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Area forecast discussion 
National Weather Service Des Moines Iowa
1144 am CST Friday Feb 12 2016

Short term /today/...
issued at 324 am CST Friday Feb 12 2016

A number of changes today may lead to some impactful conditions as
we move through the afternoon hours...and into tonight. The Thursday
clipper system is all but south of the state now with attention
turning to Great Lakes and northern plains. Subjective surface analysis
at 04z shows Arctic boundary from near Duluth to St cloud Minnesota
with Arctic high over southern Manitoba. Isolated to scattered
flurries are accompanying the boundary over Minnesota and northern Iowa early
this morning. Aloft...supporting short wave at h850 and associated
cold front separates cold h850 temperatures from deeper Arctic air now
situated over Hudson Bay Canada. With the front expected to enter
the forecast area today...it will buckle just east enough to spare
the region from the coldest portion of the airmass...taking air at
the Great Lakes and New England through the weekend. However
temperatures will be sufficiently cold to bring some subzero lows to
much of the region tonight. Winds aloft will gradually increase
today as the high builds south and lapse rates steepen this
afternoon. This will result in mixing and stronger winds/wind gusts
during the afternoon hours. Models including the hires show
subsidence and clearing line broadening across the area from 14z to
19z from north to south respectively. This will promote sunshine to
return to the area through the afternoon hours. With cold air
advection...afternoon highs and wind chills will remain cold despite
the sunshine. By late afternoon wind chills over the north will be
approaching -20f. As well...the recent two light snow events over
the region produced rather dry snow which will be easily blown by
the gusty winds this afternoon and evening. For now...headlines will
not be issued...but a Special Weather Statement may be required
throughout the day to address the potential for blowing snow and
reduced wind chills. Tonight wind chills will continue to drop to
advisory criteria for much of the north half.

Long term /tonight through Thursday/...
issued at 324 am CST Friday Feb 12 2016

A few items to focus on throughout the extended...with the first
being the cold temperatures tonight into early Saturday. Cold Arctic
high to build in with 850 mb temperatures dropping to around -15c aloft...with
diminishing winds and clear skies overnight. This will send temperatures
falling to below zero across the majority of the County Warning Area by Saturday
morning. Additionally wind chill swill fall to around 10 below to 30
below across the County Warning Area. Therefore for areas with wind chill values
below 20 below tonight into early Saturday...will be issuing a Wind
Chill Advisory.

High pressure to slide off to the east Saturday...with warm air advection/return
flow expected to set up into Sunday night. Decent lift with the
warm air advection...but amount of moisture will be more of the issue for snowfall
potential late Saturday afternoon into early Sunday morning. NAM/GFS
most bullish with this system...while the ec/Gem indicate drier air
and less impressive with the system. Therefore did increase probability of precipitation
toward the northwestern portion of the County Warning Area where deeper saturation
expected and still should see a period of light snow across much of
the County Warning Area overnight Saturday. Shortwave trough digging east
southeastward Sunday to swing a bit further north and more or less
clip the northern County Warning Area. Therefore cut back on probability of precipitation across the
south/western County Warning Area for Sunday and amounts as well. Hit the northeast
hardest which still looks to get around 2 to 5 inches of snow from
Saturday night through late Sunday afternoon. Areas across central
Iowa may see around an inch or two with amounts less than an inch
across the southwest. Some gustier winds expected Sunday with the
system moving through and tightened surface pressure gradient...therefore
did include a mention of patchy blowing snow as well across the
northern County Warning Area Sunday.

Temperatures to warm into Monday to near the seasonal averages with
a brief cool shot keeping temperatures near the seasonal averages or
slightly below into Tuesday and Wednesday before the Big Warm-up
into the end of the week. 850 mb temperatures expected to climb to +10c to
+15c by Friday as upper ridging builds into the central US.
Therefore expect temperatures to climb well above average into the 30s and
40s Thursday and could see middle to upper 50s across the southern
third of the County Warning Area by the end of the week.

&&

Aviation...12/18z
issued at 1143 am CST Friday Feb 12 2016

A strong push of cold air will keep north to northwest wind at 20g30kts across
taf locations through 00z. Ceilings will gradually become VFR but local
MVFR visibilities possible in blsn. After 00z winds will decrease some and
lose the gustiness across Iowa. After 15z the wind will become
southeasterly and with the warm advection...a middle level ceiling will
develop across taf locations.

&&

Dmx watches/warnings/advisories...
Wind Chill Advisory from 6 PM this evening to 8 am CST Saturday
for Black Hawk-Boone-Bremer-Butler-Calhoun-Cerro Gordo-Emmet-
Franklin-Greene-Grundy-Hamilton-Hancock-Hardin-Humboldt-Kossuth-
Marshall-Palo Alto-Pocahontas-story-Tama-Webster-Winnebago-Worth-
Wright.

&&

$$

Short term...rev
long term...beerends
aviation...fab

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