-- Discussion containing changed information from previous version are highlighted. --
067
FXUS63 KDVN 252334
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
634 PM CDT Sat May 25 2024

.KEY MESSAGES...

- Another storm system will bring more storms that have the
  potential to be strong to severe on Sunday.

- A change in the flow pattern aloft is expected to bring a
  period of quiet weather for much of the coming week.

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 304 PM CDT Sat May 25 2024

Dry and pleasant conditions will be seen across the area through
midnight. Attention then turns to the late night hours and Sunday.

After midnight return moisture and forcing will induce a band of
showers and thunderstorms west of the Mississippi that will move
northeast. Right around or just before sunrise additional
development will occur along the Mississippi that also moves
northeast during the morning. The development along the Mississippi
will be induced by the approaching weak surface low.

The overall time frame for this looks to be 2 to 10 AM. The overall
severe risk currently looks low with hail being the primary risk and
wind a secondary risk.

After 10 AM Sunday there will be a minima in shower and thunderstorm
activity as mid level lapse rates are fairly stable. While isolated
showers and storms will be possible the key message is that much of
the area could be dry from late morning through early afternoon.

By mid-afternoon diurnal convection will develop along the residual
boundaries left over from the overnight/morning convection. The main
boundary for this new convection looks to be in Missouri where a
nocturnal storm complex lays out a stout boundary. However,
additional boundaries further north combined with differential
heating will allow isolated to scattered storms to develop.

Based on current information areas south of I-80 look to have the
better areal coverage at 35 to 50 percent. North of I-80 areal
coverage will be lower, potentially only in the 15 to 30 percent
range.

The overall severe risk Sunday afternoon is conditional. That is it
will be dependent upon how the overnight and morning convection
evolves. The better risk for any severe storms Sunday afternoon does
look to be south of I-80 which matches the CSU severe probabilities.
The primary risks look to be hail and wind. However, any storm that
interacts with a pre-existing boundary would have the potential for
a brief tornado.

&&

.LONG TERM /SUNDAY NIGHT THROUGH SATURDAY/...
Issued at 304 PM CDT Sat May 25 2024

Sunday night through Tuesday
Assessment...medium to high confidence

Diurnal convection that develops Sunday afternoon will continue into
Sunday evening before dissipating. While areal coverage is not high
(20-40 percent with the better chances east of the Mississippi),
this time frame has the highest confidence of occurring.

Late Sunday night into Monday morning looks to be dry as high
pressure moves through the area.

Monday afternoon a weak upper level disturbance will move through
the area. The model consensus has a 20-40 percent chance of rain
occurring with the better chances across the highway 20 corridor.
However, moisture availability will be the key as to whether or not
any rain occurs. Several deterministic model runs suggest little if
any rain but there are several ensemble members from the various
models suggesting rain. Thus the rain chance is based on the
ensemble members.

Monday night look to be dry as high pressure moves east of the area
and the upper level ridge begins to move east from the Plains.

Tuesday is the most questionable day for rain chances and thus the
lowest in confidence.

Heights aloft are slowly rising which is usually a negative for
rain. Moisture also looks to be lower which would also not favor
rain. However, there are some ensemble members of the various models
suggesting rain for the area. The overall rain risk is low (20-25
percent) and is north of a line from Independence, IA to Kewanee, IL.

Given the few ensemble members suggesting rain, the possibility does
exist that Tuesday could end up being dry for the entire area.

Tuesday night through Thursday
Assessment...high confidence

The global models build an upper level high across the area which
will bring dry conditions and temperatures trending above normal.

Thursday night through Saturday
Assessment...medium confidence

The global models agree that active weather will return again late
next week.

Right now it appears there may be two systems but there is
disagreement on their respective timing. As a result of the timing
disagreements, the model consensus has a risk of rain in each period
from Thursday night through Saturday.

Based on the overall chances for rain, the Friday afternoon through
Saturday time frame appears to be favored with rain chances at 30 to
40 percent.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
-- Changed Discussion --
Issued at 634 PM CDT Sat May 25 2024

Showers and thunderstorms will move across the taf sites
overnight into Sunday morning. CIGS will lower to MVFR in the
rain and some gusty winds are expected in/near TSRA. Some
showers may linger for a few hours behind the larger area of
showers and storms. Re-development of a few thunderstorms are
possible Sunday in the late afternoon but confidence too low to
mention at this time.
-- End Changed Discussion --

&&

.HYDROLOGY...
Issued at 435 PM CDT Sat May 25 2024

Flood Warnings continue for many of the tributaries in Eastern
Iowa for flooding ranging from minor to major. A Flood Watch is
in effect for the Mississippi River from Keithsburg downstream
to Gregory Landing for the potential for minor flooding. Some
locations will experience flooding for the next several days and
even to a week from now. Please refer to the latest Flood Statements
and Flood Warnings for details.

A storm system is expected to bring numerous showers and
thunderstorms to much of the area later tonight through Sunday
evening. Widespread 3/4 to 1 inch of rain is likely with some
spots possibly receiving around 1.50 inches in any stronger
storms. This may cause higher river levels than currently forecast
at some locations if this amount of rain materializes. After this
system passes off to our east by Sunday night no significant rain
is expected for much of next week.

&&

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

&&

$$

SHORT TERM...08
LONG TERM...08/Schultz/Speck
AVIATION...Haase
HYDROLOGY...Haase