Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 262139

National Weather Service Des Moines IA
339 PM CST Sat Nov 26 2016

.SHORT TERM.../Tonight through Sunday/
Issued at 339 PM CST Sat Nov 26 2016

Few concerns through tonight and generally through period other than
timing of onset of precipitation and then eventual thunder. Tonight
will see continued push of high clouds toward the region as upper
level trough and upper level jet energy approaches by 12z Sunday.
With warmer thickness overnight expect lows to once again remain
mild for this time of the year. Guidance quite low northeast and
light southwest flow...expect to see readings nearer last nights
mins instead of projected low have raised mins
there and across the area a degree or two. Next challenge will be
timing of onset of rain Sunday as well as initial coverage of
thunder. Strong push of thetae advection will move into southwest
sections between 10-13z...initially encountering dry air aloft but
then quickly saturating over the 3 hour period. The same process
will occur over the remainder of the area through the daytime hours
with categorical precipitation chances by early afternoon from
central back to southwest Iowa. Between 21z and 00z Monday the
remainder of the forecast area will fill in as the forcing rapidly
moves northeast. Looking at most of the available data today for
possibility of thunder...and both GFS Bufr soundings as well as
Euro data strongly suggest that saturation of column will cool the
soundings enough to keep thunder out of the picture until at
least late afternoon and only over the southwest. GEFS plumes also
support little if any thunder until 03-15z period as warm sector
lifts northeast. As the dry line approaches between 06 and 12z a
better opportunity for thunder will occur overnight as warmer air
leads to some elevated instability. Highs Sunday will be highly
dependent upon surface warm air advection streaming northeast with
the strong south southwest winds during the afternoon hours. Will
maintain mid 50s over the south and upper 40s to near 50 in the
north where rain will hold on longer through the day. By mid to
late afternoon the rain is likely to become a bit less prevalent
over the far southwest though still bordering on likely. There
should be a period of lesser rainfall in the evening hours as the
front/thetae push moves east northeast.

.LONG TERM.../Sunday night through Saturday/
Issued at 339 PM CST Sat Nov 26 2016

Widespread showers and a few thunderstorms will be ongoing across
the northeast at the beginning of the period with isolated/scattered
showers in central and southern IA. With the bulk of moisture
transport lifting into Minnesota and Wisconsin during the evening,
most of the widespread precipitation will come to an by midnight.
However, some residual mid-level forcing will persist during the
night to maintain some threat of isolated to scattered shower
after midnight, especially east of the I35 corridor. Have also
continued the isold thunderstorm wording in the east as well as
weak instability will persist. Temperatures will also remain quite
warm on Sunday night with southerly flow continuing and may be
close to max minimums in places.

Upper low will sit and spin across the upper Midwest through the
middle of the week before eventually shifting to the east by the
end of the work week. Temperatures will remain well above normal
into Monday before the cold advection intensifies late in the day.
Temperatures will cool into Tuesday and Wednesday as colder air
wraps around the system with thermal trof eventually building from
the Plains and into western Iowa. This will drop readings to much
more normal levels by midweek. Lift associated with the upper low
will be grazing northern Iowa as well with on and off chances of
light rain/snow, but any amounts will be very light. Dry
conditions will return by the later half of the work week although
temperatures will remain relatively cooler.


.AVIATION.../For the 18Z TAFS through 18Z Sunday afternoon/
Issued at 1150 AM CST Sat Nov 26 2016

Main concern this afternoon is increased wind through 23z then
diminishing. High clouds will remain over region with approaching
trough/storm Sunday. Otherwise near the end of the period from
16-18z Sunday expecting cigs to lower to MVFR at KFOD and quickly
drop around 18z at KDSM. Will see continue trend of poorer
conditions from 11/27 18z to 11/28 00z as main forcing arrives
with showers and IFR conditions developing during that time. /rev





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