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000
FXUS63 KDVN 230545
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1245 AM CDT Tue Apr 23 2024

...06z Aviation Update...

.KEY MESSAGES...

- Precipitation chances tonight and Tuesday, initially battling
  dry air.

- Non-zero, but very low potential for a strong/severe storm
  Tuesday PM for parts of IL to near Miss. River.

- Colder air returns midweek with frost possible Wednesday
  night.

- Turning warmer and active by the end of the week through next
  weekend, with potential for rounds of showers and storms.
  Severe weather and heavy rain are possible.

&&

.UPDATE...
Issued at 926 PM CDT Mon Apr 22 2024

Scattered showers are quickly moving east, through remaining
isolated enough that measurable rainfall is going to be
extremely spotty this evening.

I`ve increased pops in the southern 1/3 of the area late tonight
into Tuesday, as models are now in great agreement in strong
Fgen forcing spreading along the Highway 34 corridor before
dawn, lasting through mid morning. Some thunder is possible, but
most of this should be a narrow swath of moderate rain. CAMs
have been, and now the latest NAM suite shows amounts over 0.5
are expected within this Fgen band, with the max QPF expected to
fall just southeast of the CWA in central Illinois.

The timing of this precip continues to show a transition to a
dry and breezy afternoon in most all areas behind the front.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 240 PM CDT Mon Apr 22 2024

A shortwave diving down across the Upper Midwest and Great Lakes
will usher in a couple of boundaries over the next 24 hrs.
The initial boundary/wind shift extends through the eastern
Dakotas then into the Front Range. A tightening pressure gradient
between than and high pressure over the lower Mississippi
Valley is aiding gusty SW winds across the area up to 40 mph.
Despite the increasing high cloudiness, the favorable warm SW
trajectory has pushed temperatures into the 60s areawide at 2
PM. The air remains rather dry with dew points mixing down into
the mid 20s to lower 30s owing to RH as low as around 20-25
percent. This is leading to elevated fire danger, especially in
the Ag fields.

Tonight, the initial boundary/wind shift will roughly bisect
the cwa by morning. A weak wave and warm advection will foster
some mid cloudiness and isolated to scattered shower potential
this evening mainly north, but the dry sub-cloud air may limit
this to more sprinkles if anything. Later tonight and into
Tuesday morning, a stronger bout of forcing aided by jet
dynamics along with better mid level moisture advection will
lead to scattered showers and possibly a thunderstorm, mainly
for areas along and especially south of I-80.

Winds tonight will likely remain gusty ahead of the boundary,
which aLong with cloud cover will result in warmer lows mainly
in the 50s with 40s north/west behind the boundary.

Tuesday, the shower activity should wane by late morning as
the shortwave and boundary exit. Tuesday afternoon becomes
a period that may need monitoring for a very low, but non-zero
threat for strong to isolated severe storms for portions of
the area ahead of a stronger shortwave and surface cold front.
General consensus of the guidance places dew points in the upper
40s and lower 50s ahead of the front. A very chilly airmass
aloft combined with surface heating will yield the potential
for low topped convection ahead of the front. Favorably low
wet bulb zero heights will foster hail with any cells that
manage updraft organization within a strongly sheared
environment. Strong gusty winds will also be possible. The
proxy soundings show a favorable juxtaposition of low level
buoyancy (0-3km) and low level steep lapse rates (7-8c/km),
which could also favor some low level vortex stretching and a
very low potential for a tornado provided a storm that manages
to develop can remain anchored near the boundary. This
conditional very low isolated severe potential would be a
fleeting 2-3 hour window (2-5pm), mainly focused along and east
of the Mississippi River near and southeast of the QC metro
where the best low level convergence is currently being
suggested. In the wake, we may see additional scattered showers
develop by mid to late afternoon with the cold pocket aloft,
which may foster some pea hail and potential for stronger gusts
over 40 mph with proxy soundings showing nice inverted V sub-
cloud profiles. Winds in general will be rather gusty Tuesday
PM 30-40 mph.

Colder air settles in Tuesday night and Wednesday morning with
lows dropping into the mid/upper 30s north and lower 40s
south. Winds likely to remain up to eliminate a frost threat,
and temperatures may be largely above freezing and even if a
site were to hit the freezing mark it probably wouldn`t be
for a sufficiently long enough time to warrant any freeze
headlines.

Ridging builds in Wednesday through the day on Thursday with
cool/chilly mornings and seasonable afternoons. A better
potential for at least frost is expected Wednesday night for
areas mainly north of I-80, with a low chance (20-30%) for
a light freeze.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Issued at 240 PM CDT Mon Apr 22 2024

Friday into Saturday, models agree on bringing a strong low pressure
system across Nebraska, NW IA, and southern MN. This will leave the
local area in the warm sector with strong southerly winds drawing
Gulf moisture northward. PWATs of 1.3 to 1.5 surge into the area by
Friday morning. After a lull of PWATs near 1", another trailing
surface low in the southern plains will track across eastern Iowa
bringing PWATs of 1.5 to 1.8" into the area. WPC has rainfall totals
of 1 to 2 inches Friday into Saturday, with the higher amounts in
the NW CWA. Then, for Saturday into Monday, another widespread 1.5
to 3 inches are possible.  Deep layer moisture and shear will
increase with each wave that lifts through the area, which will
bring the potential for organized storms, some possibly strong to
severe.  SPC has roughly the western half of the CWA in a 15 percent
outlook area for Friday AM into Sat AM.  Meanwhile, WPC has the
entire area in a Marginal risk for Excessive Rainfall in it`s day 5
(Fri AM to Sat AM) outlook. It also has widespread 2 to 5 inches
across much of NE MO, eastern IA, and western IL in it`s 7-day QPF.
Those individuals or businesses that are near creeks, rivers, and
poorly drained areas will want to monitor the forecast closely late
this week and this weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1240 AM CDT Tue Apr 23 2024

Mainly patches of VFR level clouds and isolated light showers
overnight, before a more organized band of showers and a few
embedded thunderstorms move out of southern NE and south of I80
locally after 4 AM. This band will affect mainly the BRL site
with MVFR CIGs and rain reduced VSBYs Tue morning, possibly
clipping the MLI site with light rain but hopefully staying at
VFR levels. A robust southwesterly LLVL jet overnight of 45 to
55 KTs making for turbulent low to mid level wind flow and will
add LLVL wind shear to the TAFs with 45 KTs at 2K FT AGL despite
southwesterly sfc winds gusting to over 20 KTs in some locations.
Clearing with a sfc wind switch to the northwest Tuesday
afternoon. NOrthwest sfc winds may gust up to 30+ KTs into early
evening behind the FROPA before decreasing as the evening
progresses. Will bank on isolated to sctrd showers/storms along
the frontal passage to stay mainly east of the TAF sites Tue
afternoon, but they may get close to MLI.

&&

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

&&

$$

UPDATE...Ervin
SHORT TERM...McClure
LONG TERM...14
AVIATION...12