Nameoki, Illinois Weather Forecast Discussion

349
FXUS63 KLSX 071928
AFDLSX
Area Forecast Discussion
National Weather Service Saint Louis MO
228 PM CDT Sun Sep 7 2025
.KEY MESSAGES...
- Dry conditions will continue for the foreseeable future, with
  temperatures gradually warming through the week.
&&
.SHORT TERM...  (Through Late Monday Night)
Issued at 227 PM CDT Sun Sep 7 2025
A large area of high pressure over the Midwest sits beneath a deep
upper-level trough per recent observations. Between this high and
northwesterly flow on the backside of the trough over the Middle
Mississippi Valley, our weather remains dry and clear. Weak cold air
advection will keep our temperatures below normal this afternoon,
though clear skies and ample sun will support values rising another
couple of degrees into the mid-70s. Tonight will be cool, but not as
cool as previous nights thanks the surface high shifting slightly
eastward and supporting some degree of light southerly flow and a
subtle bump in mid-level temperatures. This should mitigate
widespread fog, though there could still be some
isolated valley/steam fog similar to this morning.
Tomorrow, the upper-level trough deamplifies with northwesterly flow
weakening over the Middle Mississippi Valley. With this and the
surface high shifting further eastward allowing for mid-level
temperatures to moderate, we will see surface temperatures warm by a
few degrees compared to today, but still remain several degrees
below climatological normals.
Elmore
&&
.LONG TERM...  (Tuesday through Next Sunday)
Issued at 227 PM CDT Sun Sep 7 2025
Despite weak shortwave troughing over the Middle Mississippi Valley
on Tuesday, guidance consensus is that low to mid-level flow will be
southerly to southwesterly, supporting warm air advection. Ensemble
means respond by showing an approximately 5 degree jump in
temperatures Tuesday over Monday. This will mark the beginning of a
prolonged period of warmth for the region, as upper-level ridging
builds into the Midwest Wednesday into Thursday as the shortwave
departs eastward. As a result, warm air advection will only be
enhanced, with 850 mb temperatures climbing into the upper teens to
around 20 degrees C. Over the last couple of guidance
initializations, spread has actually increased slightly concerning
850 mb temperatures, causing spread to increase somewhat with
surface temperatures. This spread is mostly negligible, however, as
these values at 850 mb climatologically favor surface temperatures
around 90 degrees - warm for this time of year no matter the
specific value. Confidence is high that this warmth will continue
through at least Saturday as the ridge holds.
Given the ridge building and holding overhead through the period,
rain chances remain low to null. Guidance consensus remains that the
main fetch of Gulf moisture will remain west of the region with no
forcing mechanisms expected. Our recent lack of rain and seasonal
curring of vegetation has decreased the rate of evapotranspiration,
which will further inhibit low-level moisture. At the very least,
this will limit the level of humidity with the warmth, keeping
afternoon conditions relatively manageable and allowing for large
diurnal swings in temperature.
Elmore
&&
.AVIATION...  (For the 18z TAFs through 18z Monday Afternoon)
Issued at 1148 AM CDT Sun Sep 7 2025
Dry and VFR flight conditions will prevail at all local terminals
through the forecast period. Winds will gradually become
southeasterly late tonight into tomorrow.
Elmore
&&
.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&
$$
WFO LSX

NWS LSX Office Area Forecast Discussion