FXUS63 KDMX 182038

Area Forecast Discussion
National Weather Service Des Moines IA
338 PM CDT Mon Mar 18 2019

.SHORT TERM.../Tonight through Tuesday/
Issued at 322 PM CDT Mon Mar 18 2019

High pressure has spread across Iowa through the day, keeping
winds fairly light and variable. While dry air is in place from
the surface through the middle atmosphere, there is enough
moisture aloft for high cirrus to filter across the northwestern
half of the state through the afternoon with daytime cumulus
developing across southeast Iowa. Temperatures have not been
impacted and have climbed into the upper 30s north to upper 40s

Expect cloud cover to increase across the area overnight as a
shortwave across the Dakotas drops south. Increased moisture
transport out of the Gulf will phase with theta-e advection to
induce modest QPF across southern Iowa. Best forcing and moisture
still remains south of the area across Missouri, however a quarter
to half inch of rain is possible with this system. While
precipitation will largely fall as rain, a brief window for snow
exists on the front edge of the system as evaporative cooling acts
to cool the column. Expect minimal to no impact from any frozen
precipitation Tuesday morning before everything quickly switches
over to all snow. There is also the potential for light flurries on
the back side of this system as it exist Wednesday night, however
with very dry behind the system expect that as the column dries,
precip will simply end rather than transition to any type of wintry

.LONG TERM.../Tuesday night through Monday/
Issued at 322 PM CDT Mon Mar 18 2019

Confidence: Medium to High

Weak system expected to pass south of the area by 12z Wednesday with
ridge of high pressure again building into the Northern/Central
Plains. Though the timing is different, both the GFS/Euro show a
trough/cold front dropping south into the region Wednesday. This
should limit any additional warming over the area for about a day;
with similar temperatures expected Wednesday as Tuesday. Though
the front will likely be dry, there will be some mid to high level
clouds accompanying the boundary as it passes south through the
area. With an area of high pressure building over the Northern
Plains from Thursday into Saturday, relatively quiet and
precipitation free conditions are expected. Currently there are
some minor differences in the amount of returning warmer air aloft
between the GFS/Euro. The GFS remains slightly faster than the
Euro with a 2-3C quicker increase in H850 warming by 00z Friday.
The current forecast seems a good compromise between the two
models and generally, with Iowa situated on the backside of a
strong upper level trough, it is possible that another wave may
briefly impact the temperatures aloft for into Thursday afternoon.
The Euro would suggest mid 50s while the GFS would suggest
temperatures closer to 60 by Thursday. Looking ahead to Friday,
additional warming develops across the region ahead of a stronger
shortwave over the southwest. There remain some minor differences
between the GFS/Euro on timing into the weekend. The GFS is
trending on breaking down the ridge a bit faster while the Euro
maintains a stronger ridge over Iowa back northwest into the
Northern Plains. The 12z GFS is now closer to the Euro in terms of
arrival time, with both models bringing the main forcing in after
06z across the region between 06 and 12z. Despite the similarity
in timing, the Euro is initially forecasting a wave faster and
farther south that the GFS but then occludes the system and
lingers it over our forecast area from Saturday night through
about Monday night. Confidence drops with regard to the rainfall
potential and evolution of the storm. Signal for all rain with
some potential for convection if the upper level system tracks
close enough to our area. Temperatures remain mild with highs in
the lower 50s north to the lower 60s from central to south. Lows
generally in the 30s and 40s during the weekend.


.AVIATION.../For the 18Z TAFS through 18Z Tuesday afternoon/
Issued at 1237 PM CDT Mon Mar 18 2019

VFR conditions are expected to persist through the period. Cloud
cover will increase through the overnight with winds becoming
southerly. Chances for rain tomorrow across southern IA impacting
mainly KOTM, and possibly KDSM, however that is just beyond the
end of this period and will be addressed in future updates




SHORT TERM...Hagenhoff
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