near Tampa
northward along the coast with the more cellular convection within
the outer eastern/northeastern bands.
...Northern Rockies this afternoon/evening...
A midlevel shortwave trough now over far northern CA and OR will
progress east-northeastward toward the northern Rockies by this
evening. Though low-level moisture is rather limited, strong
surface heating/deep mixing will result in inverted-V profiles with
weak buoyancy in advance of the midlevel trough and an associated
cold front. Thunderstorm development is expected this afternoon
through early tonight in the zone of ascent preceding the midlevel
trough (and along the front). The highest confidence in storm
development coincident with the steep low-level lapse rates and some
enhancement to midlevel flow will be later this afternoon over the
Bitterroots, where a few damaging outflow gusts of 60-70 mph will be
possible.
..Thompson/Lyons.. 08/29/2023
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