-- Discussion containing changed information from previous version are highlighted. --
857
FXUS63 KDVN 122353
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
653 PM CDT Wed Jun 12 2024

...Updated for 00z Aviation...

.KEY MESSAGES...

- Rain/Storms possible through the next 24-48 hours, with strong
  to severe storms possible. Main threat for severe weather will
  be tomorrow afternoon and evening.

- Unseasonably warm temperatures will invade the area,
  especially through to the upcoming weekend. Many will see
  temperatures approach or exceed 90. Humid conditions may
  result in excessive heat for some!

&&

.SHORT TERM /THROUGH THURSDAY/...
Issued at 215 PM CDT Wed Jun 12 2024

Tonight...

Weak wave approaching from the northwest through the evening and
into tonight, which will bring the potential for a round of showers
and storms tonight after midnight. Moisture remains lacking in
areas, which will limit the spatial coverage, with lower instability
limiting the severity. Through the last couple of model runs, short
term guidance has trended in favor of scattered showers and
storms, along with their longevity. HREF guidance has even
caught on to this and also noted an increase in instability.
Timing will generally be storms moving in from the northwest
shortly after midnight, with storms reaching the Quad Cities
area between 4-6am. From there, quick decay of the storm can be
seen through the AM commute. Guidance keeps the activity below
severe limits for the most part, but some strong to severe
cannot be ruled out. SPC highlights our northwest in a Marginal
Risk for Severe Weather once again tonight and into Thursday
morning, highlighting winds and hail as the main threats in any
strong storms that we see.

Thursday...

Tomorrow has become a day that we must remain weather aware, as our
severe threat has increased and expanded throughout our area. To
preface, we now have an Enhanced Risk for Severe Weather (level 3/5)
for areas along and south of Interstate 80. Much of the remaining
area will fall under a Slight Risk (level 2/5). The timing will
generally fall within an 8-hour period, between the hours of 2pm-
10pm, with storms moving from northwest to southeast.

So, what exactly are we dealing with? Well, the cold front that
induced showers and storms for parts of the area overnight tonight
(Wednesday night) will slow down on its approach, with the cold
front generally draped west to east over the Interstate 80
corridor around noon Thursday. The location of this boundary
prior to peak heating will be key, as any location along/south
of the cold front and in the warm sector will see a chance for
severe weather. Those north of the front will have lower chances
for severe, yet nonzero, as some guidance hints at some post
frontal development tomorrow. So, with the cold front moving
through in the afternoon, our unseasonably warm and moist
conditions will allow for rapid/robust thunderstorm development.
For reference, our temperatures will largely be in the 90s,
with dewpoints in the low- mid 70s. This will result in
moderate to high instability, which will be conveniently located
in an area of sufficient shear for organized/severe storms.
Thus, we have three of the main ingredients in place for severe
storms, which is shear, instability, and surface forcing. Given
such warm and humid conditions ahead of the boundary tomorrow, I
wouldn`t be shocked to see some convective initiation earlier
in the afternoon, ahead of the main convective cluster.

Now onto storm mode and hazards. Storm mode is expected to be messy
tomorrow. While we may start out with discrete to semi-discrete
convection, we are expecting convection to grow upscale rather
quickly, with embedded supercell structures. All hazards will be
possible on the more discrete storms, with hail and winds remaining
the main threat. The earlier convection may be the best chance to see
significant hail (2" or larger), prior to upscale growth. Although,
once upscale growth begins, we will start to see that wind threat
ramp up quickly. The HRRR and NAM are catching onto this, with them
even highlighting the potential for significant winds (>75 mph). All
of this is supported by the SPC, who has much of our area hatched
for these hazards, signifying the potential for significant severe.
Thus, our confidence is increasing in the likelihood of severe
weather. The tornado threat will be low during all convective modes,
with only a 2% chance highlighted south of Interstate 80 tomorrow.
Thus, be prepared for all hazards, but keep in mind that hail and
wind are our main concern at the moment.

As was mentioned, it will be hot and mostly sunny tomorrow. So, if
outside, please take proper precautions in the heat and have
sunscreen handy! Areas along and south of Interstate 80 will have a
chance to see heat index values around 90-100.

&&

.LONG TERM /THURSDAY NIGHT THROUGH WEDNESDAY/...
Issued at 215 PM CDT Wed Jun 12 2024

Incoming LLVL ridging under temporary northwesterly steering flow
will make for some nice summer days Friday through Saturday, with
the bulk of the warm-up being seen Saturday into Sunday. Friday will
be a beautiful end to the week, with high temperatures in the
low- mid 80s and a light northwesterly breeze. One of the
failure modes for these very warm temperatures will be the track
of the ridge- riding MCSs that result from this pattern. This
would bring residual cloud cover and convection in the mornings,
shunting much of the morning heating. Although, if we fall
south of that track, we will fall under that dome of hot air.
Guidance remains quite aggressive with the heat this weekend
into next week, showing widespread low- mid 90s. If this ends up
being the case, some heat headlines may be necessary. Although,
much uncertainty exists and will refrain from any further
details.

Have plenty of water and sunscreen handy!

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
-- Changed Discussion --
Issued at 645 PM CDT Wed Jun 12 2024

Periodic chances for showers and storms exist during the TAF
cycle. Initially this evening (mainly showers) near/north of
CID and DBQ terminals in the vicinity of an outflow boundary and
a weak disturbance approaching from north central Iowa.
Another chance will occur late tonight and early Thursday AM
(08z-13z) with warm air advection with another approaching
disturbance. Then an increasing and more widespread potential
evolving by Thursday afternoon into evening ahead of a cold
front. Have opted to leave out any mention of showers at CID/DBQ
this evening given the limited coverage and impact. The late
night and early Thursday AM chance was handled with PROB30 mention.
And, despite the likelihood of storms Thursday afternoon into
evening, I`ve opted for PROB30 mention given that the timing is
in the last 6 hours of the TAF. These PM storms will have the
greatest severe weather potential in the form of large to very
large hail and damaging winds 60-80 mph. Where the stronger
convection occurs expect transitory periods of MVFR to IFR
conditions. Otherwise, VFR conditions will largely dominate.
Winds will be a bit challenging. DBQ winds will start out E/NE
5-10 kts in the wake of an outflow boundary, but then eventually
veer around to SSW around 10 kts tonight. The outflow boundary
is slowing and so lower confidence exists on it reaching CID,
thus have kept SSW winds around 10 kts there and also at MLI and
BRL tonight and also Thursday AM when likely see some periodic
gusts 12-19 kts. Thursday afternoon through evening winds will
gradually turn northerly from north to south across the
terminals, as a cold front moves through the region.
-- End Changed Discussion --

&&

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

&&

$$

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