Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 230917
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
417 AM CDT Sat Mar 23 2024

.KEY MESSAGES...

- Light snow expected west central to north central Iowa today.
  Minor accumulations, mainly on grassy surfaces.

- Potent and prolonged system begins to arrive late tonight and
  into Sunday. Accumulating snow along with wintry mix expected
  again over west central to north central Iowa. Greatest snow
  accumulations north.

- Scattered thunderstorms possible Sunday night and Monday A few
  stronger storms are possible on Monday. Strong winds also
  expected Monday.

&&

.DISCUSSION...
Issued at 412 AM CDT Sat Mar 23 2024

The active weather pattern continues into early next. Ridge of high
pressure is moving across Iowa and the Upper Midwest early this
morning and that has led to the stratus clearing for much of the
state. Strong mid-level theta-e advection is already ongoing over
central Nebraska and into western South Dakota and this has
translated to an increase in radar returns over that region. Much of
this has been evaporating before reaching the ground as the
atmosphere tries to recover from the dry air from the ridge. There
has been an increase in light snow reports though over the past few
hours. The theta-e advection will continue to move east into Iowa
today and eventually bring some light snow to the area though the
best saturation potential is over the northern half of the state.
Some light accumulations on grassy area is possible though given the
time of year, accumulations on roadways should be minimal during the
daytime with enough solar radiation penetrating thorugh the clouds
to keep those surfaces above freezing. Overall, temperatures will
remain on the cooler side again today with highs mostly in the 30s.

The bigger story today and into tonight is the lee side cyclogenesis
that will commence over eastern Colorado as a potent system begins
to translate east over the western CONUS. This will increase the
southwest flow aloft over Iowa and further intensify the theta-e
advection and moisture transport into the state as moisture races
north from the Gulf. Precipitation chances will increase as well
late tonight and into Sunday morning. Expect snow to develop over
parts of west central and into north central Iowa by Sunday morning
and that may be mixed with freezing rain or sleet at times. This is
a somewhat tricky forecast once again as the exact thermodynamic
parameters are not locked on yet, meaning timing of the warmer air
arrival, snow to rain transition times etc. There is a signal that
is beginning to show up though that would be the potential for heavy
(in weight) wet snow with strong aggregate potential for a few hours
over the location mentioned above. Snowfall rates of 1-1.5
inches per hour could occur over that few hour period. Total Snowfall
amounts of 4+ inches may occur mainly over the far northern
counties. No headline is being issued on this shift but likely
will need a headline once more clarity arrives. The surface low
will begin to eject out into Kansas by late Sunday and that will
help push the warm sector through much if not all of the
forecast area. The low will feature the warm front into far
southern Minnesota with an inverted trough north through
Nebraska. The north side of the warm front should be the focus
for winter precipitation. An increasing low level jet Sunday
night and another round of strong forcing and theta-e advection
will result in showers and a few storms moving across Iowa. Any
storms should remain sub severe as saturation limits updraft
strengths. The main system will lift through Monday and Monday
night. The is a chance a few strong storms develop Monday with
the arrival the cold front and will continue to monitor this but
certainly the shear space looks good for organized storms
should the instability be realized. Strong and gusty synoptic
winds are also expected with gusts over 45 mph possible. Finally
a transition to light snow may occur Monday night into Tuesday
with some accumulations possible.

Gradual warming arrives mid to late week and generally quiet until
possibly Friday night or next Saturday. Highs back into the 60s are
possible by Thursday for southern Iowa.&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1157 PM CDT Fri Mar 22 2024

MVFR stratus has quickly diminished this evening and should be
south of sites by 06z. On Saturday winds will shift to
out of the southeast by afternoon, accompanied by increasing
cloud cover. Precipitation increases from west to east
through the afternoon and evening with MVFR ceilings and -SN at
most sites for a few hours late Saturday.

&&

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

&&

$$

DISCUSSION...Donavon
AVIATION...Hagenhoff


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