000
FXUS63 KDVN 250902
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
402 AM CDT Thu Apr 25 2024

.KEY MESSAGES...

- Still watching frost and possible freezing temps this morning in
  northwestern IL.

- Slight Risk for rounds of severe storms Friday through Sunday.

- Chance for rainfall of several inches through this weekend may
  cause flash flooding and/or river flooding.

&&

.SHORT TERM /TODAY THROUGH TONIGHT/...
Issued at 330 AM CDT Thu Apr 25 2024

Today...Freeze/Frost headlines continue through 8 AM CDT with some
of these areas in the lower 30s ATTM. Otherwise GRT LKS sfc high
starting to edge eastward allowing for increasing east-southeasterly
sfc wind flow and some sfc temp rebound. Amplifying upper ridge
overhead into tonight to lee of upstream upper trof and cyclogenesis
acrs the southwest plains may act as an initial precip barrier until
late tonight. Back to today, dry with rounds of cirrus and some AC
filtering the insolation at times. But in dry mixing boundary layer,
high temps should still recover into the low to mid 60s acrs much
of the local area.


Tonight...A southerly LLJ increases to 40 KTs acrs the area after
midnight, but prime H85 MB flow convergence leeside upper wave lift
takes place acrs the southern to central plains into MO where the
prime convective activity tonight will take place.  But secondary
elevated precip bands and maybe some isolated thunder will look to
make it into the far west and southwestern CWA before dawn Friday.
With dry air and ridge axis to overcome, will delay POPs and cut
them back even further tonight before 12z. Southeast sfc winds
keeping low temps well up in the 40s into Friday morning.

&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...
Issued at 330 AM CDT Thu Apr 25 2024

Friday...Deepening sfc low to at least 990 mb by evening rolls up
central NE into far northwestern IA into SW MN through evening, with
the upper low feature stacking overhead of it and taking on a
negative tilt. LLJ fed elevated showers and embedded storms will
look to continue through midday and early afternoon Friday with some
decent rainfall up to an inch possible utilizing initial PWAT feed
of 90 percentile value 1.2 to 1.5 inches. Then there may be a
decrease in activity coverage acrs the local CWA while things take
focus out west. This in the currently indicated prime deep
convective axis and deep shear zone along upper jet entrance region
from just northeast of Omaha, down along the KS/MO border into
eastern OK. This also in the 72% parameter layer of supercell cases
tornadic, another shear combined with instability index. While there
may be isolated to sctrd strong to severe storms in the local area
Friday afternoon and early evening, a better chance may come later
Friday night as some of the upstream activity acrs northern MO and
south central IA propagates this way. All modes of severe posssible
on the IA and MO side of things, with threat levels then tapering
off more east-northeastward acrs northern IL away from better
support. H85 MB southwesterly jet still fcst to crank at 50+ KTs
Friday night and is always a troublesome ingredient for strong storm
support. The storms wringing out high PWAT saturated airmass will
lead to swaths of heavy rainfall by Sat morning, with some 1-2+ inch
amounts possible by Sat morning.

Depending on the main warm front retreat progression northward as
the day progresses especially with pre-cursor elevated precip,
ambient temps and sfc DPTs will rise as the day and evening move
along. Morning DPTs in the 30s and 40s will look to rise into the
mid to upper 50s late in the day and continue into Friday night. 12
hour high temps may occur close to 00z Sat, with temps steady to
slow rising over night into Sat morning. Strong southeasterly sfc
gradient winds through the day with gusts up to 40 MPH away from the
showers/storms, and higher gusts near the passing storms/enhanced
mix-downs.

Saturday...Ensemble indicated forcing and llvl jet interruption and
re-organizing trends suggest that Sat during most of the day may
still be a mainly lull period with more dry hours and just isolated
to wdly sctrd showers and a few storms passing acrs the area. With
enough breaks, extent of southerly warm moist conveyor to lee of the
next organizing trof/wave acrs the southwestern plains may boost
ambient temps into the upper 70s to lower 80s, along with sfc DPTs
in the 60s. Depending on how far west or east a lingering sfc front
wavers and the next upper low migration path northward up the plains
lays out will define how much activity can occur in the local area
Sat night. The 00z GFS is more ominous with a heavy rain produing
MCS and probably sever storms funneling up this way into Sunday
morning. This while the 00z ECMWF deterministic explodes much more
heavier convection off to the west and southwest of the DVN CWA.
While we would still have some more sctrd activity Sat night, heavy
convective systems acrs the southeast plains into southwestern MO
may be an THTA-E feed interceptor/local inhibitor. But if we get
more heavy rain, we will be primed for flooding late Sat and Sunday.

Sunday...Many details to be worked out especially with prior and
upstream convective complexes affecting what comes next, but this day
still a classic looking vort and upper jet embedded southwesterly
cyclonic steering flow sprawling out acrs the area to lee of
negatively tilted cyclone scenario. This should lead to a
significant severe wx outbreak somewhere acrs the midwest. More to
come stay tuned!

Early next week...Longer range ensembles show in the aftermath of
the weekend, Monday appears to be a breezy post-system dry slot day
with cooling temps in the 60s. Then near zonal flow may bring more
shower/storm chances to the region later Tue into Tue night.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1215 AM CDT Thu Apr 25 2024

VFR conditions to prevail through the TAF period with only
gradually increasing winds under mid- to high-level clouds.
East-southeast winds this morning will show some occasional
gusts in the mid-upper teens this afternoon, especially
locations further west of the Mississippi. Tonight will see low-
level winds increase with sustained speeds inching up through
early Friday morning when they will likely be in the 15-20 kt
range. Gusts are often sporadic at night in an east-southeast
setup, but if gusts occur they could exceed 25 kt overnight
Thursday night.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...None.
IL...Freeze Warning until 8 AM CDT this morning for ILZ001-002-007-
     009.
     Frost Advisory until 8 AM CDT this morning for ILZ017-018.
MO...None.

&&

$$

SHORT TERM...12
LONG TERM...12
AVIATION...Friedlein