Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 260505
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
1205 AM CDT Tue Jul 26 2016

.SHORT TERM.../Tonight/
Issued at 338 PM CDT Mon Jul 25 2016

Benign forecast tonight.  High pressure will remain in control over
Iowa and a fair part of the Upper Midwest into Wednesday.  The high
should shift East over night and western portions of the forecast
area may see winds switch to a more Southerly direction but speeds
will be light.  The only caveat is that forecast soundings do show
another inversion setting up tonight which would trap any low level
moisture resulting in patchy fog late tonight through daybreak.

.LONG TERM.../Tuesday through Monday/
Issued at 338 PM CDT Mon Jul 25 2016

Overview...High pressure will continue through Tuesday before
trailing off to the east by Wednesday morning. In its wake,
northwest flow aloft sets in and begins a stretch of a few days of
unsettled weather and attempting to time short waves in the flow.
Then quieter to end the weekend and weak ridging to begin the new
week Monday.

Tuesday to Wednesday Morning...Will remain a quiet period as surface
high pressure dominates the region. As it begins to ooze east
Tuesday evening, northwest flow will begin to set into the
region. In the meantime, winds will remain on the light side,
highs in the mid to upper 80s, lows in the mid to upper 60s, and
tolerable dew points in the mid to upper 60s.

Wednesday through Saturday...Main concern in this period is timing
the initial waves and whether or not they will merge. As noted by
the previous long term discussion, Euro and Canadian solutions are
strongest with a merger and deepening trough over the region and to
the east.  NAM and GFS solutions suggest waves remaining separate,
quickly shunting them to the east. Regardless, solutions have slowed
down and dried out a bit during the Wednesday time frame, continuing
the pattern of the last couple days.  Now, it looks as though
showers/storms will not move into northern/northwest reaches of Iowa
until Wednesday morning, not overtaking the state until the evening.
While Some of the question in timing resides in the dry profiles and
lack of moisture transport into the region, even with decent vort
advection. As a result, have slowed the progression fairly
significantly over guidance blends and previous packages. Severe
threat remains minimal with continued lackluster shear and weak
lapse rates. Heavy rainfall remains the primary concern, if any. GFS
now seems to be the lone wolf with the Friday/Saturday with regards
to strength, with Canadian suggesting it, while lacking in Euro. The
lack of confidence is reflected in POPs with chances and slight
chances going both days. Temps through period will be cooler with
periods of cloud cover and showers/storms, dropping highs into upper
70s and low 80s.

Sunday through Monday...Quieter period likely as series of waves
ceases and ridging builds in. Temps, should ridging build in, should
return to mid and upper 80s.

&&

.AVIATION.../For the 06Z TAFS through 06Z Tuesday night/
Issued at 1204 AM CDT Tue Jul 26 2016

Confidence has increased somewhat in radiation fog development
with temp/dewpoint spreads now dropping to a few degrees at 05z
with nearly calm wind and clear skies. Thus have added a few hours
of MVFR fog outside of KDSM which will likely be warmer due to
heat island effects. Otherwise there is a high confidence in
mostly clear skies/VFR conditions through the daylight hours
Tuesday.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...None.

&&

$$

SHORT TERM...FAB
LONG TERM...Curtis
AVIATION...Small



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