Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 301751
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1151 AM CST Wed Nov 30 2016

...18z AVIATION UPDATE...

.SYNOPSIS...
Issued at 321 AM CST Wed Nov 30 2016

Water vapor imagery and obs show vertically stacked low over east
central MN early this morning, with a broad upper level trough
extending into the Southern Plains. Occluded frontal boundary was
to our east. Incoming colder air is accompanied by large area of
stratus, which has overspread much of the cwa west of the Mississippi.
Regional radar imagery shows areas of generally light rain/snow
from the Dakotas through northwest IA into MN attendant to spokes
of energy rotating around the low.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 321 AM CST Wed Nov 30 2016

Vertically stacked low will continue to fill while shifting through
the Great Lakes during the period. Strengthening cyclonic flow will
yield considerable clouds and colder conditions, with light precipitation
chances.

Stratus shield west of the Mississippi River will continue to overspread
the rest of the cwa this morning, and could be accompanied by a stray
sprinkle or flurry in CAA. Main window for precipitation chances though
will be from late morning through early evening, as lobes of energy
currently aiding light precipitation over MN/SD rotate across the region.
Precipitation chances will be greatest north of I-80 where have likely to
categorical pops for what looks like fairly widespread light precipitation
event, which could extend down to around I-80. The precipitation will
gradually migrate/lift to northeast cwa by late evening and overnight.
Forecast soundings show deep saturation with no elevated warm layer,
thus precipitation type will simply boil down to surface and boundary
layer temperatures, and as a result will have forecast ptype of rain/snow.
Diurnal processes may result in rain being more predominate during the
daytime hours. Overall, expect this to be a high pop/low qpf event with
precipitation amounts ranging from a trace to several hundredths of an
inch. Warm ground should limit any accum of wet snow, with perhaps a
dusting or so possible on grassy surfaces and this would mostly be favored
late PM into evening north of Hwy 30.

As for temperatures, do not expect them to climb much today with readings
mostly in the upper 30s to lower 40s. Tonight, with blanket of clouds
expect narrow diurnal around 5-7 degs thus lows mainly in the
lower 30s.

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 321 AM CST Wed Nov 30 2016

Another upper level disturbance will rotate through the upper
Midwest on Thursday. The current forecast has dry conditions but I
would not be surprised if some sprinkles/flurries or even isolated
rain/snow showers occur north of highway 30.

Thursday night through Friday night quiet and dry conditions will be
seen across the area as high pressure moves through the Midwest.
Temperatures should be close to normal.

Saturday on...

The hemispheric flow pattern is becoming very energetic. When the
flow pattern becomes this energetic, model sensitivity to initial
conditions shows up as a lack of run-to-run continuity.

The model consensus for Saturday is for quiet and dry conditions.
Here the signal has been persistent so confidence is high that
Saturday will be dry with temperatures near normal.

Saturday night into Sunday the models are indicating a storm system
will move through the Midwest. Again, the signal for a storm has
been persistent but the individual models have varied on their
respective solutions. In addition, run-to-run continuity has been
poor. Thur current confidence in this time frame is low to medium.

Right now the model consensus has slight chance pops over the
southwest third of the area Saturday evening, chance pops late
Saturday night/Sunday morning, and slight chance pops over the
northeast third of the area Sunday afternoon. Precipitation would
generally be in the form of a rain/snow mix or possibly snow that
changes to all rain on Sunday. The warm ground would prevent any
accumulation.

However, some models either keep the high over the Great Lakes
longer or have a deeper layer of dry air over the area. Thus the
possibility does exist that Saturday evening may end up being dry
with precipitation moving in after midnight. The longer it takes
before precipitation beings Saturday night, the better the chances
are it will be a rain/snow mix or even rain.

Sunday night/Monday the model consensus has dry conditions as yet
another high pressure moves through the Midwest. Confidence in this
time frame is medium to high.

Monday night/Tuesday the models differ greatly on their respective
solutions. Additionally, run-to-run continuity of the individual
models is very poor. As a result, confidence in this time frame is
low.

The ECMWF has only a frontal passage with little or no
precipitation. The CMC-global/GFS/DGEX have weak to very weak
systems producing light precipitation. Yesterday, the models had
much stronger systems but poor run-to-run continuity.

Right now the model consensus has slight chance to chance pops
Monday night and Tuesday with precipitation being a rain/snow mix.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
ISSUED AT 1142 AM CST Wed Nov 30 2016

Mainly a MVFR cloud deck to continue this afternoon and into the
overnight south of a western GRT LKS cyclone. Embedded areas of
light snow or rain-snow mix will be possible at CID and DBQ this
afternoon and evening, before clearing off to the east by
Midnight. This precip will temporarily reduce VSBYs at these
sites down to 3-4SM at times, and a chance to lower the CIGs to
IFR levels at DBQ. Generally westerly sfc winds of 10-20 KTS
through the TAF period.   ..12..

&&

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

$$

SYNOPSIS...McClure
SHORT TERM...McClure
LONG TERM...08
AVIATION...12


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