Old Jamestown, Missouri 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

886
FXUS63 KLSX 161121
AFDLSX

Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
621 AM CDT Thu Apr 16 2026

.KEY MESSAGES...

- There is a chance for showers and thunderstorms this afternoon
  and early evening, mainly along and south of I-44 across the
  Eastern Ozarks.

- Thunderstorms are expected to move into northeast and central
  Missouri late Friday afternoon or early evening and continue
  through the area Friday night. Some of the storms could be
  severe Friday afternoon and evening.

&&

.SHORT TERM...  (Through Late Tonight)
Issued at 405 AM CDT Thu Apr 16 2026

The cold front which triggered last night`s storms is washing out
over Missouri and west central Illinois, and is now difficult to
discern in surface observations.  Low level southerly flow will be
reestablished across the area today ahead of the tail end of the mid-
upper level trough which was pushing the front southeast.  The
trough is attenuating quickly, and 500mb heights are forecast to
either be steady or even rise slightly just ahead of it.  However,
most short-range guidance is showing low level moisture convergence
on the southerly flow, and they produce a few hundredths of an inch
of QPF.  Several CAMs (including the latest HRRR) pop up scattered
convection over the eastern Ozarks during the afternoon as well.
GFS and RAP show a solid 1500-2500 J/Kg SBCAPE south of I-70 in
Missouri into far southeast Illinois, along with 30-40kts of 0-6km
shear.  Forecast soundings look nearly uncapped with perhaps just
the slightest amount of CINH.  However, the only obvious trigger for
afternoon thunderstorms is the aforementioned weak low level
moisture convergence, which may not be enough to force convective
initiation.  With all that in mind, I do think 30-40 PoPs are
warranted across the eastern Ozarks this afternoon into early
evening, and I would not be surprised if a few severe thunderstorm
warnings were issued.  The mid-upper level trough will be moving
east of the area and short wave ridging will build across the Mid-
Mississippi Valley this evening, so any storms that do develop during
the afternoon should either move out of our forecast area or
dissipate between 00-03Z this evening.  Remaining cloud cover
left over from overnight convection should clear the Mississippi
River by 15-16Z and then be out of south central Illinois by 17-
18Z. Lack of a decent FROPA, persistent southerly flow, and
strong April sunshine after clouds clear this morning should
push temperatures back into the low to mid 80s today, and light
southerly flow tonight will promote mild lows in the low to mid 60s
in most locations.


Carney

&&

.LONG TERM...  (Friday through Wednesday)
Issued at 405 AM CDT Thu Apr 16 2026

Attention turns to severe weather potential Friday. A strong mid-
upper level trough will move across the Plains into the Midwest
Friday into Saturday. A strong cold front will develop over the
eastern Plains Friday morning and move into northwest Missouri by
mid-late Friday afternoon. Mid levels will cool ahead of the front
as the trough moves east which will steepen lapse rates and
increase instability. GFS and RAP show 3500+ J/Kg CAPE ahead of
the front in northwest Missouri with deep layer shear increasing
to 50kts. Convection is expected to be triggered by the front as
it moves southeast during the afternoon. Supercells should be the
predominant convective mode in this environment, at least
initially. However, shear vectors are nearly parallel to the low
level boundary which should promote upscale growth into a QLCS
with LEWPs and bowing segments as it moves into northeast and
central Missouri. Damaging winds will be the primary threat as the
line moves into our area, and strong 0-1km shear will also
produce a tornado threat. Large hail will also be a threat early
on, particularly where supercells may be embedded in the line, but
the hail threat should diminish as the line continues east into
east central Missouri and southwest Illinois. I am still uncertain
as to how far east the severe threat extends. GFS and RAP show
instability falling quickly after sunset ahead of the line across
eastern Missouri into southwest Illinois. CAMs also indicate the
line will weaken quickly during the evening. The 4km NAM looks
like the most dramatic example of this weakening as the line falls
apart between 03-04Z before it reaches east central Missouri. The
HRRR also weakens the line, although it`s after 04Z after the
line has moved nearly all the way through the CWFA. This
variability does not instill a great deal of confidence in the
eastward extent of the severe threat. However the solutions which
hang onto evening instability and the favorable 0-1km kinematics
continue to warrant the severe messaging.

Briefly, beyond Friday night...  Cooler and quieter weather settles
into the Mid-Mississippi Valley Saturday behind the front.  Cool
high pressure spends the weekend moving from the Great Plains into
the Lower Mississippi Valley.  Seasonably cool temperatures in the
60s are expected Saturday and Sunday with lows Sunday morning
dropping into the mid 30s to around 40.  Low level flow returns
turns back to the south early next week which will push temperatures
back into the 70s to near 80.


Carney

&&

.AVIATION...  (For the 12z TAFs through 12z Friday Morning)
Issued at 620 AM CDT Thu Apr 16 2026

Light SSW winds are expected today under a mostly clear, VFR sky.
There is a low potential for renewed thunderstorm development over
southern MO and IL, but this is unlikely to occur far enough north
to affect any TAF location.

Kimble

&&

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

$$

WFO LSX