292
FXUS63 KDVN 271102
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
602 AM CDT Sat Jul 27 2024

.KEY MESSAGES...

- Dry conditions through the afternoon, with increasing chances
  of showers and perhaps a few isolated storms tonight

- A more active pattern develops Sunday through the upcoming week,
  with periodic chances of showers and storms

- Some strong to severe storms will be possible Monday

- Heat and humidity will build Monday through Thursday, with the
  potential for heat headlines

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 401 AM CDT Sat Jul 27 2024

Today will be our last day of this stretch of quiet conditions, so
if you have any outdoor plans, it looks to be a pretty good day for
them. A large area of high pressure will linger over the central
Great Plains region, which will help keep any showers and storms at
bay. Southeasterly return flow around the high pressure system will
stick with us through tonight. This flow regime will lead to
increasing temperatures, with highs in the lower to middle 80s.

As we head into the evening and overnight hours, a southern stream
mid-level trough will lift northwards from the southern Great Plains
into our region. The leading PVA maxima looks to move into our
southern areas after 00z/7 PM tonight. It might take some time for
precipitation to develop, given there is plenty of dry air ahead of
the trough, but eventually, some showers and perhaps a few isolated
storms will take shape, mainly after midnight. Little, if any,
noteworthy deep-layer shear will accompany the trough, so strong to
severe storms are not expected. Overnight low should fall only to
the upper 60s to near 70 for most locations.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 401 AM CDT Sat Jul 27 2024

Sunday starts off the long-term period on a more active note
compared to the previous days, as the aforementioned trough continues
to slowly move through the area. A cut-off low is progged to develop
within the trough, which will translate south and east of the local
forecast area. Shear continues to be very meager, but instability
does appear to increase to around 1000 to 2000 J/kg, per the 27.00z
GEFS ensembles, with the NBM giving between 40 to 70 percent chances
of showers and storms Sunday afternoon. A secondary shortwave trough
will quickly move through Nebraska into western Iowa Sunday night,
with a strengthening 40 to 50 kt nocturnal low-level jet concurrent
with this shortwave, which should support some additional chances of
showers and storms. Deep-layer shear does appear to increase, but
instability will take a tumble overnight, and ensemble soundings
from the ENS, GEFS, and GEPS all indicate any storms that form to
become more elevated.

For Monday through the end of the period, we will continue to have
periodic chances of showers and storms as a large area of upper-
level high pressure develops over the south-central CONUS, placing
our region on the northern end of a large heat dome, which is
depicted very well in the WPC ensemble cluster analysis. Zonal flow
aloft will become established over our region, leading to a series
of mid-level shortwaves to traverse the region. For Monday, one to
perhaps two of these shortwaves will sweep through the region, but
depending on how prior convection evolves, it will have great
bearing on how subsequent convection develops. Monday looks to be
the first day of our stretch of hot and humid conditions through
Thursday, with highs Monday warming to the middle 80s to near 90,
and dew points increasing to the lower to middle 70s. This should
result in a very unstable air mass, characterized by MLCAPE around
2000 to 3000 J/kg. In fact, the GEFS ensemble probabilities of CAPE
3000+ J/kg are around 50 to 80 percent for our area! Additionally,
mid-level flow is progged to increase to around 30 to 40 kts across
our area, which should provide ample shear for storm organization.
However, uncertainty remains on how things will evolve due to prior
convection, which has the potential to reduce the amount of
instability to work with and lessen the severe storm threat, or if
an MCS may result from the morning activity and move southward. It
is possible that if prior convection staves off, the severe storm
threat could be increased. With all of this said, SPC has introduced
a Marginal Risk, or level 1 of 5, across our entire forecast area.
Stay tuned for more details on the upcoming severe weather threat as
we get closer to Monday.

As far as the temperature forecast is concerned, it will be highly
dependent on the timing of these storms as convection during the
daylight hours will help keep conditions cooler than what the NBM is
suggesting. If storms don`t occur during peak heating, high
temperatures could reach the lower to middle 90s Tuesday through
Thursday. With increased humidity, heat indices of 95 to 100
degrees or more will be possible. Heat headlines may be needed.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 602 AM CDT Sat Jul 27 2024

VFR conditions are expected through the evening hours today
before MVFR conditions move in from the south after midnight
tonight. A daytime cumulus cloud field should develop later this
morning and linger through the afternoon. Meanwhile, a trough of
low pressure will lift northward, arriving tonight and bring
increasing chances of showers and perhaps a few isolated
thunderstorms with it. High-res models are in generally good
agreement on the timing of precipitation, so confidence is
fairly high on timing this far out. At least MVFR conditions
are expected, but some IFR ceilings may also accompany the
trough, so adjustments to the ceilings may be needed.

&&

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

&&

$$

SHORT TERM...Schultz
LONG TERM...Schultz
AVIATION...Schultz

NWS DVN Office Area Forecast Discussion