National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS63 KLSX 131106
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
606 AM CDT Sat Apr 13 2024

.KEY MESSAGES...

- Elevated fire danger is expected again today in portions of
  west-central Illinois as well as southeast, south-central, and
  east-central Missouri due to low relative humidity, elevated southwest
  winds, and dry vegetation.


- Today will kick off a string of unseasonably warm temperatures
  (widespread 80s) with highs Sunday and Monday nearing daily
  records.

- Confidence in the potential for severe weather Tuesday afternoon
  into Tuesday night is increasing. There is still uncertainty in
  details such as storm intensity, hazards, and exact timing


&&

.SHORT TERM...  (Through Late Sunday Afternoon)
Issued at 325 AM CDT Sat Apr 13 2024

Today will be the first day of several with well above average
temperatures as low-level winds back to south-westerly behind an
exiting ridge. Warm air advection and insolation will rocket our
temperatures into the mid-70s and 80s from yesterday`s widespread
60s. Daytime mixing will elevate surface winds today. Low relative
humidity, dry fine fuels, very warm temperatures, and gusty winds
will create elevated fire danger conditions again this afternoon for
portions of west-central Illinois and south-central, east-central,
and southeast Missouri. Today`s elevated fire danger is more
marginal than yesterday`s as modest moist advection may keep
relative humidity values slightly higher. This will work against
daytime mixing and the downsloping effect we typically see in
southwest flow regimes, but there`s uncertain with the extent. If
mixing and downsloping are able to overcome the moisture, elevated
fire danger conditions will be more pronounced in the lee of the
Ozarks.

The warming trend will continue on Sunday with widespread 80s
expected and daily high records in jeopardy (see CLIMATE section
below). Also on Sunday/Sunday night, a passing surface low will lay
a weak boundary somewhere across the CWA, though its exact location
is yet to be seen. Little to no convection is expected with the
arrival of this front. Low-level warm air advection will result in a
stout cap, and the mid-level pattern will keep most of the column
very dry and without lift.


Jaja

&&

.LONG TERM...  (Sunday Night through Friday)
Issued at 325 AM CDT Sat Apr 13 2024

Well to our west, a mid-level trough will traverse the Intermountain
West on Monday while its surface reflection rapidly develops and
intensifies on the Front Range. This low will pull Sunday`s weak
stationary boundary north as a warm front on Monday. This won`t have
a significant impact on our sensible weather during the day on
Monday. Although there is a slight chance for thunderstorms in
Missouri in the afternoon, the focus will be highs in the 80s
approaching daily records.

The lack of concern is because the overall system continues to trend
slower. Though we`ll have upward of 1000+ J/kg of SBCAPE on Monday,
upper level support doesn`t arrive until late afternoon/evening when
SBCAPE will be on the downswing. The lack of temporal overlap
lessens the potential for severe weather. This won`t be the case for
the central and southern Plains, however, who have a much better
potential at seeing severe weather on Monday. There is a chance that
convection in the Plains will enter our CWA on Monday night and
alter the convective environment for Tuesday`s severe weather
potential. Confidence in this occurring is low, not because it`s not
possible, but because it`s still too early to resolve finer scale
details like this.

The mid-level trough will eject northeast through the Plains on
Tuesday with its surface low following suit. Deterministic guidance
now shows more consensus that the mid-level system and surface low
passing to our northwest sometime Tuesday evening/overnight with a
moisture (thus instability) corridor pooling along the front.
Guidance has also been consistent between runs showing 750 - 1000
J/kg of SBCAPE, and even more consistent showing 60 - 70 kts of bulk
shear with it. Even though the details are still uncertain, we`re
becoming increasingly confident that our CWA will experience severe
weather on Tuesday afternoon into Tuesday night from the
environmental parameters we`ll have in place.

The cold front is forecast to pass sometime on Wednesday. Post-
frontal wrap-around rain is possible depending on how closely the
surface low hugs the CWA as it passes. It`s unclear how much this
initial cold front cools the region as seen in a 13 degree spread in
the NBM 25th - 75th interquartile range. There is consensus among
guidance that a secondary cold front will bring us back down to near
average temperatures late in the week.

Jaja

&&

.AVIATION...  (For the 12z TAFs through 12z Sunday Morning)
Issued at 525 AM CDT Sat Apr 13 2024

Dry and VFR conditions will persist through the TAF period.
South-southwest winds will become gusty (up to 25 kts) from
central Missouri through west-central Illinois this afternoon.
Winds will diminish slightly after sunset before becoming gusty
again areawide late this evening/tonight. LLWS is possible
tonight, but elevated surface winds and lack of directional
component makes it a marginal forecast. Decided to leave it out
of the TAF for now.


Jaja

&&

.CLIMATE...
Issued at 225 PM CDT Thu Apr 11 2024

DAILY HIGH TEMPERATURE RECORDS

          |=== 4/14 ==|=== 4/15 ==|
St. Louis | 92 (2006) | 89 (2002) |
Columbia  | 89 (2006) | 90 (1896) |
Quincy    | 86 (2006) | 88 (2002) |


&&

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

$$

WFO LSX