Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 182356

Area Forecast Discussion
National Weather Service Des Moines IA
556 PM CST Sun Nov 18 2018

.SHORT TERM.../Tonight through Monday/
Issued at 322 PM CST Sun Nov 18 2018

Confidence: High

Few concerns other than overnight temperatures.  With additional snow
cover across north and south, have lowered min temperatures based
on slow warming today and expected cooling tonight aided by lighter
winds in the south. Clouds on the increase ahead of upstream cold
front as low tracks across Wisconsin/Great Lakes areas east.
Monday`s highs not expected to recover much over the north with
clouds and cold air advection already beginning at 13-14z there.
Over the central and south, minor recovery in temperatures
expected before cold air advection and winds increase during the
day. With passage of cold front, may be a few flurries north half
during the day, but depth of moisture somewhat limited so have
left out for now and will have next shift look at potential once
again later tonight.

.LONG TERM.../Monday night through Sunday/
Issued at 322 PM CST Sun Nov 18 2018

/Monday Night through Thursday Night/...

Confidence: Medium to High

Few if any concerns through at least Thanksgiving Day. Once high
pressure slides southeast of the region Tuesday afternoon, winds
will turn back to a more zonal flow aloft. The well advertised
change will allow for compressional warming to occur west of us
and then advect into Iowa by late Tuesday through Thursday. The
one possible change which might suppress the warming by midweek is
a projected back- door cold front which the Euro pushes south
back across Iowa Tuesday night into Wednesday. If this should make
it south, the northeast areas would be affected by the airmass
change while the remainder of the south will be largely unaffected.
The pattern quickly shifts back to a milder regime, with west
southwest flow overtaking the region by late Wednesday night into
Thursday. Later Thursday night clouds will be on the increase once
again with the approach of the next upstream system. Overall high
temperatures will warm from the 30s/ near 40 Monday to 40s/lower
50s by Thanksgiving Day.

/Friday through Sunday/...

Confidence: Medium

Both the GFS/Euro have been advertising a system by week`s end.
Timing is similar with the GFS about 6 hours faster on Friday with
the arrival of precipitation vs the Euro; either morning or around
the noon hour. The southern stream is again the more energetic as
the system track across the region. Thermally, there are a few
differences between the GFS and Euro. The GFS remains warmer at
H850 over Iowa than the Euro. Both models, however, suggest that
rain will predominate over any snow with highs at least in the 40s
and lower 50s. The system should pull east of the area by Saturday
morning with another system digging into the Rockies late Saturday
into Sunday. Late in the weekend the models diverge more significantly.
Though both the GFS/Euro agree that a system will eject northeast
from the Southern Plains, the Euro is again slightly more aggressive
in phasing the northern/ southern streams than the GFS. This
results in a precipitation shield farther north into our area with
some potential for snow Sunday into Monday. The GFS would take
the entire system southeast of the region. Too early to express
any details regarding model choice especially since this year so
far, the Euro has been too aggressive in phasing many of the recent
systems crossing the Mississippi River Valley states. Temperatures
through the period will likely begin in the 40s to lower 50s and
lower a bit by Sunday.


.AVIATION.../For the 00Z TAFS through 00Z Monday evening/
Issued at 556 PM CST Sun Nov 18 2018

High clouds to increase across the area tonight with CIGS lowering
as a cold front approaches late tonight into Monday. Southerly
winds initially to become more westerly to northwesterly through
the period as the front moves through Monday. Dry frontal passage
expected. CIGS may drop into MVFR range through the day Monday
into Monday evening.





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