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Area forecast discussion 
National Weather Service Des Moines Iowa
651 am CDT Tuesday Jul 7 2015

Short term /today/...
issued at 334 am CDT Tuesday Jul 7 2015

Unseasonably cool temperatures and the potential of additional smoke from
wild fires in northern Canada is the focus of the short term forecast.
Surface high pressure centered over the Red River of the North River valley
will build southeast today bringing a dry day. A cooler and drier airmass
will continue to settle across the Midwest. High temperatures will be
around 15 degrees below normal for this time of the year.

Attention will be focused on a couple of smoke plumes. One plume is
over the northern and Central Plains and another smaller plume over the
Midwest. Challenging forecast with regards to the propagation and
advection of these plumes with migration dependent upon height and
depth of the suspended inversion and changing
wind speed and direction with height. Have included patchy smoke
through the morning and will continue to monitor trends through the

Long term /tonight through Monday/...
issued at 334 am CDT Tuesday Jul 7 2015

High pressure will build south across the region through tonight.
Some smoke may linger over the next day or so...though the extent of
coverage may remain low through tonight as earlier projections
suggested the high would keep the plume more west of the area. With
cool airmass in place...h850 temperatures remaining near 9c by 12z
Wednesday and ridge axis overhead...mins will be quite chilly for
July on Wednesday morning. Though records are not in jeopardy with
lows about 5 to 7 degrees higher than previous records...lows will
still drop into the upper 40s north to the middle to upper 50s in the
south. Despite the recent wet weather fog should not be a problem
tonight as light northeast winds result in lowering dew points
overnight. This should lead to a thick dew Wednesday morning...
rather than any widespread fog. With the exception of the 00z
NAM...models are now trending south with the system on Wednesday
as the Great Lakes high will depart more slowly than earlier
anticipated. This should result in generally dry conditions with
mostly sunny skies and a slight warming trend. By afternoon h850
temperatures recover to the lower teens with northeast flow. This
should help afternoon highs recover to the lower 70s most areas...
some 10 to 15 degrees below normal for July 8th. With the brief
split flow that develops Wednesday into early Thursday...the next
best chances for thunderstorms will return late Thursday afternoon
into Friday...lingering into Saturday. The GFS/Gem/Euro are in
agreement that a strong push of thetae advection along a
strengthening warm front and low level jet will increase forcing
across southwest Iowa early Thursday evening...with showers and
scattered thunderstorms building north overnight. With little
overall changes to persistent southwest flow aloft and the
moisture pool over the Southern Plains now...the rather water
loaded h850 moisture plume is likely to build back north with the
advancing warm front Thursday night. GFS precipitable water
forecasts increase to 1.75 to 2.0 inches by 12z Friday with warm
cloud depths again rising to 13 to 14kft by 12z Friday. Depending
on the extent of northeast movement of the boundary...moderate to
locally heavy rainfall may again occur through early Friday
morning diminishing later in the morning. In the wake of the
boundary the GFS brings a rather warm and moist airmass will
remain in place through the weekend...however confidence in the
weekend evolution of the boundary is lessening. The 00z Euro shows
the boundary stalling over Iowa with convection refiring and
knocking the boundary back south...keeping it near Iowa through
late Saturday evening...then lifting it northeast on Sunday. This
greatly impacts temperatures and thunder well as if
repeated rainfall may occur over the same areas. Temperatures look
to warm either way...given the increasing height fields and h850
temperatures through the period. Though thunder is possible
through at least Saturday...there is some hint that the forcing
may briefly shift North/East for Sunday before the front collapses
south again Sunday night and Monday. Given the upper level wind
fields...severe chances look limited through the period though
heavy rainfall may pose a challenge if the boundary hangs up
across the area. Too soon for an answer this will
need to monitor the next couple of days. Temperatures should warm into
the 80s to near 90 with lows in the 60s to lower 70s. There
appears to be a signal for the summertime heat to continue through
early next week.


issued at 633 am CDT Tuesday Jul 7 2015

Visibilities and ceilings will gradually improve this morning
near Ottumwa as surface high pressure builds across Iowa.
Elsewhere VFR conditions are expected with surface winds
increasing above 8 knots through middle afternoon. After
ooz...surface winds will weaken near 5 knots as the pressure
gradient relaxes.


Dmx watches/warnings/advisories...


Short term...angle
long term...rev

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