Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 130541

Area Forecast Discussion
National Weather Service Des Moines IA
1141 PM CST Mon Feb 12 2018

...Updated 06Z aviation discussion below...

Issued at 759 PM CST Mon Feb 12 2018

Couple quick updates this evening. First, temperatures after
sunset have cooled rapidly, especially over northeastern Iowa
(e.g. Waterloo has fallen to +1F). A number of other sites have
cooled beyond the forecast low. However, believe temperatures are
probably close to reaching their low point as mid/high level
clouds continue to advect in from the west...and winds will
eventually begin to turn more southeast.

Speaking of clouds, seeing a fair amount of returns on regional
radars. This is all virga, and not expecting anything to reach the
ground tonight per very dry airmass below about 650mb as observed on

Otherwise, forecast in good shape.



.SHORT TERM.../Tonight through Tuesday/
Issued at 334 PM CST Mon Feb 12 2018

Confidence: High

Quiet period will continue next 24 hours though some challenges
persist.  Clouds increasing across the region today in response to
weak warm air advection/return flow over the western Plains.  H850
warm front from an intermountain H850 low over Nevada/Utah at 12z
will continue to produce mid level clouds. Speed max rounding the
trough already ejecting some high level broken to overcast
conditions into the region now.  With cloud cover present this
afternoon...high temperatures have been held down slightly and this
trend will continue tonight. Though everyone will be warmer
overnight due to the cloud cover by about 10 to 15 degrees...the
eastern/northern portions will still likely drop to the single
digits overnight with lower to mid teens across the south. The warm
air advection will continue overnight with overnight temperatures
likely to steady off and rebound some by sunrise...though most of
the warmer air is aloft at this time so rising temperatures will be
limited.  Clouds will begin the day on Tuesday and remain for a good
share of the day with mid level predominating. Tomorrow`s highs will
be the greater challenge...due to snow cover here along with clouds.
Guidance has been split amongst the models the past few days but is
coming into better agreement for Tuesday. The Euro guidance is
higher than either the MET/MAV and may be a bit overdone given the
snow pack across the region.

.LONG TERM.../Tuesday night through Monday/
Issued at 334 PM CST Mon Feb 12 2018

The longer term is essentially quiet for much of this week as the
upper flow flattens allowing warmer air into Iowa. The warm
advection that intensifies on Tuesday will persist into Wednesday
morning with a thermal ridge entering Iowa during the morning.
This should help to support much warmer temperatures into the
middle of the week, albeit hampered by widespread deep snow cover
across Iowa. Guidance has been trying to push readings well into
the 50s with a very robust 59 at DSM from the NAM. There will be
some sunshine and favorable southwest surface winds, however the
snow cover should keep full mixing from being realized along with
much of the solar energy going into melting the snow as opposed to
warming the air. Therefore, have remained on the very low side of
mos guidance and much closer to the consensus blends. There will
be a broad surge of moisture northward toward the state by
Thursday, however this moisture will be kept out of the state by a
cold front pushing south into the state during the day.

Much colder readings are in store by Friday with a relatively
strong thermal trof enters the state. However, this colder weather
will be short lived with warm advection increasing into the
weekend as a large western trof develops. There will be increasing
threats of precipitation as well with moisture streaming back
north toward the Midwest.


.AVIATION.../For the 06Z TAFS through 06Z Tuesday night/
Issued at 1131 PM CST Mon Feb 12 2018

VFR conditions expected the next 24 hours at all terminals.
Mid level clouds continue to filter into the area from the
west...although CIGs should remain above 7k feet. Seeing some
weak returns on radar over Iowa /virga/...but all light snow
at the sfc should remain northwest of KFOD/KMCW. Light e/nely
winds overnight will gradually become southerly into Tuesday.
Could see a few gusts on Tuesday afternoon from 15 to 20 kts.




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