Area Forecast Discussion

000
FXUS63 KLSX 021121
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
621 AM CDT Mon Oct 2 2023

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 334 AM CDT Mon Oct 2 2023

Main concern continues to be with rain chances with the midweek cold
front and how much of a cool down we will see into next weekend.

The latest surface observations and nighttime microphysics are
showing some fog forming at SUS and FYG, with a 1 degree dewpoint
depressions at FAM. I suspect that fog will continue to develop in
the next few hours in the same areas that they have in the past few
nights, so will keep the forecast for patchy fog going through 9 am
this morning.

The latest water vapor imagery is still showing the upper ridge that
has been dominating our weather the past few days extending from the
western Gulf of Mexico into the Great Lakes.  The latest HREF is
showing this ridge moving slightly to the east the next 36 hours,
however it will have enough of an influence over our area to keep
our weather dry. The HREF shows the east-southeasterly winds turning
southerly by tomorrow as front moves into the Plains.

Highs today and Tuesday will be in the 87-90 degree range as 850mb
temperatures will remain in the 15-17C range and mixing up to 800mb.

Britt

.LONG TERM...  (Tuesday Night through Sunday)
Issued at 334 AM CDT Mon Oct 2 2023

All of the ensemble members remain dry through Tuesday night before
the upper ridge moves off to the east.  Then there is good agreement
in the ensemble means that a upper trough and attendant front will
move across Missouri and Illinois Wednesday night into early
Thursday.  The best chance for showers and a few thunderstorms will
occur from Wednesday night into early Thursday with 60-80% of the
ensemble members showing 6 hourly precipitation chances during this
timeframe.  Most areas during this time frame will pick up between
0.25-0.75" of rainfall, but there is a low chance (20%) for up 1" of
rain along I-44 from this system.  The rain will move out of the
area by Friday as subsidence sets in behind the trough. Then next
weekend looks mainly dry as most of the model guidance is still
showing a large high moving into the Midwest.

Above normal temperatures are still expected through Wednesday ahead
of the cold front as both the NBM and the mean ensemble forecast
interquartile temperatures are only 3-5 degrees.  Temperatures will
fall to near normal by Thursday, but the secondary cold front is now
expected to move through faster with highs Friday through the
weekend expected to be only in the 60s.

Britt

&&

.AVIATION...  (For the 12z TAFs through 12z Tuesday Morning)
Issued at 614 AM CDT Mon Oct 2 2023

Fog will continue reduce visibilities into the 1-3 mile range
through 13Z. There is some potential for additional fog at these
same airports again late tonight, but confidence is too low to
include at this time. Otherwise, dry and VFR conditions are
expected the rest of the period with winds 7 knots or less.

Britt

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion