Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 200951

National Weather Service Des Moines IA
351 AM CST Fri Jan 20 2017

.SHORT TERM.../Today through Tonight/
Issued at 351 AM CST Fri Jan 20 2017

Shortwave train in full effect with the tracks being near to the
40th parallel. Three waves to impact Iowa through the weekend...with
the first two impacting Iowa in this short-term AFD.

Fog potential...
Confidence: Medium-High

09z Water vapor imagery shows shortwave 1 stretching from northern
Illinois back into eastern MN. Similar to yesterday morning, fairly
dense fog ongoing as this shortwave has reinforced moisture across
the region. Overall airmass has remained unchanged, with Bufkit
soundings showing decoupled boundary layer and low to moderate
shear. Warm advection from the south to pick up this evening once
again, so fog will likely occur once again tonight once insolation
processes stop.

Rain potential...
Confidence: High

As shortwave 1 moves north of the area, shortwave 2...located NE of
the Four Corners region of the SW will ride the tracks northeastward
through western Iowa. As mentioned above, this low will bring in
another reinforcing shot of moisture. Confidence in precip is high,
especially after 00z Sat as a well-defined warm front will serve as
a focusing mechanism for ascent. QG frontogenetical forcing picked
up all the way to 700mb as the boundary moves northward through the
CWA, nearing the NE portion of the DMX CWA by 09z Sat, and the core
of the shortwave itself making it to western IA by 12z Sat. QPF may
need to be increased if anything...and fog headlines cannot be ruled
out...especially across eastern IA.

.LONG TERM.../Saturday through Thursday/
Issued at 351 AM CST Fri Jan 20 2017

System will be exiting north into Minnesota on Saturday morning
with bulk of rainfall. Will still see some threat of light
rain/drizzle in the north during the morning, but forcing will be
waning through midday as the system departs. Have continued the
threat of fog into Saturday morning as well as moist airmass will
continue to advect across the state. With the departure of the
system to the north, there will be little threat of precipitation
from late Saturday through Monday as the next system remains well
south of the state in the Gulf Coast states. Temperatures will
continue to remain above normal during this time with polar air
holding well north into Canada.

Attention will then focus on system expected to arrive on Tuesday
and persist into early Wednesday. GFS solution is farther north
than Euro and GFS ensembles mean even a bit farther north than the
deterministic run. This would take the bulk of forcing and
precipitation across northern Iowa and Minnesota. The Euro
solution remains farther south but the trends in both models are
to the north. Have continued high pops on Tuesday into Wednesday
but shifted them slightly northward given the recent model trends.
This would also allow warmer air across much of the state keeping
mainly rain from Highway 20 on south with snow in the far north.
Still plenty of time for changes as system remains well of the
Pacific coast at this point. In the wake of the system,
temperatures will drop to more normal levels with drier conditions
for the end of the next work week.


.AVIATION.../For the 06Z TAFS through 06Z Friday night/
Issued at 1140 PM CST Thu Jan 19 2017

All TAF locations will remain mired in LIFR/IFR stratus and fog with
only slight improvement during the early to mid afternoon period of
Friday. Towards 20/00Z the next shortwave will approach bringing
back lower cigs and increasing chances for precip.  The precip may
actually scour out some of the lower vsbys but cigs will keep
IFR conditions in place.


Dense Fog Advisory until 10 AM CST this morning for IAZ004>007-



SHORT TERM...Kotenberg
AVIATION...FAB is the U.S. government's official web portal to all federal, state and local government web resources and services.