Area Forecast Discussion
Issued by NWS Des Moines, IA

Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43
000
FXUS63 KDMX 281739
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1139 AM CST Sat Jan 28 2023

...Updated for the 18z Aviation Discussion...

.SHORT TERM.../Today through Sunday/
Issued at 322 AM CST Sat Jan 28 2023

Forecast Impacts for the week:

...Storm today with moderate/heavy snow north; blowing snow
...Much colder tonight through Tuesday
...Moderation mid to late week

Confidence Short Term: High

Main challenge/concerns is storm now entering the region today.
Overall forecast on track with minor adjustments. Forcing today
greatest this morning from 12-18z with area of stronger thetae
advection moving through and east of the region by 18z, then
lessening into the afternoon and evening hours. From a forcing
perspective, the frontal temperature gradient aloft appears to be
a bit more diffuse, which will likely spread the snow out over a
larger area and overall snow totals will end up being an inch or
so less. The amount of qpf forecast has lessened to roughly 0.30
to 0.35 over the area of greatest forcing with lighter amounts
north and south of the US 20 axis corridor; about the same
location as prior packages. The only wrinkle so far, has been a
slightly farther south shift in the initial forcing from southeast
/eastern Nebraska to briefly over southwest to central Iowa,
prior to quickly re-establishing the lift along and north of US
30 by mid morning. This may bring an addition inch or so to the
I80 corridor, but still within the confines of no headlines there.
Even with slightly lower forecast qpf, the snow ratios are
approaching 15 to 18 during the height of the event which will
keep snowfall totals in the 5 to +6 range over a slightly larger
area from near Highway 20 north to Highway 18. With less forcing
nearer the I380 corridor, amounts there fall around to just shy of
6 inches. With that in mind, have expanded the warning for several
counties east along Highway 20 and included Butler to the north.
The advisory counties have been kept the same with lesser amounts,
generally 1 to 3 inches south and north of the current advisory.
Winds this afternoon will increase with the colder air being
forced south during the afternoon and evening. Given the nature of
the snow, rather dry, there will be a fair amount of blowing snow
during the event and some patchy blowing snow into the evening
hours. Snowfall rates will be near 1 inch/hour through mid morning
with the best forcing west of I35/along north of US 20 and then
about a half inch/three quarter inch per hour from I35 east toward
eastern Iowa the remainder of the afternoon. Visibility will be
about a half mile or less at times today as the area of snow moves
over northern Iowa. A consideration for travelers on the
interstates and highways today is that given the dry nature of the
snow, vehicle traffic may result in very low visibility due to
passing vehicles and turbulence created in the wake of traffic.
This may result in more impactful traffic conditions resulting in
loss of visibility for brief periods of time; unrelated to
snowfall and background blowing snow. Temperatures through the
day will move little, only warming a few degrees during the
overnight then falling after 12z as colder air moves into the
north during the day. As the system pulls out tonight, besides
some lingering light snow and flurries through the evening, a loss
of ice introduction south will lead to some patchy freezing
drizzle or flurries. Eventually rather cold overnight mins settle
into the region by Sunday morning; lows dropping to near 10 below
northwest and around 10 above in the far southeast. Sunday will
still be partly sunny to cloudy. A weak wave dropping southeast
across the Northern Plains will bring more clouds and possibly a
few flurries later in the day into the overnight hours. Highs
Sunday will struggle to rebound to the single digits north to the
mid teens southeast. Wind chills will be quite cold tonight from
20 to 27 below across central to northern Iowa. After we are done
with the snow headlines today/evening, we will likely issue
headlines for wind chills later into the evening hours for
overnight.

&&

.LONG TERM.../Sunday Night through Friday/
Issued at 322 AM CST Sat Jan 28 2023

Confidence:  Medium to High

Monday will be another partly sunny to cloudy day. Despite cold high
pressure tracking east, more wave energy with little moisture will
pass overhead and bring more clouds across the state. With H850
temps lingering in the 18 to 22C below zero range, expect another
rather cold day to round out the end of January with highs very
similar to Sunday. Early morning wind chills Monday will again be
near the 20 below range from US 20 north. The coldest overnight
period at this time is forecast for Monday night into Tuesday
morning when lows drop to 10 to 15 below over the north half. Some
uncertainty with regard to cloud cover is still a concern. This
would tend to keep lows a little warmer, but obviously still very
cold. How quickly we drop during the evening as a ridge of high
pressure moves over central Iowa will determine the overnight mins.
The remainder of the week is rather uneventful with the cold
Canadian high moving east; upper level westerly flow returning and
milder H850 temperatures overall heading our way. Thursday may see a
brief dip in temperatures as another Canadian High slides southeast;
then milder return flow arrives again on Friday.

&&

.AVIATION.../For the 18Z TAFS through 18Z Sunday afternoon/
Issued at 1130 AM CST Sat Jan 28 2023

Main concern over the next 6 hours will be vsby restrictions for
KMCW and KALO from SN and BLSN. Precipitation will return to KDSM
and KOTM after 22z with a chance for embedded FZDZ. MVFR and
locally IFR cigs expected for all terminals with IFR and locally
IFR more likely for southern terminals.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 9 PM CST this evening for IAZ004-
006-007-028-039-044>050.

Winter Storm Warning until 9 PM CST this evening for IAZ005-
015>017-023>027-033>038.

&&

$$

SHORT TERM...REV
LONG TERM...REV
AVIATION...Hagenhoff/Jimenez


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.