Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 181815
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1215 PM CST Wed Jan 18 2017

...Noon Hydrology Update...

.UPDATE...
Issued at 1012 AM CST Wed Jan 18 2017

Major changes to the overall forecast. New forecast will be
available by 1030 AM.

Satellite shows a large expanse of low clouds across the area.
Morning sounding and RAP trends indicate the strong inversion will
remain in place through sunset suggesting clouds will persist
through the day and into tonight.

Thus the forecast has been updated to keep more clouds across the
area, lower max temperatures today, and raise min temperatures
tonight.

However, per the morning sounding and RAP trends, the moisture
layer producing the clouds is quite shallow. Satellite shows a
rather sudden hole developed in the clouds around KSTL and is
getting larger. If this trend continues, it would raise questions
regarding keeping clouds across the area.

&&

.SYNOPSIS...
Issued at 302 AM CST Wed Jan 18 2017

A large blanket of stratus covers the Midwest, with clearing
beginning from Minneapolis to Topeka. The stratus is lifting
northeast, and shows some signs of subsidence with a few holes in
the flow over southern Iowa and Missouri. Temperatures are going no
where, as we are still holding in the lower to mid 30s.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 302 AM CST Wed Jan 18 2017

The clearing of stratus will be the main challenge today. Models
move it out quickly, but that seems unlikely given the time of year,
the inversion developing, and the current stratus deck expanse.  The
flow increasing from the southwest at the surface has helped mix out
the low level RH some, and we are seeing both visibilities increase
and ceilings lift some. Thus, we will hold onto stratus through mid
morning, and show a decrease through the early afternoon. With this
cloudier than models forecast, I`ve gone a few degrees under
guidance for highs. As with all stratus waa days, this could bust
both ways, so this is seen as a least error forecast. Highs in the
lower 40s north to upper 40s southwest are forecast. Should clearing
occur quickly this morning, we could reach the lower 50s south.

Tonight, initial clear skies should allow for lows to drop the upper
20s northeast to lower 30s southwest. Clouds should arrive at mid
and upper levels again by late evening.

ERVIN

.LONG TERM...(Thursday through Tuesday)
ISSUED AT 302 AM CST Wed Jan 18 2017

Long forecast warm up with spring like temperatures is still on
track for the extended.  Temperatures are still forecast to be 10 to
20 degrees above normal through the long term.  Sporadic chances for
precip will be possible through the extended.  With the exception of
the end of the long term period, thermal profiles are warm enough
for all rain across the area.

Thursday, upper level low that is slowly lumbering across the
central United States will lead to S flow at H5.  This will help to
usher in warmer air.  With the low in the area, skies will be mostly
cloudy and could impact overall warming.  Half of the guidance
brings in QPF on Thursday as the vort max rotates north through the
area. The best chance for rain will be later during the day and
through the overnight into Friday morning. Temperatures on Thursday
and Friday could be slightly over done due to cloud cover and
potential precip. Late Friday, the wave finally moves through the
area.

Active flow into next week brings numerous chances for precip.  A
system and associated surface low will track west of the CWA on
Saturday. At this time overall QPF looks to be low. Another
shortwave is forecast through the area on Monday and will quickly
move out of the area leading to another chance of rain.  Midweek
next week, the GFS and ECMWF brings a H5 low over the area, while
the GEM advertises a ridge across the area.   Overall confidence in
the system next week is low and is expected to change.

&&

.AVIATION...(For the 18Z TAFS through 18Z Thursday Afternoon)
ISSUED AT 1122 AM CST Wed Jan 18 2017

LIFR/IFR conditions will continue through at least 18z/19 across
eastern Iowa and northern Illinois. A strong inversion was
trapping a shallow layer of moisture/clouds across the area. A
break in the clouds may allow a brief period of VFR conditions
through 00z/19. After 06z/19 patchy fog will again be possible
that might result in VLIFR conditions.

&&

.HYDROLOGY...
Issued at 1210 PM CST Wed Jan 18 2017

Rock River: Flow routed from upstream as well as ongoing ice
action may produce sudden spikes above flood stage at Como, thus a
flood warning has been issued for that site. Flood warnings for
moderate flooding continue at Joslin and Moline. At Moline, there
is still some uncertainty in routed water flow toward this site from
the Green River, and there is some concern that this location may
rise above the Major flood stage. Also, ice movement in the river
may cause rapid fluctuations in the stage at this location.

Mississippi River: The latest river stage trends indicate that
river levels continue to rise at both sites(Gladstone and
Burlington) that are in moderate flood. Increased flow from runoff
from recent rainfall, and the ongoing ice jam downstream of
Burlington will likely lead to continued rises on the Mississippi
in these areas as well as possibly a bit further upstream. Once
the ice jam erodes and eventually frees, expect the levels in the
river around the sites in flood to drop noticeably.

Other sites: Recent rainfall/run-off combined with ice action is
also producing rises to or near the flood stage at some sites on
the Iowa River in Iowa. And a localized areal flood warning is
ongoing until at least 115 PM CST this afternoon west of the
official forecast point of Geneseo IL on the Green River, for a
reported ice jam producing flooding. With ongoing uncertainties
with high water interacting with a levee near Colona IL, the flash
flood watch already in effect has been extended through 4 PM CST
this afternoon for Henry County, in case there is a breach in the
levee.

The rivers area-wide will have to be watched for more ice action
and jams possibly producing additional flooding during the rest of
the week of unseasonably mild weather and more rainfall.   ..12..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...Flash Flood Watch until 4 PM CST this afternoon for Henry IL.

MO...NONE.
&&

$$

UPDATE...08
SYNOPSIS...Ervin
SHORT TERM...Ervin
LONG TERM...Gibbs
AVIATION...08
HYDROLOGY...12



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