Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 251949
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
249 PM CDT Mon Mar 25 2024

.KEY MESSAGES...

- A few strong storms possible west this afternoon and early
  evening. The primary threat remains hail.

- A transition to a wintry mix and eventually snow is expected
  later tonight and into Tuesday morning with main impacts in
  the northwest.

- Much colder Tuesday with a period with strong northwest winds.
  Wind chills in the teens and 20s.

- Warmer and drier Thursday into Saturday.

&&

.DISCUSSION...
Issued at 248 PM CDT Mon Mar 25 2024

Surface boundary has slowly eased into western Iowa this afternoon
with a narrow ribbon of clearing ahead of the front.  Ongoing
destabilization in this area of insolation has produced some weak
surface based instability across the southwest right ahead of the
front.  This area remains the concern area through peak heating into
the early evening for storm development and potential for some
limited severe weather.  Low level lapse rates have increased nicely
within the cleared area along with increasing 0-3km CAPE over 125
J/KG.  Given proximity of the front and good low level vorticity,
brief spin-ups with the streamwise vorticity being stretched in the
updrafts cannot be ruled out.  The window for this would be from mid
afternoon into the early evening.  Otherwise, given the low freezing
levels, the threat of some marginally severe hail will also exist.

Otherwise, precipitation begins to fill back in across much of
central into northern Iowa this evening as strong low and mid level
forcing pushes northward into the state as the upper low lifts
northward toward the state.  The surface boundary makes its way
gradually east through the night with strong cold advection on the
backside with increasing northwest surface winds.  This initially
undercuts the warm air aloft and is likely to lead to a period of
freezing rain in the close wake of the boundary in northwest Iowa
this evening into the overnight with the production of some freezing
rain expected.  Eventually, the cold air deepens sufficiently for
any precipitation to change all to snow toward daybreak with some
minor accumulations expected.  Have gone with a Winter Weather
Advisory in the northwest for the icing and light snow amounts
producing travel headaches, particularly for the Tuesday AM commute.
Elsewhere, rain is the primary precipitation type through the night
with some decent amounts in central to north central Iowa along and
just west of the I-35 corridor and north of I-80 where over an
additional inch of rain is possible overnight.

The strong cold advection continues Tuesday with any lingering rain
changing to snow in the east. Some minor accumulations under an inch
may occur across portions of central Iowa with the best threat of
over an inch in the advisory area where up to 2 inches are possible.
Otherwise, the strong northwest winds produce generally miserable
late March conditions for Tuesday with any light precipitation
ending by mid afternoon.

Thereafter, conditions quiet down into the later half of the work
week with gradual moderation as the upper flow flattens.  There
remains disagreement into the weekend with the eventual
evolution of the upper pattern and hence the forecast into the
weekend and beyond.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1238 PM CDT Mon Mar 25 2024

Active period for aviation weather as low pressure moves across
the state. Threat for scattered showers and thunderstorms exists
this afternoon into the evening becoming widespread stratiform
rainfall overnight. Transition to snow is expected on the
backside as colder air filters into the state. Ceilings and
visibilities are likely to be MVFR to IFR at times in
precipitation for much of the period. South to southeast surface
winds become northwest as boundary and low pressure cross the
state tonight and increase with gusts to 30kts+ by Tuesday
morning.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 1 AM to 10 AM CDT Tuesday for
IAZ004>006-015-016-023-024-033-034-044.

&&

$$

DISCUSSION...Cogil
AVIATION...Cogil


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