Area Forecast Discussion
Issued by NWS Des Moines, IA

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194
FXUS63 KDMX 201138
AFDDMX

Area Forecast Discussion
National Weather Service Des Moines IA
638 AM CDT Thu Apr 20 2017

.SHORT TERM.../Today through Tonight/
Issued at 315 AM CDT Thu Apr 20 2017

Strong convection from last evening has moved out of the forecast
areas with surface low passing into northeast Iowa early this
morning. Surface front has also nearly cleared the forecast area
by 3 AM with modest west to northwest winds behind the front.
Temperatures cool considerably on the backside of the system with
readings dropping into the 40s across the northwest third of the
state. The thermal trof will continue to build across MN into
Wisconsin today with near northeast Iowa. With cyclonic curvature
and CAA persisting through early afternoon, will see widespread
stratus over much of the forecast area although towards the
southern border, skies more likely partly cloudy today with low
levels not nearly as saturated. The extensive clouds in the north
will limit highs today with readings holding in the low to mid
50s.

By tonight, some clearing is expected with drier air and approach
of the surface ridge. Temperatures should drop nicely in the
drier airmass, especially with the clearing skies. Would be more
concerned about lower temperatures by daybreak on Friday but
overnight winds should stay higher until sunrise, keeping readings
a bit warmer than would be expected had the winds gone still
facilitating radiational cooling.

.LONG TERM.../Friday through Wednesday/
Issued at 315 AM CDT Thu Apr 20 2017

Large and strong surface high pressure and upper level ridge
remain planted across the region Friday into Sunday keeping the
low pressure system to the south of the forecast area on Friday.
Some high clouds likely associated with this system to impact
southern Iowa Friday, but overall, conditions look dry and clear
late this week into the weekend. Sunday will be the warmest day of
the extended with the surface high shifting east enough during
the day to allow for return flow to develop over the west by the
afternoon. Surface pressure gradient increases along with decent
mixing to maybe as high as 800mb. Very dry airmass in place with
surface dew points decreasing into the 30s by Sunday afternoon.
Nudged up winds and max temperatures Sunday afternoon, mainly over
the west to coincide with the WAA developing.

The GFS/ECMWF have a 991mb/996mb, respectively, surface low moving
across southern Minnesota Monday afternoon into early Tuesday.
The front associated with the low looks to press across the CWA
Monday evening, but limited moisture availability leads to low
chance pops during this time. Lower confidence with any
precipitation Tuesday into Wednesday of next week as extended
models continue to be in disagreement with timing and location of
a system mid-week.

&&

.AVIATION.../For the 12Z TAFS through 12Z Friday morning/
Issued at 638 AM CDT Thu Apr 20 2017

Broad area of stratus will pass across the state today with IFR
ceilings this morning increasing to MVFR to VFR by the end of
today. Clearing will overspread the area tonight with VFR
conditions becoming widespread with the stronger northwest winds
dieing off through the evening.

&&

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

&&

$$

SHORT TERM...Cogil
LONG TERM...Podrazik
AVIATION...Cogil



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