364
FXUS63 KDVN 081732
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1132 AM CST Fri Nov 8 2024

...Updated for 18z Aviation and Update Section...

.KEY MESSAGES...

- Dry conditions will largely be in place today through late
  next week, with chances of showers Saturday through Sunday
  morning, and again mid-week next week

&&

.UPDATE...
Issued at 1125 AM CST Fri Nov 8 2024

Well the cirrus has thinned sufficiently across much of the
northern 1/2 to 2/3 to where we should still be on track for
upper 50s to lower 60s in those locations. Our far southern
service area trends continue to support more opaque high
cloudiness there, and so highs could potentially be lower in
those areas by a few degrees. Will continue to monitor trends
and updated if needed.


.SHORT TERM /THROUGH TONIGHT/...
Issued at 245 AM CST Fri Nov 8 2024

Surface high pressure ridging extending from Nebraska has kept our
region clear and calm, with areas of fog development mainly along
and north of Interstate 80. This fog is expected to linger through
the early morning hours, dissipating around 8 to 9 AM this morning.
After the fog dissipates, quiet conditions will prevail through the
overnight hours tonight. High cirrus clouds should begin to filter
in ahead of a larger system that will move into our region for
Saturday. More on that in the long-term section below.

We continue to have today`s high temperatures near the 75th
percentile of the NBM due to the sunshine, with highs in the upper
50s to lower 60s. Tonight`s lows will dip to the upper 30s to lower
40s.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Issued at 245 AM CST Fri Nov 8 2024

The long-term forecast period starts off with steadily increasing
chances (50 to 80%) of showers across the area. This will be driven
by a cut-off upper low that has developed over the Four Corners
region this morning, gradually lifting north-northeastward tonight.
A leading occluded front and upper-level diffluence will support
large-scale forcing for ascent. Saturday morning will largely be
dry, with plenty of dry air in place in the lowest 12 kft feet of
the column per the 08.00z HREF ensemble soundings, so onset timing
of the rain will greatly depend on when top-down saturation occurs.
This should happen eventually, given integrated water vapor
transport magnitudes over 90 percent of climatology per the ECMWF
ensembles and Pwats between 1 to 1.4 inches. A wetting rainfall is
likely for most locations, with 08.00z LREF exceedance probability
of total rainfall greater than a tenth of an inch around 60 to 80
percent for most locations. Due to little, if any, instability,
thunderstorm chances remain less than 10 percent.

By the time we get to Sunday, the upper low lifts northward towards
northern Minnesota, with an attendant surface low pressure system
trailing just north of our region. A tightening surface pressure
gradient will result in breezy southwest winds developing, with
gusts ranging around 20 to 25 mph.

Dry conditions prevail Monday and Tuesday, with seasonal
temperatures. Expect highs in the middle to upper 50s. Overnight
lows will be interesting as they will be highly dependent on cloud
cover, which will determine the radiational cooling potential.
Should skies become clear, lows in the 30s will be likely, with
lower 40s more likely if clouds stick around.

Attention turns to Wednesday as an upper-level trough sweeps from
west to east over our region. The trough appears to be more
negatively-tilted with time, but there is some uncertainty on the
timing of the trough as ensemble cluster analysis indicates the
ECMWF ensembles have the trough slightly faster than the GEFS and
GEPS ensembles. There are also differences in the degree of trough
amplification among the ensembles. Nonetheless, at least some light
rainfall will be possible, with 08.00z LREF probabilities of total
rainfall greater than a tenth of an inch of 40 to 60 percent.
Depending on the morphology of this system, chances of rain could
linger through Wednesday night.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1125 AM CST Fri Nov 8 2024

Predominantly VFR conditions expected for the TAF period. Light
westerly winds will shift to easterly tonight and increase to
around 10-15kt late into Saturday, as a storm system lifts into
the Central Plains. Banking on increasing mid/high cloudiness,
and the development of near surface boundary layer mixing to keep
fog potential too limited for mention in TAFs. Something we`ll
need to keep an eye on in the developing easterly flow for later
tonight/Saturday AM is the potential for low clouds to form
off Lake Michigan, which if occur could advect into the
terminals particularly at MLI, CID and DBQ. It is the season
for that to happen. However, the signal is very low and only
suggested by the NAMNest and HREF. This results in confidence
being too low to include, but it is something to monitor for
future TAFs. Initial bands of elevated light showers are
possible lifting up across the terminals 12z-18z, but being late
in the period and limited if any visibility impacts I have left
out any mention.

&&

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

&&

$$

UPDATE...McClure
SHORT TERM...Schultz
LONG TERM...Schultz
AVIATION...McClure