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Area forecast discussion 
National Weather Service Des Moines Iowa
725 am CST Sat Dec 27 2014

issued at 328 am CST Sat Dec 27 2014

Low pressure moving into Wisconsin will be northeast of the Great
Lakes by tonight. Weak high pressure will move over Iowa tonight.
Stronger high pressure will build into the upper Midwest for the
first part of the week as an upper level system brushes the area


issued at 715 am CST Sat Dec 27 2014

We have currently lost most of the ice introduction across
northwest and northern Iowa which is leading to precipitation being more
very light and patchy freezing drizzle. This system is pulling out
and not expected to be much of a problem. Southeast of a line from
alo to dsm precipitation is more drizzle or freezing drizzle and rain.
Satellite imagery is showing some deeper moisture streaming up
across the southeast half of the forecast area however with the
lack of appreciable forcing precipitation is mostly drizzle. The freezing
drizzle is most likely for the next couple of hours in a narrow 30
mile zone southeast of a line from alo to dsm where surface temperatures
are just below freezing. Adjustments were made to ptype through
15z. After that time precipitation should be departing.


Short term /today/...
issued at 328 am CST Sat Dec 27 2014

Precipitation type continues to be an issue and will continue to be
an issue through the event. Another problem will be the timing of
any clearing. The main band of snow across the west and north
occurred pretty much as forecast however is it clear that ice
introduction is a problem as precipitation has switched from snow to
freezing drizzle and back in this area. Here in Des Moines we had
drizzle followed be a brief period of sleet then snow and now we
seem to be losing ice introduction as well as we are transitioning
back to drizzle/freezing drizzle. It does appear that northwest of
a line from Mason City to Des Moines the column will generally be
cold enough for snow with patchy freezing drizzle from time to time
through middle morning then we should be done as forcing really pushes
out of Iowa.

Southeast of this line will be a wintery mix with rain and drizzle
changing briefly over to snow then we appear to lose ice
introduction and Switch Back to drizzle or freezing drizzle as we go
through the morning. Surface layer temperatures will determine ptype as we
go through the morning and we may warm enough middle to late morning
across the far southeast to see rain if the ice introduction
remains. I do not expect precipitation to remain past 18z and we should see
the bulk of the precipitation end by 15z...except for the far southeast.

Now for clouds. Soundings indicate middle levels drying out between 15
and 18z but an inversion sets up around 700mb and low level moisture
stubbornly remains in place. With cold advection strengthening
through the day I don't see much chance of clearing. At best we
will see breaks in the overcast and may get sun at times but then
stratus or stratocu should re-develop. Temperatures will of course be
affected by this as well. If we break out especially across the far
southeast where little if any snow is expected then temperatures should
respond some and could be a bit warmer than the current forecast.

Long term /tonight through Friday/...
issued at 328 am CST Sat Dec 27 2014

High pressure ridge will move across the state tonight with a
weak upper level system moving through the area Monday as it exits
the southwestern U.S. Trough. Do not expect a great deal of
precipitation out of this system with snowfall amounts likely
under an inch. Larger high pressure will build into the upper
Midwest for the middle of the week it will draw down a decent
chunk of cold air...but there are some concerns. With the high
pressure passing well west of the state the tendency of the models
is to over forecast the cold. Went a few degrees above MOS for
Wednesday. Even so...wind chill values will be in the advisory category
over the north in the -20 to -25 range.

The next weather system for next weekend is not clear cut by any
means. A large difference between the European model (ecmwf) and the GFS with the
European model (ecmwf) keeping the northern and southern stream more spit and thus
keeping the precipitation out of Iowa. The GFS is more consolidated and
would paint more snowfall for the state. For the time being...will
go with a chance category event and watch for later developments.


issued at 556 am CST Sat Dec 27 2014

LIFR conditions can be expected along and northwest of a line from
kmcw to kdsm. Snow or freezing drizzle will also help to reduce
visibilities. Southeast of this line clouds will be IFR with local
MVFR and precipitation will be more of a wintery mix with rain and snow and
patchy drizzle at times. This system will pull east by 18z and
precipitation will end but lower clouds and at least MVFR conditions will
persist through at least 22z. Low clouds will lift after this time
for VFR conditions. Surface winds will switch from westerly to
northerly at 10-20kt with higher gusts.


Dmx watches/warnings/advisories...
Winter Weather Advisory until 9 am CST this morning for Cerro
Gordo-Crawford-Emmet-Hancock-Kossuth-Palo Alto-Pocahontas-SAC-



synopsis...MS Dec 14
short term...fab
long term...MS Dec 14

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