Webster Groves, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

338
FXUS63 KLSX 031731
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1131 AM CST Tue Dec 3 2024

.KEY MESSAGES...

- Another cold day is on tap today, but much warmer weather is
  expected on Wednesday accompanied by gusty west winds.

- A potent cold front on Wednesday night will bring a return of
  cold/well below normal temperatures Thursday and Friday, with
  warmer weather returning during the weekend.


&&

.SHORT TERM... (Through Late Wednesday Afternoon)
Issued at 149 AM CST Tue Dec 3 2024

Stratus remains locked in across all of the CWA except for a
portion of central/SE MO. GOES imagery hasn`t shown any
definitive clearing trends as the stratus appears to be trapped
within the eastern periphery of the surface high/low-level
anticyclone. There are also some mid-high clouds within the NNW
flow aloft overspreading the stratus. Leaning on the pessimistic
side, I think the clouds for the most part will remain persistent
through at least the early morning. Progression of the eastern
longwave upper trof should result in the eastward retreat of the
surface high/low-level anticyclone today. Once this gets underway
later this morning and the low-level winds back to more
southwesterly, then I think clearing from west-east will progress
in earnest. Accordingly the temperatures should warm with the
coolest readings in SC IL. Highs will be warmer than yesterday in
most areas, generally in the 30s which is around 8 to 15 degrees
below normal.

With the continued eastward retreat of high pressure, the surface
pressure and low-level height gradient will tighten tonight and
this will result in increasing winds, a stout westerly LLJ, and
strengthening low-level WAA. The result will be mins won`t be
as cold as currently. Within this low-level WAA regime tonight,
there are some big differences in the low-level moisture profiles.
The NAM is an outlier basically showing a slug of clouds/moisture
translating eastward from the Plains starting this afternoon and
moving it across the CWA tonight. In the process it further
saturates the lowest 1 km and develops some light drizzly
precipitation which would likely be light freezing drizzle across
parts of eastern MO into SW/SC IL. None of the other CAMS or
models depict this scenario, and thus at this time I would say the
chance of it occurring is less than 10 percent.

The one "warm" day of the week is still on track for Wednesday. An
upper low/trof will dig southeastward from Manitoba into the upper
Great Lakes during the day, with continued deepening of the upper
trof on Wednesday night as the upper low moves into the eastern
Great Lakes region. In response a potent cold front will move into
the northern CWA during the later part of Wednesday afternoon and
through the remainder of the CWA on Wednesday night. Gusty
southwest-west winds and strong WAA ahead of the front on
Wednesday will result in above normal highs from the mid 40s
north to mid-upper 50s south. Strong CAA with the cold front will
bring a quick end to the short-lived warm-up.

Glass

&&

.LONG TERM... (Wednesday Night through Monday)
Issued at 149 AM CST Tue Dec 3 2024

The deep broad longwave trof centered in the eastern U.S. will
result in northwest flow across our area Thursday and Friday as it
slowly progresses eastward and eventually shifts into the western
Atlantic. As a result the post-frontal surface high will dominate
on Thursday/Friday morning resulting in well below normal
temperatures (highs in the mid 20s-low 30s and lows in the teens).
Highs on Friday will remain below normal but won`t be as cold as
Thursday with the surface high beginning its eastward retreat.

A prominent pattern change will occur over the weekend into early
next week. Initially the flow aloft flattens some Saturday and
then sometime Sunday into early Monday the flow aloft becomes more
southwesterly. A WAA regime and warming temperatures (highs in the
upper 40s/low 50s Saturday and well into the 50s on Sunday) will
accompany this change, while rain chances will also return late in
the weekend as a ejecting and weakening upper low/trof
originating in the Desert SW region kicks out across our CWA.

Glass

&&

.AVIATION...  (For the 18z TAFs through 18z Wednesday Afternoon)
Issued at 1125 AM CST Tue Dec 3 2024

While some lingering low clouds persist at CPS at the start of the
period, the vast majority of local terminals have cleared and VFR
conditions have developed. Whatever lingering clouds left at CPS
are likely to clear very shortly, and the remainder of daylight
hours are expected to be mostly clear. Overnight, low level wind
shear is expected to develop at all local terminals due to a
strengthening low level jet. A round of low clouds will also be
possible overnight, but current forecasts suggest that ceilings
are likely to remain VFR. Still, at low probability exists for a
dip to MVFR levels for a brief period. VFR conditions are likely
near the end of the period, along with gusty westerly winds.

A cold front will move through the area late Wednesday afternoon
and evening, but this is expected to occur just outside of the 18Z
TAF window for all terminals except perhaps STL, where the TAF
period extends to 00Z Thursday.

BRC

&&

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

$$

WFO LSX