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Old Jamestown, Missouri 7 Day Weather Forecast
Wx Forecast - Wx Discussion - Wx Aviation
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NWS Forecast for 3 Miles NNW Black Jack MO
National Weather Service Forecast for:
3 Miles NNW Black Jack MO
Issued by: National Weather Service Saint Louis, MO |
| Updated: 5:36 am CDT Jun 20, 2026 |
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Today
 Mostly Sunny
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Tonight
 Mostly Cloudy
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Sunday
 Heavy Rain
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Sunday Night
 T-storms
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Monday
 Slight Chance T-storms
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Monday Night
 Partly Cloudy
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Tuesday
 Mostly Sunny
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Tuesday Night
 Mostly Clear
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Wednesday
 Mostly Sunny
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| Hi 85 °F |
Lo 69 °F |
Hi 83 °F |
Lo 64 °F |
Hi 77 °F |
Lo 61 °F |
Hi 81 °F |
Lo 63 °F |
Hi 83 °F |
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Flood Watch
Today
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Mostly sunny, with a high near 85. Light and variable wind becoming north around 5 mph in the afternoon. |
Tonight
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Mostly cloudy, with a low around 69. North wind 5 to 7 mph becoming southeast after midnight. |
Sunday
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Showers and thunderstorms. Some of the storms could produce heavy rainfall. High near 83. Southeast wind 9 to 15 mph becoming south in the afternoon. Winds could gust as high as 28 mph. Chance of precipitation is 90%. |
Sunday Night
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Showers and thunderstorms, mainly before 1am. Low around 64. Southwest wind 9 to 11 mph becoming northwest after midnight. Chance of precipitation is 80%. |
Monday
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A 20 percent chance of showers and thunderstorms before 1pm. Partly sunny, with a high near 77. North wind around 10 mph. |
Monday Night
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Partly cloudy, with a low around 61. |
Tuesday
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Mostly sunny, with a high near 81. |
Tuesday Night
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Mostly clear, with a low around 63. |
Wednesday
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Mostly sunny, with a high near 83. |
Wednesday Night
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Partly cloudy, with a low around 64. |
Thursday
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A 30 percent chance of showers and thunderstorms. Mostly sunny, with a high near 81. |
Thursday Night
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A 30 percent chance of showers. Partly cloudy, with a low around 64. |
Friday
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A 30 percent chance of showers and thunderstorms. Mostly sunny, with a high near 82. |
Forecast from NOAA-NWS
for 3 Miles NNW Black Jack MO.
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Weather Forecast Discussion
938
FXUS63 KLSX 201049
AFDLSX
Area Forecast Discussion...Updated Aviation
National Weather Service Saint Louis MO
549 AM CDT Sat Jun 20 2026
.KEY MESSAGES...
- A Flash Flood Watch will be in effect from late tonight into
early Monday for the threat of heavy rainfall potentially
leading to flash flooding.
- Some storms could be strong to severe late tonight into late
Sunday evening, bringing the threat of tornadoes and damaging
wind gusts.
- Below-average to seasonably cool conditions are anticipated next
week.
&&
.SHORT TERM... (Through Sunday Night)
Issued at 220 AM CDT Sat Jun 20 2026
Regional radar imagery reveals a few isolated pockets of showers
that are percolating southeastward and are being aided by weak low-
level frontogenesis associated with a weakening boundary. Some
pockets of heavier showers featuring intermittent lightning cannot
be ruled out as pockets of MUCAPE near 250 J/kg is forecast by
guidance to linger throughout the early morning hours, but the best
chance of this is across western MO. High-resolution guidance is in
good consensus that this activity will continue through 10z mostly
across central/northeast MO and quickly fade into the mid-morning as
the previously mentioned band of frontogenesis fizzles out. The
remainder of today is expected to be dry with seasonably cool
temperatures and light surface winds continuing into tonight.
Beginning tonight, our attention turns to a developing lee-side
surface cyclone that will initiate convection across KS/NE, with
quick upscale growth into an MCS/complex with eastward extent. The
commencement of the features above are in response to a shortwave
trough that will be traversing eastward into the Great Plains within
quasi-zonal flow in the mid/upper-levels. The MCS is forecast by
CAMs to be nearing central/north-central MO shortly after midnight
as it propagates along the Corfidi upshear vectors and/or favors to
track along the eastward extending warm front. As it enters into the
area (northeast/central MO), the greatest severe threat will be
damaging winds associated largely to any bowing/surging segments
that are still present. Additionally, locally heavy rainfall is
possible as anomalous PWATs near 2" (~99th percentile of
climatology) and a strengthening LLJ leading to increased moisture
transport will all be in place. If training or back-building along
the southern flank becomes favored across the area, this will
enhance the flash flooding threat as thunderstorms will be efficient
at rainfall production with >12,000ft warm cloud layers favoring
warm rain processes. A widespread 1-3"+ is forecast from this MCS
with locations that experience training or multiple rounds of
thunderstorms may easily reach >3" of rainfall from early Sunday
morning into Sunday evening.
