Ottumwa, Iowa 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

168
FXUS63 KDMX 180841
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
241 AM CST Sat Jan 18 2025

.KEY MESSAGES...

- Bitter cold temperatures through the weekend into early next
  week. Dangerous wind chills of -20F or colder at times
  beginning tonight through Tuesday morning.

- Warm up mid-week as highs return closer to average.

- Forecast remains dry at this time, but trends are pointing
  toward a possible precip window Wednesday and/or Thursday.

&&

.DISCUSSION...
Issued at 237 AM CST Sat Jan 18 2025

Our well-advertised dip into a cold snap is underway as a deep
longwave trough carves out a home over much of the conus. Strong
cold air advection extends almost the full length of the Plains
states as blustery north winds have delivered our first round
of bitter cold air. Winds have been quite gusty within the caa
regime boosted by isallobaric forcing. Gusts of 30 to 40 mph
have been common overnight. Shallow HCRs have been observed in
both satellite and radar imagery and have produced scattered
snow flurries as the cloud-bearing layer cools through the DGZ.
Even the efficient crystal production has struggled to overcome
the substantially dry airmass, which should win out over the
next few hours and eventually cease lingering flurry activity.

Diurnal warming struggles to overcome cold air advection today as
temps only marginally improve. Highs will be in the teens to low 20s
with blustery north winds making it feel like the single digits
above and below zero. Wind chill values fall to -20F and colder
tonight into Sunday morning for all but the southern fringes of
the forecast area. The inherited Cold Weather Advisory remains
mostly on track, but did refine just a bit by adding another row
of counties south to account for marginally colder wind chill
values compared to the previous forecast. Low-amplitude
shortwaves diving south through the mean synoptic trough deliver
reinforcing shots of Arctic air, keeping the bitter cold
airmass firmly in place to start next week. Highs will only be
in the single digits and teens with lows falling below zero,
especially across the north Monday night where both the GEFS and
ECENS feature a >50% probability of temps colder than -10F.
Additional wind chill headlines are a near certainty and will be
evaluated with future updates.

Trough and bitter cold airmass are shunted east mid-week, replaced
by a period of shortwave ridging and moderating temperatures back
closer to seasonal norms. Models continue to disagree a bit on
pattern evolution with the GFS showing a deeper wave digging back
south and another stint of below normal temps toward the end of next
week, whereas the Euro is more progressive and on the warmer side of
guidance. Latest NBM remains dry through the 7 day, however ensemble
probabilities have been trending upward for measurable (>= 0.01"
liquid equivalent) precipitation toward Wed-Thu. PoPs may need
to be introduced in future updates if trends hold in that
direction.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1040 PM CST Fri Jan 17 2025

A bit more pessimistic cig forecast this period as area of
shear driven snow showers/MVFR cigs advances south into the
area. Coverage of snow showers still not high enough to include
in terminals. Have prolonged the lower cigs until mid morning
(15-16z) with gradual improvement aft 16z. Low confidence
forecast, but with winds remaining strong, lower cigs more
probable. Winds remain strong from northwest with gusts 30 to
35kts through around 10z; then remaining 25 to 30 kts through
18z most locations. VFR conditions expected to return aft 18z.
/rev

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Cold Weather Advisory from 3 AM to noon CST Sunday for
IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-081-
082.

&&

$$

DISCUSSION...Martin
AVIATION...REV