Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 272324

National Weather Service Des Moines IA
624 PM CDT Tue Sep 27 2016

.SHORT TERM.../Tonight/
Issued at 322 PM CDT Tue Sep 27 2016

Large upper level low pressure centered over Lake Superior will drop
south through the overnight to southern Lake Michigan by Wednesday
morning. This will create strong cyclonic flow over Iowa and will
drag the broad stratus field to the north into the state. Strong
short wave energy that actually first passed through the state
Saturday night, has rounded the large upper low and will pass
through the state again from the north and bring good QG forcing
across Iowa late this afternoon and early evening. This forcing
along with the increasing moisture may allow a few showers to scrape
the very northeast forecast area and generally northeast of a Mason
City to Waterloo line. Clouds should increase from northeast to
southwest overnight. A portion of the cloud shield has become
cellular therefore the areal coverage in those areas may diminish
with the loss of daytime heating. Overnight low temperatures will be
dependent on cloud cover with areas with clouds holding up while
clearing areas similar to past two nights.

.LONG TERM.../Wednesday through Tuesday/
Issued at 322 PM CDT Tue Sep 27 2016

No major changes are needed in the extended as the weather will
remain benign through the weekend.  The Great Lakes upper low will
lift North then East over the weekend pinching the upper ridge over
the Upper Midwest westward but we will see some great fall
conditions.  Humidity will be low and we will remain dry with
slightly warmer temps Friday through Sunday.

Next week with the low lifting Northeast it will allow the ridge
over us to shift to the East.  This will allow a deep trough over
the Pacific Northwest to move into the Rockies.  The result of which
will be to turn our Northwest flow into Southwest flow.  We will
warm up next week with highs expected to be back int the mid to
upper 70s.  Along with that will be increasing chances for showers
and thunderstorms especially from Monday afternoon into the middle
of next week. At this point and through the valid forecast period we
are not looking at any heavy rainfall and it is not expected to
impact river...especially since the better chances will remain to
the West.  However...going forward as the upper trough continues to
move inland and across the CONUS we will need to focus on whether
there will be a sufficient tap of moisture for heavier rainfall
perhaps in the middle to latter part of next week.  This is very far
away though and certainly outside of the current forecast period.


.AVIATION.../For the 00Z TAFS through 00Z Wednesday evening/
Issued at 536 PM CDT Tue Sep 27 2016

Concerns this period include upper level low rotating southwest
into northwest Iowa next 36 hours. Winds will relax by 00z. MVFR
cigs and potential VCSH will edge into area through 06z then lower
cigs spread southwest through most of area by 12z. Diurnal heating
and limited mixing will eventually cause clouds to become cellular
by 18-20z as mixture of MVFR/VFR conditions become more predominant.
Winds again mix aft 15z with gusts 20-22kts over northeast at KMCW
and KALO. /rev




SHORT TERM...Donavon
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