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Area forecast discussion 
National Weather Service Des Moines Iowa
641 PM CDT Monday Sep 22 2014

Short term /tonight/...
issued at 354 PM CDT Monday Sep 22 2014

Surface high pressure will slowly shift east tonight into
Tuesday morning and provide some light return flow overnight. Middle-
level Theta-E advection ahead of weak shortwave slowly moving across
Nebraska/South Dakota will provide an increase in cloud cover past
06z over western Iowa. Leaned toward the cooler nam12/sref for low
temperatures tonight...although with the weak return flow and
increasing clouds over the west...may see a few far western areas
with a non-diurnal temperature trend. Have patchy fog mentioned across the
northeast where radiational cooling looks to set up closer to the
center of the high pressure.

Long term /Tuesday through Monday/...
issued at 354 PM CDT Monday Sep 22 2014

Little sensible weather of concern through the period outside of a
window for precipitation into midweek. Upper low drifting through rockies
ridge will likely bring scattered weak convection to Iowa from late
Tuesday to late Wednesday. Do not expect widespread precipitation...much like what
is currently occurring upstream...with weak to moderate forcing
and weak instability. This should gradually drift west to east through
Iowa Tuesday with forcing and moisture initially based 3km and above.
Airmass will start quite dry below. However thermodynamic
forcing...mainly Theta-E advection with increased
moisture...should lower ceilings Tuesday night into Wednesday. By late Wednesday the
forcing and moisture appears to be mainly at or below 3km...and
remains weak...so there is never really any good phasing of
forcing and moisture with any depth. Little baroclinicity or warm
advection either based on 305/310k isent surfaces.

By Thursday the upper level ridge will continue to build from The Rockies
into the northern plains and S central Canadian provinces diminishing
forcing and moisture into Iowa as upper wave finally moves away.
Heights and temperatures will be very anomalous north of Iowa with extreme z
and T climatology percentiles in those locations as thermal ridge builds
to our north. Farther south those values will not be as extreme
or atypical with our weather dry and temperatures normal to above normal
in sustained somewhat weak southerly/southeasterly low level flow. A southern stream
wave does lift from the far Southern Plains into the Ohio Valley late in
the period...but appears too far south do to much here.

&&

Aviation...23/00z
issued at 636 PM CDT Monday Sep 22 2014

High pressure over Illinois and MO will continue east with a south flow
becoming established over Iowa. VFR through this taf period with
lower ceilings and rain remaining to the west.

Outlook...upper level low will push east over the next few days.
Conditions will deteriorate from the west later Tuesday night through
Wednesday before the next high builds in to the state.

&&

Dmx watches/warnings/advisories...
none.
&&

$$

Short term...podrazik
long term...small
aviation...MS Sep 14

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