Area Forecast Discussion

139
FXUS63 KLSX 230439
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1039 PM CST Sat Feb 22 2025

.KEY MESSAGES...

-The regional warm up will continue through at least Tuesday with
 dry conditions.

-Next best chance for rain comes Wednesday, but amounts are
 expected to be light (< 0.05").


&&

.SHORT TERM...  (Through Late Sunday Night)
Issued at 1256 PM CST Sat Feb 22 2025

We have broken freezing at all our climate sites for the first time
in 7 days (February 15)! Under sunny conditions and continued warm
air advection, a few more degrees of warming is expected through the
mid afternoon, pushing high temperatures into the mid to upper 30s
across the forecast area. Continued warm air advection along west to
southwesterly flow and slightly elevated winds (5-7 kts) overnight
will keep temperatures warmer than last night, dropping into the low
twenties.

We will remain on the northwest side of the retreating surface high
Sunday and warm air advection will persist in the low-levels. A mid-
level shortwave will move through the mid-Mississippi Valley Sunday
afternoon and evening, bringing several vorticity maxima through the
area. Despite this, very dry conditions will limit effects to a few
high level clouds. Abundant sunshine and the warm air advection will
result in another 20 degree hike in high temperatures on Sunday with
highs in the upper 40s to low 50s. High temperatures are forecast at
50 degrees or higher at all climate sites, the first time this has
occurred since February 3rd. Another night of slightly elevated
temperatures and warm air advection temperatures warmer Sunday into
Monday, with Monday morning`s lows near freezing.

Delia

&&

.LONG TERM...  (Monday through Next Saturday)
Issued at 1256 PM CST Sat Feb 22 2025

The warming trend will continue through Tuesday under deep warm air
advection. While multiple vorticity maxima will slide through the
west to northwesterly mid-level flow across the forecast area, dry
conditions and weak forcing will keep the area largely dry.
Temperatures during the first half of the work week will be the
warmest of the period, peaking in the upper 50s to low 60. The
interquartile spread is around 5 degrees during this period, and the
25th percentile is 50 degrees or warmer. Thus confidence in warm
temperatures remains high.

The best chance for precipitation will be with a stronger mid-level
trough that will slide through the mid-Mississippi Valley Wednesday.
This system will bring limited moisture with it, bringing a 50-70%
chance of at least 0.01" of rain as the cold front moves through the
forecast area. Probabilities of rain falling from the front are
highest across Illinois, closest to the surface low. The probability
of exceeding 0.05" of rain peaks around 40-50% in this area. There
remain some differences in the timing of the frontal passage and
associated rainfall, resulting in lower PoP values in the official
forecast as they are smeared across a greater time period than will
actually occur. If the front moves through during the early morning,
cold air advection behind the front could stunt high temperatures on
Wednesday several degrees compared to Tuesday. A later frontal
passage will allow for another day of warm temperatures in the upper
50s to low 60s.

After a brief cool down behind the front, warm air advection will
reestablish for the end of the work week. There is increasing
uncertainty in the details of the mid-level pattern beyond the end
of the work week as well as the strength of the warm air advection.
So while temperatures will remain near to above normal (mid to upper
40s) Thursday through the end of the period, the interquartile
spread increases to around 10 degrees. This will spell the
difference between wearing a coast versus no coat for many. A whole
week of near to above normal temperatures may lull some into the
impression that winter is over, however the CIPS Analog guidance
from St. Louis University is highlighting the first week of March
for a return of below normal temperatures. Winter is not done with
us yet.

Delia

&&

.AVIATION...  (For the 06z TAFs through 06z Sunday Night)
Issued at 1038 PM CST Sat Feb 22 2025

VFR conditions continue with only a few passing high clouds. Light
to calm winds overnight pick up a bit out of the southwest
tomorrow, but won`t be as gusty as they were on Saturday.

Kimble

&&

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

$$

WFO LSX

NWS LSX Office Area Forecast Discussion