685
FXUS63 KLSX 191858
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
158 PM CDT Wed Jun 19 2024

.KEY MESSAGES...

- Temperatures today will be warmer than yesterday. There is a
  chance for isolated showers and thunderstorms this morning
  through this afternoon mainly from central Missouri through
  west-central Illinois (20-30%).

- Above normal temperatures are expected to continue Thursday
  through next week with Friday and especially Saturday being the
  hottest. The next chance of showers and thunderstorms will be
  late Saturday into Sunday (20-60%).


&&

.SHORT TERM...  (Through Late Thursday Afternoon)
Issued at 411 AM CDT Wed Jun 19 2024

A positively tilted mid-level ridge/high over the Mid-Atlantic
region is visible in current water vapor imagery. As a result, much
of the eastern CONUS is dominated by deep high pressure and the
associated anticyclonic flow about the high is transporting a large
fetch of moisture from the Gulf of Mexico into the region. Apart
from this mid-level ridge/high is a mid-level long wave trough over
the northwest CONUS with a series of vorticity maxima within the
southwest flow over the east-central Plains. Attendant with the
long wave trough over the western CONUS is a cold front that
extends from the Upper Midwest through northwest Missouri into the
Oklahoma Panhandle. Showers and thunderstorms associated with the
cold front are seen on radar.

It is expected that this cold front will slowly continue east-
northeast over the next couple hours and stall across north-central
and northeast Missouri by mid-morning. This will be the focus for
isolated to scattered convection through the day today. Upper-level
support associated with this cold front is minimal and weak mid-
level lapse rates and around 20kts of 0-6km shear over our area.
Support in the lower-levels is greater but still rather limited and
SBCAPE values between 500-1500 J/kg will support isolated to
scattered showers and thunderstorms across central and northeast
Missouri through west-central Illinois. Northeast Missouri and west-
central Illinois have greatest chance (20-30%) for seeing a shower
or thunderstorm.

Throughout today, the mid-level ridge/high will begin its westward
movement. This will favor warmer temperatures with highs in the
upper 80s to mid 90s. A suppressor of highs is a large area of cloud
cover embedded in the southerly flow about the mid-level high. As
the mid-level ridge/high begins to shift westward, areas across
southeast Missouri and southern Illinois could see some increased
cloud cover, thus keeping temperatures on the "cooler" side of the
high temperature range.

With deep high pressure continuing to shift west tomorrow, rain
chances will be confined to northeast Missouri and west-central
Illinois and temperatures are expected to continue to warm up with
the associated height rises. Temperatures will have no trouble
reaching the low to mid 90s area wide.

MMG/Glass

&&

.LONG TERM...  (Thursday Night through Tuesday)
Issued at 411 AM CDT Wed Jun 19 2024

Dry weather and increasingly hot temperatures will continue Friday
through late Saturday afternoon as the mid-level high makes its
anticipated westward expansion. Rising heights and southwest low
level flow will favor temperatures warming up well into the 90s and
nearing 100 in the St. Louis Metro area by Saturday. This is further
supported by the NBM interquartile range of high temperatures having
a 4-7 degree spread both days. However, it is important to note that
NBM temperatures have had a few degree warm bias over the past few
days which provides uncertainty to how hot temperatures will get.

The next chance for shower and thunderstorm activity will be late
Saturday into Sunday as a mid-level shortwave and vorticity maxima
traverses across the region. This will trek a cold front across the
region Sunday with expected shower and thunderstorm activity along
and ahead of the cold front. Over 70% of ensemble guidance members
indicate precipitation during this time fame, further increasing
confidence in its occurrence.

By next week there is consensus that mid-level ridging will build in
across the central CONUS and favor a continuation of these above
normal hot temperatures.

MMG/Glass

&&

.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 153 PM CDT Wed Jun 19 2024

VFR conditions will prevail at all local terminals through the
majority of the 18Z TAF cycle. A few weak showers and
thunderstorms will be possible at a few terminals this afternoon
and evening, with showers most likely to impact UIN by a slim
margin. Even here, the probability of a direct impact to the
terminal is low (around 30%), but just high enough to support a
VCTS mention in the TAF. Briefly strong wind gusts will be
possible with showers if they do manage to directly impact a
terminal.

Showers will diminish this evening, along with breezy southerly
winds. Otherwise, while some shallow patchy fog will be possible
overnight at primarily SUS, this is not expected to be widespread
and VFR conditions will persist through the remainder of the
period.

BRC

&&

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

$$

WFO LSX