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Area forecast discussion 
National Weather Service Des Moines Iowa
351 PM CST Thursday Nov 27 2014

Short term /tonight/...
issued at 350 PM CST Thursday Nov 27 2014

High pressure centered over Iowa will drift off with strong warm air advection
setting in overnight. Pressure fall already indicating the warm
air return. Band of SC will continue to spread across the state
tonight. Have introduced flurries across the County Warning Area tonight. Though
the low levels are dry...would expect to see a lot of 9sm -sn
type stuff...certainly no measurable. Very low probability of precipitation along the Minnesota
border however where there is a better chance of saturation and
deeper moisture. In any case...decent lift is present through the
dgz. Temperatures non-diurnal tonight with rising temperatures through the night
as the cold air retreats east.

Long term /Friday through Thursday/...
issued at 350 PM CST Thursday Nov 27 2014

Iowa weather will be influenced by fairly progressive pattern
through the period with main concerns fluctuating temperatures and fog
into the weekend. Little in the way of precipitation. Period will
begin with warm air advection /waa/ well underway with 850 mb/700 mb
Theta-E advection through the MS valley and southerly low level winds.
Any precipitation in the thermodynamic forcing should remain just
north and east of the forecast area however. Friday will start a two
day period with low temperature confidence due to warm air advection over the evolving
snow pack with appreciable errors possible along the gradient. The
strength of the warm air advection should be able to boost temperatures into the 30s
NE/40s SW Friday. This persistent southerly flow will also boost dewpoints
into the 25-35f range by Friday night with advection fog/stratus
becoming a concern...especially over what is left of the snow. 20-
30kt 500m winds may hold things back slightly...but most model
signals including WRF nmm/arw and sref suggest low visibilities
and ceilings into Friday night and early Sat morning...especially NE
half. Dewpoints at and above freezing will continue to eat
snowpack Sat with temperatures continuing to be problematic. Models are
too aggressively holding onto the snowpack south and west so MOS
will likely not perform too well except north central in most
appreciable snow depth. Thus have used past experience and
sounding examination to mix temperatures out halfway between raw surface
temperatures and top of inversion which ends up very close to previous
forecast...50s central/south and 40s holding on north but still
above MOS.

The fog/stratus/temp battle will come to an abrupt end sun however
with a strong cold frontal passage sun as Arctic high settles into
the High Plains. Highs sun should be very early with falling or
steady temperatures throughout the day. A ribbon of middle level forcing will
pass through Iowa Sun night but with little support or moisture below
3km so forecast stays dry. Return flow and warm air advection will begin again Monday
night. There could be some very light precipitation with this feature
and long wave trough passage Tuesday...especially if the European model (ecmwf) is
correct...but chances not great enough to mention at the moment.
Model confidence then diminishes toward the end of the period with
GFS more aggressive pushing pieces of trough off the California coast into
and through The Rockies into the MO valley. GFS and European model (ecmwf) have
both been steadfast with their respective wet/dry solutions
respectively so have leaned toward the /if in doubt go with the
European model (ecmwf) / solution and kept days 6/7 dry for the time being.


issued at 1146 am CST Thursday Nov 27 2014

High pressure over Iowa will move to the east with flow becoming
southeasterly tonight. Band of VFR stratus will overspread the
state tonight with some light snow showers...however VFR
conditions are likely to prevail.

Outlook...stratus band will advance north and east out of the
state with mild and dry conditions for Friday into Sat. A cold front
will move through Saturday night with MVFR conditions in stratus
and snow showers expected by Sunday.


Dmx watches/warnings/advisories...none.



Short term...MS Nov 14
long term...small
aviation...MS Nov 14

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