Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 262026
AFDDMX

AREA FORECAST DISCUSSION
National Weather Service Des Moines IA
326 PM CDT Mon Sep 26 2016

.SHORT TERM.../Tonight/
Issued at 325 PM CDT Mon Sep 26 2016

Iowa remains in cyclonic flow overnight with a large upper level low
pressure system situated to the northeast of the state over southern
Ontario and Lake Superior. Surface high pressure to the southwest
will help keep the very dry air in place tonight. Dew points this
afternoon have fallen in the lower 30s to lower 40s with good mixing
up to near 750 mb. The dew points will rebound some by this evening
as the mixing ends and the ground high soil moisture begins to
influence the near surface moisture. The breezy wind will diminish
overnight so will have good radiational cooling again with low
temperatures again in the 40s. Some chance for upper 30s over the
northwest though the rebounding dew points should prevent any
further drops.

.LONG TERM.../Tuesday night through Monday/
Issued at 325 PM CDT Mon Sep 26 2016

Models have come into better alignment in handling the deepening low
dropping South across the Great Lakes into the Ohio Valley.  The
Euro did have the better handle on the situation in that it
retrogrades the low Westward and has a vort max rotating around the
low.  All models bring some kind of precip across the Northeast late
Tuesday afternoon into early Tuesday evening.  There is also some
forcing pushing across that area but at this time soundings do not
support precip...or at least measurable precip.  I suspect that
later model runs will moisten the soundings up given that they are
playing catch up to the Euro but at this point I just added a
mention of sprinkles to the grids for a brief time Tuesday
evening.

Strong cold advection will take place Wednesday as the low drops
deeper into the Ohio Valley so Wednesday will be breezy and pretty
cool with highs only expected to be in the lower to mid 60s.

Later in the week all models are in agreement that the low will lift
back North but the Euro does continue the trend of shifting it back
Westward as well however this should bring little more than cloud
cover back to the Eastern portion of Iowa.  Once that low lifts off
to the North and East later Saturday...it will allow a deep trough
off the Pacific Northwest to shift into the Rockies which will push
the ridge Eastward over the Great Lakes.  This will bring a more
West to Southwest flow back to the Upper Midwest along with
increasing moisture.  Shower and thunderstorm chances will increase
from Sunday night on with the best chances coming later Monday
through Tuesday.  Until then it will be dry with cool nights and
temps gradually warming from late week into early next week back
into the lower to mid 70s.

&&

.AVIATION.../For the 18Z TAFS through 18Z Tuesday afternoon/
Issued at 1226 PM CDT Mon Sep 26 2016

VFR conditions will persist through the forecast period. Breezy
west winds this afternoon will diminish by 00z. The wind will
become breezy once again by mid to late Tuesday morning.

&&

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

$$

SHORT TERM...Donavon
LONG TERM...FAB
AVIATION...Donavon


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