303
FXUS63 KDVN 140552
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1252 AM CDT Wed Aug 14 2024

...Aviation Update...

.KEY MESSAGES...

-  Threat for severe weather and flash flooding from Wednesday
   night and through Thursday. Stay weather aware and have many
   ways to receive notifications, especially at night.

-  Temperatures near to above normal, with most in the low-mid
   80s. Thursday will be the warmest day of the week, especially
   in the south, with heat indices near 90-95.

-  Precipitation amounts have trended down, quite substantially
   for some, over the last 12 hours. Will have to see if this
   trend continues, but still will advertise the potential for
   heavy rainfall and localized flash flooding.

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 149 PM CDT Tue Aug 13 2024

Tonight, we are expecting a quiet night as high pressure continues
to push off to our east. This will keep us in light southeasterly
flow tonight. Similar to last night, we will remain mostly clear,
with clouds diminishing in our south through the evening.
Temperatures will largely be in the low-mid 60s.

Tomorrow, we will start to see cloud cover increase through the day,
as LLVL moisture return works into the area. The surface warm front
is not expected to move in until later in the day and evening, which
is where we will start to see those surface dewpoints start to
increase. Thus, humidity-wise, much of tomorrow will be comfortable
with temperatures in the low 80s. With this initial push of moisture
in the area, we may see scattered and elevated showers develop
through the afternoon, slowly pushing north. Confidence remains low
on this, but have opted to include Slight-Chance PoPs to account for
this potential. Although, we are expecting that much of the day
remains dry for the area, with the severe threat being low until the
evening and nighttime.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Issued at 149 PM CDT Tue Aug 13 2024

Wednesday Night...Organizing wave aloft with a short wave embedded
in diffluent cyclonic flow aloft will provide the lift, combined
with a re-invigorating SSW 35+ KT LLJ to induce another MCS
somewhere acrs the northeast plains/MO RVR Valley/southern MN and
acrs IA this period. Initial development will probably occur
upstream acrs the MO RVR Valley, and then feed eastward acrs
IA/southern MN into Thu morning. Some worry that it may be a mature
squall line or linear type MCS as it pushes acrs the local area
which would mean a possible damaging wind threat if it`s sfc/near
sfc rooted or utilizing cold pool mechanics and projected effective
shear of 45+ KTs. PWAT`s currently are still projected to be very
high from 1.9 to 2.3+ inches, which would fuel intense rainfall
rates. But if the system is progressive, that would limit a flash-
flood threat but the line would still dump rain at high rates just
for a shorter period. A more classic storm cluster MCS with some
back-building potential would bring a high flooding threat and the
chance for several inches of rain by Thu morning. This would bring
about several hydro concerns such as rising rivers and streams
besides the flash-flooding. General timing for the MCS will be
anytime after midnight and to about sunrise on Thursday, give or
take a couple of hours. Ahead of the line, some guidance is starting
to hint at a warm advection band of precipitation at the nose of the
LLJ. This will be an area to watch, as it can provide a focus for
the MCS to follow and potentially surge along, as well as lead a an
isolated elevated hail threat ahead of the impending MCS.

Thursday...An uncertain scenario day, with what ever occurs and
evolves out of Wed night and where it`s remnants lay out for
additional lift and heating later in the day Thu to act upon for
redevelopment. LLVL triple point/shear focus may occur acrs WI, with
other fronts and outflow boundaries ringing the local area from
northeast to the south. Thus the redevelopment may occur along these
zones and largely out of our area of concern. We may just have
secondary weaker re-development locally in the wake of a strong Wed
night MCS. A lot of details still to be worked out for this day and
can`t let the guard down yet. A Slight Risk (level 2/5) exists for
areas along/east of the Mississippi River, highlighting that
potential for strong/severe redevelopment that afternoon to
evening. This is very conditional though, so stay tuned!

Latest trends in guidance have been cutting back on precipitation
totals, generally with a 1.00-2.00" range for the heavier hit areas
when all is said and done. Although, areas that see multiple
rounds of storms may see amounts above that range. Will have to
continue monitoring these trends over the next 24 hours and
hone in on a QPF forecast.

Friday through Monday...Latest suite of medium range ensembles and
upper jet progs suggest the upper wave to evolve into a closed upper
low acrs the northwestern GRT LKS by week`s end, with the area
suspect to diurnal afternoon sctrd pop-up showers on the system`s
western flank through at least Friday. If this system can
meander far enough to the east, it may leave a fair wx weekend
with seasonable temps for the local area in it`s wake.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1248 AM CDT Wed Aug 14 2024

Will go with a VFR TAF cycle again through Wed evening, with
just decaying debris clouds and possible light rain/sprinkles
out of the current NE activity coming acrs IA later today. Will
also play the lower VFR to MVFR stratocu deck acrs MO into
south central IA staying west or lifting to VFR levels later
today. Light and variable sfc wind regime will go southeasterly
and increase with tightening pressure gradient from upstream
storm system as it moves in from the west...8-12 KTs with gusts
up to 20 KTs Wed afternoon. The main precip action that will
impact the TAFs will be more likely after 06z Thu.

&&

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

&&

$$

SHORT TERM...Gunkel
LONG TERM...Gunkel
AVIATION...12