153
FXUS63 KDVN 231726
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1126 AM CST Mon Dec 23 2024

...Updated for 18z Aviation...

.KEY MESSAGES...

- Patchy fog possible tonight, some fog could be dense as well.

- Warmer temperatures along with several chances for rain will
  finish out 2024 with very little sunshine.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 310 AM CST Mon Dec 23 2024

The advertised schc (<20%) chance of drizzle/freezing drizzle
continues for this morning. The threat area has decreased as low
level moisture has been slow to materialize. Guidance continues
to show this rapidly develop near 12z, so have kept pops because
of this. Most of the area has temps at or above freezing,
however with drier air, wetbulb temps are below freezing,
especially across northwest Illinois where a snowpack remains.
When the sun comes up we will still have this threat until the
forcing pulls out of the area. That said, any freezing drizzle
that does develop will likely fall when the sun is up. This
usually makes it a little harder to accumulate. Untreated and
elevated surfaces would be the main area to see a light glaze of
ice.

Tonight, once the forcing pulls out of the area, we find
ourselves on the east of a surface high moving into the area. At
the same time, we quickly have WAA return to the area as
another wave from the SW moves towards us. This will setup us up
for fog tonight. We will definitely have low level stratus.
Some of the guidance even has vsbys at or below a quarter mile.
Low confidence on timing and location of dense fog will keep me
from issuing a dense fog advisory. We could end up with one
later this evening.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 310 AM CST Mon Dec 23 2024

Pattern remains active through the long term period as a series
of upper systems affect the region through the weekend. At the
same time these systems will bring warmer more moist air into
the area as well. The forecast for the next few days looks
rather cloudy with some chances for rain. Definitely going to
have a brown Christmas across the area and likely cloudy. The
end of the week sees a longwave trof move across the western US
with a series of compact and powerful shortwaves rotate around
it.

With the active pattern expect the specifics to change with each
run of the guidance. What is clear is that the thermal profiles
across our area will lead to rain from any of these systems. It
also looks like our overall rainfall amounts through the weekend
will be under an inch. In fact, most of the rain looks to be
light and long lived stratiform rain. If one of these systems
slows down and pulls further west, then we may see ourselves
more in a warm sector and could see some convective showers
which could increase precip totals. Regardless, for late
December and this active of a pattern we are lucky that we are
above freezing and that clouds and likely low clouds are the
main impacts we have.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1120 AM CST Mon Dec 23 2024

Predominantly VFR conditions for the start of the TAF period. A
weak low pressure system is passing across far NE Iowa and
S Wisconsin. This will bring a quick shot of sprinkles and
light rain to portions of the area mainly near/north of Hwy 30
including the CID/DBQ terminals within the first 1-2 hours
of the start of the TAF period. No impacts are expected. The low
will drag a cold front across the area through late afternoon.
SW winds around 10 kt and locally gusting higher 15-20 kt will
shift to the N/NW with the passage then slowly diminish tonight.
Low clouds will also be advected into the region with ceilings
lowering to lower MVFR and IFR late this afternoon through
evening from N to S across the terminals, and remain for the
rest of the period as low level flow weakens with a building
surface high leading to a trapping subsidence inversion. Some
fog is also possible later tonight into early Tuesday morning,
but confidence on extent and magnitude is low due to the
likelihood of stratus. Will keep any visibility restriction IFR
to MVFR to match with ceilings, but there is a low signal for
potentially pockets of LIFR/VLIFR.

&&

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

&&

$$

SHORT TERM...Gibbs
LONG TERM...Gibbs
AVIATION...McClure