What remains quite uncertain is the evolution of this MCS
(intensity, speed, and track), as is typical with these systems.
Lingering cloud cover/thunderstorms associated with the remnant MCS
throughout the day would decrease instability and thus lower the
afternoon/evening severe threat, while less of the above would favor
the opposite. Another feature previously mentioned will be a surface
cyclone that some guidance resolves will traverse across the area on
Sunday. If a surface cyclone does indeed cross the area at an
optimal time (afternoon/evening), that would locally enhance the low-
level shear, ultimately leading to a greater threat for tornadoes on
Sunday, especially near the warm front/surface cyclone. Otherwise, a
cold front is progged to be entering western MO Sunday evening which
should work to initiate additional convection, particularly near any
remnant outflow boundaries left behind from the earlier MCS. With
sufficient effective bulk shear (>30kts), organization of
thunderstorms is expected with a linear mode favored as the shear
vector is forecast to be nearly parallel to the boundary. Analysis
of the LREF IQR spread for MUCAPE highlights the uncertainty as the
25th-75th spread is around 1,000-1,500 J/kg across the area.
Regardless, with potential overlap of shear and instability, strong
to severe thunderstorms will be possible Sunday afternoon/evening
with the threats being damaging winds, tornadoes, and large hail.
Also, with the mean flow becoming increasingly parallel to the
forecast boundary, training of thunderstorms leading to locally
heavy rainfall will also be a threat into Sunday night.
As a result, a Flash Flood Watch has been issued for the entire area
with a range of start/end times in a window from late tonight
into Monday morning.
Peine
&&
.LONG TERM... (Monday Morning through Friday)
Issued at 220 AM CDT Sat Jun 20 2026
By Monday, the main shortwave trough axis will be crossing over the
area which is expected to bring an end to the widespread showers and
thunderstorms from west to east Sunday night into Monday morning. A
few subtle pieces of mid-level energy are progged by long-range
guidance within the wake of the shortwave, which may lead to some
lingering shower activity across the area early on Monday. Also, as
the surface cyclone lifts to the northeast, it will drag the cold
front through the region leading to ample low-level CAA on Monday.
As a result, Monday will feature high temperatures around 10 degrees
below average.
Northwesterly flow aloft will take hold over the region Tuesday into
the end of the week, resulting in a stretch of largely dry
conditions along with seasonably cool temperatures. Generally, highs
in the upper 70s/lower 80s and lows in the low/mid 60s look to
prevail, which is about 5-10 degrees below climatological normals.
This is supported well by the LREF, which has narrow 3-5 degree
temperature IQR spread through the end of the week.
Peine
&&
.AVIATION... (For the 12z TAFs through 12z Sunday Morning)
Issued at 542 AM CDT Sat Jun 20 2026
Dry and VFR conditions are expected with light winds through 06Z
tonight. Then there will be an increasing chance for showers and
thunderstorms from the west that will first affect UIN/COU/JEF so
have included a PROB30 group at these terminals beginning at
08-09Z, and also at STL starting at 15Z on Sunday. There will be
some MVFR restriction in visibilities, though MVFR and IFR
ceilings and visibilities in moderate to heavy rain will be more
common on Sunday as thunderstorms become more widespread.
Britt
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Flood Watch from Sunday morning through late Sunday night for
Franklin MO-Saint Charles MO-Saint Louis City MO-Saint
Louis MO.
Flood Watch from Sunday morning through Monday morning for
Crawford MO-Iron MO-Jefferson MO-Madison MO-Reynolds MO-
Saint Francois MO-Sainte Genevieve MO-Washington MO.
Flood Watch from late tonight through Sunday evening for Audrain
MO-Boone MO-Callaway MO-Cole MO-Gasconade MO-Knox MO-Lewis
MO-Lincoln MO-Marion MO-Moniteau MO-Monroe MO-Montgomery MO-
Osage MO-Pike MO-Ralls MO-Shelby MO-Warren MO.
IL...Flood Watch from Sunday morning through late Sunday night for
Bond IL-Fayette IL-Greene IL-Jersey IL-Macoupin IL-Madison
IL-Montgomery IL.
Flood Watch from Sunday morning through Monday morning for
Clinton IL-Marion IL-Monroe IL-Randolph IL-Saint Clair IL-
Washington IL.
Flood Watch from late tonight through Sunday evening for Adams
IL-Brown IL-Calhoun IL-Pike IL.
&&
$$
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