Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 262342
AFDDVN

Area Forecast Discussion
National Weather Service Quad Cities IA IL
542 PM CST Sun Feb 26 2017

...00z AVIATION UPDATE...

.SYNOPSIS...
Issued at 248 PM CST Sun Feb 26 2017

A west to southwest breeze gusted over 30 mph during the early
afternoon, and brought milder air into the region. Early afternoon
temperatures ranged from the low 40s to low 50s. Clouds were on
the increase over the southwest third of Iowa, into western
Illinois.

&&

.SHORT TERM...(This Evening through Monday)
ISSUED AT 248 PM CST Sun Feb 26 2017

Short term forecast issues include consideration of light
precipitation over parts of the forecast area into this evening,
as well potential for fog.

In the near term, a robust CU field continues to develop along a
weak moisture convergence axis from southern Iowa to near the Quad
Cities. Most high-res models suggest some light rain/sprinkles
developing during the late afternoon, mainly along and south of
Interstate 80. This is supported by recent radar trends.
Channeled vorticity moving into the area should help light
precipitation continue after sunset. The 18z 12km WRF is lingering
this precipitation after midnight, with cooling near surface temps
allowing for some light snow. Confidence in this scenario playing
out is low, and only have a mention of scattered sprinkles
through early evening. Overnight, the weak convergence zone is
forecast to lift slowly north across the forecast area. Do not
believe widespread dense fog is going to happen, as the more
favorable low level moisture does not look to be coincident with
the convergence, but have matched neighbors with a mention of
patchy fog after midnight.

For Monday, WAA will continue ahead of the next wave set to
arrive Monday night. Expect an even milder day across the area,
with highs in the upper 40s north to upper 50s south.

.LONG TERM...(Monday Night through Sunday)
ISSUED AT 248 PM CST Sun Feb 26 2017

An active weather pattern will be seen over the next 7 days with a
warming trend the first part of the week. Cooler temperatures will
be seen the second half of the week but temperatures should
generally average above normal.

A river flood watch has been issued for parts of the main stem
Mississippi. Refer to the hydro section for information on area
rivers.

Strong return flow will usher moisture back into the area Monday
night. As forcing increases after sunset, isolated to scattered rain
showers will develop. Forcing will increase further after midnight
with a passing upper level disturbance that has the potential to
develop some isolated thunderstorms.

On Tuesday, isolated to scattered rain showers will be seen across
the area during the morning as a slightly stronger storm system
moves northeast from the southern Plains. Tuesday afternoon, rain
showers will increase in areal coverage and isolated to scattered
thunderstorms will also develop as the storm system moves into the
area.

Areas south of a Kirksville, MO to Sterling, IL line have the best
chances of seeing thunderstorms Tuesday afternoon and evening.
However, isolated thunderstorms will be possible across the entire
area Tuesday afternoon.

Tuesday night into Wednesday the storm system will move east of the
area. Colder air being pulled in behind the storm will allow snow to
mix with the rain late Tuesday night into Wednesday morning before
ending during the afternoon. Much cooler conditions will be seen
across the area on Wednesday with temperatures near normal.

Wednesday night on...

Quiet and dry conditions look to be in store Wednesday night as high
pressure moves through the area ahead of an approaching clipper type
system. Temperatures should be close to normal.

On Thursday, a weak clipper type system will move through the area
bringing a threat of light snow or a rain/snow mix. Moisture is
limited and the better forcing is north of the area so any snow that
occurs should be a dusting at best.

Thursday night through Saturday night the model consensus has dry
conditions for the area as high pressure moves through the Midwest.
There is a weak disturbance moving through the flow aloft around
Friday that may or may not produce some precipitation. Return flow
developing Friday night will result in temperatures above normal for
Saturday.

On Sunday the model consensus has slight chance to chance pops over
mainly the eastern half of the area as another storm system moves
through the area. There are differences between the model solutions
which could delay the arrival of the precipitation until Sunday
night. Temperatures Sunday will average well above normal.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday Evening)
ISSUED AT 523 PM CST Sun Feb 26 2017

Main focus is with fog potential. More guidance on board with fog
development late tonight through Monday AM, especially from
around MLI through BRL. Sprinkles/light showers have aided in
moistening of boundary layer in these areas with dew points in
the upper 20s to lower 30s. Also, clearing skies later tonight
and light winds ahead of a developing warm front will lead to
a favorable fog setup. Have trended conditions down from previous
TAFS with IFR vis/cigs at BRL and MLI late tonight through mid
morning Monday. LIFR/VLIFR conditions are being suggested at MLI
and BRL by several pieces of guidance, but confidence not there
just yet and prefer to trend toward such a scenario. I have kept
a period of MVFR visibilities around daybreak at CID and DBQ.
Some guidance is showing IFR to possibly even LIFR developing into
CID toward mid morning ahead of the advancing warm front, but not
as much model consensus thus too low of confidence to include any
lower conditions.

&&

.HYDROLOGY...
Issued at 248 PM CST Sun Feb 26 2017

Rain expected this week combined with warmer temperatures will add
additional water to area rivers. This additional water will then
combine with routed flow coming from upstream to help push river
levels higher. Individuals with interests along area rivers should
pay attention to weather and river forecasts over the next 7 to 10
days.

Iowa tributary rivers...

Iowa tributary rivers will see rises over the next 7 to 10 days,
especially the Wapsipinicon, Cedar, and Iowa rivers. Several
locations are forecast to approach flood stage. The Cedar river near
Conesville is expected to crest around 0.5 feet above flood stage
early this week. How much rain occurs this week and how quickly the
snow melts across northern Iowa will be critical factors in
determining how high river levels will get.

Mississippi River...

The overall trend of the forecast for the Mississippi River has been
consistent. As a result of this consistency, confidence has
increased to the point that river flood watches have been issued for
portions of the Mississippi river. Additional river flood watches
for other parts of the Mississippi river are possible over the next
3 days.

Predicted rainfall later this week and how much snow will melt up
north are not accounted for in the current river forecasts. The flow
input from the Wisconsin river, which will be considerable, has been
slightly delayed but will be getting into the Mississippi river
basin this week.

How much rainfall occurs this week and how much of the snow up north
melts will be key factors in determining river levels on the
Mississippi over the next 10  to 14 days.

Northwest Illinois tributary rivers...

The Pecatonica, Rock, and Green rivers are still forecast to remain
below flood stage. However, these forecasts do not include predicted
rainfall this week. How much rain occurs this week will be important
in determining river levels in northwest Illinois over the next 7 to
10 days.

&&

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

$$

SYNOPSIS...RP Kinney
SHORT TERM...RP Kinney
LONG TERM...08
AVIATION...McClure
HYDROLOGY...08



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