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Area forecast discussion 
National Weather Service Des Moines Iowa
1143 am CST Tuesday Dec 1 2015

issued at 1034 am CST Tuesday Dec 1 2015

Updated pop grids to better reflect current radar trends and
expectations through the light snow/snow showers expected
to increase in coverage through the day especially across the
north as the upper low spins through the state. Therefore
increased probability of precipitation into the likely category across the north and added
in flurries for the southern County Warning Area as a few flakes may fall through
early afternoon in light returns on radar across central and
southern Iowa. Otherwise any snow accumulations to still be light
across the did not change snow amounts with around an
inch or less of additional accumulation possible. Visibilities
have been reduced to around 3 to 4 miles with the light snow...and
at times around a mile or less in a brief snow burst. Did also
lower temperatures some with cold air advection expected aloft through the day...clouds
and precipitation not expect temperatures to move much from their
current readings especially across the north/northwestern County Warning Area.


Short term /today/...
issued at 323 am CST Tuesday Dec 1 2015

Primary concern will be precipitation trends and fate of headlines. Much of
the precipitation has ended for the time being with kinematic forcing and
lowest static stability axis north of Iowa and none Thermo support
here. The siouxland upper low is expected to reach the upper MS
river by 00z with mainly neutral but some patchy forcing at best
into Iowa as it pulls away. Even though the lift is quite
marginal...deep moisture remains in place with a few exceptions and
the dendritic growth zone /dgz/ depth increases quite a bit with
time. Thus expect another round of some light snow or snow showers
later in the day. Low level lapse rates steepen by afternoon as well
and support some token positive energy even though they remain quite
shallow so the precipitation may become more showery. The GFS also depicts
the dry slot wrapping around back into far northwestern Iowa by afternoon so a
brief flip back to freezing drizzle is not out of the question
there. The deep dgz will elevate snow ratios somewhat...but with quantitative precipitation forecast
amounts still rather light would expect most additional snow amounts
to be less than an inch.

These expectations certainly do not support the continuation of a
Winter Storm Warning headline so it will be canceled. Considered
downgrading to a Winter Weather Advisory but with little ongoing at
the moment felt that another 15 hours straight of headlines seemed
like overkill. Road temperatures are expected to rebound well above
freezing during the afternoon and precipitation rates are not anticipated
to be high enough to justify that either. Any travel concerns could
be covered by targeted statements as necessary. Expect air temperatures to
drop through daybreak...and then rebound back close to current
levels during the afternoon.

Long term /tonight through Sunday/...
issued at 323 am CST Tuesday Dec 1 2015

A relatively quiet long term forecast period is in store across
the forecast area. From tonight into Wednesday the large middle/upper
level cyclone that has been affecting the region will gradually
shift off to the east...bringing and end to precipitation and
eventually some clearing skies by Wednesday night. In the
meantime...light precipitation will remain possible especially
tonight through Wednesday morning. Despite only shallow
atmospheric moisture and modest to minimal forcing...believe at
least flurries/light snow showers will remain scattered around
through tonight. Forecast soundings depict a persistent low level
saturated layer...with some possibility that it may be limited to
warmer subfreezing temperatures and produce freezing drizzle...but
a higher probability and consensus among various forecast models
that ice Crystal introduction will occur and the precipitation will more
likely come in the form of light snow which may or may not

Once any lingering light precipitation clears out on Wednesday the
forecast is then dry through the weekend. Weak southwesterly low
level flow will return from Thursday into Friday...then turn to
south and pick up just a bit by Saturday. Initially...around
Wednesday night and Thursday night...we may see some local low
cloud and/or fog development given the light winds and wet
ground/snow melt...but confidence is too low to add it to the
forecast at this time. Otherwise the big story will be moderating
temperatures...especially outside of areas that have snow
cover...with highs rebounding into the 40s across most of Iowa by
the end of the week and even some 50s possible in the south by
Saturday. There is no real threat of additional precipitation
until at least early next week and more likely beyond that.


issued at 1143 am CST Tuesday Dec 1 2015

Area of light snow pushing through much of central Iowa today into
tonight...mainly impacting the northern taf sites with reduced
visibilities at times to mainly MVFR although brief IFR not out of the
question. Possible IFR conditions with ceilings through the
period...with MVFR holding on much of the time. Winds to shift
around to the southwest to northwest through the forecast period
as well.


Dmx watches/warnings/advisories...none.



short term...small
long term...Lee

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