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000
FXUS63 KDMX 252000
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
300 PM CDT Thu Apr 25 2024

.KEY MESSAGES...

* Quiet to round out daytime hours today, giving way to first round
  of shower/storms tonight and an overall active period through the
  weekend.

* Best severe weather threat W/SW Friday evening, with strongest
  threats for large hail and a few tornadoes. Primarily W/SW Iowa
  late afternoon/evening, then lifting NE. Currently SPC Enhanced
  Day 2 west of I-35.

* Severe potential continues Sat/Sun, and at least partially
  dependent on previous rounds of convection. Including hydro threat
  Sat evening/night. Current SPC Slight Day 2 (Sat), SPC Day 4 15%
  (Sun). WPC ERO Slight Sat.

* Quieter to begin next week.

&&

.DISCUSSION...
Issued at 257 PM CDT Thu Apr 25 2024

The calm before the storms today, so to speak. Aside from a few
sprinkles/light rain W/SW this morning, dry conditions have
prevailed across the state with highs into 60s and breezy SE winds.
Overall dry conditions will continue into the evening before western
trough exerts increasing influence across the Plains with surface
low beginning to move off the Colorado Front Range. This will see
southerly flow, moisture advection, and broad lift increase. While
the surface front will lag behind, strong low to mid-level theta-e
advection will yield elevated thunderstorm activity at/above an 850-
800mb warm nose during the overnight and into Friday morning before
activity subsides as it slides eastward into less supportive air
mass. Continue to expect these storms to remain sub-severe, though
effective shear may be just supportive enough to allow a few storms
to flirt with impactful hail. Nominally bolstered with
RAP/HRRR soundings in western areas depicting up to around 1500 J/kg
elevated CAPE. Any strong/severe concern would be  over western
areas with initial storms as upscale growth is expected with
widespread lift ongoing and less supportive air mass east. During
this time, surface winds will remain breezy, and increasing gusts,
as surface low moves out into the Plains. Expect gusts into the 30s
mph to continue overnight tonight.

Activity will linger into the Friday morning hours, and slide
eastward, leaving in its wake cloudy skies. Additional/continued
theta-e advection may result in scattered non-severe shower/storm
activity through the remainder of the morning and into the
afternoon, as well as helping re-prime the environment for severe
potential later Friday, as seen in the SPC Day 2 Enhanced broadly
west of I-35. Primary window of concern Friday will begin around 21z
in/around the Iowa-Nebraska border, and storms will move
northeastward into the evening. Strongest threat does continue to
look to be in the aforementioned Iowa-Nebraska border area as broad
CAM guidance highlights a corridor of SBCAPE values of
2000-3000+ J/kg with nominal (~25 J/kg) to no CIN. Hodographs
continue to strongly point towards organized convection with
sweeping low level hodographs yielding 0-1km streamwiseness
values around or in excess of 90% and moderate streamwise
vorticity values of around 0.25/s. Wind fields above about 2km
take on a less supportive overall structure, but should be
strong enough to keep these storms vented. Add in CAMs
consistently depicting 0-1km SRH values in excess of 200 m2/s2,
and it becomes pretty apparent that a leading threat may be
tornadoes, in conjunction with large hail. Threat will be
greatest with initial storms, which are expect in eastern NE/KS
areas around 21z, where above mentioned environment will be most
supportive. As activity translates eastward late afternoon into
evening, guidance is consistent in the environment slowly
degrading with less supportive mid-level lapse rates eroding
SB/MUCAPE. Even so, effective inflow wind fields will remain
supportive of rotation, so tornadic activity and some hail
cannot be ruled out as storms approach I-35 corridor
around/after 00z. These storms will be moving relatively fast with
progs of 40 to 50 kts. All in all, SPC Enhanced area appears to
be in a good spot, if not a hare too far east.

Phew. That`s not all though with additional strong to severe storm
potential expected into Saturday. Some of this will depend on where
the surface boundary ends up laying across the state, with a SW to
NE orientation expected as the upper level trough and surface low
pass to the NW/N of the state early Saturday. In conjunction,
another western trough will be inducing surface low development in
the Colorado Front Range, and help initiate another round of
convection over Central Plains. That activity may drift up into SW
portions of the CWA in/around the warm front and would pose the
greatest risk for traditional severe weather, with hail and
tornadoes the primary risks with any supercellular/organized
activity. Aside from that, additional activity in/along the
surface front expected as LLJ further enhances Saturday night.
Storm motion vectors roughly parallel with the front raise the
eyebrow for potential hydrologic issues. Some synoptic and CAM
guidance have pointed toward the potential for some areas
picking up 3 to 5 inches or more. As hinted, location remains in
flux with some uncertainty in final location of boundaries. SPC
Day 3 Slight and WPC highlighting southern areas remain
reasonably placed at this point in time.

Another round of convection will move through Sunday as the second
western trough and surface low eject and move northeastward across
the Plains. Suffice it to say that additional severe weather
potential exists with low tracks moving across western into central
Iowa mid-day into the evening. Have not dove into substantial detail
here with previously mentioned two rounds of greater focus and
cascading effects from those rounds likely to affect Sunday
potential to some degree. But again, do not sleep on Sunday
potential, as the existing Day 4 SPC 15% is more than warranted,
even with a quick casual look.

Quieter to begin next week, with scattered/sporadic precipitation
activity hinted late-end of next week.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1232 PM CDT Thu Apr 25 2024

Initial VFR conditions will give way to degrading cigs and
periods of TSRA/SHRA. Primary degradation of flight conditions
will occur after 06z as TSRA/SHRA develop and track
northeastward. Expect all sites to see MVFR/IFR. Throughout, SE
winds will be breezy, initially around 15 to 20 kts with limited
wind gusts, then increasing to 20+ kts sustained and gusts into
the lower 30s kts overnight and into Friday. Does appear
possible periods of LLWS, but have withheld due to sporadic
nature appears within guidance and soundings.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Curtis
AVIATION...Curtis