SPC 0730Z Day 3 Outlook

Day 3 Outlook Image

Day 3 Convective Outlook  
NWS Storm Prediction Center Norman OK
0228 AM CDT Tue May 04 2021

Valid 061200Z - 071200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THURSDAY ACROSS
PARTS OF NORTHERN FLORIDA AND EASTERN PORTIONS OF THE FLORIDA
PENINSULA...

...SUMMARY...
Strong thunderstorms may impact parts of northern Florida and
Atlantic coastal portions of the Florida peninsula Thursday, a few
of which may pose at least some risk for large hail and damaging
wind gusts.

...Synopsis...
While upstream flow over the northern mid-latitude Pacific trends
more zonal during this period, models suggest that mid-level ridging
and troughing on the leading edge of this regime will remain
amplified.  Eastward progress of the troughing inland of the Pacific
coast, and the ridging across the Rockies, will be slowed, as
blocking in the downstream flow (centered near the Labrador Sea)
persists.  

A broad and deep mid-level closed low is forecast to remain centered
near James Bay, with troughing to its south amplifying east of the
lower Mississippi Valley in response to at least a couple of digging
short wave impulses.  Models indicate that this will be accompanied
by substantive lower/mid tropospheric drying as far south and east
as the northern Gulf of Mexico, central portions of the Florida
peninsula and the Atlantic waters off the south Atlantic coast by
late Thursday night.

Destabilization, largely supported by seasonably strong mid-level
cooling across parts of the middle Mississippi into lower Ohio and
Tennessee Valleys, as well as across parts of the northern U.S.
intermountain region, aided by surface heating, may contribute to a
risk for thunderstorms during the day.  Steepening lapse rates
associated with seasonably strong daytime heating may also
contribute to some risk for thunderstorms across the southern
Rockies, aided by orographic forcing.  Seasonably high
boundary-layer moisture content will largely be confined to ahead of
a surface frontal zone advancing southward into the Florida
peninsula.

...Florida...
Models suggest that the front, or a pre-frontal convective outflow
boundary, initially extending across northern Florida early
Thursday, may become a focus for increasing forcing for ascent by
early afternoon.  It appears that this will be supported by
increasingly cyclonic and difluent mid/upper flow, in the presence
of modestly steep low-level lapse rates, convective instability and
CAPE on the order of 1000+ J/kg.  Beneath 30-40+ kt westerly flow in
the 700-500 mb layer, the environment might become at least
marginally conducive to organized storms capable of producing severe
hail and damaging wind gusts.

Wind fields will be weaker, but with pronounced veering with height
along the sea breeze near or inland of the Atlantic coast, where
low-level convergence will become focused Thursday afternoon.  In
the presence of somewhat steeper low-level lapse rates and larger
CAPE, a supercell or two might not be out of the question. 
Otherwise, stronger storm development may become capable of
producing strong downbursts, before diminishing/spreading offshore
Thursday evening.

..Kerr.. 05/04/2021

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