058
FXUS63 KDVN 141757
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1257 PM CDT Tue May 14 2024

...18z Aviation Update...

.KEY MESSAGES...

- Scattered showers and storms will come to an end this afternoon

- Additional chances of showers and storms are in the forecast for
Wednesday night through next weekend, with the most likely chances
appearing on Thursday

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 252 AM CDT Tue May 14 2024

Near vertically stacked low pressure was centered across north
central Missouri early this morning, with a stationary front
extending out of this system northeast across our CWA into the
Great Lakes. Rain showers were ongoing across the front mainly
along and south of Interstate 80, and were slowly lifting north
and west.

This system will remain the primary driver of our weather over the
next 24 hours, bringing additional rounds of showers and storms to
the area. This threat will remain mainly along and south of
Interstate 80 where lift will remain maximized with the help of low-
mid level frontogenetical forcing and moisture convergence. Little
in the way of steering flow will keep activity relatively slow
moving. Bearing this in mind, showers and storms will be capable of
producing heavy rain with PWATs high in the 1.25-1.50" range; this
is well above climatology for this time of year as referenced in the
previous discussion. Forecast QPF is around 0.50-0.75" south of
Interstate 80, with lesser amounts to the north. Locally heavier
amounts > 1.00" will be possible where showers and storms persist
longer. Severe weather is not expected with very low deep vertical
shear present (~10-20 kts) and lapse rates around moist adiabatic.

Outside of rain showers, it will remain gloomy and humid with cloudy
skies and temps in the low to mid 60s. Some relief in the humidity
is expected tonight with the stationary front drifting south,
allowing northeast flow to advect dewpoints in the 40s.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 252 AM CDT Tue May 14 2024

The long term period starts off pleasant Wednesday with mostly
sunny skies and near seasonable temperatures in the low to mid
70s.

Our next chance (50-80%) of showers and storms will come Thursday
with a shortwave moving across the area. Latest deterministic
guidance is backing off a bit on more widespread coverage, favoring
a more scattered nature to showers similar to this current system.
Moisture advection ahead of the shortwave will ensure heavy rainfall
as a threat with activity as PWATs climb back over 1.00", though the
threat of severe weather will remain low with weak shear and
marginal instability.

Beyond Friday, there is great uncertainty in the forecast as
guidance struggles with shortwave and trough placement across the
Midwest. Regardless, there are chances of showers and storms each
day (20-40%). Temperatures look to average above normal with highs
back in the 80s in time for the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1252 PM CDT Tue May 14 2024

Low MVFR to IFR cloud deck continues to rotate westward acrs the
area north of a low pressure system acrs east central MO.
Embedded showers and even an isolated thunderstorm(south of
I-80) will continue to move southwestward around the low as well
through late afternoon and early evening before diminishing. The
heavier rain may briefly reduce VSBYs down to one mile at times
with BRL the most likely to be impacted by these passing
heavier showers or storms through late afternoon. Improving
conditions as the evening and overnight progress, with
northeasterly sfc winds of 5-10 KTs. VFR conditions on Wed with
a continuing light east to northeasterly sfc wind regime.

&&

.HYDROLOGY...
Issued at 221 PM CDT Mon May 13 2024

New forecasts by the North Central River Forecast Center this
evening showed little to no change for the Wapsipinicon River
near DeWitt. The river should reach flood stage before 7am
tomorrow morning and slowly rise to 11.4 feet over the next 3
days. Depending on where additional rain falls this afternoon
into this evening, more rises may be possible. However, at this
time the highest totals are expected south of the Wapsi basin.
The Flood Warning was continued with this forecast issuance.

The forecasts for the Cedar and Iowa Rivers have come in lower this
morning. The Cedar River near Conesville forecast was kept just
at flood stage for now due to the incoming QPF uncertainty. For
this reason, have kept the Flood Watch going there.

Flood Watches have been issued for the Mississippi River at
Gladstone and Burlington due to routed flow as well as rainfall
amounts forecast through Tuesday.

Taking a deeper dive into the QPF, widespread rainfall in the 0.5"
to 1.5" range is expected in the next 24 hours, with some
localized higher amounts. The 12z HREF probability-matched mean
QPF values through Tuesday morning are painting a swath of
rainfall in excess of one inch, with some isolated amounts over
two inches slightly northward closer to the downstream portions
of the Iowa, Cedar, and Mississippi River basins. This QPF
placement and how much runoff occurs will be very important to
whether additional rises are seen and if warnings will be
needed.

&&

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

&&

$$

SHORT TERM...Speck
LONG TERM...Speck
AVIATION...12
HYDROLOGY...Cousins