Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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459
FXUS63 KDVN 251142
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
542 AM CST Sun Feb 25 2018

...HYDROLOGY UPDATE...

...AVIATION UPDATE...

.SYNOPSIS...
Issued at 345 AM CST Sun Feb 25 2018

Strong upper level shortwave and deepening 992 mb surface low
were lifting into the upper Great Lakes early this morning. The
tight pressure gradient and pressure rises in its wake were
resulting in windy conditions over the forecast area with west
winds from 20 to 30 mph and some gusts near 50 mph earlier
tonight. Satellite imagery showed associated low clouds in the
cyclonic flow covering northern Illinois extending west over much
of eastern Iowa Iowa at 3 am. Temperatures were in the upper 20s
and lower 30s.

&&

.SHORT TERM...(Today and Tonight)
ISSUED AT 345 AM CST Sun Feb 25 2018

Quiet weather dominates the short term with temperatures the primary
forecast challenge. Initially brisk west winds will gradually
decrease today as high pressure moves into the Ohio River Valley
under a weakly confluent flow aloft. The low clouds should shift
east of the forecast area by mid morning, followed by near full
sunshine through at least mid afternoon. There is then a likelihood
for a period of high level cloud cover moving in late afternoon into
the evening with a passing upper level shortwave. Sunshine and
sufficient mixing today support model blend highs from the mid 30s
north to mid 40s south. Tonight, winds become light southwest
with skies returning to mostly clear by midnight. This should
allow temperatures to cool to lows in the 20s.

.LONG TERM...(Monday through Saturday)
ISSUED AT 345 AM CST Sun Feb 25 2018

Monday and Tuesday

Southerly winds and an increasing late February sun angle will lead
to mild temperatures more typical for late March or early April.
Forecast highs are 40s and 50s on Monday, then 50s and 60s on
Tuesday. A taste of spring for sure!

Wednesday through Thursday

An area of low pressure will bring widespread precipitation to the
forecast area, especially from Wednesday evening or night into
Thursday.

The ECMWF has come more in line with the other models on the
evolution of the low, but it remains a weaker outlier with
significant cyclogenesis occurring to our east over Ohio. The GFS,
GFS ensemble mean, and CMC have more run-to-run consistency with the
phasing of two upper shortwaves further to the west. The CMC and GFS
ensemble mean track the surface low from the Oklahoma Panhandle to
NW Indiana, the deterministic GFS is slightly further north. Either
track would tap into a plume of Gulf of Mexico moisture.

Precipitation Amounts and Type:

There is potential for an inch or more of precipitation across parts
of the area, although it`s still early and confidence is low at this
lead time on placement of the heaviest band (GFS PWATs are slightly
over 0.75 inches or 1-1.5 standard deviations above the late
February mean). Thermal profiles are mild ahead of this system which
supports rain as the dominant precipitation type initially.
Depending on the amount of cold air the low can wrap in, and on the
degree of dynamic or evaporative cooling, a period of snow is
possible on the backside of the low, mainly across the north. Winds
could also be fairly strong across the entire area.

Friday On

Expect seasonable temperatures and dry conditions to end the week
with a 500mb ridge over the Central U.S. A chance for precipitation
returns on Sunday. Uttech

&&

.AVIATION...(For the 12Z TAFS through 12Z Monday Morning)
ISSUED AT 542 AM CST Sun Feb 25 2018

Low clouds associated with a departing storm system will exit the
terminals early this morning, with clearing skies and VFR
conditions to follow through the rest of the forecast period.
Strong, gusty west winds early this morning will decrease to a 12
to 15 kt range by midday. Winds will then drop below 10 kts by
evening and become southwesterly.

&&

.HYDROLOGY...
Issued at 542 AM CST Sun Feb 25 2018

Moderate to major flooding continues on portions of the Rock River
and Pecatonica River in Illinois.

Tributary rivers in Iowa were on the rise this morning due to
runoff from yesterday`s rainfall on top of the saturated ground.
The Wapsipinicon and Maquoketa rivers were showing the most
response and fastest rises. A flood warning for minor flooding was
issued this morning for the Wapsi at Dewitt with the river
expected to reach flood stage by 8 am. Elsewhere, the rises are
expected to remain within banks.

Rock River: Major flooding is on-going at both Joslin and Moline.
Latest reports from Saturday suggest river ice is not having a large
impact on river levels. At Joslin, river levels were receding after
having crested Friday and Saturday. Downstream at Moline, the river
appears be in the process of cresting around 15.3 and latest
readings suggest it may be beginning to fall. At both sites, stages
were falling a bit slower than forecasts and updated forecasts
that account for runoff from yesterday`s rainfall, continue to
delay the the rate of fall. Further upstream, Como is slowly
rising just below flood stage and this rise is expected to
continue, pushing the stage back into Minor flooding this morning.

Pecatonica River: Moderate flooding was occurring and latest
readings showed it approaching Major flood stage of 16 feet early
this morning. This may result in renewed rises and impacts along
portions of Yellow Creek.

&&

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

$$

SYNOPSIS...Sheets
SHORT TERM...Sheets
LONG TERM...Uttech
AVIATION...Sheets
HYDROLOGY...Sheets



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