187
FXUS63 KLSX 272325
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
625 PM CDT Thu Mar 27 2025

.KEY MESSAGES...

- Showers and thunderstorms are expected to decrease in coverage through
  this evening. There is still some potential for an isolated
  severe thunderstorm this evening that could produce up to
  quarter sized hail north of I-70.

- There will be several chances for showers and thunderstorms
  Friday night into Sunday. A few strong to severe thunderstorms
  are possible on Sunday.


&&

.SHORT TERM...  (Through Late Friday Night)
Issued at 255 PM CDT Thu Mar 27 2025

Showers and thunderstorms continued along and north of I-70 in a
band of strong moisture convergence on the nose of a low level jet.
The RAP is showing this convergence gradually decreasing and moving
off to the northeast over the next few hours which should cause the
showers and thunderstorms to become less concentrated. There is a
warm front which has now moved to just south of the area of the
area of convection, roughly over central and southeast Missouri.
There will still be a chance (20-40%) for additional showers and
thunderstorms) outside of this band of showers and thunderstorms
along and north of the warm front. As the warm front lifts
northward this evening, and the LLJ increases in strength once
again, we should see additional thunderstorms develop late this
evening and overnight across northeast Missouri into west central
and south central Illinois. There still remains some potential for
an isolated strong to severe thunderstorm with this activity,
with the main threat being large hail up to size of quarters.

There is a currently marked difference in temperatures across the
warm front with upper 40s and lower 50s where it is raining to the
middle 70s just southwest of the CWA.  I still believe these warmer
temperatures will make it into central and southeast Missouri this
afternoon.  Highs on Friday still look to be around 80 degrees
behind the warm front.

Still expect Friday to be a dry day as shortwave ridging moves
across the area.  We will begin to see a chance (20-30%) of showers
move into the southeast half of the CWA by late Friday night ahead
of a southern stream system.


Britt

&&

.LONG TERM...  (Saturday through Next Thursday)
Issued at 255 PM CDT Thu Mar 27 2025

We are still on track to have an active pattern over the weekend
with two systems of note.  The first will be the aforementioned
southern wave which will bring likely PoPs (50-70%) over southeast
Missouri and southwest Illinois on Saturday.  The second will be a
more pronounced trough that will move into from the west.  We will
be maintaining high PoPs on Sunday with the passage of this trough
and the attendant cold front (70-90%). It still appears that the
best chance for strong to severe thunderstorms will be on Sunday
when the LREF is showing joint probabilities of MUCAPE>500 and 0-
500mb shear >30 knots reaching 70-90%. It should still be stated
that this system is not expected to be as severe as what we saw
two weeks ago as the operational ECMWF/GFS mass fields are not
nearly as strong.

There will be another trough the middle of next week which will
bring a chance of showers and isolated thunderstorms to the area by
the middle of next week.  The cluster analysis are all showing this
trough, but there is a spread in how quickly it will move through
the area.

Temperatures will fall behind the front over the weekend with
NBM/LREF both showing highs only in the 50s and 60s but rebounding
into the 70s by the middle of next week.  The IQR spread is fairly
small with the cool down, but increases as we go through next week
given uncertainty with how quickly the next trough moves through.


Britt

&&

.AVIATION...  (For the 00z TAFs through 00z Friday Evening)
Issued at 619 PM CDT Thu Mar 27 2025

Earlier convection continues to trend downward in coverage and
intensity as it drifts eastward away from the local terminals
early this evening. However, the low-level jet will ramp up later
this evening, leading to additional convection as well as a very
low chance for low-level wind shear. The chance for the latter is
so low and nebulous across the area, that it has been left out of
the TAFs for now. As for additional convection, the best chance
for isolated to scattered showers is near KUIN. A brief
thunderstorm is also possible here, but with confidence already
lower in direct impacts from showers, the mention of thunder has
been left out until/if confidence increases in where thunderstorms
will form relative to the terminal. Otherwise, VFR flight
conditions are expected through the forecast period.

Elmore

&&

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

$$

WFO LSX