Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 200442
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1142 PM CDT Thu Oct 19 2017

...06Z AVIATION UPDATE...

.SYNOPSIS...
Issued at 242 PM CDT Thu Oct 19 2017

18Z surface data has a weak boundary from northern Ohio, into
southeast Iowa, and back into the eastern Dakotas. North of the
boundary dew points were in the 20s and 30s. South of the boundary
dew points were in the 40s and 50s.

&&

.SHORT TERM...(This Evening through Friday)
ISSUED AT 242 PM CDT Thu Oct 19 2017

Quiet and dry conditions will be seen through sunset Friday. Breezy
conditions are expected west of the Mississippi on Friday.
Temperatures will average above normal.

.LONG TERM...(Friday Night through Thursday)
ISSUED AT 242 PM CDT Thu Oct 19 2017

Wet for the weekend then turning much cooler next week.

Quiet and dry conditions will continue Friday evening across the
area. Attention then turns to the approaching storm system for the
weekend.

Late Friday night moisture will move into the area ahead of the
storm system. The atmosphere will initially be quite dry so the
forcing present will initially go into cloud production. Internally,
the models are showing some unstable air aloft that may allow some
sprinkles or possibly rain showers to develop. Right now the model
consensus has slight chance pops over the western third of the area
where the moisture is slightly higher.

The overall large scale picture for Saturday/Saturday night points
to a general rain with the front. The better forcing continues to be
along and behind the front. Ahead of the front the forcing continues
to be weak. Thus there are questions to how far east the rain will
get before sunset on Saturday. Right now the model consensus has
slight chance to chance pops along and west of the Mississippi
during the day on Saturday.

Saturday night the main precipitation event will occur as the front
moves through the area. A general rain will be seen with this system
with embedded thunderstorms. The model consensus has likely to
categorical pops for the entire area.

On Sunday, the rain will end from west to east during the day.

Sunday night on...

Mainly dry conditions will be seen Sunday night and Monday as an
upper level low develops over the Great Lakes. Temperatures should
be close to normal.

Starting Monday night and continuing through Wednesday the global
models diverge regarding the evolution of the upper low developing
across the Great Lakes. The CMC global has the upper low further
west and maintains it longer before pushing it east. The ECMWF is
further south than the CMC global but pushes the upper low east more
quickly. The GFS has only an upper level trof that pushes quickly
east.

As a result of these differences, the model consensus has slight
chance to chance pops in each period Monday night through Wednesday.
A majority of the precipitation should be diurnally driven with the
higher pops in the afternoon/evening hours. However, given the
disturbances rotating around the upper low and cold air aloft, some
showers are expected to persist through the night. Temperatures will
average below normal due to cloud cover and precipitation.

Wednesday night the model consensus has dry conditions for the area
as the upper level low moves into the Ohio Valley.

On Thursday the models indicate another cold front will sweep
through the area. Moisture availability is in question with high
pressure from the Ohio Valley into the Gulf. The GFS/ECMWF have a
dry frontal passage while the CMC global has precipitation. The
better forcing looks to be from Minnesota into Wisconsin with what
moisture is available. Right now the model consensus has slight
chance to very low chance pops across the northeast third of the
area.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday Night)
ISSUED AT 1141 PM CDT Thu Oct 19 2017

Light surface winds, below southwest winds around 30 to 35 kts
above 1000 ft agl, will result in low level wind shear conditions
overnight at CID and DBQ. MLI and BRL are expected to have lower
speeds aloft, below LLWS criteria, and thus LLWS was not included
in the forecast. Otherwise, VFR conditions will continue with dry
air and mostly clear skies. Surface winds will again become gusty
from the south during the afternoon hours Friday. Friday night,
LLWS may again be an issue by late night, and may be included in
later forecasts.

&&

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

$$

SYNOPSIS...08
SHORT TERM...08
LONG TERM...08
AVIATION...Sheets



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