Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 122317
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
517 PM CST Mon Feb 12 2018

...00Z AVIATION UPDATE...

.SYNOPSIS...
Issued at 330 PM CST Mon Feb 12 2018

Temporary bout of both sfc and upper ridging to continue through
tomorrow, before these systems give way to a temperature
moderating trend from the west into mid week. Minor precip systems
to monitor Wed into Thu, before a cold front Thu night brings
about a chill down into Friday. Then moderating temps again with
flattening flow over the weekend.

&&

.SHORT TERM...(This Evening through Tuesday)
ISSUED AT 330 PM CST Mon Feb 12 2018

Rounds of cirrus tonight streaming up acrs the region along and
south of west-soutwest 100+ KT upper jet axis should limit a temp
bottom out acrs ongoing deep snowpack acrs much of the fcst area.
Plus there may be some mid deck advecting acrs the area as well
late tonight into Tue. But still want some temp drop off buffer
with low DPTs in place and of course the snowpack, and will
undercut most guidance lows. There could be some non-diurnal temp
trends before dawn if east to southeast sfc winds can increase
enough. Expect rounds of mid and high deck clouds to continue on
Tue for a mostly cloudy day or at least filtered sunshine at
times. South to southeast sfc winds continue to organize as the
day progresses to the west of departing ridge axis, thus the
initial onset of the warm air advection pattern commences. But
with cloud cover and the deep snowpack acrs most of the area, am
leery about going too warm for Tue highs. Will keep the mid to
upper 20s north of I80, to the low 30s to the south. The extreme
southern tier of CWA counties that have lighter snow cover may get
into the mid to upper 30s. Not as cold of night Tue night if
cloud cover and return flow hold up...a lot of upper teens and
20s.

.LONG TERM...(Tuesday Night through next Monday)
ISSUED AT 330 PM CST Mon Feb 12 2018

Wednesday and Thursday...On Wed, the latest 12z run models lift up a
wave in steering flow west-southwesterlies along and south of the
region. LLVL flow will look to become southwesterly and breezy as
the day progresses adding to the warming process. But the trick will
be if deep enough LLVL moisture under building inversion aloft will
occur to allow precip to break out. Most models do break out at
least some light spotty precip over the central into eastern CWA,
maybe hinting at some drizzle. If the precip takes place out of the
top-down saturation above the inversion, feel deep dry layer
associated with the inversion would prevent any precip from reaching
the surface. So a low confidence precip scenario on Wed. Despite the
strong warm air advection(more of it realized into building warm
wedge aloft), like the previous shift mentioned much of it/LLVL WAA
going into the snow melt process and will rob from the warm up
potential on Wed. Will undercut most guidance highs and keep them in
the upper 30s to low 40s, and worried this may be too mild except in
the far south. Will also keep the fog mention later Wed night into
Thu morning with snow melt and increasing sfc DPTs juicing up the
sfc layer.

May have to keep in mind some drizzle possible later Wed night in
any developing lower stratus cloud deck. Thursday, the next wave
ripples along incoming cold front for a better precip chance. again
the models vary on low level baroclinicity lay out and precip
handling, such as the 12z GFS keeping most of the rain southeast of
the DVN CWA, while the 12z ECMWF streams up anywhere from 0.05 to
over 0.15 of an inch of rainfall acrs most of the area as the day
progresses...ending by Thu evening as the post-frontal cold push
deepens from the northwest. For now will carry low to moderate CHC
POPs acrs most of the area as a happy medium. The algorithm
continues to break out a period of freezing rain and sleet on the
northwest flank of the precip shield acrs the northwestern CWA THu
morning. But with onset of precip timing here possibly delayed until
mid to late morning when sfc temps recover above the freezing mark,
this another lower confidence scenario...if these areas get any
precip at all on Thu.

Friday through next Monday...Cold push and Canadian high pressure
settle in for a chill down by Friday, high temps knocked down well
into the 20s or even upper teens in the northwest, with cold
Saturday morning lows-single digits possible north of I80. Then the
up-and-down temp regime continues, as passing upper trof leads into
a flattened westerly flow pattern acrs the mid CONUS, allowing for
temp moderation again from the south. Much will depend on
deterioration of the ongoing snowpack, but signs of a return to the
30s and even some 40s in the south by Sat. Some fog potentail Sat
night, followed by another increasing warm flow sector possibly
boosting temps area-wide in the 40s by Sunday. Increasing moisture
return as well up along a LLVL thermal ribbon aligning from NE-to-SW
along and west of the DVN CWA may fuel increasing rain and drizzle
chance by Sunday afternoon and evening, and depending on the model,
some precip type issues popping up if the precip lingers well into
sunday night and monday morning. The 12z GFS says snow chances by
next Monday, while the EURO is further west with stalled front and
warmer for more of a rain or rain-snow mix scenario.   ..12..

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday Evening)
ISSUED AT 516 PM CST Mon Feb 12 2018

High pressure over the region today will provide VFR conditions
through Tuesday. Light winds will turn to the south around 10 kts
by Tuesday afternoon.

&&

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

$$

SYNOPSIS...12
SHORT TERM...12
LONG TERM...12
AVIATION...Sheets



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