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000
FXUS63 KLSX 270423
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1123 PM CDT Fri Apr 26 2024

.KEY MESSAGES...

-Showers and a few thunderstorms are expected to continue to move across
 the area through this evening. A few of these storms could
 produce locally heavy downpours and gusty winds.

-Showers and thunderstorms are likely over the area on Saturday
 and Sunday. A few severe thunderstorms are possible over western
 parts over the area on Saturday and across the entire area on
 Sunday. Large hail, damaging winds, and an isolated tornado are
 possible with the strongest storms as well as a localized flash
 flooding threat.


&&

.SHORT TERM... (Through Sunday)
Issued at 428 PM CDT Fri Apr 26 2024

A band of showers and scattered thunderstorms is moving northeast
across the CWA this afternoon ahead of a shortwave trough with a
band of low level moisture convergence moving northeast across
Missouri and Illinois. The latest run of the HRRR and other CAMS are
showing this batch of rain continuing to move northeast across the
CWA through the early evening before it exits the CWA.  There is
also a low chance (<30%) that storms now developing over eastern
Kansas will hold together and enter central and northeast Missouri
late this evening, though only the NAMNest is showing this
possibility. Otherwise, we have stayed well north of the warm front
today in the cool air and the SPC objective analysis is showing most
of the CWA with MUCAPES of 100 J/kg or less.  Expect most storms to
stay below severe limits because of this lack of instability.


Additional showers and thunderstorms will be possible during the day
on Saturday, though the coverage is not expected to be as extensive
as a shortwave ridge will be building as it moves across the area.
The best chances (around 50%) will be across southeast Missouri into
southwest Illinois where a weak mid-level impulse will combine with
925-850mb moisture convergence to bring a chance of showers and
thunderstorms.  Another area will be across northeast Missouri into
west central Illinois which will be closer to a surface front with
little capping.  There will be an increased chance for showers and
thunderstorms Saturday night into Sunday as another shortwave trough
rounds the Great Plains upper low and increases mid-level lift at
the same time that the low level jet increases in speed on Saturday
night.  Expect to see a gradual increase showers and thunderstorms
that will move into the area from the west on Saturday night.  This
will continue to move east across the day on Sunday as both the
NAM/GFS are showing a maximum in mid-level ascent/low level moisture
convergence moving across the the CWA.  This goes along well with the
LREF showing a band of high probabilities (>90% for 0.01" precip)
moving across the CWA from Saturday night into Sunday night in
concert with the NAM/GFS forcing.  A few severe thunderstorms remain
possible mainly during the late afternoon and evening hours when
heating will be maximized.  Saturday`s threat will mainly be over
the western part of the CWA and be limited somewhat by weaker deep
layer shear compared to Sunday which will cover much of the CWA and
have stronger deep layer shear.  While most of the global models
show the shortwave trough moving across Missouri and Illinois during
the evening and early overnight hours, the surface front does not
move into the area until Monday.


Britt

&&

.LONG TERM...  (Sunday night through Next Friday)
Issued at 428 PM CDT Fri Apr 26 2024

Global models are showing the front getting hung up over Missouri
and Illinois next week in quasi-zonal flow aloft. There will be
some instability available along the front which will allow
showers and thunderstorms to develop along it each day. CIPS and
CSU guidance are showing some low probabilities for a few strong
to severe thunderstorms over the area into next week. Temperatures
will remain above normal as 850mb temperatures will be in the
10-15C range.

Britt

&&

.AVIATION...  (For the 06z TAFs through 06z Saturday Night)
Issued at 1119 PM CDT Fri Apr 26 2024

Isolated showers and thunderstorms will continue to be possible
across much of the area through the period. The most likely times
will be right at the beginning of the period from 06Z to around
10Z, then again on Saturday afternoon/early evening. Did not
mention thunder in this TAF cycle due to the timing uncertainty
and likely low coverage of storms. Otherwise, VFR ceilings which
will occasionally scattered out at times and southerly flow
gusting up to 25-30kts is expected to prevail. There will also be
a few patches of MVFR ceilings early in the period, mainly across
central and northeast Missouri.

Carney

&&

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

$$

WFO LSX