National Weather Service Raw Text Product

Displaying AFOS PIL: AFDDMX Received: 2018-02-09 06:01 UTC

FXUS63 KDMX 090601

Area Forecast Discussion
National Weather Service Des Moines IA
1201 AM CST Fri Feb 9 2018

.SHORT TERM.../Tonight through Friday/
Issued at 334 PM CST Thu Feb 8 2018

Still online for significant snow event across northern Iowa 
overnight as system passes through the upper Midwest.  Strong 
isentropic lift has moved into the state this afternoon and is 
currently producing snowfall across the northern half of the state. 
Have seen good amount of dendrites with the snow and picked up a 
quick 0.8" at this office through 3PM and reports of around 2" near 
Churdan.  This axis will be shifting configuration from NW-SE axis 
to more of an W-E the next few hours.  This should keep the bulk of 
precipitation into this evening along and north of Highway 30. 
Eventually stronger mid level forcing associated with the shortwave 
will arrive later this evening with another round of relatively 
intense lift.  Cross sections show relatively weak static stability 
across central/northern Iowa which will aid in lift.  In fact, some 
upright instability was noted with the equivalent potential 
temperature surface folding over on themselves.  Banded snow is 
likely if not one intense band somewhere near the Highway 20/30 
corridor.  Anticipate a rather quick decrease in conditions with any 
northward travel to the north of I80 tonight.  The upgrade to 
warning also appears in line with 5-7 inches likely in those areas. 
Surrounding these areas the advisory will also remain in place with 
amounts of 3-6 inches in northern Iowa and 2-5 on the southern edge, 
although anticipate a very rapid drop off in amounts to the south.  

Forcing will become progressive late tonight with the approach of 
the shortwave and lift will drop southward.  The overall lift will 
also be decreasing with dynamics shifting eastward with the upper 
system.  Snowfall rates will begin to slowly diminish by daybreak 
with areal coverage also decreasing.  However, with snow occurring 
just before or during the early portions of the commute, difficult 
travel conditions are expected in the headline areas.  

Lingering lift will persist into Friday with some snow continuing 
but with drier air arriving and the passage of the shortwave, the 
snow should decrease through the morning.  However, some very weak 
forcing will exist across the southern half of Iowa into the 
afternoon and may be sufficient for some additional light flurries 
or even some freezing drizzle with some drier air at mid levels and 
loss of ice introduction at times.

.LONG TERM.../Friday night through Thursday/
Issued at 334 PM CST Thu Feb 8 2018

Friday night...the next short wave pushes through Friday night into 
Saturday but by this time the cold front is well into Missouri. 
Models show the forcing into central Missouri but mid levels still 
have some across southern Iowa and as such, we will see another 
potential for snow mainly across southern Iowa but some very light 
snow still possible as far north as the I-80 corridor.  This will 
not be on the magnitude of the snow earlier Friday but we will still 
see around 2 to 3 inches for the far south.  

On Saturday/Saturday night another deep trough sweeps the region 
with surface high pressure in place over Iowa.  This system will be 
impacting areas further south and Iowa should be mainly dry but we 
will be cold.  As the trough exits, it may bring some light snow 
into far southeast Iowa but for the most part, this will be 
negligible.  Beyond Sunday, a system digs deep into the southwest 
U.S. buckling the flow over the central Plains/Upper Midwest and 
brining warmer temps back to the region and we should finally get a 
break from the snow.  For the most part we will be dry through at 
least Wednesday in the extended.  A couple of caveats would be a a 
weak impulse riding through the flow that may bring light snow or 
flurries north Tuesday morning.  The GFS wants to bring a system 
through in the Wednesday/Thursday timeframe but the Euro is dry so 
with model discrepancy that far out, I left model blended solutions 
in the forecast for now.


.AVIATION.../For the 06Z TAFS through 06Z Friday night/
Issued at 1201 AM CST Thu Feb 8 2018

Low CIGS and VSBYS with the snow across the northern TAF sites to
continue through the overnight hours. Snow to being to taper off
from north to south toward sunrise into early Friday morning. Snow
then to move south toward late Friday. Some VFR periods expected
across the north, with clouds moving back in late. Winds to be
northerly and increase through the critical taf period. 


Winter Weather Advisory until 9 AM CST Friday for IAZ044-057>062-

Winter Storm Warning until 9 AM CST Friday for IAZ023>028-

Winter Weather Advisory until 6 AM CST Friday for IAZ004>007-