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Area forecast discussion 
National Weather Service Des Moines Iowa
639 PM CDT Sat Oct 25 2014

Short term /tonight/...
issued at 305 PM CDT Sat Oct 25 2014

A tranquil night is in store with high pressure settling into the
state. With dew points falling off this afternoon quite
nicely...expect to see temperatures fall fast this evening under clear
skies and light and variable winds. Went below MOS for lows
tonight with that in mind.

Long term /Sunday through Saturday/...
issued at 305 PM CDT Sat Oct 25 2014

No significant changes were made to the long-term period of the
forecast. Relatively quiet weather is still expected. Main
opportunities for precipitation will be Monday into Monday night...and
Wednesday night into Thursday morning.

Forecast period begins with departing surface pressure ridge. Return flow
on its back side and Theta-E advection follow it closely will
affect the County Warning Area during the day on Sunday...as a warm front
approaches the region. Relative humidity values within the column are not
expected to be high enough to facilitate precipitation...so have continued
the trend of partly to mostly cloudy only. GFS and NAM bring in
low-level moisture from Sun afternoon through Monday morning. If low
clouds end up being more plentiful than expected Sun afternoon then
forecast maxes may be too high. Subsequent shifts will have to monitor
for potential tweaks to Sunday maximum temperatures in that regard.

Elevated thunderstorms are possible Sunday night from northeast Iowa into
WI as elevated instability combines with ample forcing within the
warm air advection regime there. At this time believe the best combination of instability
and forcing will remain northeast of the County Warning Area so have left the forecast
dry during the time.

Cold front is prognosticated to push through the County Warning Area on Monday. Although
moisture will be minimal...sufficient forcing and instability will
be sufficient for at least isolated-scattered precipitation in vicinity of the boundary.
Instability will be high enough for at least some isolated thunderstorms and rain
especially across the southeast half of the County Warning Area...where MUCAPES of
400+ j/kg are prognosticated to exist. Although fog remains a possibility
Monday morning before the boundary arrives...confidence was not high
enough for it to be impactful enough to mention. Subsequent shifts will
have to monitor for potential impacts to forecast maxes and cloud
cover.

After the system departs the County Warning Area Monday night...next chance of
precipitation will arrive Wednesday night into Thursday morning. Brief
ridging builds in behind the departing system Wednesday...but then
heights fall again as the next system approaches. Although
moisture will be limited...forcing will be ample enough for some
scattered rain showers mainly across the eastern County Warning Area.

Models begin diverging noticeably in their solutions of this
particular system...with the European model (ecmwf) being the strongest/coldest.
Regardless of particular model...though...they are in agreement
with a seasonably cool Canadian air mass filling in behind it.
Forecast mins on Friday morning are in the 20s and 30s.

&&

Aviation...26/00z
issued at 637 PM CDT Sat Oct 25 2014

Relatively tranquil aviation weather tonight into Sunday. Will see
widespread VFR conditions overnight as surface ridging passes
through the state. Moisture will return on Sunday with increasing
southeast winds. Likely to see some VFR ceilings increase through
the day as Theta-E advection passes through the state.

&&

Dmx watches/warnings/advisories...none.

&&

$$

Short term...MS Oct 14
long term...zogg
aviation...cogil

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