Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 140834

Area Forecast Discussion
National Weather Service Des Moines IA
334 AM CDT Wed Mar 14 2018

.SHORT TERM.../Today through Tonight/
Issued at 334 AM CDT Wed Mar 14 2018

A cool front currently crossing the Canada/U.S. border into North
Dakota and Minnesota will move southward today, reaching northern
Iowa this afternoon and the Missouri border tonight. This will cause
southwest winds this morning to swing around to north by tonight.
Ahead of the front we will see significant warming today, given warm
air advection and decent mixing along with resplendent sunshine.
This will push temperatures up into the low to mid 60s across much
of Iowa, roughly south of Highway 20 and west of Highway 218.
Further north, up toward the border, temperatures may only peak in
the 40s due to the front moving through before the diurnal peak
heating time. However, the front will be dry and other than the
change in temperature and wind direction there will be no sensible
weather effects. Tonight we will cool down again behind the front,
with lows in the 20s to lower 30s south and mostly clear skies.

.LONG TERM.../Thursday through Tuesday/
Issued at 334 AM CDT Wed Mar 14 2018

Tranquil but cooler conditions will be in place on Thursday with
weak cold advection. Will begin to see the influence of the next
shortwave by late in the day with increasing forcing in the far
southwest and an increase in clouds. This forcing will increase
across the southwest into Thursday night although the GFS and Euro
remain at odds with timing of precipitation into the state. Main
concern will be the strengthening low level easterly flow and the
relatively dry air contained within this flow. Historically in the
spring, this flow has delayed the onset of precipitation or if
precip does make it to the ground, keeps the intensity rather
light. In addition, evaporative cooling will affect precipitation
types and anticipate some very light mixture of sleet/fzra toward
daybreak in the southwest where deeper saturation seems most
likely. Amounts appear quite low and impacts don`t appear very
high at this point.

A better push of moisture northward into the state is expected on
Friday with precipitation spreading north during the day. This
will primarily be a cold rain with surface temperatures in the mid
30s to lower 40s. The discrepancies between the GFS and Euro
continue during this time with GFS farther north with its warm
advection and subsequent QPF field. Confidence into Friday night
remains low as cooling temperatures overnight lead to rain
transitioning to light freezing rain before ending on Saturday
morning. The diurnal range is likely a bit too large and the dry
air aloft in the GFS seems a bit too much and feel that the
freezing rain in the forecast is probably overdone a bit much.
Even with the mention, QPF amounts are not sufficient to cause
much impact and given the warm surfaces overall, not much glazing
is expected should it occur on Friday night. Forcing departs
quickly on Saturday with a relatively quiet weekend.

Next system approaches by early next week with precipitation
spreading into the state on Monday. GFS once again is a bit
farther north than the Euro which has the bulk of forcing and
precip just south of the state. In either case, some light
precipitation is expected at a minimum with rain in the south and
rain or snow in the north before cooler air arrives Monday night
with transition to all snow.


.AVIATION.../For the 06Z TAFS through 06Z Wednesday night/
Issued at 1156 PM CDT Tue Mar 13 2018

VFR conditions will prevail through the forecast period despite a
cold front passing through the state. Winds will increase in the
morning and soundings indicated that near the front there will be a
brief period of LLWS before surface winds increase. This should
mainly impact KFOD.





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