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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: 1:51 am CDT Aug 10, 2026 |
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Overnight
 Partly Cloudy
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Monday
 Slight Chance T-storms then Partly Sunny
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Monday Night
 Partly Cloudy
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Tuesday
 Hot
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Tuesday Night
 Partly Cloudy then Slight Chance T-storms
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Wednesday
 Chance Showers
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Wednesday Night
 Chance Showers then Chance T-storms
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Thursday
 Chance T-storms
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Thursday Night
 Chance T-storms
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| Lo 77 °F |
Hi 95 °F |
Lo 80 °F |
Hi 97 °F |
Lo 79 °F |
Hi 95 °F |
Lo 76 °F |
Hi 90 °F |
Lo 73 °F |
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Extreme Heat Warning
Overnight
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Partly cloudy, with a low around 77. South wind around 9 mph. |
Monday
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A slight chance of showers and thunderstorms between 7am and 10am. Partly sunny, with a high near 95. Heat index values as high as 104. Southwest wind 7 to 9 mph. Chance of precipitation is 20%. |
Monday Night
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Partly cloudy, with a low around 80. Southwest wind 5 to 8 mph. |
Tuesday
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Sunny and hot, with a high near 97. Heat index values as high as 107. Southwest wind 8 to 10 mph. |
Tuesday Night
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A slight chance of showers between 1am and 4am, then a slight chance of showers and thunderstorms after 4am. Partly cloudy, with a low around 79. Southwest wind 5 to 7 mph. Chance of precipitation is 20%. |
Wednesday
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A chance of showers and thunderstorms before 7am, then a chance of showers between 7am and 1pm, then a slight chance of showers and thunderstorms after 1pm. Mostly sunny, with a high near 95. Chance of precipitation is 30%. |
Wednesday Night
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A 50 percent chance of showers and thunderstorms. Partly cloudy, with a low around 76. |
Thursday
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A 30 percent chance of showers and thunderstorms, mainly before 1pm. Partly sunny, with a high near 90. |
Thursday Night
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A 50 percent chance of showers and thunderstorms. Mostly cloudy, with a low around 73. |
Friday
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A 30 percent chance of showers and thunderstorms, mainly before 1pm. Partly sunny, with a high near 88. |
Friday Night
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A 20 percent chance of showers and thunderstorms. Partly cloudy, with a low around 73. |
Saturday
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A 20 percent chance of showers and thunderstorms. Mostly sunny, with a high near 91. |
Saturday Night
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A 20 percent chance of showers and thunderstorms. Partly cloudy, with a low around 74. |
Sunday
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A 20 percent chance of showers. Mostly sunny, with a high near 89. |
Forecast from NOAA-NWS
for 3 Miles NNW Black Jack MO.
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Weather Forecast Discussion
758
FXUS63 KLSX 100359
AFDLSX
Area Forecast Discussion
National Weather Service St Louis MO
1059 PM CDT Sun Aug 9 2026
.KEY MESSAGES...
- Dangerous heat and humidity will continue across the area at
least through Wednesday. An Extreme Heat Warning and Heat
Advisories therefore remain in effect.
- The chance for rain increases late Wednesday into the end of
the week. Therefore cooler temperatures are forecast, however
there are some indications that above normal temperatures could
linger beyond Wednesday.
&&
.SHORT TERM /THROUGH TUESDAY/...
Issued at 251 PM CDT Sun Aug 9 2026
Low level south-southwest flow will continue through the short term.
This will keep a hot and humid airmass locked into place over the
Mid Mississippi Valley. Models have been consistently showing 22-
25C temps in the low level thermal ridge which mixes down to 95-100F
at the surface which continues to agree well with NBM max
temperature forecasts. Dew point temperatures are in the mid 70s
across the area this afternoon, and there`s no reason for Tds to be
any lower Monday and Tuesday. This will result in 100-110 degree
heat index readings both afternoons, with the higher end of those
readings generally along and east of the Mississippi River in
southwest Illinois where highest humidity tends to pool due to
transpiration from agriculture. With this in mind, The Heat
Advisories and Extreme Heat Warning look to be in good shape
and no changes are needed at this time.
Short range guidance shows a modest low level jet developing over
Missouri and western Illinois tonight. Some models also produce
precip, although most are dry. While confidence isn`t particularly
high, there`s enough of a signal to include some mention of precip
tonight, so slight chance PoPs across parts of northeast Missouri
into west central and south central Illinois seemed appropriate. Any
precip that does occur should dissipate after sunrise as the low
level jet weakens. The jet strengthens again Monday night, however
guidance shows the resulting moisture convergence to the east-
northeast of our forecast area. Have therefore kept Monday
night`s forecast dry.
&&
.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 251 PM CDT Sun Aug 9 2026
Ensemble guidance continues to show a chance for rain Wednesday as a
short wave trough moves from the Great Plains into the Mid
Mississippi Valley. The GFS shows a couple of QPF bullseyes
between 1.5 and 1.75 inches of rain Wednesday afternoon, but the
ECMWF is much more conservative. A lot of afternoon convection
could keep heat index values well below advisory/warning criteria,
however forecast soundings for Wednesday afternoon show a
substantial low-level capping inversion in the pre-storm
environment. I`m therefore skeptical about convective initiation.
Therefore think the heat headlines are still good for Wednesday...and
could in fact be needed into the end of the week.
The latest medium range guidance is now shifting the western upper
level ridge east into the Mississippi Valley Thursday into Friday.
This is a change from yesterday`s runs where the ridge retreated to
the west and a long wave trough dug into the Great Lakes and
southeastern U.S. The change means that the back door cold front
which was supposed to move through the area in the Thursday/Friday
time frame only makes it to central/northern Illinois. This would
have profound impacts on the temperature forecast for the rest of
the week into the weekend, and the rainfall forecast for the period
as well. The latest NBM still shows a significant temperature drop
on Thursday from the low to mid 90s on Wednesday to the low to mid
80s for most of the area for Thursday through Sunday. The LREF mean
high temperatures also follow this pattern. In contrast, the 12Z
GFS extended MOS (MEX) high temperatures at KSTL for Thursday
through Sunday are 95, 98, 98, and 94 respectively. EC MOS is
similar at 97, 96, 96, and 89. Digging a little deeper in the LREF,
the max T probabilities are shifted to favor temperatures below 90
degrees both Thursday and Friday. The histogram is more even for
the weekend, but still slightly favors highs AOB 90 degrees. With
this in mind, will continue to keep the cooler and wetter forecast
for the end of the week.
&&
.AVIATION /00Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1059 PM CDT Sun Aug 9 2026
Mainly dry and VFR flight conditions are anticipated through the TAF
period. However, there is a low chance of showers and a few
thunderstorms late tonight into Monday morning along and north of I-
70 with the highest chance of impacts at KUIN. Elsewhere, confidence
in impacts is lower. LLWS caused by a 40-kt southwesterly low-level
jet will persist until it weakens during the morning and surface
winds strengthen and veer to southwesterly. A few gusts of 15 to 20
kt are forecast during Monday afternoon.
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...Heat Advisory until 8 PM CDT Wednesday for MOZ018-019-026-027-
034>036-042-052-072>075-084-085-099.
Extreme Heat Warning until 8 PM CDT Wednesday for MOZ041-
047>051-059>065.
IL...Heat Advisory until 8 PM CDT Wednesday for ILZ058>060-064-065-
070-095>099.
Extreme Heat Warning until 8 PM CDT Wednesday for ILZ069-074-
079-100>102.
&&
$$
SHORT TERM...Carney
LONG TERM...Carney
AVIATION...Pfahler
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