Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 231128
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
628 AM CDT Fri Jun 23 2017

.SHORT TERM.../Today through Tonight/
Issued at 401 AM CDT Fri Jun 23 2017

The cold front is along a line from near Dubuque to Des Moines to
near Clarinda and continues to move off to the southeast with a
cooler and drier airmass arriving behind the front as winds switch
to the northwest. The stronger thunderstorms were over north
central Missouri as of 9z with much more scattered showers and a
few thunderstorms lingering between the stronger storms and the cold
front. Most of the showers and storms will be out of central Iowa
early this morning as larger scale subsidence evident in water
vapor imagery moves by. Will still likely be able to develop
scattered cumulus clouds this afternoon, especially over the
north. Forecast soundings in this area show a dry atmosphere this
morning, but by afternoon mid-levels and to a limited extent lower
levels moisten with cloud bases developing between 3500 and 4000
feet. Have also included low end slight PoPs over far north
central Iowa for the possibility of a few isolated showers or
thunderstorm. CAMs along with some of the global suite of models
show light precipitation breaking out mainly in the afternoon and
with MUCAPEs between 500 and 750J/kg, may be able to get some
peals of thunder. Otherwise, winds from the northwest will
increase this morning and become gusty and have adjusted winds and
gusts up from initial guidance. Temperatures and dewpoints were
adjusted toward the colder/drier end of MOS guidance for
highs/dewpoints today.

For tonight, as clouds clear early in the evening, it would be a
good radiational cooling setup with the exception of the winds.
Still, trended slightly cooler with lows for Saturday morning, but
not as cool if winds were very light.

.LONG TERM.../Saturday through Thursday/
Issued at 401 AM CDT Fri Jun 23 2017

Below normal temperatures, drier air, and gusty daytime winds will
prevail this weekend as northwest flow takes hold aloft with surface
high pressure sliding into the area. For both Saturday and Sunday,
have upped winds from initial guidance similar to the short term
period. Also lowered lows Sunday morning a few degrees at most
sites. With winds dropping off, especially over the Nishnabotna
River Valley, may see temperatures really fall off in this area. A
500mb vorticity maximum drops out of North Dakota in the northwest
flow towards southeast Minnesota, southern Wisconsin and northeast
Iowa. As this feature reaches our area in the afternoon, expect
scattered showers and a few thunderstorms over the northeast
quadrant of the state. This pattern repeats on Sunday as another
modest vorticity maximum drops into the region.

The cooler weather and northwest flow will persist into Monday as
surface high pressure begins to slide off to the east. Yet
another, albeit more subtle, 500mb vorticity maximum passes
through bringing clouds and a few showers and thunderstorms to
the state.

Large scale ridging begins to build into the Midwest as the high
moves over the Ohio Valley on Tuesday. As winds become breezy from
the southeast and south, warmer and moister air will return.
Meanwhile, a shortwave trough will enter the Pacific Northwest and
race eastward over the northern states. Increasing chances of
showers and thunderstorms are expected Tuesday night through
Wednesday night as this trough moves through the region and
temperatures return to near seasonal levels. A cold front moves
through late in the week providing yet another round of showers and
storms.

&&

.AVIATION.../For the 12Z TAFS through 12Z Saturday morning/
Issued at 628 AM CDT Fri Jun 23 2017

While VFR conditions will prevail through the period, it is not
a challenge free period. Of most imminent concern is some patchy
fog producing IFR ceilings at KALO, which will dissipate shortly
into this TAF period. Other concerns are clouds over the Dakotas
that will arrive plus diurnal clouds. Ceilings should be FL035 or
higher and arrive/develop from northwest to southeast, though
don`t expect them to reach KOTM. An isolated shower may also occur
over KMCW this afternoon, but confidence is low so left out
mention. Only other thing of note today will be gusty winds from
the northwest with peak gusts between 20 and 30 knots. Clouds will
break and clear this evening and winds will lessen.

&&

.DMX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM...Ansorge
LONG TERM...Ansorge
AVIATION...Ansorge



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