704
FXUS63 KLSX 010335
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1035 PM CDT Sun Jun 30 2024

.KEY MESSAGES...

- Pleasant summer conditions will linger through at least
 Monday as temperatures will be 5-10 degrees below normal.

- Hot and humid conditions return Tuesday into Wednesday. The pattern
  becomes active once again Tuesday night onward with several
  rounds of showers and thunderstorms. Locally heavy rainfall will
  be possible as well.


&&

.SHORT TERM...  (Through Late Monday Night)
Issued at 243 PM CDT Sun Jun 30 2024

Strong surface ridge continues to build into the region this
afternoon with much drier air filtering in. By tonight as the flow
becomes easterly, will see dewpoints dip down into the mid 40s to
mid 50s with the driest air mainly along and east of the
Mississippi River. This area is co-located with ridge axis and
lightest winds, so low temperatures will be in the low to mid 50s,
with 55 to 60 for areas west of the Mississippi River. Will be
close to record lows, mainly at Quincy (52 in 1988) and St. Louis
(56 in 1937), while Columbia`s record low (45 in 1892) will be
hard to break.

Monday will be another below normal day with highs only in the mid
70s to low 80s. In the meantime, as the surface ridge slides off to
the east and upper ridge begins to build in, some weak shortwaves
try to undercut the surface ridge. A number of the latest CAMs
develop scattered showers especially over portions of central
Missouri on Monday. However, the latest forecast soundings for KCOU
have a lot of dry air in the low levels, thus confidence is low for
any precipitation on Monday and kept mentionable POPs to our west.
Otherwise, with southerly flow returning to the central CONUS,
plenty of moisture is drawn northward into Kansas and western
Missouri during the day on Monday. Temperatures begin a slow
moderation by Monday night, but lows will still be slightly below
normal in the low to mid 60s.

Byrd
&&

.LONG TERM...  (Tuesday through Next Sunday)
Issued at 243 PM CDT Sun Jun 30 2024

The ridging pattern will continue to shift eastward this week while
another broad upper trough slides east along the U.S./Canadian
border. The return of low level moisture to the forecast area will
be a bit slower with mid to upper 70s dewpoints not returning to the
entire region until Wednesday. Otherwise, highs on Tuesday will be
in the upper 80s to mid 90s, with heat index values 100-105 across
portions of central/northeast MO Tuesday afternoon where dewpoints
will be in the low to mid 70s. The far eastern portions of the
forecast area will still see pleasant conditions on Tuesday with
dewpoints only in the upper 50s to low 60s.

In the meantime, as the cold front associated with the trough slides
east into central IA and northwestern Missouri by Tuesday evening,
south to southwest low level jet will ramp up to 30-40kts ushering
in copious amounts of moisture (PWATs 2-2.5", well over 90th
climatological percentile in latest NAEFS/GEFS). The latest
deterministic and ensembles now have similar location and timing of
the front with convective initiation developing ahead of the front
over Iowa late Tuesday afternoon, then moving into northeast MO/west
central IL after 03z Wednesday. With increasing MU CAPEs (2000-3000
J/kg) as well as increasing deep layer shear (0 to 6km 30-40kts,
though parallel to the boundary) and decent convergence along the
front, could see some strong to severe storms move into northeast
MO/west central IL during the late evening. However, a majority of
the latest deterministic as well as ensembles have instability
weaken across the forecast area during the late evening/overnight
hours, so confidence is low on how far south the strong to severe
storms will make it. So will continue to monitor over the next
couple of days.

The front could hang up over the region through at least Friday,
including the Fourth of July, so will see several rounds of showers
and storms. The latest deterministic as well as ensembles have
differences in location, timing and strength with each wave, but are
coming into better agreement that the strongest shortwave will move
through late Wednesday night into Thursday morning. There will be
plenty of upper ascent over the surface boundary, all within a
region of deep layer moisture. Also, PWAT values will still be
around 2-2.5 inches, which points to heavy rainfall the night of the
3rd and heading into the 4th.

Beyond Friday, the latest deterministic and ensembles have some
agreement with upper trough shifting off to the east with surface
ridge building in once again by next weekend.

Byrd

&&

.AVIATION...  (For the 06z TAFs through 06z Monday Night)
Issued at 1033 PM CDT Sun Jun 30 2024

Dry northeast winds on the periphery of a departing surface high will
promote VFR conditions through the TAF period. A few weak showers
may impact central Missouri late Monday morning, but the
anomalously- dry air will work strongly against any rain reaching
the ground.

MRB

&&

.CLIMATE...
Issued at 344 AM CDT Sun Jun 30 2024

Record Lows
                   7/1

St. Louis      56 in 1937

Columbia       45 in 1892

Quincy         52 in 1988


&&

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

$$

WFO LSX