National Weather Service Weather Forecast Office

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

000
FXUS63 KLSX 121700
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
1200 PM CDT Fri Apr 12 2024

.KEY MESSAGES...

- Elevated fire danger is now expected to threaten all of eastern
  and central Missouri as well as west-central Illinois this
  afternoon due to low relative humidity, windy conditions, and
  dry fine fuels.

- Saturday through mid-week will be unseasonably warm with Monday
  and Tuesday`s high temperatures approaching records.

- The potential for multiple rounds of showers and thunderstorms
  still exists early next week, with a threat for strong to severe
  thunderstorms. Very little has changed regarding the uncertainty
  surrounding this potential.


&&

.SHORT TERM...  (Through Late Saturday Afternoon)
Issued at 336 AM CDT Fri Apr 12 2024

Weak, narrow surface high pressure continues to slowly build into
the region ahead of a mid-level ridge than spans most of the western
half of the CONUS. Despite the surface high closing in on us today,
gusty conditions will continue into this afternoon. Efficient mixing
up to 750 - 800 mb will allow us to overcome the weak high and gust
to up to 30 kts in portions of northeast Missouri southeast through
south-central Illinois.

Gusty winds have all but completely dried finer fuels across the
area with RAWS data showing yesterday`s 10 hr fuel moisture at 7 -
10% from Moberly to Farmington. With dry fine fuels, gusty winds,
and warm weather (60s highs), elevated fire danger is expected for
all of our Missouri counties and for portions of west-central
Illinois.

The low-level ridge axis will pass Friday night into Saturday
morning leaving the Mid-Mississippi Valley in southwest flow. Warm
air will quickly flood the region, catapulting temperatures into the
70s and 80s by Saturday afternoon. This unseasonable warmth will
extend well into next week. This is supported by high ensemble
(>75%) probabilities of exceeding 75 degrees nearly every day from
Sunday through Wednesday and the NBM 25th percentile for KSTL
bottoming in the 80s during that period.

Jaja

&&

.LONG TERM...  (Saturday Night through Thursday)
Issued at 336 AM CDT Fri Apr 12 2024

Sunday opens with a mid-level ridge covering most of the CONUS and a
closed low entering the California coast. At the surface, a weak low
pressure system will traverse the Northern Plains and Great Lakes
regions, laying a boundary somewhere across northern Missouri and
central Illinois Sunday night. On Monday, a surface low pressure
system tied to the mid-level low will deepen in the lee of the Front
Range. This system will lift the aforementioned boundary north on
Monday as a warm front while intensifying warm air and moisture
advection into the Mid-Mississippi Valley. This will increase
instability Monday afternoon and open the door for warm sector
convection. Like in previous forecasts, the best jet level and mid-
level dynamics appear to remain to our west on Monday. Ensemble
guidance show the highest potential for 500 J/kg SBCAPE coincident
with 30 kts of bulk shear to our west as well. Bulk shear increases
drastically overnight into Tuesday to 60 - 70 kts with the arrival
of a potent low-level jet. Although instability appears to be lesser
than on Monday, this amount of shear ahead of the system`s cold
front creates concern for strong to severe thunderstorms regardless.

Although this is consistent with previous forecasts, it`s important
to note the amount of uncertainty that`s going into the forecast.
WPC cluster analysis all show a mid-level trough in the
Intermountain West by Monday evening, but the similarities stop
there. Each cluster shows a different trough in depth, amplitude,
location, and tilt. All of these factors will impact the potential
for strong to severe thunderstorms early next week, from the amount
of moisture return we receive to the timing and placement of fronts.
At the time of writing we can confidently say that it will storm
early next week and that there is a potential for these storms to be
severe. However, there are too many inconsistent variables to key in
on any specifics at this point.

Guidance suggests that the early week "cold" front won`t do much in
the way of cooling the region down or removing much of its moisture.
A second cold front later in the week will do the heavy lifting on
that front, bringing cooler and drier air into the region as well as
another chance for showers and thunderstorms.

Jaja

&&

.AVIATION...  (For the 18z TAFs through 18z Saturday Afternoon)
Issued at 1200 PM CDT Fri Apr 12 2024

Dry and VFR flight conditions will persist through the TAF period.
West-northwesterly winds with occasional gusts of 25 to 30 kt will
quickly slacken this evening and then become variable at times. On
Saturday, winds will become southerly and gradually strengthen
through midday.

Pfahler

&&

.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