Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 280527

National Weather Service Des Moines IA
1127 PM CST Sun Nov 27 2016

.SHORT TERM.../Tonight through Monday/
Issued at 308 PM CST Sun Nov 27 2016

A large, stacked cyclone will move from Nebraska up across eastern
South Dakota overnight, then stall along the North Dakota/Minnesota
border on Monday. A large swath of showers and a few thunderstorms,
associated with the initial surge of moisture advection and vertical
forcing on the leading flank of the cyclone, is crossing our
forecast area at this time and will continue through the evening
before moving off to the northeast. In its wake a relative dry slot
will move in, however, forecast soundings and upstream observations
indicate that a very shallow but persistent saturated layer will
reside beneath the dry slot. Given that this feature will mostly be
moving into our area after dark, climatologically this fits the
model of stratus with some fog and drizzle overnight. Given the
strength of synoptic low-level flow around the nearby cyclone it is
believed that any fog will be light and spotty, so have not
mentioned it in the outgoing forecast. However, did maintain high
sky cover for most of the forecast period along with some lingering
light POPs overnight. On Monday afternoon the cold front trailing
from the departing gyre will finally push across our area. Between
the frontal passage and expected cloud cover, have advertised Monday
high temperatures only a few degrees above morning lows for much of
the area, excepting the southeast where more warming may occur ahead
of the front.

.LONG TERM.../Monday night through Sunday/
Issued at 308 PM CST Sun Nov 27 2016

Monday Night through Friday...Confidence Medium to High

Few major concerns this period given the time of year. Filling
H500 low over the eastern Dakotas will continue to wobble east
southeast in the next 3 to 4 days bringing persistent clouds and
slightly below seasonal high temperatures to the region through
the period. Following the occluded front Monday night the upper
level circulation will spread some clouds and potential for light
rain or snow Tuesday through Thursday Mainly north of US30.
Overall precipitation amounts will be light so any snow that might
fall either during the day or overnight will only bring a dusting
or so at most with less than an inch accumulation expected even
with the best forcing Wednesday. The better chances for any
measurable precipitation will be Wednesday afternoon and evening
as a vort lobe/trough swings through the region as it pinwheels
around the rather dominant upper level low. Later on Thursday as
the upper level features pulls out another vort lobe/boundary will
push southeast on the back side of the low. This should result in
a period of flurries across most of the region. Highs through the
period Thursday through Saturday will remain in the 30s with lows
in the 20s.

Friday Night through Sunday...Confidence Medium

Looking ahead with the Euro...a large H500 hemispheric trough has
been developing over the United States. Upstream energy over the
Pacific and western Canada continues to suggest an expansion of
the trough with time. This would result in overall seasonal to
slightly below normal temperatures with more clouds than sunshine
during the remainder of the extended. Toward the very end of the
extended a high amplitude trough deepens over the lower Mississippi
Valley. A northern stream shortwave is currently slightly faster
in its eastward progression than the southern stream. Though an
area of light snow develops near Iowa between the waves along an
expecting phasing trough appears that the northern and
southern streams are not close enough to fully phase until the
systems reach the New England states. Will monitor for any phase
shifts...should the northern stream slow a bit then there might be
a greater potential for phasing over the Great Plains. At this
point it looks unlikely. The GFS appears to be even faster with
these features which inhibits any large scale storm development...
even over New England.


.AVIATION.../For the 06Z TAFS through 06Z Monday night/
Issued at 1127 PM CST Sun Nov 27 2016

Much of the precip has ended across the area with some drizzle
remaining. IFR CIGS in place and expect them to lift some
overnight with clouds breaking up toward late Monday. Dry slot to
move through later tonight into Monday and may end up with clouds
clearing earlier than expected. Gusty southerly winds expected
through the majority of the period, with winds diminishing and
shifting toward the southwest Monday evening.





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