462
FXUS63 KDVN 300516
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1216 AM CDT Tue Apr 30 2024

...Updated for 06z Aviation...

.KEY MESSAGES...

- Active forecast remains through the long term, with near daily
  chances for precipitation beginning Tuesday night.

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

- River flooding is now on the falling limb on most tributary
  rivers that were over flood stage.

&&

.SHORT TERM /THROUGH WEDNESDAY/...
Issued at 202 PM CDT Mon Apr 29 2024

Cold cyclonic flow continues around low pressure, resulting in a
blustery, cloudy, cold day with occasional showers...but that`s not
here, and as we approach May, it`s less likely to be us again until
Fall. Our area is on the southern periphery of this cyclonic flow,
with mainly scattered cumulus based around 4000 ft, and gusty winds
of 15 to 25 mph. With the exception of our far northwestern
counties, today probably qualifies as a nice spring day, albeit a
bit on the fresh/breezy side.

Tonight, after a day of dry advection, we`re set to lose any
remaining clouds in the north by mid evening, and with dewpoints
already falling to the 40s today, we`re set for temperatures to fall
tonight, near 40 north to near 50 south. Winds will quickly decrease
this evening, turning light and variable by 9 PM.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Issued at 202 PM CDT Mon Apr 29 2024

Tuesday, a day of warm advection is expected, with mostly sunny
skies and a slow increase in moisture given that the Plains are
currently shut off from the GOM. By afternoon, dew point values in
the lower to mid 50s are expected, which seems plausible, but
far lower than some CAMs that have 60+ Tds in place by evening.
This is important, as those models are rather aggressive on
spreading a strong line of storms through our area Tuesday
evening. What actually seems more likely, is a split. As the
main dynamics aloft are better with the short wave to the north,
convection may hold north of the area into southeast MN and
northern Iowa through the evening, while other more robust
storms in western Iowa and Nebraska dive / develop southward
towards the moist axis/MUCAPE which would take them into
Missouri, only brushing our area. Thus, we end up with the NBM
pops of 70-90% being too high. I`ve lowered these by about 10%
and still feel I`m being too bullish, but with the areas north
and west being supported by this scenario, I`ll keep them in the
high chance to likely there. Farther east, capping pops in 30-
40 will be enough to allow this to miss that area. QPF has been
lowered by more than 50% from earlier WPC forecasts for this
period.

Following a dry Wednesday morning, the upper pattern becomes active
again with moist warm advection by afternoon and evening, with
chance to likely pops spreading back in. A developing warm front to
our south along with low pressure forming in the Plains will make
this a much more likely threat for widespread rainfall.

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 persistent showers/storms for the
remainder of the week. This will be a wet period, with the potential
to see quite a bit of rain. With recent rains and more forecast,
some rises along area rivers are expected. The parent wave
developing is the one that has our attention though. Although, 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, this will bring the potential for strong to
severe storms late in the week. Although, it is too soon to say for
sure. WPC is highlighting our area in the risk for Excessive
Rainfall from midweek through the end of the week, as they are
currently forecasting between 1-3+ inches of rain by the week`s end
for some. Thus, flash flooding will be possible, as well as rises
along area rivers. So, just be mindful and stay up to date on our
forecasts!

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1210 AM CDT Tue Apr 30 2024

VFR conditions are expected through much of the period. Ideal
radiational cooling with light winds and clear skies could lead
to patchy shallow fog after 09z through 12z, but confidence is
too low for any mention. As the high departs Tuesday AM winds
will turn southerly and become gusty at 15-25 kt by afternoon
ahead of a low pressure system approaching the Upper Midwest.
Elevated warm advection could lead to a few high based showers
developing into portions of eastern Iowa by mid to late afternoon,
but probability appears too low for PROB30 mention at this time.
Otherwise, a line of storms is expected to develop to our west
this afternoon ahead of a cold front and move into eastern Iowa
this evening, while gradually weakening. Before doing so, there
is the potential for gusty winds and hail to accompany the storms,
particularly at KCID and KBRL which appear to have the better chances
for storms.

&&

.HYDROLOGY...
Issued at 1006 AM CDT Mon Apr 29 2024

The flood warning in effect for the Skunk River at Augusta has
been cancelled this morning, as the river crested just below
action stage overnight and continues to fall this morning.

Elsewhere, flood warnings continue for Wayland (Fox River) and
Colmar (La Moine River). The former will drop below flood stage
this afternoon, while the later remains on track to see moderate
flooding through Wednesday as routed flow from overnight rains
work through the basin.

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. 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...Uttech
LONG TERM...Ervin
AVIATION...McClure
HYDROLOGY...Speck