504
FXUS63 KDVN 151911
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
211 PM CDT Sat Jun 15 2024

.KEY MESSAGES...

- Chances of showers and thunderstorms increase late tonight,
  some of which could be strong

- Conditions becoming hot and humid Sunday, lasting through
  Tuesday

- A relative break from the heat is expected by Wednesday as a
  cold front moves through the area, supporting periodic chances
  of showers and storms through Friday

&&

.SHORT TERM /THROUGH SUNDAY/...
Issued at 208 PM CDT Sat Jun 15 2024

This afternoon, we continue to see the remnants of AM showers and
storms continuing to move into our region. As this activity moves
through, it will continue to diminish as it encounters a very dry
air mass in place, so local impacts should be minimal.

There will be increasing chances of showers and storms late tonight,
mainly after midnight, which should be more robust as a mid-level
shortwave skims across our northwestern areas. Additionally, a
southwesterly 40 to 50 knot low-level jet will accompany the
shortwave, which will aid in forcing for ascent. CAMs are struggling
a bit on the exact timing and areal coverage of convection across
our northwestern forecast area, and it remains uncertain just how
far south storms will develop. In any case, some strong storms will
be possible as deep-layer shear is now progged around 30 to 40
knots, and most-unstable CAPE values around 500 to 1500 J/kg per the
HREF ensemble mean. Soundings indicate convection to be more
elevated in nature, but with meager mid-level lapse rates, locally
gusty winds will be the main threat, with a lesser threat for hail.
SPC continues to paint a Marginal Risk (level 1 of 5) across our
western tier of counties for tonight.

Eventually, the aforementioned shortwave trough will lift
northeastward by mid-morning Sunday, bringing any lingering showers
and storms to an end. Attention will quickly turn to a breezy, hot
day on Sunday. A large upper-level ridge will develop over the
eastern CONUS, with a large upper-level high pressure system over
the southeastern CONUS, which will support a prolonged period of
southerly flow/warm air advection into our region. Humidity will
also be noticeably higher, although there are some questions on just
how high the dew points will be, given a spread of nearly 4 to 8
degrees off the HREF 25th and 75th percentiles. However, with 850 mb
temperatures between 19 to 21 degrees C per the GEFS and EC
ensembles, which are over 90 percent of climatology, temperatures
warming to the lower to middle 90s are expected, along with heat
indices in the middle to upper 90s for most locations. We are not
planning any Heat Advisory headlines at this time as the likelihood
for locations reaching 100 degree heat indices is a bit low and
isolated at this time.

Southerly winds will be breezy Sunday, with gusts between 20 to 30
mph expected. These winds could help provide some relative relief to
the heat.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Issued at 208 PM CDT Sat Jun 15 2024

Hot and humid conditions continue Monday and Tuesday as the large-
scale pattern changes very little. Monday is likely to be a hair
warmer/more humid than Sunday, with higher probabilities of Tds in
the upper 60s per the LREF, which takes into account the GEFS, ENS,
and GEPS ensembles. 850 mb temperatures per the GEFS and ENS appear
to be pretty consistent over the last several runs, with values
continuing around 18 to 21 degrees C. The NBM continues to be on the
high side of the model spectrum, with values generally over the 75th
percentile, so we did cool the highs slightly for Monday, but still
largely remaining in the middle to upper 90s for highs. Max heat
indices will continue to be in the middle to upper 90s for most of
the area as well, so make sure to take extra precautions to protect
yourself from the heat. As mentioned over the last few forecast
packages, record high temperatures should remain intact, but we have
the potential for breaking several record warm lows Sunday night and
Monday night, with overnight lows in the middle to upper 70s. Please
see the Climate section below for the records that could be tied or
broken.

A pattern change is expected to occur by mid-week next week, as the
upper-level ridging over the eastern US breaks down, and a longwave
trough develops over the Intermountain West region. As the trough
approaches, an attendant cold front will sweep through the area
around Wednesday, which will bring widespread chances (30 to 60%) of
showers and storms. This should bring at least some relative relief
to the upcoming heat and humidity, although high temperatures in the
upper 80s to lower 90s remain possible for Wednesday through Friday.
A few additional mid-level shortwaves are expected to overtop the
ridge into our area, so additional chances of precipitation will be
in place through the end of the week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1221 PM CDT Sat Jun 15 2024

Largely VFR conditions are expected through the TAF period. Our
main focus for this set continues to be on a round of showers
and storms expected late tonight. The latest high-resolution
models show quite a bit of spread in the areal coverage of
storms, so confidence is lower on the timing for any storms
that impact local terminals. However, CID and DBQ remain the
most likely terminals to see any storms, so continued the PROB30
groups for them, with brief MVFR/IFR conditions possible under
the heaviest storms. As we get closer to the event, TEMPOs will
likely be needed. Additionally, a 40 to 50 kt southwesterly low-
level jet is expected tonight, so we have introduced LLWS to
the TAFs to account for it. Gusty southerly winds are expected
at times, especially during the daylight hours Sunday.

&&

.CLIMATE...
Issued at 315 AM CDT Sat Jun 15 2024


Record High Temperatures:

June 17:
KBRL: 98/1944
KMLI: 98/1897


Record Warm Minimum Temperatures:

June 17:
KDBQ: 74/1921
KMLI: 78/2018

June 18:
KDBQ: 74/1921
KMLI: 77/2018

June 19:
KDBQ: 76/1931
KMLI: 78/1953

June 20:
KDBQ: 74/1923

June 21:
KDBQ: 72/1995
KMLI: 75/1923

&&

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

&&

$$

SHORT TERM...Schultz
LONG TERM...Schultz
AVIATION...Schultz
CLIMATE...Schultz/Uttech