Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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565
FXUS63 KDVN 021103
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
603 AM CDT Sat Nov 2 2024

.KEY MESSAGES...

- An active pattern is expected tonight into Tuesday as an
  upper trough and very moist air mass interact to produce
  rounds of showers and thunderstorms (80-100%). Heavy rainfall
  amounts of several inches are likely by Tuesday morning.

- Temperatures will trend warmer Sunday and Monday to above
  normal levels, before a cold front drops highs back into the
  50s by mid next week.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 300 AM CDT Sat Nov 2 2024

Today and Tonight: Southeast return flow will develop today,
albeit light, as high pressure shifts to the east over the Great
Lakes. Steady warm air advection and plenty of sun to start the
day will lead to above normal temperatures in the low 60s on
average. Anticipate mainly dry conditions through the afternoon
as the lower atmosphere will take time to saturate with
dewpoints holding in the upper 30s to lower 40s. Increasing low
to mid- level theta-e advection, on the eastern periphery of a
40-60 kt southerly LLJ, will eventually lead to the development
of scattered showers and isolated thunderstorms tonight,
becoming more likely after midnight. The highest precip chances
are across the western portion of the outlook area, with a
range from 100% in the west to 20-30% in the east. The
showers/storms could produce narrow swaths of heavier rainfall
with 0.50"+ possible over the west/northwest section of the
forecast area by early Sunday AM.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 300 AM CDT Sat Nov 2 2024

A digging longer wave trof pushing into the west coast/Pacific
NW will utilize rounding upper jet energy to continue to
establish a large upper trough acrs the western Rockies by
Sunday evening. This long wave will then look to dig acrs the
western plains through Tue morning, with a squeeze play between
it and southeastern CONUS ridging inducing an optimal southerly
warm moist conveyor/LLJ feed off the western Gulf and up along
and west of the MS RVR Valley. High amplitude steering
southwesterlies will also shuttle occasional upper wave pieces
up out of the trof base and acrs the eastern plains and into the
upper MS RVR VAlley through Tuesday. These ejecting vort
maxima/shortwaves and their lift will utilize the gulf moisture
feed to produce rounds of rain (bouts of heavy rain look on
target) for much of the mid to upper MS RVR Valley.

Model averaged precipital water feed (PWATs) through Tuesday is
showing very unseasonable PWATs near 1.5 inches streaming acrs
the area by Sunday morning. Top-down saturation to full depth on
Sunday, with fcst soundings then maintaining the deep vertical
saturation with minor dry undulations aloft all the way through
Tue morning. The extent of the southerly warm moist conveyor and
fcst PWATs of an inch and a half are rare this time of year --
near the 99th percentile to climatological max!

WPC has a Slight Risk of excessive rainfall across portions of
the area from Sunday through Monday night, with the highest
surges of rain expected Sunday night and again late
Monday/Monday night. WPC rainfall potential at this juncture
ranges between 2-4"+, heaviest swath near our area of concern
from northeastern MO, to northeast IL through Tuesday. Recent
rainfall softening the soil for more absorption, and the
duration of "waves" of rainfall over 2 to 3 days will hopefully
limit the overall flash flood threat. But the advertised
widespread heavy amounts may eventually lead to slower paced
areal flooding in low-lying, urban, and poor drainage areas by
Monday/Monday night. As for the rivers, thinking there will be
some substantial rises from current levels and may be near
bankfull on tributary rivers in some of the harder hit basins.
Confidence on a tributary or two reaching flood stage remains
low and uncertain at this time.

With eventual column saturation and fcst marginal mid layer lapse
rates/MUCAPEs, the prospect for severe storms appears low at least
through Monday during the day. Effective shear profiles are not bad
ranging from 30 to 45 KTs, but the other parameters are not
favorable. There may be a chance for a portion of a squall line
to sweep acrs portions of the DVN CWA (probably the southeast
third to half) Monday night into Tuesday morning, and SPC has
introduced a Marginal Risk (level 1 of 5) for severe storms over
the east-central to southeast portion of the outlook area.

With the strengthening return flow and thickness increase/advection
from the south, temps will be on the rise in the warm sector
Sunday and especially Monday when there will be some 70s
possible. Also with sfc DPTs in the 60s Monday, a muggy/humid
feeling day more like later spring as opposed to November.
Breezy conditions on Monday,and the LLJ is progged to ramp up to
50+ KTs at 4-5K FT AGL. Post-system cool down and some ridge
infusion for a then needed dry period by mid to late week. Highs
mainly in the 50s from Wed on into Friday.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 555 AM CDT Sat Nov 2 2024

VFR will prevail today with light southeasterly winds. Increasing
high and mid clouds are expected later this afternoon into this
evening, with chances for scattered showers and isolated
thunderstorms holding off until tonight. Showers are likely
late tonight/early Sunday morning at CID with lower chances for
the other terminals to the east. Ceilings will gradually
decrease to 3000-6000 ft AGL late in the period as the
atmosphere continues to saturate. Held off on any thunder
mention with this update due to low confidence.

&&

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

&&

$$

SHORT TERM...Uttech
LONG TERM...12/Uttech
AVIATION...Uttech