Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 202315

Area Forecast Discussion
National Weather Service Des Moines IA
615 PM CDT Fri Apr 20 2018

.SHORT TERM.../Tonight through Saturday/
Issued at 219 PM CDT Fri Apr 20 2018

Large storm system over the Rockies and western Plains will begin
to shift into the southern Plains. The large cloud shield from
this system extends all the way to the northern Plains and has
pushed into the Upper Midwest. As the storm system slowly slides
across the southern Plains into the southeast U.S. the clouds will
stay over the Upper Midwest through the weekend. This will have
some impact on temps. For tonight a ribbon of higher mid/high
level moisture will work across mainly northern Iowa and Minnesota
along with some weak forcing. The problem, based on soundings is
that there is a lot of low level dry air so while there may be
precip aloft, it will likely only translate to some very light
rain or sprinkles across the north this evening as it translates
northeastward. Temperatures tonight will not be as cold but with
the cloud cover in place on Saturday, highs will not reach their
full potential either. I have generally gone 50s for the state for

.LONG TERM.../Saturday night through Friday/
Issued at 219 PM CDT Fri Apr 20 2018

Saturday night and Sunday the Southern Plains system swings into
the southeast U.S. so we will see less cloud cover and thus, highs
on Sunday will be a category or so warmer. Still keeping 50`s
across the north but low to mid 60s should be common across the

Monday will be the warmest day with little cloud cover and a more
zonal flow in place across Iowa. For Monday night and Tuesday an
upper trough swings across the Northern Plains and into Iowa for
Tuesday through Wednesday. The Euro is not is deep with the trough
while the GFS digs it well into the Plains. Further differences
lie with the models surface features. The GFS develops a low over
Wisconsin with a frontal boundary dragging across the state while
the Euro is slower and develops a surface low over the central
Plains and drops it south. This would put rain more into southwest
Iowa Tuesday night while the GFS develops showers along the front
on Tuesday. In either solution, instability is weak so not really
looking at thunderstorms...just showers.

Both models swing the system through for Wednesday then repeat
the scenario dropping a second trough through the region for
Thursday. There is actually more consensus for the Thursday trough
than the Tuesday one. Given the low confidence still for the
Tuesday system, I kept chance PoPs going for then and would have
went with higher PoPs for Thursday but since it is further out in
time and there may be some impact from the Tuesday system, chance
PoPs were also kept in for Thursday. Friday at this point looks
dry and a little warmer.

Speaking of temps...we remain in a general northwest flow aloft
so while we won`t see unseasonably cold temps...we won`t be
particularly warm either. Normal to slightly below normal is all
we can expect for the foreseeable future.


.AVIATION.../For the 00Z TAFS through 00Z Saturday evening/
Issued at 615 PM CDT Fri Apr 20 2018

VFR conditions expected through the TAF period. Winds to mainly be
from the east to northeast through the period.





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