Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 090922
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
322 AM CST Sat Dec 9 2017

.SHORT TERM.../Today through Tonight/
Issued at 322 AM CST Sat Dec 9 2017

Cold front moving through the state this morning and winds have
begun to gust across the northern half of the CWA. A few gusts
over 30 knots through 12z seem reasonable with a decent punch of
PV across the east to northeast portions of the forecast area.
Winds atop the mix layer generally range from 30-35 knots before
gradually decreasing past 12z this morning. By this afternoon they
range from 20-25 knots. Thus, the strongest winds will be early
this morning but still looking at a brisk day across central Iowa.
Low stratus across the north to northeast may linger through the
morning hours and there may be a few flurries prior to 12z this
morning. Once this cloud deck moves east, mid to high clouds look
to push into the same area towards the afternoon and into the
evening. Have increased cloud cover during this period across the
northeast. Went slightly below MOS guidance today for max
temperatures with the sporadic cloud cover this morning and decent
CAA throughout the day.

.LONG TERM.../Sunday through Friday/
Issued at 322 AM CST Sat Dec 9 2017

Deep northwest flow will continue for much of the longer term
across the central United States although with some flattening of
the pattern toward the end of the period. A surface trof will have
just pushed through the forecast area at the beginning of the
period but thermal advection will generally be neutral for much
of the day. However, as the next wave approaches Sunday night,
stronger warm advection will develop across the state with a
thermal ridge crossing the forecast area on early Monday morning.
Decent isentropic lift will also lead to cloudiness with the warm
advection overnight, however pressure deficits remain high enough
that precipitation appears unlikely across the forecast area.

Surface cold front will pass through the forecast area on Monday
morning with strong cold advection developing during the day. The
cold advection combined with the decent pressure gradient and
subsidence will lead to windy conditions on Monday with near
advisory winds. Soundings indicate a shallow mixed layer during
the day with winds of 40-45kts at the top of the layer and will
continue to highlight the potential of the strong winds in the HWO
for Monday. Another wave will approach later Wednesday into early
Thursday with another up and down ride with temperatures during
this time. The flow begins to flatten somewhat toward next weekend
with warmer temperatures as modified Pacific air pushes into the
state. Precipitation chances will remain relatively limited during
this time with a general absence of deeper moisture.

&&

.AVIATION.../For the 06Z TAFS through 06Z Saturday night/
Issued at 1142 PM CST Fri Dec 8 2017

Main concerns this forecast continue to be winds and cloud cover.
A front currently over southern Minnesota will sweep through the
state overnight with gusty winds from the northwest following
behind it. Wind gusts up to around 30 knots will be possible,
especially at the northern terminals. Highest confidence in MVFR
ceilings are over the eastern terminals, namely KMCW and KALO.
Extrapolating current infrared satellite imagery over the next few
hours shows these sites most likely to have MVFR conditions with
KFOD and KDSM on the fringe of the stratus clouds. With both of
these latter sites, ceilings may bounce between MVFR and VFR
conditions. Ceilings will improve into VFR conditions by late
morning at all sites with VFR conditions prevailing through the
end of the TAF period with winds decreasing by Saturday evening.

&&

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

&&

$$

SHORT TERM...Podrazik
LONG TERM...Cogil
AVIATION...Ansorge



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