Andalusia, Illinois Weather Forecast Discussion

822
FXUS63 KDVN 160744
AFDDVN
Area Forecast Discussion
National Weather Service Quad Cities IA IL
244 AM CDT Tue Sep 16 2025
.KEY MESSAGES...
- Unseasonably warm weather will continue through most of this week
  before finally cooling down a bit toward the weekend.
- Better rain chances return with an upper level system Thursday
  night and especially Friday.
&&
.SHORT TERM /THROUGH TONIGHT/...
Issued at 240 AM CDT Tue Sep 16 2025
Today...Rather complex blocking upper pattern continues to reign
acrs most of the CONUS, with narrow upper ridge lobe maintaining
acrs the southeastern plains up through the northeastern GRT LKS.
Upstream upper trof acrs the west central Rockies into Manitoba will
continue to be a synoptic weather maker with storminess from
eastern CO into the northwestern GRT LKS. Upper support more
nebulous further southeastward toward our neck of the woods with
isolated to sctrd diurnal convection more common just off to the
west of the DVN CWA acrs central into western IA. But will keep low
CHC POPs acrs the far west central and northwestern CWA this
afternoon into early evening in case something can manage to bleed
this way off tight west-to-east CAPE gradient. Similar to this
Monday afternoon and evening looks like a low shear-high CAPE
scenario and any stronger cell would be able to produce at least
small hail and gusty winds up to 50 MPH with cell collapse. High
temps today generally in the mid 80s to lower 90s in light east to
southeast sfc wind regime, and manageable sfc DPTs in the low to mid
60s.
Tonight...Mainly a dry night under continued ridge influence and
light east to southeasterly sfc flow. This will make for a continued
sfc DPT pool gradient from east-to-west, as well as ambient temps
ranging from the mid 50s in the far east, to the lower 60s west. The
drier sfc DPTs should limit fog production besides the normal river
valley occurrence.
&&
.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 240 AM CDT Tue Sep 16 2025
Wednesday...Slowed up blocked pattern may make this day similar to
Tuesday, with only low CHC POPs warranted in the far west central to
northwestern CWA for diurnal convection closer to the organizing
upper trof or even into closed upper low formation acrs the west
central plains. The rest of the area remaining dry into Thursday.
Currently projected thermal profiles suggest Wednesday could be a
degree or two cooler than Tuesday but still a very warm day.
Thursday on...With continued Canadian upper troff/wave
energy influence and action, the upper low/troff to our west
will eventually get here and when it does it will bring rain
chances and a shift back toward cooler temperatures, or at least
closer to normal for mid September.
While long range guidance does generally agree that we will
transition from the weakening ridge to the eastward nudging trough,
when that occurs and what the trough looks like when it begins to
impact our weather still varies. The trough itself becomes cut off
from the flow to the north by a ridge developing in western Canada.
This type of cut off low scenario is notorious for being more
unpredictable with wider timing uncertainty than normal. Being as
the trough itself is encompassed by a broader ridge, the
temperatures experienced in the core of the trough won`t be all that
cool. Not like what we saw from our cool spell earlier this month.
But the trough does come with cooler temperatures aloft leading to
more cloud cover and rounds of showers and thunderstorms which
really help to tone down the heat. The uncertainty on the arrival of
this trough is shown in part in the NBM interquartile range for high
temperatures which for most of this week is only 2 to 3 degrees
across our forecast area. However from Friday onward it`s more on
the order of 7 to 10 degrees, indicating that greater uncertainty on
when that cooler air arrives and how cool each subsequent day will
be (it depends on cloud cover).
As far as rain goes, when the trough does finally nudge closer to us
we`ll see the best widespread rain chances we`ve seen in a while.
Among the 00Z ensemble guidance, 70 to 90 percent of members produce
measurable rain across our forecast area in the 24 hours ending
Friday evening indicating higher confidence that we will eventually
get at least some rain. Our daily PoP from NBM is lower than that
due to uncertainty on whether that rain comes Thursday night or
Friday. It could be a substantial rainfall as well, with access to
at least modest moisture as the trough arrives (precipitable water
gets close to 1.5 inches) along with associated instability.
However, rain being at least partly of a convective nature indicates
amounts will be variable based on where deeper convection
develops.
&&
.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1217 AM CDT Tue Sep 16 2025
Ongoing high pressure center just off to the east and light east
to southeasterly sfc flow to maintain a VFR TAF cycle through
the period. Some chance for some MVFR fog toward dawn at a few
of the sites, but confidence is low and will keep any VSBY
restrictions out of the TAFs for now. Tue afternoon and evening
isolated showers/storms should stay west of any TAF site.
&&
.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.
&&
$$
SHORT TERM...12
LONG TERM...12/Kimble
AVIATION...12

NWS DVN Office Area Forecast Discussion