Area Forecast Discussion
Issued by NWS La Crosse, WI

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269
FXUS63 KARX 241928
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
228 PM CDT SUN JUL 24 2016

.SHORT TERM...(This evening through Tuesday Night)
Issued at 228 PM CDT Sun Jul 24 2016

The upper level ridge is expected to remain over the southwest
part of the country through the period. The ridge is not very
amplified which leads to a flat zonal flow from the Pacific
Northwest into the Upper Midwest. This flow looks to be pretty
quiet through Monday night but then a couple of short wave troughs
are expected to come across the region. The first of these waves
is expected to cross northern Minnesota and move into northern
Wisconsin Tuesday afternoon with the second wave taking a more
southern route across South Dakota into northern Iowa Tuesday
night. The 24.12Z GFS indicates the best pv advection in the
500-300 mb layer with the first short wave trough will remain
north of the area with just some very weak pv advection as far
south as about Interstate 90 or so. The isentropic up glide on the
305K surface is concentrated across northern Wisconsin ahead of
the short wave trough. The moisture transport with this wave is
not very strong and wraps around the low level ridge axis across
western Minnesota into northern Wisconsin. With such weak forcing,
will only have a small chance of rain across the northern sections
of the area.

As the second wave comes in Tuesday night, some weak pv advection
in the 500-300 mb layer starts to come into the western sections
of the area late in the night. The isentropic up glide on the 305K
surface looks to be on the order of 1 to 3 ubar/s and comes across
in a couple of rounds after 06Z Wednesday. The low level moisture
transport axis remains west of the area but should start to move
east and the GFS suggests the eastern and convergent side of this
could come into the western sections late Tuesday night. In
general, this forcing looks better than with the wave for Tuesday,
but still not very strong and will keep the rain chances in the 20
to 40 percent range.

.LONG TERM...(Wednesday through Sunday)
Issued at 228 PM CDT Sun Jul 24 2016

The upper level ridge will remain over the southwest part of the
country into next week. It is expected to start amplifying over
the West Coast by late in the week which will allow the flow over
the Upper Midwest to become more northwest. The 24.12Z ECMWF and
GFS both show this flow to contain several weak short wave troughs
with none of them looking to be all that strong at this point.
This will necessitate keeping some rain chances in for each day,
but difficult to tell how widespread this activity will be as
there does not look to be any synoptic scale surface boundaries in
place to help focus the activity.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1231 PM CDT Sun Jul 24 2016

VFR conditions are expected through the TAF period. A FEW to SCT
cumulus are possible this afternoon with cloud bases around 3500
ft. Also, cirrus will overspread the TAF sites becoming BKN at
times at least through early evening. Winds will become light
tonight as high pressure builds in. Drier air moving in tonight,
along with winds just above the surface staying in the 15 to 20 kt
range, should prevent fog formation despite KLSE seeing 1.35
inches of rain yesterday.


&&

.HYDROLOGY...
Issued at 228 PM CDT Sun Jul 24 2016

Runoff from the rains Saturday has caused some rises on area
rivers. The Grant River near Burton looks to be cresting this
afternoon and will likely go below the flood stage late this
afternoon or early this evening. Other notable rises are occurring
on the Turkey River where Elkader is forecast to go to flood
stage. Fortunately, a couple of dry days will allow the rivers to
go back down pretty quickly.

&&

.ARX Watches/Warnings/Advisories...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...04
LONG TERM...04
AVIATION...WETENKAMP
HYDROLOGY...04



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