FXUS63 KDMX 240523

Area Forecast Discussion
National Weather Service Des Moines IA
1123 PM CST Sun Feb 23 2020

...Updated for 06z Aviation Discussion...

.DISCUSSION.../Tonight through Sunday/
Issued at 313 PM CST Sun Feb 23 2020

Tonight...Tonight will be fairly quiet.  The upper wave and surface
low are both progged to be well south of Iowa and as these both lift
northeast towards 12Z. The result should only be an increase in
low to mid level cloudiness. There may be some very light precip
developing right along the Missouri border towards daybreak but
will not have an impact to any morning commuters. Temperatures
will be cool up north where snowpack remains...with lows in the
teens to lower 20s but further south, lows will be from the mid
20s along highway 20 to the lower 30s south.

Monday...On Monday the low begins to lift into the Great Lakes
and models vary as to how far north the surface low will be. Even
the northern most models only clip the far southeast and the 18Z
model runs are even further southeast than the 12Z runs were. I
have some light qpf as far as the Des Moines metro but low
confidence that we will see anything that far north. Main areas to
see precip will be from Lamoni to Ottumwa and any precip that may
fall as snow in the morning will melt by early afternoon as temps
rise into the mid to maybe upper 30s.

Monday night through Wednesday morning...Monday night a second upper
level system drops through the Plains and quickly lifts northeast
across northern Missouri and southern Iowa into the Great Lakes.
Models hint that some of the energy from this second wave gets
ingested into the departing wave and as it lifts into the Great
Lakes, it may retrograde west.  The precip in the deformation zone
of this system becomes impressive...mainly east of our forecast area
but during the day Tuesday does impact our eastern forecast area.
Snowfall amounts were increased from yesterdays forecast this
morning as were refined some with the latest model runs which take
the higher precip further south.  The result is a swath of 5 to 7
inches from south of Ottumwa to Marshalltown and as far west as
Knoxville.  The metro area does have around 3 inches in the forecast
now as well.  In addition, winds increase to produce blowing and
drifting snow and along the I-80 corridor which will have an
impact on travel. A winter storm watch has been posted for this
area of concern where highest snowfall totals are expected.
Further refining will occur as the system develops but Tuesday
will not be a good travel day given the snowfall and wind. The
snow will taper off Tuesday evening with only light amounts
possible into the overnight but winds will remain brisk with some
potential for drifting snow and bitter cold wind chills as colder
air spills in.

Wednesday afternoon through Thursday evening...By Wednesday
afternoon the upper trough and surface low are well east of the area
and we will be in a northwest flow that will have improving
conditions with diminishing winds. It will however be very cold.
Lows Thursday will be in the single digits and teens across the
state with highs in the teens north to around 30 south.

Thursday night through Sunday...Models differ in this period as to
timing of weak shortwaves dropping through a northwest flow.  The
Euro is a little quicker and further west dropping a weak wave
across northwest into south central Iowa overnight Thursday through
mid Friday morning.  The GFS has a wave further east during this
time then drops a wave through us in the same general area but
Friday afternoon and evening.  The Euro also has a second wave but
this one is further north and east and doesn`t really impact Iowa.
In any event...these have little moisture with them and would be
inconsequential if they did produce any precip.  Although still on
the cool side, temps will be warming through the period with Sunday
the warmest day.


.AVIATION.../For the 06Z TAFS through 06Z Monday night/
Issued at 1122 PM CST Sun Feb 23 2020

Kept with VFR conditions at all non-KOTM sites through TAF period.
Dropped KOTM to MVFR towards the end of the fcst period for mixed
precip beginning. Accumulations, if any, should be very minor.


Winter Storm Watch from late Monday night through late Tuesday
night for IAZ038-039-048>050-060>062-073>075-084>086-095>097.




NWS DMX Office Area Forecast Discussion