Area Forecast Discussion
Issued by NWS Des Moines, IA

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FXUS63 KDMX 271139

National Weather Service Des Moines IA
639 AM CDT Thu Oct 27 2016

.SHORT TERM.../Today/
Issued at 327 AM CDT Thu Oct 27 2016

A surface high pressure area will slide across Iowa this morning
then retreat toward the Great lakes this afternoon. It will be
replaced by south southeast low-level flow, resulting in the erosion
of the current cloud shield from the southwest by around midday and
into the evening. It appears likely that most or all of the area
will clear out before sunset, with clouds perhaps lingering in the
northeast. Given the clearing and modest warm air advection from the
southwest, the high temperature forecast for today continues to call
for readings several degrees over yesterdays levels. Of course
Friday will be significantly warmer as discussed in the long term
section below.

.LONG TERM.../Tonight through Wednesday/
Issued at 327 AM CDT Thu Oct 27 2016

Tonight through Monday Night/...Confidence Medium to High

Few changes expected for most of the extended period...with better
confidence early this morning regarding the overrunning
precipitation potential for Saturday afternoon into Saturday night
across portions of northern through east/southeast sections of the
forecast area. In the short term...we continue on track to warm
significantly later tonight and Friday with ample sunshine
south...brisk southwest flow and plenty of mixing. Across the north
and east...there may be some overnight patchy fog and clouds early
...the few more clouds may hold temperatures from warming as much as
across central and southern Iowa...but it should still be a nice
fall day...though breezy. Models have been consistent for the past
few days with rather warm afternoon in store for late October with
Friday highs in the 70s to nearly 80 across the area. Bufr soundings
show mixing to reach about 880 mb but not quite mixing out
inversion. Winds will likely be 25 to 35 mph in the south with gusts
in the upper 30 mph range at times. Over the north..winds will not
be quite as strong. A cool front is still expected to drift south
overnight Friday night into Saturday morning generally bisecting the
area leaving the south in the warm sector through 12z and the north
in the cool sector though eventually the fronts sags south into
northern Missouri by 00z Sunday capping heating for the day. Per
previous upper level boundary between H850/H700
begins to form over southern Minnesota. This will create some
overrunning light rain from northern Iowa southeast to southeast
Iowa from Saturday afternoon through Saturday night. High pressure
and cooler temperatures will settle into the area Sunday but only return to a quick transition of southerly flow arrives
by Monday. This will once again push afternoon highs back into the
60s and 70s over much of the region with mid to upper 70s across the
south. As the northern stream shortwave responsible for the warming
tracks east toward Lake Superior by 06z Tuesday...a cold front will
be pushed southeast through the region cooling temperatures.

Tuesday through Wednesday...Confidence Medium

Consensus in model solutions continues to vary somewhat for the last
portion of the extended.  At least for now...the output is more
consistent than yesterday with the onset of any rainfall occurring
late Tuesday night into Wednesday. It also appears that overrunning
light rain will occur with the first wave of moisture...then
following that a more organized low pressure will track toward the
area bringing the possibility of convection late Wednesday evening.
Temperatures will remain cool with highs in the 50s and 60s.
Depending on how quickly and where the larger more organized area of
low pressure ejects from the southwest US next week...we may
experience the wetter portion of the week very late.


.AVIATION.../For the 12Z TAFS through 12Z Friday morning/
Issued at 639 AM CDT Thu Oct 27 2016

A large stratus shield covering the region has begun to slowly
erode early this morning. However, satellite imagery is obscured
by cirrus clouds streaming overhead so the details of the erosion
remain unclear. In any event, the low clouds will slowly break up
and clear from southwest to northeast later this morning and
afternoon. Within the next several hours MVFR ceilings will
remain prevalent, then by 18Z FOD/DSM/OTM should clear out. Later
 in the TAF period there is uncertainty as to whether MCW/ALO will
 clear or remain under the edge of the cloud shield tonight. This
will determine whether they have associated low ceilings again, or
 whether they clear out but potentially develop radiation fog as a
 result. These details will be fleshed out later today.





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