Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 141808
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1208 PM CST Tue Nov 14 2017

...18z AVIATION UPDATE...

.SYNOPSIS...
Issued at 322 AM CST Tue Nov 14 2017

High pressure centered at the surface has pushed east into the
lower Great Lakes allowing widespread stratus over the southern
and central Plains to spill back north and east across all of
Iowa and into far northwest Illinois early this morning. Under the
clouds, temperatures across the forecast area ranged from the
lower 30s north to lower 40s south, while readings had cooled into
the upper 20s in the clear skies over northern Illinois. Some
light fog had developed overnight mainly north of Interstate 80,
but surface winds of 5 to 10 mph has kept visibilities above 3
miles.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 322 AM CST Tue Nov 14 2017

Cloudy, cool and damp conditions will be the focus today and
tonight. Today, low level isentropic lift overspreads the area in a
warm advection pattern ahead of a cold front approaching from the
plains. Drizzle, developing over central IA early this morning will
spread eastward with isolated showers currently over western MO
possibly reaching into the far southwest this morning. Overall, the
setup is more favorable for drizzle during the day with sufficient
winds keeping fog from being an issue. Temperatures will continue to
rise to a range from the lower 40s northeast to upper 40s south by
afternoon.

Tonight, showers will be focused along and ahead of a cold front
progged with decent agreement among the models to push into eastern
IA toward morning and have highest pops after midnight. Steep mid
level lapse rates may support at least an isolated elevated
thunderstorm well in advance of the boundary across northeast MO,
far southeast IA into west central IL after midnight. Temperatures
will remain nearly steady in the 40s through the night. With only
modest forcing and limited moisture, qpf looks light for this
system with most areas well below a quarter of an inch.

.LONG TERM...(Wednesday through Monday)
ISSUED AT 322 AM CST Tue Nov 14 2017

The storm system will depart the area on Wednesday. The best chances
for rain will be east of the Mississippi during the morning hours
with dry conditions developing across the entire area during the
afternoon. Temperatures should be close to normal.

Quiet and dry conditions are then expected Wednesday night and
Thursday as high pressure moves through the Midwest. Temperatures
are expected to average below normal. Attention then turns to the
next storm system.

Return flow develops ahead of the next system Thursday afternoon but
the proximity of the high over the Great Lakes means that Thursday
evening will be dry. After midnight, the model consensus has chance
pops for the area.

However, there are questions regarding how much moisture will be
available to generate precipitation. Each global model has been
slowly backing off on the overall amount and areal coverage of
precipitation late Thursday night. If this trend continues then the
possibility does exist that part of the area may remain dry late
Thursday night.

The return flow also raises questions regarding precipitation type.
Cooling of the atmosphere when the precipitation begins raises the
possibility of a rain/snow mix or perhaps all snow before changing
over to all rain.

Friday on...

The storm system moves through the area Friday and Friday night with
it exiting the area Saturday morning. There are differences in the
overall timing and track of the system. The GFS is the fastest and
further north while the ECMWF/CMC global are slower and more to the
south. As a result, the model consensus has likely to categorical
pops Friday, chance to categorical pops Friday night, and slight
chance to chance pops Saturday.

The track of the system will be important regarding precipitation
type. Right now precipitation looks to be in the form of mainly rain
with possibly a rain/snow mix developing as the precipitation ends
from the west late Friday night into Saturday. There does appear to
be a low risk of thunderstorms Friday evening when the strongest
forcing associated with the cold front moves through the area.

Saturday night through Monday the model consensus has quiet and dry
conditions for the area as high pressure slowly moves through the
Midwest. Temperatures will average below normal with Sunday looking
to be the coldest day with highs in the 30s.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday Afternoon)
ISSUED AT 1155 AM CST Tue Nov 14 2017

Low MVFR Cigs and VSBYs from fog and drizzle this afternoon to
deteriorate into IFR or even bouts of LIFR conditions tonight
into early Wed morning. The drizzle to be replaced in spots to
more of organized sctrd showers from mid evening and into the
early Wed morning hours. An elevated thunderstorm even possible
in the VCNTY of MLI and BRL after midnight. All this occurring
while most of the area experiencing low CIGs under 1000 FT AGL
and areas of fog. Then northwest winds increasing to at least
15-25 KTS by mid to late Wed morning behind a passing cold front,
also helping to lift CIGs.   ..12..

&&

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

$$

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



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