Area Forecast Discussion
Issued by NWS Des Moines, IA

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000
FXUS63 KDMX 171424
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
924 AM CDT Sun Mar 17 2024

.KEY MESSAGES...

- Cooler and blustery today and cold tonight into Monday
  morning.

- Possibility of elevated fire weather conditions on Tuesday.

- Chances for generally light precipitation return at times from
  Thursday through Saturday, then a significantly more active
  weather pattern may set in from next weekend into the
  following week.

&&

.UPDATE...
Issued at 924 AM CDT Sun Mar 17 2024

Updated forcast for flurries/sprinkles and extensive cloud
cover for the remainder of the day. Upstream stratus coverage
and HRRR guidance confirms that most of the day will be mostly
cloudy with a few patches of sunshine over the forecast area.
Otherwise, seeing flurries on radar which may change to
sprinkles as temps rise to the upper 30s later today. /rev

&&

.DISCUSSION...
Issued at 223 AM CDT Sun Mar 17 2024

Iowa remains within and beneath a brisk northwest flow regime
tonight in wake of yesterdays cold front, promoting cooler
temperatures along with patchy stratus clouds. An energetic
mid-level shortwave is rounding the cyclonic flow over
Minnesota and the eastern Dakotas and will move over our area
today, resulting in a resurgence of winds and lower
temperatures flowing in. This will make for a cold and blustery
day, with highs only in the mid 30s to lower 40s, and wind
chills often in the teens and 20s. Just a reminder that in spite
of our recent record-warm meteorological winter, Iowa isn`t
quite done with winter weather yet. As the shortwave moves
through we should see an increase in cloud cover, further
assisting in holding temperatures down. A few flurries have also
been observed beneath this feature in Minnesota, however,
deeper mixing depth and more limited moisture in our area should
preclude more than a fleeting flake or two and the official
forecast remains dry.

Temperatures will fall farther tonight, bottoming out in the mid
teens to lower 20s with northwest breezes persisting. On Monday,
however, the 500 mb trough will begin to push off to the east
and a gradual moderating trend will begin in a somewhat more
modest and benign northwest flow regime. Southwesterly surface
flow will briefly return on Tuesday allowing for a return of
milder temperatures, with highs in the 50s to lower 60s, but
unfortunately this will be immediately succeeded by a large high
pressure ridge and more northwest breezes, as highs fall back
into the upper 30s and 40s for Wednesday and Thursday. The
forecast remains dry from Monday through Wednesday and winds
will remain below advisory criteria, however, the brief period
of relative warming on Tuesday may result in elevated fire
weather conditions once again as RH falls into the 30s during
the afternoon.

The latter part of the week through next weekend is shaping up
to be more active than we have seen in a while. By Thursday
morning a large 500 mb gyre will become established over much of
central and eastern Canada, remaining entrenched there through
the end of the week and placing Iowa beneath the far southern
periphery of its cyclonic influence with subtle shortwave
impulses moving quickly across Minnesota and northern Iowa.
Meanwhile, a couple of southern stream troughs will move over
the central and southern Plains states and Ozarks. The long-
range models have been understandably erratic in their
resolution of the evolution of this scenario, timing of
shortwaves, interaction between the streams, and resulting
placement of precipitation potential. At this time it appears
the best POPs will be north and south of Iowa, however, there
may be exceptions. The last couple runs of both the GFS and
ECMWF have depicted a rather robust clipper system rocketing
through the northern flow regime over Minnesota and northern
Iowa around Thursday, likely producing a streak of accumulating
snowfall. By Friday and Saturday some solutions also generate a
broad trough over the High Plains with a boundary extending near
Iowa and resulting in more POPs for us, however, that scenario
is more uncertain as a smaller percentage of members are in that
camp. Regardless, we are carrying 20-40 POPs during this time
frame in the extended range.

Finally, things may get even more interesting right at the end
of the 7-day forecast and beyond, from around next Sunday into
the early part of the following week. The GFS, EC, and GEM have
been consistently evolving a deep western U.S. trough during
this time, then ejecting out waves of energy across the Midwest
before finally swinging through or near Iowa. Accordingly, these
models are indicating high probabilities of substantial
precipitation in our region, though at such long range things
are very much subject to change, and any details of
precipitation type remain inscrutable. Accumulating snowfall is
definitely one possible outcome, but temperatures may also
remain warm enough for most of the precipitation to fall as
rain. Time will tell, but in the coming week our eyes will be
increasingly turning toward what promises to be a prolonged
period of active weather, the first we have seen since mid-
January.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 626 AM CDT Sun Mar 17 2024

Stratus clouds spreading in from MN will result in prevailing
ceilings at the northern terminals this morning, and at least
intermittently at DSM/OTM, before gradually breaking up in the
afternoon and evening. Most ceilings will remain VFR, but MVFR
ceilings around FL025-030 will be possible in the next few hours
at FOD/MCW and have included TEMPO groups there accordingly.
Otherwise, expect strong and gusty NW winds again today, slowly
subsiding tonight.

&&

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

&&

$$

UPDATE...REV
DISCUSSION...Lee
AVIATION...Lee


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