004
FXUS63 KLSX 162350
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
650 PM CDT Thu May 16 2024

.KEY MESSAGES...

- Isolated to scattered showers and thunderstorms are possible across
  the area through the evening hours. The greatest chance for an
  isolated strong to severe thunderstorm is across southeast
  Missouri and southern Illinois with the threats being 60 mph
  winds and quarter sized hail.

- Light winds overnight will favor the possibility of patchy fog
  areawide.

- This weekend will be mainly dry with temperatures warming up to
  around 10 degrees above normal. This warming trend will continue
  into next week in addition to another active period.


&&

.SHORT TERM...  (Through Late Friday Night)
Issued at 329 PM CDT Thu May 16 2024

Current water vapor imagery shows that there is an upper level
trough north of the Mid-Mississippi River Valley that is helping
keep the region in southwesterly flow aloft. Amidst this
southwesterly flow is an vorticity maximum that will trek across the
southern portions of the CWA through the afternoon hours. This
vorticity maximum will be help support isolated showers and
thunderstorms through the early evening hours. There is a marginal
chance that a few of these isolated thunderstorms could become
strong to severe, primarily across southeast Missouri and southern
Illinois. The 19Z SPC Mesoanalysis shows that there is around 1500
J/kg of SBCAPE as well as 30-35 kts of 0-6km of shear in the
aforementioned areas. Should a thunderstorm become severe, the
primary threats will be gusty winds up to 60 mph and quarter sized
hail. The strong to severe thunderstorm potential will decrease
around sundown as daytime heating and instability becomes limited.

Continued shower activity is possible through the overnight hours
along and south of the I-44 corridor in Missouri and I-70 corridor
in Illinois as the vorticity maximum and increased low level
moisture convergence continues east/northeastwards. Southeast
Missouri and southern Illinois has a greater chance (50-80%) of
seeing overnight rain showers. Winds will become light and variable
overnight. These light and variable winds in addition to the
saturated grounds will provide the possibility for patchy fog across
much of the area early Friday morning.

By Friday another shortwave and associated vorticity maximum will
swipe across southeastern Missouri and southern Illinois. This will
provide another chance (30-50%) of showers in those areas.
Persistent cloud cover across those areas will help keep daytime
instability rather limited and limit the thunderstorm potential.
Temperatures on Friday will be in the 70s, with the highest
temperatures across the northern portions of the CWA where cloud
cover will be limited.

MMG/Glass
&&

.LONG TERM...  (Saturday through Next Thursday)
Issued at 329 PM CDT Thu May 16 2024

An upper level trough will be exiting to the east through the day on
Saturday with ridging and height rises building in behind it. At the
same time near the surface, ensemble guidance is in agreement that
surface high pressure will also be shifting into the Mid-Mississippi
River Valley. This combined with the upper level height rises will
favor dry weather and increasing temperatures into the mid to upper
80s on Saturday. The current forecast has a slight chance of showers
during the day on Saturday, however we will likely end up being dry
given the current forecast trends. By Sunday, NBM quartile spread
has high temperatures in the upper 80s to low 90s. These high
temperatures are around 10 degrees above climatological normal for
mid May.

A more active pattern will set up next week as an upper level low
sits itself over the south-central region of Canada. Rounding this
upper low will be multiple shortwave troughs and associated surface
reflections swinging through the Mid-Mississippi River Valley Monday
through early Wednesday. Thunderstorms are forecasted through the
early week, however, the greatest chances for thunderstorms is late
Tuesday into Wednesday.

MMG/Glass
&&

.AVIATION...  (For the 00z TAFs through 00z Friday Evening)
Issued at 650 PM CDT Thu May 16 2024

Dry weather at KUIN. However, scattered showers and a few storms
through 02z for KCOU and KJEF, while they will linger through 06z
for St. Louis metro sites. Otherwise, as precipitation exits could
see MVFR ceilings and/or fog tonight. Then ceilings and
visibilities will lift and scatter out by 14z-16z Friday. Winds
will remain light and variable.

Another round of showers and storms possible in the St. Louis
metro area Friday afternoon, after 17z Friday, so added vicinity
storms.

Byrd
&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

$$

WFO LSX