693
FXUS63 KDVN 031049
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
549 AM CDT Mon Jun 3 2024

...Updated for 12z Aviation...

.KEY MESSAGES...

- Active summer-like pattern early this week with warm/muggy conditions
  and multiple chances of showers and storms. Strong to a few severe
  storms possible this afternoon/evening, and again Tuesday PM/evening.

- Mainly dry mid week into the weekend with pleasant temperatures and
  lower humidity.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 320 AM CDT Sun Jun 2 2024

Water vapor imagery early this morning depicts an active zonal
flow pattern from the Northern Rockies through the Upper
Midwest, with several embedded low amplitude shortwaves aiding
convection across parts of KS/NE/NW IA/MN within a large
plume of rich moisture advection with PWATs over 1-1.5 inches.
The feature of most interest for our area is a convectively
enhanced vort max or MCV apparent in radar and satellite over
eastern Nebraska. Guidance generally lifts this across Iowa and
into southern Wisconsin/far northern Illinois by this evening.
As it approaches, increasing isentropic ascent with a veering
nocturnal LLJ should foster some spotty elevated convection
mainly across west/northwest sections of the service area this
morning through midday. Some small hail can`t be ruled out
should any storms occur given modest mid level lapse rates (7+c/km).

As this MCV makes inroads this afternoon into early evening,
increasing ascent into a largely uncapped, moderately unstable
airmass (MLCAPE 1500-2000+ j/kg) will support scattered storm
development across the area. Deep layer shear is not overly
strong (generally less than 30 kts), but nonetheless given the
moderate instability will lead to at least some severe weather
potential. Primary concern will be gusty/damaging winds or
wet microbursts with any congealing cold pools or organization
of multicell clusters. Proxy soundings suggest potential for around
1000+ j/kg of DCAPE. Isolated large hail would be possible as
well early on in pulse type environment. A tornado can`t also
be totally ruled out with any boundary-storm interaction in
the presence of gusty southerly inflow today 20+ mph today along with
manageable LCLs aided by increasing surface dew points into the
upper 60s to around 70. SPC has placed a Slight Risk or level
2 of 5 from around the Quad Cities north/east where the better
ascent is generally suggested, and a Marginal Risk or level 1 of 5
surrounding that with the back edge near a Dubuque to Iowa City line.
In addition to the severe weather potential, there is also the
potential for locally heavy rain as PWATs climb to around 1.5 inches
or above the 90th percentile for KDVN sounding climatology for the
date. Given this and progged slow meso-beta convective elements
will have to keep an eye out for localized flash flooding possibly.

Outside of the convection today, the other focus will be the very
warm and summery feel today. Convective trends could put a
bit of a wrinkle in the high temperature forecast for some areas, but
overall anticipate sufficient solar insolation with the gusty southerly
winds to boost highs into the 80s. If more sunshine and less convective
influence occurs then thermal parameters are potentially there to
support some upper 80s.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Issued at 320 AM CDT Sun Jun 2 2024

Heading into mid to late week the guidance continues to support
a pattern change with an eventual deepening northern stream
trough shifting into the eastern CONUS. An initial shortwave
driving this pattern change will evolve eastward across the
Northern Rockies and along the International border with ND/MN
Tuesday into Wednesday. This will drive a strong cold front through
the area Tuesday night bringing the potential for strong storms
in the presence of above normal warmth and anomalously high
moisture (PWATs over 1.5 to near 1.8 inches above 90th percentile
for KDVN sounding climatology and near record). The deterministic
ECMWF has stayed fairly consistent over the past several
nights painting in the QPF the look of a mature MCS developing
to our northwest on Tuesday, and then propagating E/SE into
the reservoir of instability and deeper moisture across
the region Tuesday night. This would most certainly harbor
some wind potential given ramping deep layer shear. However,
there is a lot of uncertainty as well and this is largely
attributed to the potential that showers and storms could be
around parts of the area for much of the day on Tuesday, which
if occurs could limit instability and temper subsequent strength
of any convection Tuesday night with the cold front. As of
right now given the uncertainty SPC has placed a Marginal Risk
or level 1 of 5 for western areas, which has the best potential
for seeing a line of storms prior to nightfall. Otherwise, much
uncertainty exists with the extent of severe weather potential
Tuesday night further east toward the Mississippi River and
eastward. As mentioned, the anomalously high moisture content
will support heavy rain and guidance is depicting this signal
with areas of 1-2 inch amounts, especially west of the
Mississippi River.

The cold front passing Tuesday night will begin the process of
ushering in a cooler airmass, which will be reinforced by an
upper trough evolving over the Great Lakes and eastern CONUS
by late in the week and heading into next weekend. This is
likely to result in mainly dry conditions, and below normal
temperatures with pleasant days (highs mainly in the 70s) and cool
nights (lows in the 50s to possibly a few 40s).

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 535 AM CDT Mon Jun 3 2024

At least scattered coverage of showers and storms is expected at
times through this evening, with the timing/location somewhat
of a challenge.

Spotty showers have developed early this morning west of the
Mississippi River ahead of an approaching upper disturbance
from Nebraska. We are likely to see additional spotty showers
and possibly a couple of storms through midday. Have opted to
leave out mention for this activity due to the rather sparse
coverage and subsequent low confidence on occurrence at a
terminal, but will continue to monitor trends and amend if
needed.

Otherwise, this afternoon into evening is favored for additional
development of showers and storms although the extent is a bit
unclear. It would appear as though KCID and KDBQ have the
higher probabilities, but some of the recent CAM guidance
including the NAMNest and HRRR models would lend support to
extending those higher probabilities further south to include
at least KMLI but largely predicated on outflow boundary
propagation. Overall, confidence to upgrade over PROB30 mention
is low at this time but expect refinement and possibly some
increase in mention in later updates as mesoscale trends become
better defined. Aside from any convection or attendant
outflow resulting in variable winds and potentially stronger
gusts, winds will be predominantly from a southerly direction
throughout at around 10 kts, but will occasionally gust to near
20 kts today.

&&

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

&&

$$

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