997
FXUS63 KDVN 311900
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
200 PM CDT Fri May 31 2024

.KEY MESSAGES...

- Mainly dry and continued pleasant into early tonight.

- Chances for showers (40-80%) from late tonight (and possibly a
  few storms) into Saturday.

- Active pattern next week, with near daily chances for showers
  and storms. May have to watch Tuesday into Wednesday for a
  chance of stronger storms.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 145 PM CDT Fri May 31 2024

Quiet and comfortable weather is expected this evening into
early tonight with dry conditions and temperatures falling from
the 70s into the 60s.

An open mid-level wave is forecast to track across the Mid
Mississippi Valley region late tonight into Saturday, bringing
light rain to much of eastern Iowa and northwest Illinois.
Despite weaker forcing aloft, isentropic lift to the northeast
of the shortwave and persistent lower tropospheric moisture
advection will result in periods of light rain or occasional
showers. The activity will spread in from south to north,
reaching NW sections of the outlook area the latest. The
steadiest rain is anticipated for the counties approximately
along and east of the Mississippi River where chances peak in
the 60-80% range. Across the NW counties, probabilities drop off
to 30-40%.

Gulf of Mexico moisture advecting northward along the eastern
periphery of the low will push PWATs to near 1.5", and when
combined with the relatively long duration of forcing, some
areas in eastern to southeast counties may pick up over a half
inch of rainfall. Outside of the heaviest swath of rain,
anticipate much of the area to receive between 0.10 - 0.40".
There is a slight chance for embedded thunder late tonight into
Saturday morning; however, mid-level lapse rates are only near 6
C/km and HREF MUCAPE is on the order of a few hundred J/kg. As
diurnal instability increases during the mid/late afternoon, a
few isolated storms may develop with no severe weather expected.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 145 PM CDT Fri May 31 2024

A brief bout of 850 hPa ridging builds in Sunday making for
largely dry conditions. However, by Sunday night the high
will quickly retreat and isentropic lift will rapidly
strengthen ahead of an emerging shortwave in the Central Plains.
The brunt of the low level jet and attendant advection and
convergence looks to focus mainly to our west, but nonetheless
will expect shower and storm chances to ramp up late Sunday
night through Monday AM with a veering jet and passing shortwave.

For much of early to mid next week the pattern looks to become
predominantly fast zonal. This will keep the weather active
across the region, as multiple disturbances are shuttled quickly
in the flow. There is considerable differences in timing,
strength and placement of these waves in deterministic and
ensemble guidance, as to be expected given many of these are low
amplitude. As a result, we continue to have many days of broad-
brushed and higher PoPs while in reality it favors smaller
windows or time periods of high PoPs with still many dry hours.
A stronger mid level shortwave by mid next week may provide the
opportunity for some stronger storms Tuesday into Wednesday.
CSU`s machine learning guidance is highlighting much of the
Upper Mississippi Valley with a strong to severe thunderstorm
threat for Tuesday/Tuesday night, the details of which are
unclear this far out.

Beyond that, it looks to turn cooler while remaining unsettled
heading into late next week and next weekend, as the
preponderance of the deterministic and ensemble guidance
supports a cut-off low traversing the Midwest and Great Lakes
regions. This will foster continued periodic chances for
showers, as spokes of energy rotate around the low. The clouds
and eventual northwest flow aloft will favor cooler conditions.
The Climate Prediction Center (CPC) Week 2 temperature outlook
for June 7-13 has probabilities (40-50%) leaning toward below
normal temperatures.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1220 PM CDT Fri May 31 2024

VFR will prevail today into the first part of tonight. Then a
weak area of low pressure will bring periods of light rain or
showers from late tonight into Saturday morning. There is a low
chance (20%) for thunder but did not include in the TAFs due to
low confidence. Ceilings will gradually deteriorate into
Saturday morning with MVFR likely at BRL and MLI; brief IFR is
possible.

&&

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

&&

$$

SHORT TERM...Uttech
LONG TERM...McClure/Uttech
AVIATION...Uttech