Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 021134 AAA
AFDDVN

Area Forecast Discussion...UPDATED
National Weather Service Quad Cities IA IL
534 AM CST Fri Dec 2 2016

...12z AVIATION UPDATE...

.SYNOPSIS...
Issued at 320 AM CST Fri Dec 2 2016

A weak surface trof drifted south across the CWA this morning.
This trof was associated with a low pressure located northwest of
the Great Lakes. Weak sfc convergence along this boundary led to
the development of drizzle and even some isolated snowflakes early
this morning. This boundary is expected to sag south through the
day and will be the primary weather producer in the short term.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 320 AM CST Fri Dec 2 2016

Zonal to slightly NW flow at H5 will aid in advecting in slightly
drier and cooler air today as a sfc trof slowly drifts south.
Most of the spectral and gridded synoptic models mix this boundary
out across the area as it slowly sags south. On the other hand,
hires guidance suggests that this convergence will lead to
isolated drizzle again today across the area. Not entirely
convinced that we will see this drizzle as I can`t seem to find
much rising motion across the area. At this time, will lead the
mention of drizzle out of the forecast and pass on to later shifts
the potential.

Cloud cover and neutral to cold air H85 temp advection will lead
to a repeat of yesterday for most of the area. Temps will range
from the mid 30s to the low 40s across the CWA.

.LONG TERM...(Saturday through Thursday)
ISSUED AT 320 AM CST Fri Dec 2 2016

Colder and unsettled with increasing chances of snow or snow/rain
mix this weekend and especially by late next week.

Long Term Forecast Confidence Assessment...poor or below average
with timing and amounts of snow or rain/snow a challenge. Large
changes inter model and model run to runs. The amounts of snow for
this weekend may easily be off by 50% with a 1 to 3 solution a
decent best fit curve on mostly grassy surfaces along and south of
highway 34 and slushy main roads I-80 north in AM.  Then, increasing
regime flow quite favorable for a significant storm system middle of
next week with snow or rain/snow changing to snow near or over the
forecast area.

Saturday and Saturday night...fair early then increasing clouds and
seasonably cold, with high pressure overhead. Highs mostly 35 to 40
degrees with light winds.  Saturday night...should see clouds to
continue to thicken with areas of light snow arriving in the west by
daybreak.  Any snow accumulations should be mostly less than a half
inch and mainly in the western sections.  Lows should be mostly in
the lower to middle 30s and with our warm ground should limit snow
accumulations to mostly the grassy surfaces, especially along and
south of highway 34.  Winds to be light and southerly.

Sunday...Areas of light snow in the morning with a rain/snow mix by
mid to late day before ending mid PM.  Local forcing tools support
another half inch to locally 2 inches of snow possible with again
mostly grassy surfaces as highs rise into the upper 30s to lower 40s
by afternoon.  Sunday night...clearing with lows around 30 degrees
in the forecast but any snow cover may result in lows 3+ degrees
colder for later shifts to reconsider.

Monday...skies to become cloudy with a chance of light rain or
possibly a rain/snow mix with late PM and overnight with next
disturbance ejecting ahead of deep trough in the west. Temperatures
should see highs in the lower 40s with lows to more likely be
in the middle 30s Monday night for later shifts to reassess.

Tuesday...Colder air to arrive from Canada with low POPS that may be
able to be removed with ridging ahead of main low developing in the
southwest US.  Highs 35 to 40 degrees suggested with lows in the low
20s NW to upper 20s SE that will allow for ground to cool ahead of
next system.

Wednesday and Thursday...all trends support a moderate to possibly
very strong storm system to eject near or over the region. Local
track analogs suggest risk of several inches to well over 6 inches
of snow over much of the region before system moves northeast by
late Thursday is very possible and will be better known next 24 to
36 hours.  Local techniques also suggest 20 to 40+ MPH winds by
Thursday as low moves east with temperatures staying at or below
freezing for the precipitation event with teens or single digits by
Thursday and especially Thursday night.  Will emphasize the possible
significant snow event in HWO product.

Friday...at some partial clearing and quite cold and likely temps
are too mild for highs by 3+ degrees with any snow cover.  Lows with
clear skies friday night may be near to below zero in favored
locations.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday Morning)
ISSUED AT 534 AM CST Fri Dec 2 2016

Mostly MVFR cigs, with brief periods of VFR cigs are expected
today as a weak surface trof sags slowly across the area. Winds
are not expected to be strong. Some drizzle is possible today,
however confidence is low in this occurring. If drizzle occurs
later in the day and into the evening, there is a very low chance
that this could turn to a frdz at the TAF sites. Later shifts will
need to keep an eye on this.

&&

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

$$

SYNOPSIS...Gibbs
SHORT TERM...Gibbs
LONG TERM...Nichols
AVIATION...Gibbs



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