Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 151821
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1221 PM CST Sun Jan 15 2017

.UPDATE...
Issued at 1159 AM CST Sun Jan 15 2017

Based on latest model guidance, radar trends, and sfc obs across
southern Iowa and northern Missouri...delayed start time of
portions of the Winter Weather Advisory, mainly in the counties
along and north of I-80, to 12 AM tonight or later. Please see
the latest advisory products for details on county specific timing
and precip amounts.

&&

.SYNOPSIS...
Issued at 321 AM CST Sun Jan 15 2017

Early this morning a 1032 surface high was located over western WI
and eastern MN. This allowed colder air and drier air to filter
into the area. South of the area, precipitation was breaking out
on a wing of warm advection. Temperatures across central MO were
conducive to freezing rain across the area. Higher aloft, a
closed H5 low sat over the far southwestern United States as a
wave from the Pacific started to move on shore. This H5 closed low
will be the primary weather driver in the short term forecast.

&&

.SHORT TERM...(Today thru 18z Monday)
ISSUED AT 321 AM CST Sun Jan 15 2017

Current guidance has continued to slow the arrival time as
previously discussed in other AFDs. This has lead to a slowing of
the onset of precip and changes in the forecast there. H5 low is
still located to the over the Baja of California this AM. Aloft H5
ridging will continue to keep the llvl moisture at bay. At H85,
guidance supports the best convergence to the south of the CWA
until late afternoon today to around 00z Monday. As a result of
this, have slowed down the arrival of pops this morning as well as
the overall POPs. Best forcing for POPs will be as the H5 low
approaches the area, sometime on Monday afternoon.

Ptype will change through the event as warmer more moist air is
mechanically forced north by the strong H5 CVA. A mix of snow,
sleet and fzra expected this afternoon across the far south. As
warmer aloft surges in, this snow will change to all sleet and
then to freezing rain. Current guidance keeps overall QPF low
tonight as the best forcing for precip is associated with the H5
low later Monday. As the chance for rain spreads north through the
period so does this ptype change until temperatures are forced
above freezing from south to north. Overall amounts of ice are
relatively unchanged from earlier shifts, with the exception of
the NW CWA where slightly more has been added.  Across this area,
a prolonged period of fzra may occur, especially if the sfc low
track changes slightly. However, current guidance makes this seems
unlikely . The main impacts from the fzra, sleet and snow will be
overnight tonight. These impacts will quickly end as the fzra
turns to all rain and melts any ice. Untreated surfaces will
become slick and will be the primary impact. At the current time,
no impacts to trees or powerlines are expected.

Current model guidance and forecast points to no change to the
headlines. A headline for the rest of the CWA may be needed as
details about QPF for this area become clearer today.

.LONG TERM...(18z Monday through Saturday)
ISSUED AT 321 AM CST Sun Jan 15 2017

Wet bulb temperatures in the boundary layer are the most important
feature of the forecast Monday afternoon and night. The low level
feed of air will be arriving from the east to southeast, which will
eventually be taping air with dewpoints of 35 to 45 degrees Monday
afternoon and night. This is important, as the advection of the
deeper low level moisture will be what pushes the area above
freezing ending the freezing rain threat. There could be road
temperatures lingering below freezing that may need some extension
of the headlines, but we can address that with higher confidence at
that during the day Monday when we can accurately forecast that.

Otherwise, we will see a strong progressive upper low move over the
area Monday night, with a surface low going directly over the heart
of the CWA. This will draw in moisture efficiently, and bring a
widespread rain, with some possible thunder Monday evening as the
low passes by. Rainfall of 0.50 to 1 inch is possible, with the
higher totals occurring where the convective elements move through
Monday evening. Temperatures and dewpoints should hold in the mid
30s to near 40 during this process, resulting in little if any
additional ice after the transition during the day Monday.
Deformation zone rains may linger into Tuesday morning but will be
much lighter than what occurs through 3 AM.

Tuesday, will see some patchy light rain, possibly mixed with snow
north, but is unlikely to represent any kind of hazard as we remain
in the mid 30s west to near 40 east.

Tuesday night will see some partial clearing, but this is not
certain. For now, will go with guidance lows in the mid 20s to upper
20s. After this, the remainder of the week will be progressively
warm. Highs in the upper 30s to mid 40s Wednesday will rise to the
mid 40s to lower 50s Friday, and warmer yet over the weekend. Rain
chances will increase towards Sunday and early next week, as both
the GFS and EC show deep trof interacting with a moisture plume out
of the gulf in the Midwest at that time.
ERVIN

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday Afternoon)
ISSUED AT 1159 AM CST Sun Jan 15 2017

Main concern next 24 hrs is likelihood for -FZRA to create icy
conditions. A changeover to plain -RA/RA is expected to occur
through Monday morning from south to north. KDBQ may hang on to
-FZRA into the midday timeframe or slightly beyond.

Aside from the precip type concerns...large upper-low with
copious amounts of moisture to bring IFR conditions. Ceilings
will drop quickly as moisture advects in from the south. There
could be periods of LIFR but kept IFR in the TAFs for now. Through
Monday morning, do not think visibilities will drop to LIFR with
ongoing -FZRA/RA. However, beyond this TAF period as the sfc low
moves across E IA/NW IL, periods of dense FG are possible. Uttech

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Winter Weather Advisory from 3 AM to noon CST Monday for
     Buchanan-Clinton-Delaware-Dubuque-Jackson-Jones.

     Winter Weather Advisory from 3 PM this afternoon to noon CST
     Monday for Des Moines-Henry IA-Jefferson-Keokuk-Washington.

     Winter Weather Advisory from midnight tonight to noon CST Monday
     for Benton-Cedar-Iowa-Johnson-Linn-Louisa-Muscatine-Scott.

     Winter Weather Advisory until 9 AM CST Monday for Lee-Van Buren.

IL...Winter Weather Advisory from 3 PM this afternoon to noon CST
     Monday for Henderson-Warren.

     Winter Weather Advisory from midnight tonight to noon CST Monday
     for Henry IL-Mercer-Rock Island.

     Winter Weather Advisory until 9 AM CST Monday for Hancock-
     McDonough.

MO...Winter Weather Advisory until 9 AM CST Monday for Clark-Scotland.

&&

$$

UPDATE...Uttech
SYNOPSIS...Gibbs
SHORT TERM...Gibbs
LONG TERM...Ervin
AVIATION...Uttech


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