484
FXUS63 KDVN 230514
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1214 AM CDT Mon Sep 23 2024

.KEY MESSAGES...

- Isolated showers or occasional sprinkles are possible into
  this evening; most of the area should stay dry due to low coverage.

- Cooler weather is expected today and Monday with highs only in the
  60s to low 70s.

- Low confidence in the forecast regarding late this week into
  next weekend as an upper low interacts with the tropics in a
  blocking pattern.

&&

.SHORT TERM /THROUGH TUESDAY/...
Issued at 215 PM CDT Sun Sep 22 2024

Midday WPC surface analysis had a low near the Hudson Bay with
a cold front extending to the southwest. As of 2 PM, the front
was positioned from NE Wisconsin to along the Iowa/Illinois
border and down into NE Oklahoma.

It`s been a rather gloomy day with low overcast, steady NW to N
winds, occasional showers or sprinkles, and afternoon
temperatures only in the 60s. Heading into this evening and
tonight, drier air will advect into the region with dewpoints
dropping into the 50s and 40s. Thus we can expect mainly dry
conditions for the overnight period, along with decreasing cloud
cover. Forecast lows are in the mid 40s NW to mid 50s SE.

Monday: Seasonable mid to late September weather is expected with
highs in the upper 60s to low 70s. A 500mb shortwave trough
approaching from the Central Plains may bring a round of showers
to locations along and south of Highway 34 by the afternoon
(20-30%). More widespread rain is forecast for the overnight
period as the wave tracks across eastern Iowa and northwest Illinois.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
Issued at 215 PM CDT Sun Sep 22 2024

The long term period begins 00 UTC Tuesday with a deep trough across
the Central US and ridging along the West Coast. A weak shortwave is
forecast to move along the Iowa/Missouri border Monday night with
the trough axis exiting to our east on or shortly after 12 UTC
Tuesday. This shortwave will bring rain showers or light rain to the
area mainly south of Interstate 80 (40-60%). Think that the
bulk of rain will exit to our east by 12 UTC on Tuesday. Low
temperatures on Tuesday morning will be in upper 40s along the
Highway 20 corridor to the mid 50s south of Interstate 80.

A digging shortwave on the western side of the Central US trough is
forecast to become a closed low over the mid Missouri Valley on
Tuesday but models disagree on the timing of this occurring but they
do agree that this feature will linger across the region through the
middle of the week. Mid level lapse rates in the closed low and
trough are not very steep and do no think this will bring the risk
of showers through midweek but this will depend on where this low
tracks. Otherwise, high pressure is forecast to build into the area
at the surface. There will be large diurnal changes in temperatures
with low temperatures in the upper 40s to lower 50s and high
temperatures in the mid to upper 70s.

Beyond Thursday, the forecast depends on the models handling of a
closed low over lower to mid Mississippi Valley and a potential
tropical system in the northeast Gulf of Mexico. Models do show
these systems merging but vary on the timing and placement impacting
the forecast into next weekend. The ECMWF and Canadian show a
broadening of the closed upper low and show it lifting north toward
the area and then is absorbed into the 500 MB flow while the GFS has
a more compact storm system that moves slowly northward late in the
period before being absorbed in the 500 MB flow this next weekend.
The ECMWF and Canadian solutions bring chances of showers to the
area as early as Thursday night with periods of showers through next
Sunday while the GFS limits this to Saturday night into Sunday. High
temperatures during this period will be in the mid to upper 70s with
lows in the mid to upper 50s.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1211 AM CDT Mon Sep 23 2024

Dry north to northeast wind have established a VFR condition at
all sites except for BRL late this evening. These VFR sites will
continue to remain quiet VFR through the period, but BRL, and
southeast Iowa/western Illinois will be slow to improve cig
height, as there`s a lot of low level moisture remaining just
south of the area, and the dry advection is not strong at this
point. I`ve gone rather pessimistic for BRL, as the cig has been
lowering to around 2000ft in the past couple hours, and this may
continue through the night now. I`ll transition them to VFR by
15Z Monday morning.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...None.
MO...None.

&&

$$

SHORT TERM...Uttech
LONG TERM...Cousins
AVIATION...Ervin