Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 012355
AFDDMX

AREA FORECAST DISCUSSION
National Weather Service Des Moines IA
555 PM CST Thu Dec 1 2016

.SHORT TERM.../Tonight through Friday/
Issued at 237 PM CST Thu Dec 1 2016

Broad cyclonic flow to continue over Iowa tonight into Friday as the
upper low continues to spin off to the northeast. A deep trough
will begin to establish itself across the desert southwest with
ridging building in from the southern plains into the upper
midwest. The result will be a slow lifting of ceilings with some
clearing across the far South of Friday. Temperatures tonight will
not be as cold as some of the model guidance was suggesting due
to the cloud cover so lows were nudged up in most places...except
the Nish valley and lower areas. Highs on Friday will be a bit
trickier depending on where the clouds are and given that we will
still have a northwest wind at the surface. For now warmed temps
about a degree or two except for the south where warmed temps 2
to 4 degrees above guidance. If clouds lift or break up some
further north then temps north of I-80 will need to be raised as
well.

.LONG TERM.../Friday night through Thursday/
Issued at 237 PM CST Thu Dec 1 2016

Little changes through the mid/long range with the main focus on
temperatures and precip chances this weekend and again into the
middle of next week. Large area of high pressure in control to begin
the period Friday night with the sfc high shifting east into
Saturday. Energy continues to eject east/northeastward from the cut-
off upper low across western Mexico. At the same time, expect a
northern stream upper trough to move through the central US. This
energy phases some into late Saturday/Sunday which will bring
chances for precipitation to portions of the CWA Saturday night into
Sunday. Some question as to how far north and west the moisture will
push, this pops across the northern and western CWA have been
reduced some especially Saturday night. Kept the highest pops across
the far southeast with only chance pops at this time. Some
uncertainty with the thermal profile as well. Have warmed
temps/dewpoints across the south as latest soundings indicating snow
on the gfs and rain with the nam. Therefore wanted more of a mix of
rain/snow mentioned, and cut down any accumulations as well. Even
though previous forecast only calling for around half an inch, have
dialed it back to around a tenth or two. Any lingering precip into
Sunday should switch over to all rain late Sunday morning, with
precip expected to push east of the CWA by Sunday afternoon.

Cut-off to the southwest finally progresses eastward as a large
upper level trough digs into the intermountain west toward early
next week. Some energy also getting shoved eastward into the central
US toward Tuesday. This will bring cloudiness and set up a
baroclinic zone across the state and could bring some very light
precip Monday night. Broad western US upper trough then moves east
into mid to late week with a strong cold front dropping through the
state. This will send h85 temps into the teens below zero Celsius
and set up intermittent chances of light precipitation. Could see
initially a mix of rain/snow, with precip then changing over to all
snow with the push of colder air. Temps expected to drop well below
average at the end of the period with highs in the 20s expected by
Thursday.

&&

.AVIATION.../For the 00Z TAFS through 00Z Friday evening/
Issued at 554 PM CST Thu Dec 1 2016

There is fairly high confidence that little change will occur
through the nighttime hours with steady MVFR ceilings either side
of 2K ft. Confidence decreases some into Fri however with some
potential for pockets of VFR. Will keep MVFR going however with
changes not likely until IA escapes the broad cyclonic low level
flow.

&&

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

&&

$$

SHORT TERM...FAB
LONG TERM...Beerends
AVIATION...Small



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