806
FXUS63 KDVN 011031
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
531 AM CDT Sat Jun 1 2024

...Updated for 12z Aviation...

.KEY MESSAGES...

- Rainy first half of today before gradually diminishing into
  early evening.

- Fog overnight and Sunday morning, which could be dense in some
  areas.

- Active/Unsettled Sunday night through Tuesday night with
  several chances for showers and storms. Some potential for
  stronger storms Monday PM (conditional upon development) and
  Tuesday night ahead of a cold front.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 255 AM CDT Sat Jun 1 2024

A shortwave trough over Missouri with an attendant weak surface
low reflection early this morning will translate generally
eastward over the next 12-18 hours. 30-35+ kt low level jet
and attendant moisture transport coupled with the upper forcing
is resulting in widespread showers south of I-80 lifting
northward. Overall, much of the area will see rain this morning.
Isolated elevated convection can`t be totally ruled out,
especially on the backside of the more widespread shower
coverage where weak instability will reside attendant to better
low level forcing. This afternoon as the mid/upper trough axis
makes inroads the greater coverage of showers should migrate east
of the Mississippi River. Most areas will see rain amounts of
0.5 inch or less, however with PWATs ramping up to 1.5 inches
there is likely to be pockets of higher amounts to around an
inch given slow cell motions and with any training of heavier
showers. Given the cloud cover and rain, I have lowered highs
in most areas today with highs generally from the mid/upper 60s
east to the lower 70s. If enough sunshine can occur in the west
as the rain tapers off this afternoon then some mid 70s would
be possible. This evening, we may have a few lingering showers
far east, while also can`t rule out a few showers or weak
storms propagating into our northwest counties should they form
along a weak boundary across north central to far northeast
Iowa this afternoon. This potential will be dependent on just
how warm it gets this afternoon to our west, more likely if highs
get well into the mid to upper 70s.

By late evening and overnight we should quiet down as a surface
high pressure ridge builds in. The light winds and low level
moisture aided by rain today will likely set the stage for fog
potentially dense, especially near to west of the Mississippi
River where the ridge axis is progged. Lows tonight are likely
to drop into the 50s in most locations.

The surface to mid level ridging will provide a short period of
largely dry weather on Sunday. Highs will warm back to
seasonable levels and generally in the upper 70s to lower 80s,
and the humidity will be noticeable making for more of a
summer-like feel.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 255 AM CDT Sat Jun 1 2024

A shortwave and cold front look to provide the focus for convection
Sunday PM/evening across the Plains. This will advance into the
region primarily overnight Sunday night into Monday morning, while
likely weakening as it outpaces the better moisture transport
and instability. Depending on the timing of the shortwave, we
may need to keep an eye on Monday PM for any redevelopment and
at least a low threat for a few strong storms. Soundings show a
stronger deep layer shear potential likely augmented by the
shortwave for some concerns over organized multicell storms with
gusty winds should PM convection occur. Latest CSU machine
learning probabilities for Monday do reach the equivalent of a
Slight Risk for severe weather for wind across south/west
portions of the service area. Largely south/southwest low level
flow/ warm advection will foster above normal warmth, which
coupled with increasing humidity will continue to make it feel
summer- like heading into midweek.

Toward mid to late next week the guidance continues to support
a pattern change with an eventual deepening northern stream
trough shifting into the eastern CONUS. An initial shortwave
driving this pattern change will evolve eastward across the
Northern Rockies and along the International border with ND/MN
Tuesday into Wednesday. This will drive a cold front through
the area Tuesday night into Wednesday bringing the potential
for strong storms due the above normal warmth and moisture
fostering greater instability. 00z ECMWF deterministic QPF
has the look of a mature MCS developing to our northwest on
Tuesday and diving E/SE into the instability across the region
Tuesday night with wind potential given ramping deep layer
shear, and this potential certainly bears watching over the
next few days. Beyond, there`s quite the uncertainty in the
deterministic and ensemble guidance on strength and position
of the upper trough heading into late next week and next
weekend. This owes to lower confidence on temperatures, as
illustrated by NBM with Interquartile ranges as much as 10-15
degrees on highs over several days from Thursday through
next weekend ranging from the lower 70s to the lower to mid 80s.
Confidence in precipitation chances late week into next weekend is
also low, modulated by the location of the upper trough.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 526 AM CDT Sat Jun 1 2024

Conditions will continue to deteriorate to widespread MVFR with
areas of IFR from south to north this morning in low clouds and
showers, as a weak low pressure system moves into the area. The
precipitation will gradually diminish in coverage and shift
east this afternoon with the low departing. The ceilings will
be slower to improve into this evening with lingering low level
moisture and weak flow. Late this afternoon into early this
evening there is a low chance (15-30%) for a shower or storm to
propagate and/or develop into CID and DBQ ahead of a weak surface
boundary. Due to uncertainty in development pending cloud cover
and how warm it gets this afternoon, this potential was left out
of the TAFs. The forecast then toward 06z and beyond through 14z
Sunday will focus on the likelihood of fog, as weak high pressure
builds in. 00z HREF membership with visibilities less than 2 miles
is roughly 60-70%, especially west of the Mississippi River, so
confidence is high on IFR conditions developing at most of the
terminals for a few hour period either side of 12z Sunday with
a chance (30-50%) for LIFR/VLIFR conditions.

&&

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

&&

$$

SHORT TERM...McClure
LONG TERM...McClure
AVIATION...McClure