Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 150913

Area Forecast Discussion
National Weather Service Des Moines IA
413 AM CDT Sun Apr 15 2018

.SHORT TERM.../Today through Tonight/
Issued at 350 AM CDT Sun Apr 15 2018

Strong system will be slowly moving east today.  Large moisture fetch
is wrapping around the upper low which will keep snow going through
much of the day today.  Currently eastern quarter of the state has
some dry air feeding into the area which is producing some freezing
precip due to loss of ice introduction.  This will end as the system
shifts east and the moisture wraps in changing precip to snow. An
enhanced band of snow has been nearly stationary from roughly Boone
County through Clarke County and is slowly beginning to pivot
southeast and lift off to the northeast.  This enhanced band was
responsible for a little heavier snow along the I-35 corridor down
to about Osceola.  Plow cams showed low visibility and poor
conditions so the winter weather advisory was expanded a little
further south through the morning.  Winds have subsided north and
west and visibilities have improved so the blizzard warning was
downgraded to a winter weather advisory.  Additional snowfall today
of 1 to 3 inches is likely but winds will not be as strong.

Tonight the upper low will be over eastern Iowa with the surface low
in Illinois.  There may be some light snow or flurries east and
maybe north with only very light accumulations possible this
evening. Precip ends overnight with gradually diminishing clouds
across the west and cold temps.  Teens and low 20s west with mid 20s
east making for temps more like January than April.

.LONG TERM.../Monday through Saturday/
Issued at 350 AM CDT Sun Apr 15 2018

/Monday through Tuesday/...Confidence Medium to High

System finally pulling east of the region Monday with lingering
cloud cover east of I35 into the afternoon hours. With high pressure
moving across the region...highs will be colder tomorrow especially
north where snow cover will be deeper. Highs Monday will only reach
the mid 30s over the north with lower to mid 40s across the south.
Clear skies and light winds Monday night will likely bring lows down
into the teens to lower 20s north half and in the lower to mid 20s
south. Some recovery is anticipated on Tuesday as south winds
increase in the afternoon hours and bright sunshine helps to warm
the region with readings in the upper 30s/lower 40s north to the mid
to upper 50s south.

/Tuesday Night through Saturday/...Confidence Low to Medium

Models diverge somewhat already by Tuesday night as Euro/GFS handle
the next fast moving system a bit differently. The GFS is faster
than the Euro with earlier onset of precipitation across the north.
Both the GFS/Euro suggest that a rain/snow mix possibly also a bit
of light freezing rain will begin over the northwest and quickly
transition to snow over the north during the early morning hours on
Tuesday. As the system tracks east during the day...windy conditions
will develop...but also a possible mix of rain/snow as well. QPF is
quite impressive with Euro dropping about .80 to .90 inches while
the GFS is hinting at over an inch of qpf north...and much less
south. Ptype forecast is the real issue right now and suspect it
will still be a challenge up to the event. Both models suggest
dynamic cooling and the potential for a wet-heavy snow over the
north but the challenge will be how quickly this occurs and how
quickly saturation occurs aloft. This could lead to another round of
light to moderate accumulating snowfall-especially north on top of
areas currently still seeing snowfall. Given some uncertainty with
model guidance today...will need to resolve the differences before
any mention of amounts becomes plausible. Temperatures recover
Wednesday afternoon to the mid to upper 30s north and the lower to
mid 50s in the south. The system exits by Thursday with another
quiet and cool period expected for Thursday and a warming trend into
Friday.  Poor model agreement on Friday into Saturday suggest low
confidence for the remainder of the period. The GFS is much farther
north with the late Friday/Saturday system and also faster. Both
models suggest the main surface low will track far enough south and
occlude southwest of the area prior to reaching the mid-Mississippi
River Valley to for now reduce the chances for any severe weather.
However...attempting to forecast the chances for precipitation/
sensible weather at this time appears to be too difficult given the
differences in the output. Will side with a blend for now with some
rain chances late week and early weekend and highs in the 40s/50s
both Friday and Saturday.


.AVIATION.../For the 06Z TAFS through 06Z Sunday night/
Issued at 1133 PM CDT Sat Apr 14 2018

Little change to the latest TAF update. Widespread winter weather
will persist through the overnight hours and into Sunday morning.
This will keep most terminals at or below IFR prevailing
conditions, but some parts of north central Iowa may see LIFR
conditions at times due to 1/4 mile visibility in the more intense
snow and blowing snow. Although the snowfall coverage will
improve tomorrow, cigs generally around 1000 to 2000 feet will
hang around through much of the day. Additional scattered snowfall
activity may redevelop tomorrow afternoon, but low predictability
in the coverage and impact precludes any mention in the TAF at
this point.


Issued at 350 AM CDT Sun Apr 15 2018

Main concerns remain the Cedar River basin and also the river levels
at Estherville. Most areas expected to see some within bank rises
this week as both snow melt and some additional precipitation
reaches the region by Wednesday.  Some concerns downstream of Mason
City along the Shell Rock River overnight as levels have come up.
Trends suggest that the Shell Rock River at Shell Rock should remain
below flood stage as per forecast...with some minor impacts along a
few roads near the river. The Iowa River will see some within bank
rises. At Rowan the river is expected to rise but remain below flood
stage. River flood warnings are in effect for both the Cedar River
at Cedar Falls and the West Fork of the Des Moines River at


Winter Weather Advisory until 1 PM CDT this afternoon for

Winter Weather Advisory until 4 PM CDT this afternoon for

Winter Weather Advisory from 1 PM to 4 PM CDT this afternoon for



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