FXUS63 KDMX 170545

Area Forecast Discussion
National Weather Service Des Moines IA
1145 PM CST Sat Nov 16 2019

...Updated Aviation Discussion...

.DISCUSSION.../Tonight through Saturday/
Issued at 301 PM CST Sat Nov 16 2019

Combination of partial sunshine and strong mixing have led to warm
temperatures this afternoon. As sunset approaches, the winds are
forecast to weaken as mixing diminishes and the gradient begins to
also slacken with the approach of the surface trof. Clouds will
thicken into the evening as lift steadily increases. However, the
relatively dry airmass will limit clouds to mid and high levels
initially. Continued forcing into tonight will eventually lead to
saturation through the column right ahead of the boundary.
Soundings indicate primarily rain with the low levels barely above
freezing over the bottom few thousand feet. This should be enough
to keep precipitation liquid ahead of the front. However, the
cold air is somewhat deeper in the far northeast toward daybreak
and there may be some rain/snow mix but not expecting much of any
accumulations. The precipitation will linger in the south and east
during the morning, but increasing subsidence and drier air will
end the threat by midday across the forecast area as cold
advection continues.

By Sunday night, warm advection begins almost immediately in the
evening ahead of the next shortwave dropping through the northern
Plains. This continues into Monday with a modest rebound in
temperatures albeit muted somewhat by clouds over the state. There
may be some sprinkle or light showers across the north during the
day as well, but any precipitation is forecast to remain light as
moisture remains limited. This system is quite weak with almost no
push of any cold air on the backside. In fact, warm advection
essentially remains in place as a more robust upper low enters the
southwest United States. There continues to be disagreement in the
handling of the system with the operational GFS bringing the
system through Iowa with a significant amount of precipitation.
The operational run does continue to be on the high end of the
GEFS output across the state suggesting the more southern Euro
track may be a bit more reasonable for a solution. Both solutions
would produce precipitation across central Iowa on Wednesday night
with strong moisture advection into the state. As cold advection
increases late that night, some transition to snow is expected on
the northwest edge of the precipitation shield but to what extent
remains unknown given the differences in the model runs. At this
point, accumulations would be relatively light but will continue
to monitor closely. Thereafter, the roller-coaster of temperatures
persist into next weekend with shortwaves dropping southeast into
the region from Canada.


.AVIATION.../For the 06Z TAFS through 06Z Sunday night/
Issued at 1135 PM CST Sat Nov 16 2019

Rain still anticipated to move across the state overnight into
Sunday morning. Ceilings upstream haven`t quite lowered yet to IFR
conditions but models remain on track to lowering ceilings to
around 1000 feet or slightly less by 12-15z Sunday. Then fairly
high confidence to see MVFR ceilings for much of the day Sunday
into Sunday evening.






NWS DMX Office Area Forecast Discussion