SPC 1730Z Day 2 Outlook
Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1236 PM CDT Sat Aug 03 2024
Valid 041200Z - 051200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF
FL AND FAR SOUTHEAST GA...OVER THE NORTHERN HIGH PLAINS...AND THE
UPPER MS VALLEY...
...SUMMARY...
Widely scattered strong thunderstorms may pose at least some risk
for severe weather across parts of Florida and adjacent southeastern
Georgia, portions of the upper Mississippi Valley and portions of
the northern High Plains Sunday through Sunday night.
...Synopsis...
Expansive upper ridging is expected to be centered over the Four
Corners early Sunday morning, influencing the sensible weather over
much of the Southwest, Great Basin, and central/southern Plains. A
deep upper low is forecast to move across the Hudson Bay /northern
Quebec, with a belt of modestly enhanced westerly flow aloft between
this upper low and the Southwest upper ridge, extending from the
Pacific Northwest through the Upper Great Lakes. Several shortwave
troughs are possible within these westerlies, including one expected
to move into the Upper MS Valley during the afternoon and another
one farther west that is expected to move through the northern High
Plains and into the northern Plains.
Farther east, modest upper troughing is forecast to extend from the
Northeast through the Carolina early Sunday, before gradually
shifting eastward/northeastward throughout the day. A tropical
system initially over the western Gulf of Mexico is expected to
strengthen as it tracks northeastward, likely making landfall as a
strong Tropical Storm in the FL Big Bend Monday morning.
Most significant surface feature Sunday morning, aside from the
deepening tropical cyclone, will be the weak frontal zone that
extend from a low over eastern MT southeastward to another low near
the SD/NE/IA border intersection vicinity and then back
northeastward through central WI and central Upper MI. This boundary
will likely remain stationary throughout the day, likely sharpening
amid strong mixing to its south.
...Eastern FL Panhandle/FL Peninsula into Far Southeast GA...
A tropical cyclone is forecast to begin the period centered well off
the coast of southwest FL before progressing north-northeastward
throughout the day and deepening. Rainbands associated with this
system will likely spread across FL in several rounds throughout the
day, with the highest coverage of thunderstorms and greatest several
potential from 16Z to 00Z when daytime heating could boost buoyancy
slightly. Low-level wind fields will likely strengthen as the
overall system strengthens, with moderate to strong veering
low-level profiles expected throughout the period. Any deeper, more
persistent updrafts could briefly organize, with some brief
tornadoes possible. A few strong convectively augmented gusts are
possible as well.
...Northern High Plains...
Increasing large-scale forcing for ascent and mid-level moisture
attendant to a shortwave trough progressing through the northwestern
periphery of the upper ridge will likely contribute to thunderstorm
development from northwest WY into central MT Sunday afternoon.
These storms will likely continue into more of eastern MT during the
evening, encountering better low-level moisture and potentially
interacting with the surface low at the western end of the frontal
zone described in the synopsis. Low-level easterly flow will help
increase deep-layer vertical shear within this region as well. A few
strong to severe gusts are possible with the earlier more cellular
activity but a relatively greater potential for strong gusts is
anticipated farther east across southeast MT when better low-level
moisture and easterly/southeasterly surface winds will be in place.
Some potential exists for loose organization across the cold pool,
but capping issues from far southeast MT into the western Dakotas
will likely limit the eastern extent of the severe threat.
...Northern Plains into the Upper Mississippi Valley...
Guidance varies on the impact of boundary layer mixing and warm
mid-level temperatures across the southern MN/northern IA/southwest
WI vicinity during the afternoon and evening. Some guidance allows
for enough low-level moisture and strong buoyancy and the potential
for robust updrafts capable of strong gusts and/or large hail.
However, other guidance keeps the capping in place, with the strong
heating south of the boundary still not enough to overcome the warm
mid-level temperatures. This merits keeping low severe
probabilities, although higher probabilities maybe needed if trends
indicate an increased likelihood for afternoon/evening convective
initiation.
Elevated thunderstorms are likely across the northern Plains
overnight Sunday as the northern High Plains shortwave trough
continues eastward into the northern Plains. A few stronger storms
are possible, but most the these storms are currently expected to
stay below severe thresholds.
..Mosier.. 08/03/2024
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