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Area forecast discussion 
National Weather Service Des Moines Iowa
553 PM CDT Sat Jul 4 2015

Short term /tonight/...
issued at 319 PM CDT Sat Jul 4 2015

Surface ridge continues to slide away from the state this afternoon
with increasing southerly winds as warm advection intensifies. The
winds will weaken into this evening as mixing decreases with light
flow overnight. System entering the northern plains will produce
thunderstorms across the Dakotas and northern Minnesota but well
north of Iowa overnight. Some additional isolated to scattered
convection is expected in Nebraska in axis of strong low level jet overnight
but this too will remain west of the state. In general...quiet
weather is expected into the overnight with seasonably cool
readings. Some smoke is expected to continue to drift overhead but
with generally minimal impact.

Long term /Sunday through Saturday/...
issued at 319 PM CDT Sat Jul 4 2015

Active weather will return on Monday...followed by more relatively
cool and quiet weather for the remainder of the work week. At 500
mb...the ridging moving overhead today will depart by Sunday
leaving more of a weak neutral flow...with a longwave trough
slowly dipping from Canada down into the northern U.S. Rockies and
moving over the Dakotas by sunrise Monday. At the surface this
will result in benign and warm weather on Sunday...with mostly
sunny skies and modest southerly flow allowing for temperatures to
rise into the middle to upper 80s with increasing humidity. On Sunday
night a cool front attendant to the 500 mb trough will then
approach Iowa from the northwest...and cross the state as the
trough moves overhead on Monday. By the time the front reaches our
forecast area most of the supporting upper level dynamics will be
moving off to the north of the surface boundary over
Minnesota...however there should be enough instability and ambient
shear to support a severe weather threat...particularly across
about the southeast half of our area during peak heating Monday
afternoon/evening. This threat is well outlined in Storm Prediction Center outlooks.

In wake of the early week trough...broadly zonal 500 mb flow will
reestablish itself from at least Tuesday through Thursday. This
will allow a cool surface high moving in behind the surface
boundary to build across the region and make for generally quiet
weather. However...the boundary that crossed our area on Monday
will remain stalled across Missouri and may drift up to affect far
southern Iowa at times. Also...there is consensus that a weaker
shortwave trough will move through the 500 mb flow and over our
area around Wednesday night...supporting low probability of precipitation...but moisture
and instability should be limited so coverage and any impacts are
expected to be minimal.

Looking toward the end of the week and next weekend...the GFS and
ec are in general agreement in building a 500 mb trough along the
Pacific U.S. Coast and a warm high pressure bubble downstream
across the southern High Plains and panhandles. If this pans out
is could place US on the northeastern flank of the dreaded ring of
fire...as impulses ejected out of the western trough overtop the
ridge and generate periodic convective systems that would then
move east southeast across Iowa. Of course at this range
confidence is not particularly high...but such a scenario is
certainly realistic and for now justifies a return of chance probability of precipitation
toward next weekend.

&&

Aviation...04/00z
issued at 552 PM CDT Sat Jul 4 2015

VFR conditions are expected to continue to prevail through the
period. High cirrus passing through overnight. Possible for scattered
cumulus by Sunday afternoon. Light south winds tonight becoming
breezy middle to late Sunday morning.

&&

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

$$

Short term...cogil
long term...Lee
aviation...donavon

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