264
FXUS63 KDVN 111727
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1227 PM CDT Sun Aug 11 2024

.KEY MESSAGES...

- Below normal temperatures expected through early week, before
  moderating closer to normal by the end of the week.

- Rain chances return during the week ahead, particularly
  focused late tonight/Monday and Wednesday/Thursday.

&&

.SHORT TERM /THROUGH MONDAY NIGHT/...
Issued at 250 AM CDT Sun Aug 11 2024

Surface to 850 hPa ridging will be in place today providing
a continuation of dry weather and below normal temperatures.

Tonight into Monday morning, a shortwave will slide ESE from
the Northern Plains. Strong moisture advection over a
surface warm front will serve as a focus for a complex of
showers and storms across portions of KS/MO. Further north
there should be sufficient elevated theta-e advection
for additional showers and some storms evolving across
portions of the Northern Plains. These will track/develop
ESE to the Mid-Mississippi Valley late tonight and Monday AM.
DESI Grand Ensemble and NBM favor the highest PoPs and
bulk of accumulating rainfall occurring to the south/west of
the Quad Cities, which seems reasonable with that region
in close proximity to the better 850 hPa moisture transport.
The Grand Ensemble and NBM generally have probabilities of
40-70% for rainfall amounts of 0.5 inch or greater across
extreme SE Iowa, NE Missouri and a portion of WC Illinois.
Rain amounts are then expected taper off quickly further north
while rain chances diminish north/east of the Quad Cities due
to residual surface to mid level ridging. The clouds and
increase in low level moisture should result in lows not as
cool tonight across our southern areas and in the upper 50s to
lower 60s. Meanwhile, drier low level air and at least partial
cloud breaks within the ridge axis will support cooler lows in
the lower to mid 50s across far NE Iowa and NW Illinois. The
precipitation across our southwest 1/2 or so on Monday should
diminish by late morning with the waning LLJ and attendant
moisture advection. However, we will keep a chance (20-40%) for
showers and storms Monday PM into early evening with the passage
of the shortwave. The clouds and wet ground should limit highs
in the upper 60s to around 70 south/west of the Quad Cities on
Monday, while some sun peaks and drier antecedent conditions
should allow for highs into the lower to mid 70s further north/east.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
Issued at 250 AM CDT Sun Aug 11 2024

In the wake of the shortwave we look to get a renewed bout of
surface to 850 hPa ridging, which should lead to mainly dry
conditions later Monday night through Tuesday night. However,
we do look to turn active once again Wednesday through at least
Thursday, as the next shortwave ejects from the Northern
Rockies traverses north of a surface boundary to our south.
Monsoonal moisture fetch with PWATs increasing over 1.5-2.0+
inches by Wednesday into Thursday coupled with favorable jet
dynamics supporting/enhancing large-scale lift continues to
suggest this period mentioned will be one to watch for heavy
rain potential. The pattern, timing (largely Wednesday
night/Thursday AM for the bulk of the rain), and slightly below
normal temperatures all combined don`t scream severe weather
potential at this time. Of note the CSU machine learning
forecasts focus very low severe probabilities mainly to our
south/west during this time. That being said, we`ll still want
to keep an eye out for any potential changes with it being still
several days away. The day to watch would likely be Thursday for
any slowing of the surface low and triple point.

Beyond, the NBM has some daily low PoPs (15-30%) Friday through
Sunday and seems reasonable for now, as models are struggling a
bit with the potential lower amplitude perturbations /ridge
riders/ traversing through the mean amplifying central U.S. ridge.
Temperatures also look to moderate closer to normal late in the
week and next weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1220 PM CDT Sun Aug 11 2024

VFR conditions will prevail through much of the TAF period, with
showers/storms moving in late tonight, which may lower cigs and
vis. Currently have this covered with a PROB30, as there remains
some uncertainty on coverage and timing. Although, between
09-12z, we can expect showers to start filling in from the west.
BRL and CID have the best chance to see precipitation, with
chances decreasing as we go north. Winds today are light and
variable for the most part, with a general west-northwest
orientation when the winds pick up. Otherwise, tonight we will
go light and variable throughout, with increasing cloud cover.
Where the showers/storms set up, we can see cigs decreasing to
1500-3000 ft tonight.

&&

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

&&

$$

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