Marion, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

008
FXUS63 KDVN 241141
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
541 AM CST Sun Nov 24 2024

...Updated for 12z Aviation...

.KEY MESSAGES...

- Potential for some accumulating snow and travel impacts for
  portions of the area late Tuesday night into Wednesday is
  increasing.

- Monitoring for the potential of another storm system with
  a chance for additional accumulating snow Wednesday night
  into Thanksgiving. Confidence is low in the track/strength and
  subsequent snow potential and extent of any impacts. Continue
  to monitor the forecast!

- The pattern change that occurred last week will remain active
  through early December. Temperatures will likely (70-90%) be
  below normal into early December.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 326 AM CST Sun Nov 24 2024

An upper level shortwave will shift from the Northern Rockies
into the western Great Lakes by Monday night. Surface lee
troughing will strengthen in response and shift eastward
today with an eventual surface wave forming to our SW over
portions of N Missouri along a sharpening cold front. This
will lift a warm front into areas mainly south of I-80 this
afternoon. Strengthening warm advection aloft with 925 hPa
temperatures climbing into the range of around 6c N to 12c S
will set the stage for a warmer day from Saturday, with the
anticipated range on highs from the upper 40s/around 50 N to
around 60 south. Increased moisture advection on a SW low
level jet will foster lower clouds overspreading the area
from SW to NE from mid afternoon through this evening. Just
enough low level saturation and lift exists to support some
sprinkles and scattered light showers to eventually accompany
the clouds, as the low lifts up across S/E portions of the
service area this evening. The sprinkles/light showers should
diminish overnight as the low begins to pull away accompanied
by a cold frontal passage. Prior to that occurring there will
be a few to several hour period potential for some fog and
drizzle as the low moves through. Cold advection won`t really
ramp up in earnest until after 12z on Monday, so tonight
should be mild with most areas only dropping back or staying
into the 40s, which is near normal highs for this time of year.

Monday will be blustery/windy with NW winds gusting 25-35+ mph.
Temperatures in the strengthening cold advection look to
gradually drop during the day with most areas in the 30s at
sunset and possibly even some upper 20s far NW portions of the
service area. Combination of the winds and dropping temps will
make it feel more like the 20s, so a markedly colder feel coming
off the above normal warmth of Sunday. Some drizzle or flurries
are possible Monday morning, especially north with the arrival
of the colder air and the passage of the shortwave trough in the
Upper Midwest.

High pressure building in Monday night will bring about diminishing
winds and lead to the coldest night of the season for most, with
widespread lows in the low to mid 20s. A few upper teens are even
possible far W/NW sections if winds can fully decouple. Any wind
will make it feel even colder and more like the teens to possibly
nearing single digits N... Brrrrr!

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 326 AM CST Sun Nov 24 2024

The next western trough is forecast to move into the Plains on
Wednesday. In advance, we`re noting an increasing model signal
for strengthening warm advection and frontogenetical forcing
induced ahead of the developing Plains low and upper trough late
Tuesday night and Wednesday. We`ve collaborated to add some snow
chances (20-30%) for many areas late Tuesday night, which persist
on Wednesday. It`s still several days away, but will have to watch
for a narrow Fgen band of accumulating snow (1-2+ inches) and
potential travel impacts late Tuesday night and Wednesday,
particularly near and north of I-80 as it looks right now although
location is subject to change.

The concern then shifts to another potential period for accumulating
snow and holiday travel impacts Wednesday night into Thanksgiving.
With regards to this system we`re seeing 2 distinct camps of solutions.
The medium range deterministic American models (GFS, GEM) and their
ensembles (GEFS and GEPS) generally support less phasing of the
southern stream with the northern stream. This leads to a more
southerly track and somewhat weaker system that misses the area. Any
precipitation chances (snow showers and flurries) would not be until
late week or next weekend with additional northern stream energy.
Meanwhile, the deterministic ECMWF and it`s ensemble (ENS) generally
favors more phasing of the northern stream and southern stream. This
results in a stronger system that tracks further northward in/near the
Ohio Valley. Consequently, much of the area is swiped by precipitation
on the northern side of this deepening system. Based on thermal
parameters this would largely be snow, with potentially some rain
initially far south before changing to snow aided by dynamical cooling
from ascent. This would lead to the likelihood of some accumulating
snow with the potential for travel impacts Wednesday night into
Thanksgiving, with the higher PoPs and better potential for several
inches of accumulation residing mainly south of I-80. Our current
forecast using the NBM looks like the ECMWF scenario, as it`s got a
lot of weight into the NBM at 61-84 hours out and especially beyond 84
hours. I am noticing in the Dprog/dt of the deterministic ECMWF in the
past couple of runs a more southerly shift. Bottom line, there is still
a lot of uncertainty on the track/strength of this system and whether
we`ll see any wintry impacts. Just continue monitoring updated data,
forecasts and trends. Stay tuned!

Beyond, confidence remains high on turning much colder and well
below normal at the end of November and beginning of December, as
there`s good agreement on a blocking pattern developing in the NE
Pacific entrenching the region in northwest flow aloft and bouts of
Arctic air. Easily looking at the coldest weather of the season so far
next weekend through the start of December.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 535 AM CST Sun Nov 24 2024

VFR conditions to start the TAF period with just some high
level cloudiness. Some low stratus with IFR to LIFR CIGs
though are not far away from DBQ and currently cover portions
of NW Illinois. Flow in the cloud bearing layer from the SW
supports this continuing to lift northward and staying east
of the terminal and so have left out mention. Still, needs to
be watched for any changes. Otherwise, I have kept mention of
LLWS through daybreak for BRL with VWP plots to the southwest
showing 40-50 kt SW low level flow at 1500-2000ft agl. VFR
conditions are expected to dominate for much of the day today
with strengthening E/SE flow around 10-15 kts with occasional
higher gusts possible. A weak surface low is forecast to move
into southern portions of the area tonight along a warm front.
Sufficient low level saturation and convergence exists for the
development of lower CIGs and spotty light rain/drizzle with
predominantly MVFR conditions. Some lower conditions (IFR/LIFR)
in fog and low clouds is possible, but not confident enough to
add mention. Late tonight as the low departs winds will shift
to the NW and begin to inrease.

&&

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

&&

$$

SHORT TERM...05
LONG TERM...05
AVIATION...05