Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 100415
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1115 PM CDT Mon Oct 9 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 307 PM CDT Mon Oct 9 2017

At 3 PM, a band of 700 to 500 mb frontogenesis was producing a
narrow band of precipitation from central Minnesota southwest into
southeast South Dakota and eastern Nebraska.  This precipitation is
mainly rain. However, there is bright banding near Sioux Falls
South Dakota, so they may be seeing some snow in that area. The
09.12Z models are in general agreement that this frontogenetic
band will shift southeast into southeast Minnesota, northeast
Iowa, and west-central Wisconsin this evening as a northern stream
short wave trough moves to our north. This band will then quickly
weaken between 10.03Z and and 10.06Z as this wave moves away from
the region. While there is strong forcing associated with this
wave, the soundings show very dry air in the sub cloud layer. Due
to this, kept the rain chances in the 20 to 40 percent range. The
highest rain chances will be near the Interstate 35 corridor.

For late tonight, the combination of clear skies, dry dew points,
and light winds in Taylor County will allow temperatures to fall
into the lower to mid 30s.  This will result in areas to widespread
frost. A Frost Advisory is in effect from midnight tonight to 8
AM Tuesday. There could be additional patchy frost north of
Interstate 90 tonight, but due to the coverage of the frost and
uncertainty of cloud cover and winds opted to just issue a Special
Weather Statement for those locations.

On Tuesday, a closed upper level low will move northeast from Kansas
into Iowa.  This will bring rain into northeast Iowa and southwest
Wisconsin during the morning and then spread northward into
southeast Minnesota and west-central and central Wisconsin during
the afternoon.  Dry air advecting into areas along and north of
Interstate 94 will limit the northern extent of this rain.

.LONG TERM...(Tuesday night through Monday)
Issued at 307 PM CDT Mon Oct 9 2017

Main forecast concerns in the long term are on rain chances Tuesday
night into Wednesday. Focus then turns to low chances for rain on
Thursday with higher chances for the weekend.

Better forecast model agreement today regarding low pressure
tracking across southern Iowa Tuesday evening then lift northeast
toward southern Lake Michigan late Wednesday. With a dry
northeasterly flow at the surface there is some question as to how
far north the showers will get. At this point it continues to
look like areas along and south of Interstate 90 will have the
greatest chances for rain. We are not expecting thunderstorms at
this time with the warm sector and CAPE displaced well to the
south of the local area.

The low will then exit the area Wednesday afternoon into Wednesday
evening. Weak warm air advection Wednesday night into Thursday
morning. Forecast models have been indicating some very light
precipitation with this feature. However, confidence is low any
precipitation will be seen over the region so will keep a dry
forecast.

A baroclinic zone then sets up across the region Friday into
Saturday. Meanwhile several weak shortwaves will move over the
area and interact with this zone brining chances for showers. See
much less forecast model agreement today for this timeframe
versus yesterday. What looked to be widespread rain across the
area for much of the weekend may now be periods of rain through
Saturday with the potential for a dry Sunday. There remains a lot
of uncertainty for late this weekend through the weekend will
continue with a model consensus blend for precipitation chances.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1115 PM CDT Mon Oct 9 2017

Cigs: mostly bkn mid level vfr cloud shield through Tue
evening...generally above 6 kft. Should see some lowering overnight
Tue as an area of low pressure slides south of the local area.
mvfr/ifr looking likely for Wed morning.

WX/vsby: frontogenetic band of -shra associated with a shortwave
trough moving across the Upper Mississippi river valley close to I-
90 late this evening, with the meso models more or less holding it
in place and gradually diminishing it overnight. Looks reasonable.
No vsby restriction with the -shra with minimal impacts. Showers
could return Tue evening as low pressure moves across the mid
mississippi river valley. Latest model runs not as aggressive with
bringing the shower threat as far north as previous runs - so will
hold off on adding to the forecast for the moment.

Winds: north winds will gradually become more northeast Tue evening.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Frost Advisory from midnight tonight to 8 AM CDT Tuesday for
     WIZ017.

MN...None.
IA...None.
&&

$$

SHORT TERM...Boyne
LONG TERM...Wetenkamp
AVIATION...Rieck



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