Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 241142

Area Forecast Discussion
National Weather Service Des Moines IA
642 AM CDT Sat Mar 24 2018

.SHORT TERM.../Today/
Issued at 347 AM CDT Sat Mar 24 2018

Confidence: Medium to High

...Major storm continues over the area this morning....

Storm continues to evolve and with the dynamic nature of the system
already seeing some of the northern areas with up to 8 inches of
snow as of 1 am.  Adjustments have been made again to pull the
headlines slightly back to the southwest. HREF and HRRR show that
changeover and lingering snow over the region into the afternoon
hours will likely push totals northeast up to about 12 to 14 inches
with locally higher amounts in the most productive area of
snowfall...still expected to be from near Mason City to around
Waterloo and southeast from there. There are some counties that have
just a about northeast half or a northeast third of the county within
a headline and decided to add these for the sake of getting the word
out of possible travel hazards nearby.  Polk fits this category with
others just touching or portions touching warning and have added
them as well.  Still a tricky snowfall forecast due to dynamic
nature of snow and also some mix from time to time.  Upper level low
now over the area in western Iowa and expected to be a strong
producer of snowfall from 12 to 18z with upwards of 1 or more inches
per hour in the northeastern counties of the warning.  Have also
extended the warning/advisory areas until 21z.  Western counties
will not see precip that long ... but lingering effects and wind
will likely keep hazardous conditions for much of the afternoon...
especially east of I35. Look for some updates to headlines through
the day today as the system pulls east.  Winds will be strong and
near-blizzard conditions still possible for the morning and
afternoon as gusts approach 40 mph or briefly higher at times.

.LONG TERM.../Tonight through Friday/
Issued at 347 AM CDT Sat Mar 24 2018

Impressive system from today will be exiting the far southeast early
this evening.  Other than a lingering light wintry mix in the far
southeast for a couple of hours this evening  we should be precip
free.  We will still be dealing with a brisk wind and colder temps
tonight.  This will not make conditions better for the areas that
received the heavy wet snow as now it will freeze.

On Sunday we will be in between systems.  An upper ridge will be
east of the region as a deep trough pushes into the Rockies.  A
surface low will develop over the Rockies and central Plains and
deepen through the day.  This will create an east to southeast flow
over Iowa on Sunday.  While not a particularly warm flow it will
create some moderation in temps where there isn`t a foot of snow.
Unfortunately for much of northern/eastern Iowa temps will struggle
to push much above freezing.

On Monday, as the upper trough deepens over the west it will amplify
the upper flow over the Upper Midwest and temps...especially over
southern/southwest Iowa will warm into the lower to mid 50s.  there
will be a sharp temp gradient across the northwest into east central
portion of the state as these locations will still be digging out.
During the day, the surface low will shift out of the western Plains
and will develop into an elongated trough as it pushes east and
noses into Iowa.  Warm least aloft...will move into Iowa
ahead of the surface low and forcing with the low will begin to
develop precip Sunday night across the west and will likely be a
rain/freezing rain mix going to all rain during the day Monday. As
the surface low moves east, instability will increase across much of
the forecast area and we should still see thunderstorms...some of
which may be strong but the better instability now appears to be
moving in during the evening.  This time of year is not conducive to
strong/severe storms at night so just how strong these storms will
be is somewhat in question.  Southwest Iowa would still have the
best chance to see this with more general thunderstorms for the rest
of the CWA.

This system departs on Tuesday with rain coming to an end from west
to east during the day.   For the rest of the long term, the upper
trough that was over the west will shift into the Plains and Upper
Midwest. While periodic disturbances moving through the flow cannot
be ruled out, nothing really stands out as seeing a specific precip
chance through Friday.  We will see plenty of cloud cover and
seasonally cool temps through this period.  By the start of next
weekend, the upper trough shifts into the Great Lakes putting us in
a solid northwest flow.  Models do hint at a shortwave coming across
the Northern Plains Saturday brining some precip chances to northern
Iowa. Precip would be snow at night changing to rain in the day.


.AVIATION.../For the 12Z TAFS through 12Z Sunday morning/
Issued at 641 AM CDT Sat Mar 24 2018

IFR to LIFR conditions to continue over most of the area through
18z with improvement thereafter. Particularly poor conditions at
KALO and KMCW with visby at or below 1/4sm at times through 18z.
East to northeast winds of 20g35kt also likely at these two sites.
KFOD will see similar conditions as well. At KDSM and KOTM...less
impacts expected but RA may become mixed with and change to SN
prior to ending around 20 to 21z. /rev


Winter Weather Advisory until 4 PM CDT this afternoon for IAZ034-

Winter Storm Warning until 4 PM CDT this afternoon for



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