Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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543
FXUS63 KDVN 191802
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
1202 PM CST Mon Feb 19 2018

.UPDATE...
Issued at 1201 PM CST Mon Feb 19 2018

Surface low was over south central Iowa late this morning with
a warm front reaching eastward through southeast Iowa into west
central Illinois. Showers and thunderstorms were north of this
boundary along a more elevated warm front, producing heavy
rainfall and possibly some small hail just north of the highway 30
corridor from Cedar Rapids to Clinton. In the warm sector,
temperatures were climbing into the upper 50s to lower 60s, with
dewpoints in the 50s, while north of the front, temperatures were
much cooler with widespread fog and a corridor of dense fog.

Clearing trends on visible satellite point toward increasing low
level instability in the warm sector in southeast Iowa.
Considering thiS along with strong shear and the timing of the
cold front sweeping through in the wake of the low lifting
northeast this afternoon, will be watching trends closely for
possible strong storms. Forecast max temperatures will likely need
to be further adjusted upwards across the south, where mid to
upper 60s are not out of the question.

Also, will continue to monitor fog trends, as the fog may linger
through the day over the north and northwest along the path of the
surface low. A dense fog advisory may be needed at some point,
likely continuing through the overnight.

&&

.SYNOPSIS...
Issued at 315 AM CST Mon Feb 19 2018

At 2:30 AM CST scattered showers and embedded storms are developing
south to west of the area with trends suggesting upper midwest slowly
moistening up as weak front slowly intensifies just west of the area.
Upstream energy suggests area to stay in the mild air ahead of boundary
into at least tonight with periods of rain and embedded storms until
front passes on Tuesday

&&

.SHORT TERM...(Today) ISSUED AT 315 AM CST Mon Feb 19 2018

Short term forecast confidence assessment...fair to poor with main
issue periods and amounts or rain and embedded storms today. Local
tools all suggest mostly quarter inch or less amounts today with
slowly lowering ceilings and visibilities as moisture pools today.

Today...seasonably quite mild with lower 60s southwest to around 40
degrees today far northwest. Have categorical pops most areas by late
morning with light rain and embedded storms with most locations receiving
less than a quarter of inch and embedded storms possibly seeing up
to a half inch of rain. Locations north of highway 34 by afternoon
could see patchy fog with visibilities at or below a mile in some
locations with moist air over cool ground.

.LONG TERM...(Tonight through Sunday) ISSUED AT 315 AM CST Mon
Feb 19 2018

The winter storm watch has transitioned into a winter weather
advisory. While there is a risk for freezing rain, confidence is low
on where that band will set up. The advisory may shrink or expand in
coverage as the risk area become better defined later today.

Tonight, the first round of forcing exits the area during the
evening followed almost immediately by the second round. Rain with
embedded thunderstorms will be seen generally east of a Dubuque to
Ottumwa line.

In the advisory area, the atmosphere will slowly cool increasing the
risk for freezing rain. What is not entirely know is how far east
the freezing rain will move into the area. Buchanan county and the
northwest part of Benton county should see some freezing rain.
Additionally, there will be a very narrow band where ice
accumulations could exceed one quarter inch. Exactly where this very
narrow band sets up is unknown.

Tuesday, rain will continue across the area during the morning while
the freezing rain changes to more rain in the advisory area.
Attention then turns to Tuesday afternoon and night.

Tuesday afternoon and night the cold front sweeps through the area
changing the rain over to snow. During the transition there will be
a period of sleet and freezing rain. Depending upon how long the
transition lasts and its timing, headlines may or may not be needed.

On Wednesday quiet, dry, and much colder conditions will be seen
across the area as high pressure moves through the Midwest.

Wednesday night the model solutions diverge on their solutions. The
GFS and CMC global keep the area dry while the ECMWF bring a weak
disturbance across the area generating light snow. Based on these
differences, the model consensus has slight chance to chance pops
for the area.

Thursday on...

The weather pattern will remain fairly active through next weekend
with several systems moving through the Midwest. However, there are
differences in regards to track and overall timing. As a result of
these differences, the model consensus has an almost daily risk of
precipitation for the area. Based on what the models are suggesting,
the better chances for precipitation looks to be Thursday night and
again Saturday night.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday Morning)
ISSUED AT 1201 PM CST Mon Feb 19 2018

A low pressure system moving through the area, then lingering
frontal boundry will present a continued challenging, low
confidence aviation forecast. LIFR to VLIFR conditions due to low
clouds and fog look likely at CID and DBQ for the afternoon,
potentially lingering through Tuesday morning. There will also be
rounds of showers and at least isolated thunderstorms into the
overnight hours. Thunderstorms were not mentioned in the forecasts
for now. At MLI and BRL, there will likely be a period of MVFR to
VFR conditions this afternoon, before conditions deteriorate to
IFR to possibly VLIFR overnight into Tuesday morning, along with
several hours of showers and possible thunderstorms.

&&

.HYDROLOGY...
Issued at 315 AM CST Mon Feb 19 2018

River flood watches remain in effect for the Rock River. Across Illinois
rainfall over the next 48 hours may be 1 to 1.5 inches on top of frozen
ground. Depending upon how much rain occurs across the Rock and Green
river basins, moderate flooding may occur at Joslin and Moline. These
forecasts will change depending upon the timing and overall rainfall
amounts. Please see the latest river forecasts and watches for the
most up to date information.

Much smaller streams and creeks may also flood depending upon how much
rain falls over the next two days.

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...Winter Weather Advisory from 9 PM this evening to noon CST
     Tuesday for Benton-Buchanan-Delaware.

IL...NONE.
MO...NONE.
&&

$$

UPDATE...Sheets
SYNOPSIS...16
SHORT TERM...16
LONG TERM...08
AVIATION...Sheets
HYDROLOGY...08



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