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003
FXUS63 KDVN 191724
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1224 PM CDT Thu Oct 19 2017

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 338 AM CDT Thu Oct 19 2017

A trough of low pressure at the surface moved into northeast Iowa
overnight as scattered high clouds overspread the area. Behind
the trough, temperatures were dropping into the 40s. Ahead of the
trough, readings were mostly in the 50s.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 338 AM CDT Thu Oct 19 2017

A stretch of dry and mild weather will continue today. Based on
Wednesday`s highs, 850 mb temps around 13-14C, and the location
of the stronger southeast flow today, have again favored the warm
end of temperature guidance. Expecting highs near 70 around
Freeport, to the mid 70s in the southwest counties.

For tonight, lows are forecast in the upper 40s to low 50s, about
10 degrees above normal for mid October.

.LONG TERM...(Friday through Wednesday)
ISSUED AT 338 AM CDT Thu Oct 19 2017

Friday...
Rather breezy and unseasonably mild day still looks to be
on tap.  Even marginal mixing up into base of sharp H85 Mb inversion
produces widespread mid to upper 70s, with a chance at an 80
somewhere. Mid to afternoon sfc layer wind flow backing to the
southeast may limit stronger winds aloft from mixing down to full
potential as well as even warmer temps. Still see SSE sfc winds of
15 to 20+ MPH. If sfc DPTS can mix down lower than fcst more in the
40s for lowered RH values, there may be an enhanced agricultural
field fire threat possibly worth mention in a few products like the
HWO especially west of the MS RVR, but not headline worthy.

Fcst soundings still suggest very dry sub-H5 to H7 MB layer to
overcome, but deep southwest flow will start to top-down saturate in
developing warm and more moist conveyor up off the western Gulf as
Fri night progresses. Convergent elevated warm air advection wing
will look to break out a few elevated showers and possibly an
isolated thunderstorms late Friday night after midnight mainly west
of the MS RVR, but again with such dry low to mid level air column
to saturate, wonder if latest models overdoing coverage an may be
just a few high based sprinkles, virga or light showers skirting the
far west through 12z Saturday morning anyway. Mild overnight lows
well up in the 50s with some areas not all that far away from normal
highs for this time of year.

Saturday and Sunday...
As upstream upper L/W trof organizes and shifts east acrs the
Rockies into western plains, sat still appears to be a breezy mild
day with isolated to sctrd showers still of elevated nature moving
northward acrs the CWA. The latest 00z run models suggest more
coverage with main elevated warm frontal push Sat morning through
midday, before a temporary lull/re-focus back to the west, occurs
during the afternoon. Enough mid level/shower bearing layer MUCAPES
and lapse rates to support thunder Sat, with deep shear values
increasing to near 30 KTs in the afternoon. But uniform southwest
flow in the elevated storm bearing layer suggests only a low to
minimal chance for a severe storm/hailer on Sat. Despite more
clouds, higher sfc DPTs, and passing precip, highs should still make
it in the 70s acrs most of the area for Sat.

The latest run medium range models have slowed some with timing of
the incoming main front and precip event Sat night into Sunday. Any
wave development on the sfc front just to lee of incoming mid and
upper level trof axis may make for a secondary def zone of post-
frontal rains late Sat night though midday Sunday before sweeping
east during the afternoon. Back to Sat night, enough lingering
instability and shear for embedded thunder in any along and post
frontal conveyor of rain, but that should wane after midnight. Even
tapering back the 00z NAM and GFS PWAT feed of 1.2 to 1.4+ inches
up along the front Sat night, still high enough/unseasonable
saturation to fuel widespread rain amounts of a half inch to near 2
inches by midday Sunday...the higher amounts will look to occur acrs
the western third of the DVN CWA in best combo of shear and
saturation Sat night/early Sunday morning. Cooler highs Sunday in
the 60s.

Monday through next Wednesday... Latest 00z run suite of medium
range models are handling digging upper jet intrusions and L/W trof
phasing differently for a lack of confidence in details this far
out. But the general idea is the development of a high amplitude
upper trof acrs the upper midwest and even much of the mid conus
next week, will allow for the spilling down of much colder air out
of Canada Tuesday and possibly later in the week as well/re-
enforcing shot. Highs in the 40s possible by Wed, with tue night
through Wed nigh lows well down in the 30s even with cloud cover.
Afternoon into early evening instability showers possible as well,
with rain-snow mix parameters possible not all that far aloft a few
of those days if showers persist. The Models still got to get a
handle on phasing issues and timing next week for more confidence on
temps/precip trends at this point, but the signal is there.    ..12..

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday Afternoon)
ISSUED AT 1220 PM CDT Thu Oct 19 2017

VFR conditions will be seen through 00z/21 with high pressure in
the Ohio Valley and a storm system in the Plains. After 00z/20 a
marginal LLWS risk develops that will continue through 15z/20. Low
level mechanical turbulence is possible after 15z/20 as deep
mixing of the atmosphere begins.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.
&&

$$

SYNOPSIS...RP Kinney
SHORT TERM...RP Kinney
LONG TERM...12
AVIATION...08