Area Forecast Discussion
Issued by NWS Des Moines, IA

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048
FXUS63 KDMX 222139
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
339 PM CST Mon Jan 22 2018

.SHORT TERM.../Tonight/
Issued at 339 PM CST Mon Jan 22 2018

The focus was obviously on the ongoing blizzard over
western to northwest portions of the CWA into tonight along with the
transition from rain/wintry mix to snow late this afternoon into the
evening as the deformation zone pushes east across the forecast
area. Utilized a blend of the hires models for timing of precip
tonight.

Surface low centered directly over central Iowa, in fact as of 21z
it was between Polk and Dallas Counties, will continue to track east-
northeast this afternoon and evening. The deformation zone has begun
to pivot more southwest to northeast over western to northwest Iowa.
The strong omega within the dendritic layer looks to begin to
decrease during this pivot period, but still can see up to 1-1.5"
per hour snowfall rates prior to 00z Tuesday. The forcing begins to
wane after 00z as the low continues to pull further east, but the
column does cool considerably and thus the snow ratios increase
slightly. The strong CAA coincides with the snow band moving east
this evening. Winds atop the mixed layer range from 40-45 knots and
with should help quickly transition the rain/wintry mix to snow b/t
00-03z tonight over central portions of the forecast area. Plus,
there is an small enhanced band just east of the blizzard conditions
from around Carroll north to Pocahontas where heavy sleet has been
reported within this band. There is no indication of lightning attm,
but certainly cannot rule out the thundersnow/thundersleet potential
with still negative EPV present this afternoon. This will only
enhance the snow rates for a short period.

Expanded the winter weather advisory further east to incorporate the
DSM metro for the visibility concerns tonight with the deformation
zone and very strong winds. Certainly could impact travel with the
refreeze due to the strong the CAA and provide some very slick
roads. Snow amounts in this location remain around an inch or less.

.LONG TERM.../Tuesday through Monday/
Issued at 339 PM CST Mon Jan 22 2018

Little weather concerns throughout the mid and long range with
mainly quiet and mild conditions expected. Initially Tuesday
expect cloudy conditions as low stratus remains in place behind
the upper level system exiting the region. A weak shortwave to
drop through the state late Tuesday into Tuesday night reinforcing
cloud cover and bringing a quick shot of some light flurries.
Moisture still somewhat limited, so kept the mention to flurries
as the soundings saturate briefly Tuesday night. Otherwise
clearing skies into Wednesday with upper level ridging into
Thursday. Will have moderating temperatures and dry conditions.
Kept temperatures a bit lower than guidance grids across the far
north/northwest where new snowpack is in place. Still have the
upper trough pushing through the region to the north of Iowa by
Friday into Saturday. This will lead to mainly an increase in
clouds with any precipitation chances with this system remaining
across the Dakotas and Minnesota. Given the warming temperatures
expected through the end of the week and into the weekend, snow
melt runoff across the north will be of concern with the high
moisture content of the snowfall earlier today. Therefore will
have to monitor rivers especially in the north/northwest portions
of the forecast area by late week into the weekend for
rises/possible flooding and ice jams. Mainly zonal flow continues
across the central US into early next week which will keep mainly
dry conditions across the state. Temperatures to remain near or
above the seasonal averages into Monday.

&&

.AVIATION.../For the 18Z TAFS through 18Z Tuesday afternoon/
Issued at 1136 AM CST Mon Jan 22 2018

Tricky aviation forecast today with large storm system and center
of sfc low pressure moving across the area. Warmer air portion of
the system impacting KALO, KDSM and KOTM with some dry periods
this afternoon and showers developing across the area by mid/late
afternoon. As cold air moves in this evening into the overnight
hours could see a wintry mix/light snow before precipitation
tapers off completely. Winds to become gusty and northwesterly by
late in the period. Further north at KFOD and KMCW, both sites on
the edge of the wintry precip and still expect a dry period this
afternoon before more mixed/frozen precipitation moves back in
late this afternoon into this evening. Winds to become gusty out
of the northwest as well. Winds to begin to diminish toward
sunrise Tuesday with low stratus remaining in place. CIGS mainly
LIFR to IFR across much of the area, some pockets of VFR in the
south/east initially with everything trending down to IFR/LIFR
tonight.


&&

.DMX WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until midnight CST tonight for IAZ017-
025-026-035>037-045>048-057>060-070>072.

Blizzard Warning until midnight CST tonight for IAZ004>006-015-
023-033-044.

Winter Storm Warning until midnight CST tonight for IAZ007-016-
024-034.

&&

$$

SHORT TERM...Podrazik
LONG TERM...Beerends
AVIATION...Beerends



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