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FXUS63 KDVN 310927 CCA
AFDDVN

Area Forecast Discussion...CORRECTED
National Weather Service Quad Cities IA IL
327 AM CST Fri Jan 31 2025

.KEY MESSAGES...

- Widespread dense fog expected into mid-morning and a dense fog
  advisory remains in effect.

- Widespread rainfall is expected through midday. Rainfall totals
  will range between 0.25" to 0.75" for many locations. Locations
  near and especially north of a Cedar Rapids to Freeport line
  may not see much in the way of measurable rain.

- Areal flooding is possible in low-lying locations, as the
  frozen ground will result in significant runoff. This threat
  is highest across parts of SE Iowa into N Illinois where a
  narrow band of 1-2" is possible, and as a result a Flood Watch
  has been issued for today.

- Above normal temperatures continue through much of the
  forecast period with Sunday expected to be the warmest day.

- A pattern change is pointing to a period of active weather
  over the next two weeks, leading to more frequent chances for
  precipitation.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 309 AM CST Fri Jan 31 2025

Water vapor imagery shows an oblong cutoff low from portions of
Kansas to the Red River of the south. Warm, moist advection
and increasingly diffluent flow aloft is fostering a rapid
uptick in coverage of rain south of I-80 early this morning.
Outside of the rain, considerable low clouds, areas of dense fog
and drizzle is being observed. Overall, over the next 12-18+
hours the models are in good agreement on depicting the closed
low opening up/weakening and eventually picking up speed while
passing south of the area, aided by some northern stream influence.
Prior to doing that, models also are in very good agreement on
developing a deformation zone on the northwest flank of the
mid level circulation through the first half of today. This
band will have an anomalous moisture fetch with PWATs of around
200% of normal and between 0.7 to 0.9 inch. As a result, we`re
seeing a pretty good signal in some of the hi-res guidance
including the HRRR, NAMNest and 00z HREF 24 hr QPF Localized
Probability Matched Mean (LPMM) of a 1-2 inch band of rain
potential focused into parts of SE Iowa and N Illinois where
even isolated rumbles of thunder can`t be totally ruled out. This
band may likely be a county or two in width focused where the
stretching/shearing deformation aloft enhances and stretches the
existing surface precipitation along the dilatation axis, and
oriented NE to SW along the 1000-850 hPa mean flow. Either side
of the band will likely feature sharp gradients/cutoff on
PoPs and amounts. Had hoped the warmer weather of the past few
days did more of a thaw, but unfortunately as of yesterday
morning much of the area is still above 12" for a frost depth.
This amount of rain falling on the frozen ground and on any
creeks, streams and smaller rivers with ice will bring concerns
for significant runoff and flooding. As a result, we have issued
a Flood Watch for portions of far NE Missouri, SE Iowa and
N Illinois where the model consensus favors the heaviest rainfall
to occur. For more on the flooding threat please refer to the
Hydrology section below.

Outside of the rain, areas of dense fog will likely persist into
at least mid-morning, and so have extended the Dense Fog Advisory
through 15z. The rain should taper off from NW to SE this afternoon
and will be followed up by decreasing clouds. Warmest readings
today will actually be favored across our northern counties due to
seeing more sun, which should get highs into the mid to upper 40s.
Meanwhile far S/E may be limited to the lower 40s for highs pending
the cloud trends. High pressure quickly traverses the region
tonight. Initially lows dropping into the lower to mid 20s tonight
before some leveling off or rise occurs late, as return flow
southerly winds begin to strengthen.

Attention late Saturday and especially Saturday night turns to
a fast moving shortwave zipping across the northern tier in
fast, zonal flow aloft. Low level warm advection will continue
to strengthen Saturday into Saturday evening, with gusty southerly
winds to 30+ mph. Most of the precipitation will be found to the
north of our area closer to the track of the shortwave. That
being said, we continue to see more support in the ECMWF and
EPS and also GEFS of measurable precipitation potential (>0.01)
extending further south from NBM, especially into far NE Iowa
and N Illinois and because of this I have expanded the PoPs to
account for this potential, but can`t rule out needing to
further increase and expansion if current trends persist. Soundings
favor snow initially as the dominant precip type before warming
temps lead to a rain/snow mix possibly ending as some drizzle
late Saturday night or very early Sunday, mainly north of Hwy 30.
Impacts look to be very limited/low.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 309 AM CST Fri Jan 31 2025

On Sunday, the shortwave will aid in sending a cold front through
the area. Timing of this front will be critical to highs.
For now we`re advertising highs mostly in the lower to mid 50s.
However, if the front is more timed by peak heating like the
ECMWF suggests then deeper mixing of 925 hPa temps of 6C to 10C
dry adiabatically would easily support mid 50s to lower 60s, with
possibly more widespread upper 50s/lower 60s aided by compressional
heating. This would put some record highs in jeopardy. Winds
would be lighter and with the solar insolation would result in
a fantastic day for outdoor activities!

Next Week

Upper level flow remains westerly through much of the week, with
bouts of shortwave energy passing through the semi-zonal flow aloft.
Moisture return looks to be limited at least until midweek,
resulting in a dry and cooler start to the week, as we are left
in a post-frontal airmass. Wednesday/Thursday looks to be the next
chance for precipitation, but there is a lot of differences in timing/
track, strength and amount of moisture. In addition, there is also
some significant temperature differences, which will dictate the
precipitation type. Thus, it`s really far too soon to give many
details other than to say that Wednesday through Thursday will be
the chance for precipitation, with the NBM providing 20-50% chance
PoPs. Temperatures next week do seem to largely remain above normal
still, but trending closer to seasonal normals.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1003 PM CST Thu Jan 30 2025

Poor flying conds through Friday morning with LIFR CIGS/VIS in
fog, rain, and drizzle. Conds gradually improve by afternoon.
Winds becoming northeast to north overnight into Friday.

&&

.HYDROLOGY...
Issued at 309 AM CST Fri Jan 31 2025

Rainfall is expected across much of the area today, with
the exception possibly being the far north/west. The heaviest
amounts around or greater than 1 inch is forecast in a narrow
corridor from NE to SW roughly between Highway 34 and I-80.
The deep frost layer of 12 inches or greater combined with this
amount of rain will lead to the concern for significant runoff
and the potential for flooding, and as a result a Flood Watch
has been issued for portions of SE Iowa into N Illinois.

For tributary rivers or smaller creeks and streams that have
some ice cover, there will be a risk for break up ice jams due
to the combination of the rain and mild temperatures in the
30s and 40s. Two tributary rivers with the highest risk for ice
jams are near the Quad Cities on the Rock River and on the
Skunk River near Augusta. Any areas that see over 1 inch of
rain on frozen ground may see a flooding risk, with the
potential for flooded roadways and flooding in low-lying and
flood prone areas, with also some ponding water and street
flooding possible in urban areas.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Dense Fog Advisory until 9 AM CST this morning for IAZ040>042-
     051>054-063>068-076>078-087>089-098-099.
     Flood Watch through this afternoon for IAZ067-068-077-078-
     087>089-098-099.
IL...Dense Fog Advisory until 9 AM CST this morning for ILZ001-002-
     007-009-015>018-024>026-034-035.
     Flood Watch through this afternoon for ILZ009-015>018-024>026.
MO...Dense Fog Advisory until 9 AM CST this morning for MOZ009-010.
     Flood Watch through this afternoon for MOZ009-010.

&&

$$

SHORT TERM...McClure
LONG TERM...McClure/Uttech
AVIATION...Haase
HYDROLOGY...McClure/Uttech