Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 161731
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1131 AM CST Thu Nov 16 2017

.SHORT TERM.../Today through Tonight/
Issued at 359 AM CST Thu Nov 16 2017

Stratus has expanded across northern Iowa and continues to sink
gradually south with the light north flow. This drift will
continue through sunrise before winds shift to a more southerly
direction with the passage of the surface ridge. In the meantime,
have increased the cloud coverage over the north through the
morning as the stratus should linger, especially given the
climatological favorability. Otherwise, warm advection will
intensify today on the backside of the surface ridge with
strengthening southeast surface winds. Have seen expanding mid to
high clouds in northern Nebraska/southern SD early this morning
where the mid level warm advection is quite good. These clouds
will expand into northern half of Iowa today but relatively dry
low levels will preclude any precipitation. Temperatures in the
north will be limited by the clouds, topping out in the upper 30s
to near 50 in the far southwest where some sunshine is expected.

The warm advection continues into tonight with the arrival of low
level moisture late. This moisture will be accompanied by an
expanding deck of low clouds which should move rapidly northeast
into and across the state by Friday morning. As the clouds arrive,
temperatures will likely level off overnight and become steady or
even rise in a few locations.

.LONG TERM.../Friday through Wednesday/
Issued at 359 AM CST Thu Nov 16 2017

The low clouds and warm advection will continue into Friday ahead
of an approaching boundary. Soundings indicate the low level
moisture will deepen to around 3-5kft which should be sufficient
for some drizzle development by mid to late morning in most
locations. Drier air aloft should limit any hopes of heavier
precipitation until after frontal passage. The southerly flow will
ensure that highs on Friday will be relatively warm for this time
of year. Fropa is expected on Friday evening across most of the
forecast area with increasing cold advection. This system will be
deepening with time with a tightening pressure gradient. Winds
should be quite brisk by Saturday morning and even continue to
increase through midday with the strong cold advection and decent
pressure gradient. The sustained winds and gusts may approach
advisory criteria during this time and will need to monitor but no
action is required as of yet. Otherwise, after the frontal
passage, saturation deepens with the arrival of the upper system.
The increased lift associated with the strong mid level forcing
should eventually be sufficient for light rain across much of
central Iowa by late Friday night into early Saturday morning
before the system races east of the state. Therefore, highest pops
continue late Friday night into Saturday morning. Cold air may be
deep enough on the northern edge for some transition to snow, but
at this point it doesn`t appear to be problematic.

The forecast beyond this system appears relatively quiet for the
upcoming Thanksgiving holiday week. Temperatures will warm quickly
into Monday before another front on Monday night send readings
down into Tuesday. Warmer readings appear likely into the later
half of the work week along with little threat of precipitation at
this time.

&&

.AVIATION.../For the 18Z TAFS through 18Z Friday afternoon/
Issued at 1108 AM CST Thu Nov 16 2017

Stratus deck over much of northern and eastern Iowa retreats
northward the afternoon. This will eventually lead to improving
conditions at KFOD, KMCW, and KALO. VFR is likely across the area
this evening and into the overnight hours before our next round of
low cigs and visbys begins to move in from the south by Friday
morning. High confidence in MVFR or lower cigs expanding north
after 10z. Drizzle may begin to develop after 14z, however
confidence is lower with respect to the spatial extent and it`s
impact on visibility. Left most sites at 4sm for now, but this may
shift once there is a better handle on forecast trends.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Cogil
LONG TERM...Cogil
AVIATION...Martin



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