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Area forecast discussion 
National Weather Service Des Moines Iowa
1151 PM CDT Friday Oct 31 2014

Short term /tonight/...
issued at 314 PM CDT Friday Oct 31 2014

Other than being one of the coldest nights of the season...the
weather will be benign. High pressure both at the surface and
aloft will drift over Iowa. Winds will diminish to under 5 miles per hour
and with clear skies there will be excellent radiational cooling
tonight. Dropped overnight lows another degree or so mainly across
the north and the nish valley and we may still be too warm
elsewhere but confidence is not high enough to lower elsewhere.
Towards 12z wind over most of the forecast area will switch to the
southeast. Although winds will be light they may be enough to at
least level temperatures out towards daybreak. One thing of note...I do
expect temperatures to fall quickly this evening to freezing or below so
people will need to dress warmly for any outdoor activity.

Long term /Saturday through Friday/...
issued at 314 PM CDT Friday Oct 31 2014

Main forecast issue dealt with precipitation chances Monday into Tuesday
and winds/temperatures Sunday. Leaned toward the warmer European model (ecmwf)/sref
Saturday and Sunday...then slightly more weight towards the European model (ecmwf)
the rest of the forecast period. However...the GFS/Canadian are
in good agreement with the European model (ecmwf) trends through much of next week.

Saturday and Sunday...large surface high pressure will dominate
the weather pattern as it slowly migrates eastward through the
weekend. Return flow looks to begin late Saturday afternoon and
gradually increases Saturday night into Sunday. Northwest
portions of the forecast area will be fairly windy both
days...with Sunday being the windiest day across the entire
forecast area. On Sunday...winds atop the mix layer range from
35-40 knots and the surface pressure gradient increasing ahead of
next low pressure system developing over the central to northern
plains. Tweaked winds up slightly on Sunday as well as maximum
temperatures...mainly across the southwest where should be a warmer start
as warm air advection develops past 06z Sunday in that area. Potential for non-
diurnal temperature trend the far southwest Saturday night into
Sunday...but left out mention at this time as it looks to be fairly
subtle.

Monday into Tuesday...low-level Theta-E advection combined with
some weak isentropic lift along the 290-300k surface moves across
central Iowa after 06z Monday and continues through much of the
day Monday. Pulled back timing of probability of precipitation until after 12z Monday
for the entire County Warning Area and even still have low confidence with any
widespread rain with a decent amount of dry air in place above
800mb. The stronger forcing and moisture looks to pool over the
southern and eastern portions of the forecast area by Monday night
with the trough/cold front pushing through the state. System
quickly moves east after 12z Tuesday and lowered probability of precipitation across the
southeast Tuesday.

Wednesday through Friday...northwest flow aloft looks to persist
the rest of the work week and may see a weak shortwave or two ride
the flow southeast...but timing and location look to remain north
and left dry forecast for now.

&&

Aviation...01/06z
issued at 1149 PM CDT Friday Oct 31 2014

Quiet aviation weather will continue for the duration of the
forecast with widespread VFR conditions. Light and variable
surface winds overnight will increase from the southeast on
Saturday and become gusty by afternoon as pressure gradient
increases.

&&

Dmx watches/warnings/advisories...none.

&&

$$

Short term...fab
long term...podrazik
aviation...cogil

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