Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 160529

Area Forecast Discussion
National Weather Service Des Moines IA
1129 PM CST Fri Feb 15 2019

...Updated for 06z Aviation...

.SHORT TERM.../Tonight through Saturday/
Issued at 252 PM CST Fri Feb 15 2019

Summary...Light snow chances, dusting to a half inch, in far S/SW
will continue into the early evening before subsiding as main
chances push off to the S and SE. Otherwise, predominantly benign
weather through around 3pm Saturday as surface high pressure
influences the area ahead of the next snow producing system later
Saturday and Sunday.

Tonight and Tomorrow...No major concerns through tomorrow afternoon
with regards to consequential weather. Shortwave sliding through the
upper level flow currently will exit the area this evening, leaving
the remainder of the area snow free. As it exits, surface high
pressure sliding east across southern MN and brief and weak upper
level ridging will influence the area with depleting cloud cover
and weakening. With next system quickly digging out of the west and
on the heels of aforementioned surface high and upper ridging, window
of clear/clearing skies is a bit in question, which would have at
least some consequence in overnight lows. Regardless, cold
temperatures once again overnight with area wide single digits below
zero north and single digits above zero south. Saturday will see
cloud cover increase thorugh the day as broad upper level trough and
associated surface low increase their influence through the day.
Majority of the area will see snow hold off until around 6pm, but
will quickly spread once it does reach the state.

.LONG TERM.../Saturday night through Friday/
Issued at 252 PM CST Fri Feb 15 2019

All eyes are on the winter storm anticipated across much of the
region this weekend. This storm remains on track from previous
forecasts, except that model POP/QPF trends have come around to
what forecast soundings were indicating the last couple days,
which is snow persisting longer through Sunday and even Sunday
night. Despite rates being lower by that time as the system slowly
fills in and weakens, the longer duration has boosted storm total
accumulations into the 5 to 7 inch range across a good chunk of
the forecast area, and locally higher amounts are certainly
possible. However, that 5 to 7 inches will accumulate over roughly
a 24 to 30 hour period which is below warning criteria, and much
of it will fall overnight on a weekend with relatively light
winds. Therefore, travel impacts will be mitigated compared to
what they might otherwise be for accumulations of that magnitude.
Therefore, a winter weather advisory has been issued for most of
the forecast area, excepting the far south/southwest where
confidence is lower as the snow could end sooner on Sunday. It
should be noted that soundings continue to indicate once
saturation occurs accumulating snowfall will begin rather quickly,
so while initial rates will only be perhaps half an inch per hour
or thereabouts, those traveling on Saturday evening or early
Saturday night could find roads going from dry to snow covered
pretty quickly. Those planning travel this weekend should keep a
close eye on forecasts and road conditions before setting out,
and may need to adjust their plans accordingly. There is also a
possibility that some portion of the winter weather advisory could
need to be upgraded to a winter storm warning if forecast amounts
continue to trend upward, or if factors enhancing hazardous
impacts come to light.

After the snow tapers off around Sunday night we will have a brief
spell of relatively quiet weather from Monday into Tuesday as a
mid-level ridge moves overhead. However, another trough will then
swing through on Tuesday night and Wednesday bringing additional
snowfall chances. A few days ago the timing of this system was all
over the place, but ever since yesterday the longer range models
have been in lock-step with the overall timing/evolution of this
trough, and on the 12Z runs today it has been stronger with more
QPF/snow. However, at this range 4-5 days out there is still some
variability and more focus was placed on the weekend system. We
will be keeping an eye on this midweek system in the coming days
as details become clearer. Quiet weather will then return at the
end of next work week before another system approaches the
following weekend. In terms of temperature, no significant cold or
mild spells are seen in the seven day forecast, as the steering
pattern of quickly alternating ridges/troughs and the snow pack
already in place, and enhanced by additional snowfalls, will keep
temperatures relatively stable. Daily highs will generally be in
the teens and 20s, with morning lows generally in the single
digits and teens, occasionally dipping below zero in the


.AVIATION.../For the 06Z TAFS through 06Z Saturday night/
Issued at 1128 PM CST Fri Feb 15 2019

VFR conditions are expected through much of the day on Saturday.
Winds will gradually switch from northerly overnight easterly
through tomorrow. Cloud cover will increase across the state
through the day as a system approaches from the west. MVFR to IFR
cigs/vis begin around 02-05z across all sites as snow begins to


Winter Weather Advisory from 6 PM Saturday to 6 PM CST Sunday
for IAZ004>007-015>017-023>028-033>039-044>050-057>062-070>075-



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