-- Discussion containing changed information from previous version are highlighted. --
205
FXUS63 KDVN 011104
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
604 AM CDT Wed May 1 2024

...Updated for 12z Aviation...

.KEY MESSAGES...

- Pattern remains active with periodic showers and storms
  through early next week.

- Risk for heavy rain and a Marginal risk for severe weather
  Thursday into Thursday evening.

&&

.SHORT TERM /THROUGH TONIGHT/...
Issued at 318 AM CDT Wed May 1 2024

Cold front was nearing the Mississippi River at 2 AM, and will
exit eastern areas prior to sunrise. Northwest winds post-
frontal will remain gusty through midday/early afternoon,
especially north of I-80 where gusts to 30 mph possible before
winds diminish mid to late PM as high pressure builds in.
Anticipate ample solar insolation today mixed with some
mid/high cloudiness, especially early on and then again later
today. The dry advection and sunshine should get highs back
into the upper 60s to mid 70s, which is near to a little above
average for the start of May.

We may see some returns this afternoon on the radar as elevated
warm advection commences, but dry low levels with the surface
high should preclude any precipitation from reaching the ground.

Otherwise, tonight 850 hPa moisture advection and transport will
ramp up ahead of a mid level shortwave ejecting from the Central
Plains. This will lead to a burgeoning of showers across the
area, with a few to scattered storms overnight on the nose of
40-50 kt LLJ while 0-4km CAPE increases to upwards of around 500
j/kg and 850 hPa - 500 hPa theta-e lapse rates go negative. A
little CAPE exists in the growth zone while mid level lapse rates
steepen over 7-8 c/km, so can`t totally rule out small hail being
possible with the strongest convection.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Issued at 318 AM CDT Wed May 1 2024

Thursday will feature rounds of showers and storms between the
lifting warm front during the day and cold front Thursday
evening/night. PWATs increase to near 1.5 inches will support
heavy rain potential with any repetitive convection, and
the 00z HREF layer probability matched mean QPF for 24 hrs
ending 00z Friday supports this idea indicating swaths of 1-2+
inches. This could lead to localized flooding concerns
particularly if it occurs in areas that have seen recent days
of rainfall and where soil moisture is above average,
particularly across portions of the south and eastern service
area. Deep layer shear is more than sufficient to support
organized convection, however the uncertainty lies with the
extent of destabilization due to the clouds and precipitation.
If some areas were to see a lull in precipitation and some
breaks owing to heating, then we could see the potential for
a few stronger storms with gusty winds and marginal hail.
Would also have to keep an eye on the warm frontal position
as where that resides a low-end tornado risk could develop
should sufficient low level instability occur.

Friday, NBM continues to linger precipitation chances 30-50%
across the area however, much of the deterministic guidance
is progressive with the front and would allow for more
subsidence and drier conditions. As a result of collaboration
with neighbors we`ve lowered PoPs Friday/Friday night toward
a drier scenario.

Beyond, the pattern is set to stay active through early next
week, as initially a couple of shortwaves eject across
the Midwest over the weekend ahead of another deep western
trough that looks to eject out early next week. This will result
in continued periodic bouts of showers and storms.

&&

.AVIATION /12Z TAFS THROUGH 12Z THURSDAY/...
-- Changed Discussion --
Issued at 557 AM CDT Wed May 1 2024

VFR conditions are expected into this evening. Northwest
winds will be gusty at times to 25 kt, especially north of I-80,
through midday/early PM before diminishing by mid to late PM.
Tonight, surface winds will turn from the northeast and east
at 5-10 kt, as a boundary stalls south of the terminals. Moist
advection on the nose of a 40+ kt LLJ will lead to increasing
showers and a few storms this evening and overnight. Periodic
MVFR conditions (visibility) will be possible in the stronger
showers and storms.
-- End Changed Discussion --

&&

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

&&

$$

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