605
FXUS63 KLSX 110333
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1033 PM CDT Mon Jun 10 2024

.KEY MESSAGES...

- Temperatures will trend higher Tuesday into Wednesday with above normal
  warmth favored from midweek onward. Widespread 90s could arrive
  by next weekend to bring the warmest air so far this year.

- An active pattern to the north could bring a couple glancing
  rounds of showers and thunderstorms Thursday into next weekend.


&&

.SHORT TERM...  (Through Late Tuesday Night)
Issued at 301 PM CDT Mon Jun 10 2024

A relatively quiet period is expected for a change with the primary
focus being on warming temperatures.

The synoptic overview shows surface high pressure straddling the
U.S.-Canadian border and gliding into the Great Lakes Region this
afternoon. Northerly surface flow is complimented by north-northwest
flow aloft, resulting from a broad upper trough over the New England
Region and mid/upper level ridging over the northern Plains and
Upper Midwest. The pattern has supported refreshing, slightly-below-
normal temperatures with mid to upper 70s accompanied by comfortable
dewpoints in the low to mid-50s. The only caveat to the pleasant
conditions is the scattered to overcast cloud cover that extends
along a trough currently draped from north-central Missouri through
east-central Missouri and southern Illinois. Cloud cover has held
temperatures down a couple degrees versus areas in full
sunshine. It has been inconsequential otherwise.

As we progress through the remainder of the short term period, the
eastward translation in the surface high and mid/upper ridge will
lead to return flow at the surface. Warm air advection draws
temperatures closer to the 80 degree along and west of the
Mississippi River Tuesday. Cooler mid-level temperatures (8-10C)
hang on long enough to the east that Illinois locations remain in
the mid/upper 70s. It looks like yet another pleasant, early summer
day with plenty of sunshine. Only scattered high clouds edge into
central and northeast Missouri during the afternoon.

A weak cold front attempts to push in late Tuesday, but latest
guidance continues to show little moisture to work with and even
suggests surface flow largely remains out of the west and southwest.
It makes it difficult to say that it will have much more impact than
a brief wind shift over northern sections of Missouri into west-
central Illinois as it becomes west-east oriented and southward
progress stalls. Meanwhile, 850mb temperatures continue to warm
through midweek, rising into the upper teens Wednesday. Therefore,
the main story will be the return to summer-like warmth with 60-70%
of the grand ensemble members showing highs above 85. Though Warmth
is not expected to be oppressive, there will be ever-so-gradual
increase in moisture as dewpoints creep back into to the 60s from
west to east.


Maples

&&

.LONG TERM...  (Wednesday through Next Monday)
Issued at 301 PM CDT Mon Jun 10 2024

There are a couple of chances for precipitation through the long
term period. However, the inherent uncertainty with each round keeps
warming temperatures the primary focus.

An active, quasi-zonal pattern sets up over the northern Plains by
midweek with upper level ridging building out of the southwest into
the southern and central Plains. Several shortwaves are introduced
into the northern periphery of the upper ridge, ejecting them into
the Upper Mississippi River Valley late Wednesday and late Thursday.
Unfortunately, this is a pattern that introduces a great deal of
uncertainty with limitations on the placement and timing of
resulting thunderstorm potential. Nonetheless, the first round looks
to be well enough north (eastern Dakotas to northern Iowa) to avoid
much in the way of thunderstorm as dying convection pushes east
southeast around the upper ridge. A remnant shower cannot be
entirely rule out in the pre-dawn hour early Thursday morning, but
the potential is low given the surface to mid-level ridging that
encompasses the eastern third of the Conus.

Though Wednesday`s system isn`t expected to have much sensible
impact, the track and evolution of the thunderstorm complex could
very well determine the southward reinforcement of a slow-
approaching cold front from the the north Thursday night into
Friday. With the second shortwave just coming into view of the mid-
range guidance, there are some discernible, unsurprising difference
in the latitudinal placement of the shortwave and surface front. The
general theme is for most convection to initiate somewhere north of
the Missouri/Iowa border, focused around the better ascent in
relation to the track of the upper wave. MUCAPE south of the west-
east oriented front builds to around 3-4k J/k along the
Missouri/Iowa border. Initial thoughts are than the CAPE gradient
and west-northwest flow drives the bulk of convection through
northern Illinois, while the trailing cold front slowly sinks
southward into northern Missouri. While there is shower and
thunderstorm potential along the front, confidence in thunderstorm
intensity and overall southward spread remains low given the
questions with the track of the shortwave and surface to mid-level
height rises to the south.

The boundary returns back to the north as a warm front as upper
ridging continues to build in late this week. Isolated to scattered
thunderstorms could line the front, but much of the upper support
remains over the northern Plains into the Upper Midwest. The main
story remain the temperature with the potential for widespread 90s
by Sunday into early next week.


Maples

&&

.AVIATION...  (For the 06z TAFs through 06z Tuesday Night)
Issued at 1033 PM CDT Mon Jun 10 2024

Dry and VFR flight conditions will continue through the rest of the
TAF period with light winds. Light and variable overnight winds will
become southerly then southwesterly by Tuesday afternoon as surface
high pressure shifts to the east.

MMG/Glass

&&

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

$$

WFO LSX