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afdilx

Area forecast discussion
National Weather Service Lincoln Illinois
1156 PM CDT Tue Sep 17 2019

Synopsis...
issued at 258 PM CDT Tue Sep 17 2019

Unseasonably warm and dry conditions for mid September will
continue for the remainder of the work week. High temperatures
will range from 85 to 90 degrees across all of central and
southeast Illinois through Friday. The next chance for rain in
the area will be this weekend.

&&

Update...
issued at 805 PM CDT Tue Sep 17 2019

High pressure will bring mostly clear skies and light southeast
winds to central Illinois overnight. Lows should reach the low to mid
60s. Less fog is expected than the previous few nights, but model
guidance continues to suggest patchy fog from around Canton to
Bloomington northward, coincident with slightly higher moisture
and lower temperatures. Have added fog to forecast grids in this
area, but otherwise no significant changes are needed this
evening.

&&

Short term...(this evening through wednesday)
issued at 258 PM CDT Tue Sep 17 2019

Very warm and dry conditions will continue across the forecast
area as an upper level ridge axis from the Tennessee Valley across Illinois to
the western Great Lakes slowly shifts eastward.

The main concern for tonight is whether or not some fog will
redevelop. Two nights ago radiation fog developed, where last
night the fog advected in from NE Illinois/northwest in. Am expecting some
light fog to develop north of a Canton-Bloomington line well after
midnight, but not as widespread or dense like early this morning.

Plenty of sunshine, with only scattered cloudiness on Wednesday
will allow temperatures to climb into the 84-89 range once again,
with a light southeast wind.

Long term...(wednesday night through tuesday)
issued at 258 PM CDT Tue Sep 17 2019

As the upper level ridge moves east and starts to flatten out, a
weak shortwave trough from the Central Plains will move toward the
upper Great Lakes during the day Thursday. At this time it appears
that any forcing with this will stay well to our northwest.
However, a stray shower/isolated thunderstorm could move as far
east as Galesburg, so have introduced a slight chance of
precipitation for early Thursday evening.

The main weather impacts in the longer term will be toward this
coming weekend. The medium range models are displaying their usual
tendencies of pushing the upper level ridge axis toward the east a
bit quicker, so will hold off on any mentionable pops for
showers/T-storms until Friday night west of I-55 and across the
rest of the area until Saturday. A slow moving frontal boundary
with a southwesterly low and mid level flow and an upper level
trough axis lifting out through Midwest later on Sunday will
result in several periods of rainfall Saturday and Sunday.

At this point, the best upper level jet dynamics and tropical
moisture advecting into the Midwest with very high precipitable
water values greater than 2.00 inches, are expected from Saturday
evening into much of Sunday. These ingredients would be favorable
for widespread heavy rainfall around 2.00 inches or greater for
central Illinois, with 1-2 inches in southeast Illinois. Will definitely
be keeping an eye on how the models handle this the next few days,
but so far they are fairly consistent.

There is quite a bit of model disagreement regarding the forecast
for early next week with the GFS, European and Canadian all
showing different solutions aloft and at the surface. I have a
hard time thinking the surface front will get too far past the
Ohio Valley Monday and Tuesday, so will keep at least chance pops
in the forecast for southeast Illinois Monday, and all of central Illinois
Tuesday as the front may try to lift back northward.

&&

Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 1156 PM CDT Tue Sep 17 2019

There is a good chance of MVFR conditions in fog from 09z-14z at
kpia, kbmi, and kcmi where slightly moister and/or cooler
conditions have been noted in obs and model guidance consensus
tends to favor for fog formation. Otherwise, VFR conditions are
expected, with east-southeast-south-southeast winds under 8 kts expected through the 06z
taf forecast period.

&&

Ilx watches/warnings/advisories...
none.

&&

$$

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