324
FXUS63 KDVN 281729
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1229 PM CDT Sun Apr 28 2024

.KEY MESSAGES...

- Chance for strong to severe storms this afternoon/evening.
  Slight Risk, level 2 of 5, remains for areas along/south of
  Highway 34.

- Active forecast remains through the long term, with near daily
  chances for precipitation after Monday.

- Temperatures will remain above normal through midweek,
  trending towards normal for the end of the week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 251 AM CDT Sun Apr 28 2024

Deep upper wave continues to slowly push northeast through the
central United States, becoming negatively tilted through the day.
Surface low associated with the system will start to slowly traverse
northeast through Sunday. Stationary boundary that has been draped
over northern portions of our CWA will remain in place through much
of the day, as the surface cold front grows stronger and pushes
through our area. This cold front will be the feature to watch, as
it will bring the necessary surface forcing to see showers and
storms through the day, especially in the afternoon/evening. Ahead
of the cold front is a favorable environment for some strong to
severe storms. Although, confidence remains low. In either case, we
will still see a line of showers and storms push through the area
late in the afternoon and evening. These will also bring a brief
period of heavy rainfall, but the flash flood threat remains low for
the area tomorrow.

Instability will be low-moderate in area, with the shear being the
main driver for storm organization and severity. The extent to which
we see showers/storms through the day will either decrease or
increase chances for severe weather. Guidance is favoring
showers and storms through much of the day, which would limit
the severe potential. The main thing that would help get severe
storms in this scenario would be the overall forcing produced by
this dynamic storm system. Thus, we will not rule out the
chance for severe. If we do see severe storms, the primary
threats will be severe winds and hail, with tornadoes being the
secondary threat.

Confidence remains low on the severe threat tomorrow, but it will be
something that we will continue to message the potential for. Thus,
remain weather ready tomorrow. The SPC has areas along/south of
Highway 34 in a Slight (level 2 of 5) Risk for severe weather, with
a Marginal (level 1 of 5) for the remainder of the area. It is
important to note that there has been a southerly trend in the
severe threat, especially in the last 24 hours.

Tonight...

After the line of convection moves through tomorrow evening, much of
the area should remain dry and breezy after midnight. Given some
bouts of energy continuing to hit our area after the main wave, I
wouldn`t be shocked to see a few showers after the main line of
convection passes. Some guidance is hinting at this, but confidence
is low. This will be the end of the severe threat for Sunday though,
with temperatures dropping into low 50s to near 60.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 251 AM CDT Sun Apr 28 2024

Looking at the whole long term, it would seem that Monday has the
best chance to be the only dry day of the week. The pattern goes
zonal briefly after the system passes on Sunday, but this will be
short-lived. A few disturbances are forecast to pass through the
flow midweek, with the potential for a more potent wave to impact
the area Friday/Saturday. Much of the week, above average
temperatures will be seen, with most in the mid-upper 70s. Towards
the end of the week, temperatures moderate near normal, as we will
be socked in clouds and rain showers.

Tuesday, an upper wave will pass through the area, with a relatively
strong vort max passing through late in the day. Guidance is in
general agreement on seeing showers/storms with frontal passage that
evening/night, but there are some differences with moisture content.
Timing is generally captured well amongst guidance, with them also
indicating that this will move through quickly. Confidence is low on
severe potential, but will continue to monitor as more short term
guidance comes in.

After that system, we will start to see a potent wave deepen over
the Rockies mid-late week. We will see a few leading impulses pass
through the area, leading to occasional showers/storms for the
remainder of the week. This will be a wet period, with the potential
to see a bit of rain. While it is too soon to figure out the
flash flood potential, it is safe to say that we can expect some
rises along area rivers if we see this persistent rain. The
parent wave developing is the one that has our attention though.
There is plenty of uncertainty with this, as well as major
timing differences amongst guidance. Although, all long term
guidance shows this system. If this wave deepens enough and we
get that negative tilt upon arrival, we may see the potential
for strong to severe storms late in the week. Although, it is
too soon to say for sure. So, just be mindful and stay up to
date on our forecasts!

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1212 PM CDT Sun Apr 28 2024

Variable conditions will be seen throughout the TAF period with
low pressure passing to the west of the area and moist air in
tow. Look for mainly MVFR conditions over the next 24 hours,
with lower visibilities and ceilings to IFR possible in rain
showers. An isolated thunderstorm will also be possible. Late in
the period, a return to VFR conditions is possible mainly at
KMLI/KBRL. Winds will prevail from the south initially with
gusts around 20-25 kts at times, before veering to the west late
in the period.

&&

.HYDROLOGY...
Issued at 1124 AM CDT Sun Apr 28 2024

Several tributary rivers are now over flood stage in our
southern portions of the CWA due to last night`s 1-2 inch
rainfall on top of moist soil conditions and already elevated
river stages. Other rivers will see significant in-bank rises to
action stage, to the north of this rainfall swath. The rates of
rainfall last night were initially very heavy, but the QPF was
split from this heavy first 1" to a more conservative 0.20/ hr
rate that fell the rest of the night. Thus, the rises may be
more steady, rather than sharply felt this morning following
the first few hours of rapid rises observed early today.

La Moine River near Colmar...
This river is above flood stage, and rising steadily today.
Forecast rises to the upper end of moderate flooding is forecast
by the RFC...and that could have a chance on exceeding the Major
flood threshold of 24 feet Wednesday. This forecast is the one
to watch most closely over the next 24 hours.

Fox River near Wayland...
The Fox saw the heaviest QPF upstream, but
already seems be slowing it`s rise, near 16ft. A forecast of
moderate flooding is in place cresting near 19ft late
tonight/early Monday.

The Pecatonica at Freeport and Rock River from Moline through
Joslin... Rise to action stage are forecast by the end of the
work week.

Skunk River at Augusta...
Another site that saw very heavy qpf fall in this basin, over 2
inches in some cases. The stage is rising rapidly this morning,
a bit faster than modeled. Though it will be watched carefully,
it appears likely to top out shy of flood stage Wednesday. This
is the 2nd most needed to be watched carefully through tomorrow,
and could potentially lead to a minor flood warning.

Heavy rains remain possible later this week again as forecast by
WPC. The timing of this rain would fall just past the crest on
most active tributary rivers, and near the crest or just prior
on the Rock River. Keep a general awareness of rivers in the
week ahead, as this wet pattern continues to evolve.

&&

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

&&

$$

SHORT TERM...Gunkel
LONG TERM...Gunkel/Speck
AVIATION...Speck
HYDROLOGY...Ervin