000
FXUS63 KDVN 241737
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1237 PM CDT Wed Apr 24 2024

.KEY MESSAGES...

- Cool backdoor high pressure influence may allow for a frost or
  freeze across portions of northwest IL tonight.

- Increasing warmth and humidity ahead of strong low pressure
  systems will make for a stormy end of the week through the
  upcoming weekend, with potential for strong to severe storms
  at times along with bouts of heavy rainfall.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 330 AM CDT Wed Apr 24 2024

Today...After Lake MI fetch stratocu seeps south and diurnally
decays this morning, backdoor sfc ridge and northeasterly boundary
layer(BL) flow regime will make for a sunny and near seasonable day
with most of the area reaching the upper 50s to mid 60s. Low sfc
DPTs will make for a dry/low humidity day but at least the winds
won`t be as brisk today.

Tonight...The GRT LKS high pressure will start to edge eastward
enough to start to allow east to southeasterly LLVL return flow to
commence, but the lighter sfc winds may have a longer residence time
acrs portions of northwestern IL, and combined with ongoing low DPTs
may allow for temps to crash into the low 30s and bring about a
chance for frost or freeze. Some cirrus will look to stream acrs
the area from the northwest tonight, but may be thin enough at times
especially late to not have that much blanketing impact. For now
will issue a Freeze Watch for the suspect counties and let the day
shift refine coverage and type of advisory or warning.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 330 AM CDT Wed Apr 24 2024

Thursday...A dry and warming day under mid CONUS upper ridge lobe,
and even with some cirrus or AC at times, mixing southeast sfc winds
should help boost temps into the mid 60s even after the cool start
to the day. The now well advertised strong upper trof/low center
organizing over the west central plains will look to start to induce
leeside strengthening warm moist conveyor aided by a SSW LLJ of 50+
KTs up acrs the region. Elevated H85 MB flow convergence progs/
ensembles suggest that this up-lift zone to form elevated
convection does not make into the southwestern CWA til well after
midnight, and POPs may have to continue to be slowed Thu night.
Southeast sfc winds keeping low temps well up in the 40s or low 50s
into Friday morning.

Friday...Sub-990 mb sfc low rolls up central NE into southeastern SD
through evening, with the upper low feature taking on a negative
tilt. Assessing strong convective parameter overlays on ensembles
and nose or gradient of the prime deep convective index and upper
jet entrance regions, it seems the prime severe wx zone Friday
afternoon lies acrs the central and southern MO RVR Valley down into
the southeastern plains. Locally we may ongoing elevated showers
and storms in the morning from the initial bout of convergent H85
warm air advection(WAA), but there may be some midday through mid
afternoon lull or decrease before the main warm front tries to
retreat northward acrs the CWA. Still low sfc DPTs in the 30s and
40s Friday morning will look to surge into the upper 50s to around
60 late in the day and Friday night. Continuing robust LLJ impacts
and 100+ KT upper jet edging closer, Friday evening and into the
night may be the severe weather focus time for the local area with
all severe modes possible. Or upstream activity from Friday
afternoon may also try to feed this way from the northwest MO
convective hot zone. Very heavy rain will also be possible if the
currently projected PWAT feed of 1.3 to 1.50 inches(90 percentile
values) are close to being correct and get wrung out by strong
convection.

Saturday through Monday...Longer range ensembles still show that
Saturday may be a bit of a reprieve day while a lingering piece of
upper low energy invigorates in the lingering upper trof base acrs
the southern/central Rockies. The southeastern plains into the may
be the hot zone that day. Then the upstream upper low will look to
take the same ejection path as Friday`s system, if not a bit further
to the east. Classic looking vort and upper jet embedded
southwesterly cyclonic steering flow sprawling out acrs the area to
lee of negatively tilted cyclone, spells trouble for the home team
or somewhere acrs the mid to upper midwest with the chance for a
significant severe weather outbreak. In the aftermath, Monday
appears to be a breezy post-system dry slot day with cooling temps
in the 60s.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1235 PM CDT Wed Apr 24 2024

VFR (SKC) through much of this taf cycle. Northeast winds less
than 10 kts becoming light southeast tonight then southeast
around 10 kts on Thursday morning.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...Freeze Watch from midnight CDT tonight through Thursday
     morning for ILZ001-002-007-009.
MO...None.

&&

$$

SHORT TERM...12
LONG TERM...12
AVIATION...Haase