Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 051140
AFDDMX

AREA FORECAST DISCUSSION
National Weather Service Des Moines IA
540 AM CST Mon Dec 5 2016

.SHORT TERM.../Today through Tonight/
Issued at 306 AM CST Mon Dec 5 2016

Status field continues to linger just east of the forecast area
overnight with a narrow ribbon of fog on backside of status in the
eastern forecast area.  The fog has been locally dense at times with
visibilities below one quarter of a mile from time to time.
Visibilities have been jumping around at locations and with higher
clouds beginning to stream overhead, not sure the fog will be as
thick over the next few hours.  Will continue to monitor for
possible advisory and will issues an SPS to highlight the areas of
concern.  Otherwise, warm advection continues through the day as
thermal ridging builds to the state.  Strong south to southwest
winds are expected into the afternoon ahead of an approaching cold
front.  Temperatures will climb quickly with the strong mixing
occurring although clouds moving overhead will limit how warm it
will get overall.  Readings will still be well above normal with
highs in the 40s in most locations although have tempered the
readings a bit in the far east where melting snow cover will limit
the heating a bit.  Will see mid level forcing increase across the
north this afternoon with the approach of the front and a few
showers will be possible by late in the day into the evening with
the front as it swings through the state.  However, moisture is
quite limited, therefore only isolated to scattered coverage is
expected across the north as the boundary pushes through the state.
Much colder air will arrive later tonight with increasing northwest
winds signaling the beginning of a much colder airmass for the
upcoming work week.

.LONG TERM.../Tuesday through Sunday/
Issued at 306 AM CST Mon Dec 5 2016

Overall a fairly quiet mid/long range with some spotty chances for
light snow and main focus on temperatures with a surge of cold air
expected into the state. A broad upper level trough to dig into the
western/central US into Tuesday with the first upper level system to
deepen and move through the northern plains into Ontario Tuesday
into early Wednesday. Much colder air will push into the state
behind this system with H85 temps dropping to around -10C Tuesday.
Another batch of energy to dig into the Rockies and begin to eject
eastward cutting through southern Iowa Wednesday into Wednesday
night. This may bring some light snow to the far southern CWA with
maybe a dusting of snow expected. Dry conditions are then in store
for Thursday into Friday with brief upper level ridging in place
across the state. The next larger system is set to eject eastward
from the Rockies into next weekend with another chance for some
light snow, with the greatest chances currently looking across the
northern half of the CWA with near zonal flow across the CWA
Saturday into Sunday.

A chilly start to the mid range as the first push of arctic air
moves into the state for mid-week and should see high temps in the
teens and 20s for Wednesday and down to the teens for Thursday as a
reinforcing shot of cold air moves in. Overnight lows in the single
digits and teens are also expected. Did lower guidance grids in the
areas prone to cold climatologically such as the far north and the
Nish Valley areas. Cold air aloft begins to moderate into the end of
the week/weekend with the brief upper ridging moving in aloft and a
weak thermal ridge building in as well. This should allow for some
warming, however temperatures are still expected to stay below
the seasonal averages through the weekend into early next week.

&&

.AVIATION.../For the 12Z TAFS through 12Z Tuesday morning/
Issued at 540 AM CST Mon Dec 5 2016

Areas of dense fog will persist through mid morning east of a
KLWD-KDSM-KMCW line with surface visibilities under one quarter of
a mile. After sunrise, surface winds will increase rapidly this
morning from the south with the fog burning off after 15Z with VFR
conditions becoming widespread. Cold front will pass through the
state tonight with isolated to scattered rain and snow showers in
northern Iowa with a brief period of MVFR ceilings in the north.
Winds will become west to northwest by end of period at all sites
behind the front.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Dense Fog Advisory until 9 AM CST this morning for IAZ028-038-
039-049-050-061-062-074-075-084>086-094>097.

&&

$$

SHORT TERM...Cogil
LONG TERM...Beerends
AVIATION...Cogil



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