Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 192037

Area Forecast Discussion
National Weather Service Des Moines IA
337 PM CDT Thu Apr 19 2018

.SHORT TERM.../Tonight through Friday/
Issued at 337 PM CDT Thu Apr 19 2018

Surface ridge in southern Minnesota will drift very slowly
southeast into Iowa tonight. Associated deep layer dry air and
subsidence will provide cloudless skies overnight along with light
winds. Concern is that melting snow today will add moisture to the
near surface layer. With good radiational cooling tonight, there
is likely to be at least some fog development in and near the
snowpack areas and have continued the mention in the zones. In
addition, lows will be near record levels once again and will
also continue to mention this as well.

Quiet weather will persist into Friday, although with large low
across the southern Rockies, will begin to see some high clouds
overspread the area as warm advection commences. Temperatures will
be slightly warmer although with some loss of sunshine by
afternoon, especially west, it will be hard pressed to get too much
warmer than today.

.LONG TERM.../Friday night through Thursday/
Issued at 337 PM CDT Thu Apr 19 2018

The upper low will pass from the southern Rockies into the
southern Plains/southern Mississippi River valley by Sunday
morning. Iowa will be on the northern fringe of this system with
lift increasing late Friday night into Saturday. While there is
decent saturation through the mid levels, low levels remain quite
dry with dry easterly flow. This will prevent much in the way of
precipitation from reaching the ground with mostly virga
through Saturday although an errant sprinkle or isolated shower
remains possible. Clouds and some evaporative cooling will keep
temperatures in check on Saturday and may actually be a few
degrees cooler than Friday. The influence of this system will wane
on Sunday with a modest thermal ridge building into the state by
Monday. Temperatures are expected to rebound with 50s and 60s in
most locations by Monday afternoon.

The next system will approach later Tuesday into Tuesday night
which will be the next best threat of precipitation. It appears to
be mostly a rain event with only light amounts as the Gulf will be
mostly out of play for this system. Temperatures will cool into
the middle of next week behind this system with rain chances
ending into midweek.


.AVIATION.../For the 18Z TAFS through 18Z Friday afternoon/
Issued at 337 PM CDT Thu Apr 19 2018

Main concern with aviation will be overnight into Friday morning
with snowmelt adding low level moisture to the near surface
atmosphere. This may lead to the development of fog in and near
the snowfield overnight given the light winds and clear skies.
Elsewhere, widespread VFR conditions are forecast for the entire
forecast. Winds will be light overnight and become east to
southeast on Friday with a slow increase.





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