SPC AC 080718
Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0218 AM CDT Fri Sep 08 2017
Valid 101200Z - 111200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE FL
PENINSULA AND COASTAL GA/SC...
A few brief tornadoes are possible across portions of the Florida
Peninsula and coastal Georgia and South Carolina Sunday as Hurricane
Irma impacts the region.
Based on the latest forecast track from the National Hurricane
Center, the center of Hurricane Irma is expected to be onshore
across the far southern FL Peninsula. It is then expected to
continue north-northwestward along the spine of the FL Peninsula,
reaching the north-central FL Peninsula by 12Z Monday. Refer to the
National Hurricane Center for the most up-to-date information
regarding Hurricane Irma.
Elsewhere, upper ridge extending from the southern Plains through
the Great Basin will change little throughout the period. An upper
low off the southern/central CA coast will drift slightly
northward/northwestward while deepening. Shortwave trough initially
over western portions of the Upper Midwest will eject northeastward
into northwestern Ontario.
...Hurricane Irma - FL Peninsula/Coastal GA and SC...
Given the anticipated track of Irma, a tropical cyclone tornado
environment will likely exist across the majority of the FL
Peninsula during the day and then expand northward into coastal
portions of GA and SC. Eastern portions of the FL Peninsula do not
look overly favorable for tornadoes given the current forecast track
but uncertainties regarding the actual track and the overall size
and strength of the storm merit the inclusion of the entire
peninsula in a 5% severe area.
Mid-level flow around the eastern periphery of the upper low off the
southern CA coast will increase Sunday evening/Monday morning as the
system gradually deepens. This moderate, largely unidirectional flow
will result favorable shear across the region. Airmass appears
supportive of elevated thunderstorms over coastal portions of
southern CA Sunday evening and overnight. Severe coverage is too
uncertain at this time to introduce any probabilities across the
region but outlook areas may be needed in subsequent forecast if
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