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000
FXUS63 KDMX 162059
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
359 PM CDT Tue Apr 16 2024

.KEY MESSAGES...

- Tornado threat continues across portions of northern Iowa.
  Confidence decreasing in additional severe weather in
  southern Iowa.

- Very windy conditions behind dry line passage. Damaging winds
  nearing 60mph are possible immediately behind the front.

- Cooler conditions for the remainder of the week with rain
  chances Thursday. Frost/freeze headlines likely needed at the
  end of the week.

&&

.MESOSCALE...
Issued at 400 PM CDT Tue Apr 16 2024

Thunderstorms from this morning and early afternoon have moved
east of the area. Two main areas of focus for the area both are
along the dry line. The first area is in northwest Iowa near the
occlusion point. Storms here have a history of producing
tornadoes as they interact with the warm front. Additional
updrafts are visible on radar downstream in Hamilton and Story
County. Tornadoes will be possible with these storms as they
migrate north towards the warm front within the next few hours.
An outflow boundary noticeable on satellite will diminish
tornado chances as it arrives.

The second area of concern is further south on the dry line from
the I-80 corridor southward. Updrafts continue to struggle to
maintain themselves. CAMs have backed off from further
development on this segment of the dry line. Dry air in the
soundings proves that updrafts have little moisture to work with
aloft. Confidence is decreasing in further development in this
region.

&&

.DISCUSSION...
Issued at 400 PM CDT Tue Apr 16 2024

Short Term:

Thunderstorms from this morning continue to move east this
afternoon. Shortly behind these storms in the dry line with
agitated cumulus along it. Updrafts continue to struggle
maturing in the worked air with poor lapse rates. Wind gusts
over 40kts have been reported behind the dry line due to low
level jet stream winds mixing to the surface. Severe wind gusts
(49kts) are possible for an hour or two after the fropa. Have
decided to forego upgrading the current Wind Advisory since the
impact window is so brief, but will continue to monitor in the
short term.

A few more features to note are in Nebraska and into northwest Iowa.
Destabilization has led to dominating landspout processes this
afternoon near the low and along the trailing cold front. Moisture
is being provided on the back side by the TROWAL. Will continue
to evaluate the evolution of these storms as they move east.
Current thinking is there will be enough dry air over the state
to hinder them. Further ahead of the low at the opening of the
occlusion, enhanced stretching potential and vorticity from the
low have helped produce tornadoes. Expect this threat to
continue in the daytime hours when near-surface instability
continues.

Winds will pick up on the back side of the low tonight and angle
into southern Iowa, keeping winds aloft overnight. The increased
winds will lift into the rest of the state through the morning as
the low exits northeast. Winds will be nearing advisory criteria
around sunrise as mixing begins. Cloud cover will keep temperatures
near 60 north. Some upper 60s will be found in the clearing skies
over southern Iowa.

Long Term:

The closed low impacting the state today will phase with the broader
region of troughing. Northwest flow will be introduced behind the
departing system and cool temperatures for the remainder of the
week. An fgen band will set up on Thursday and bring additional
chances for rain and some thunderstorms. Meanwhile the trough
will dig into the northern US and keep the cool airmass in place
into Saturday where highs will only top out in the low to mid
50s. Clear skies and dry air will allow for lows to drop below
freezing. High pressure keeps the state dry through the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1258 PM CDT Tue Apr 16 2024

Thunderstorms with MVFR/IFR cigs to continue moving east within
the next 6 hours. Clearing will reach KFOD and KDSM within the
next 2 hours, but will not last. Additional rain and storm
development is expected in the northwest with severe weather
possible. Aside from storms, gusty winds exceeding 40kts at
times are expected for the remainder of the day. MVFR to IFR
cigs to move in overnight with rain continuing north.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Wind Advisory until 7 PM CDT this evening for IAZ004>007-
015>017-023>028-033>039-044>050-057>062-070>075-081>086-
092>097.

&&

$$

MESOSCALE...Jimenez
DISCUSSION...Jimenez
AVIATION...Jimenez