839
ACUS01 KWNS 182000
SWODY1
SPC AC 181958

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0258 PM CDT Sat May 18 2024

Valid 182000Z - 191200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR WESTERN
PORTIONS OF THE UPPER PENINSULA OF MICHIGAN INTO CENTRAL
WISCONSIN...

...SUMMARY...
Large hail and damaging winds remain possible in the western Great
Lakes region this afternoon.

...20Z Update...
Cloud cover has remained across portions of southeast Georgia into
North Florida. Furthermore, outflow from convection has surged south
of Jacksonville. Storms are initiating on this boundary, but are
quickly being undercut. Wind probabilities have been reduced in
these areas as the environment has generally become more stable in
the wake of the boundary.

A few marginal supercells have develop both near/north of Orlando
and along the sea breeze boundary in eastern Florida, the 5%
wind/hail probabilities have been adjusted to account for this
activity. The 15Z Cape Canaveral sounding showed 7.3 C/km mid-level
lapse rates and 43 kts of effective shear. Marginally severe hail
and damaging winds are possible, but weak mid-level ascent and
warmer temperatures aloft (-7 C) should limit overall storm
organization/intensity.

Elsewhere, the outlook remains unchanged other than adjustments to
the general thunderstorm areas to account for current observations.

..Wendt.. 05/18/2024

.PREV DISCUSSION... /ISSUED 1129 AM CDT Sat May 18 2024/

...North FL/South GA...
A persistent band of widespread showers and thunderstorms extends
from the FL Panhandle into southern GA.  This band will sag
southward through the day, with occasional intensification along the
leading edge as daytime heating destabilizes the upstream
environment.  Locally gusty/damaging winds appear to be the main
threat.

...FL East Coast...
Strong heating is occurring along the FL peninsula, where hot/humid
conditions will be present this afternoon.  Westerly low-level flow
will focus a rather strong sea-breeze circulation, with most CAM
solutions suggesting scattered thunderstorm development.  It is
uncertain whether the activity will be along the immediate
coastline, or offshore.  However, sufficient vertical shear and CAPE
profiles indicate a risk of supercells capable of large hail and
perhaps a tornado/waterspout or two.


...Western Great Lakes into Central Plains...
A surface cold front will extend from western WI into parts of
IA/MO/KS by mid-afternoon.  Scattered thunderstorms are expected to
form along the front from the MN Arrowhead southward into western
WI, with more isolated convection from there southward into the
Plains states.  Forecast soundings in MI/WI/Upper MI show favorable
vertical shear profiles for a few supercell structures capable of
hail and damaging wind gusts.  Therefore have added a SLGT risk area
for that scenario.  From IA south, relatively weak winds in the
lowest 6km and a deep sub-cloud layer suggest outflow dominant
storms with a more marginal severe threat.

...CO/Western KS...
Model guidance and water vapor imagery show a plume of mid-level
moisture spreading into central CO.  This should result in a cluster
of thunderstorms over the mountains by mid-afternoon, spreading
eastward into the Plains this evening.  Inverted-v sounding profiles
and favorable westerly flow aloft will promote gusty/damaging wind
potential in some of this activity.

...MS/AL into the Carolinas...
A relatively moist and unstable air mass is in place today across
the TN Valley into the Carolinas.  Little cap and pockets of daytime
heating will lead to scattered afternoon thunderstorms throughout
the region - with some potential for locally gusty/damaging wind
gusts.  Areas of slightly greater focus for concern of strong storms
are 1) Ahead of the MCV currently over northern MS, and 2)  an axis
from northern AL into central NC along the northern edge of slightly
stronger winds aloft.

$$