Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 251133

Area Forecast Discussion
National Weather Service La Crosse WI
633 AM CDT Tue Jul 25 2017

.SHORT TERM...(Today and Tonight)
Issued at 341 AM CDT Tue Jul 25 2017

At 3 AM, warm air advection ahead of a short wave trough has
result in showers and storms across central Minnesota and west
central Wisconsin. The models are in general agreement that this
area of strong warm air adection will move east across the area
through early this afternoon. This will result in a band a couple
bands of showers and isolated thunderstorms moving across the
Upper Mississippi River Valley. With limited instability and shear
this morning, not anticipating any severe weather.

For tonight, a cold front will move slowly southeast into the
region. However, by the time this front arrives, instability will
be waning. With this said, will have to watch out, because this
will be the time period in which we will see the best deep shear.

.LONG TERM...(Wednesday through Monday)
Issued at 341 AM CDT Tue Jul 25 2017

On Wednesday and Wednesday night, a cold front will move southeast
through the Upper Mississippi River Valley. The models continue to
show that the moisture transport will increase across eastern
Iowa during the afternoon and evening as a weak surface low moves
along this front. While these have been consistent signals, there
is still much uncertainty on how much instability will be located
across the region. At this time, it looks like the 0-1 km mixed
layer CAPES will range from 1500 to 2500 J/kg. This is similar to
what the NAM has been forecasting the past 2 days. Meanwhile, it
is 1-2 K J/kg less than previous runs of the GFS. Like the past
couple of days, the 0-3 km and 0-6 km appear weak. However, with
this said, will have to watch where the low tracks. This could
potentially increase the shear enough that there could potentially
be some supercells.

In addition to severe weather, we will have to watch for the
potential of heavy rain. Precipitable water values along the front
climb into the 2 to 2.25 inch range and warm cloud layer depths
are in the 4 to 4.5 K foot range. However, the moisture
convergence along the front remains weak and this will greatly
affect the areal coverage of precipitation across the region. Due
to this opted, not to issue a Flash Flood Watch at this time.


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 633 AM CDT Tue Jul 25 2017

A small batch of showers and thunderstorms continues to work east
out of central Minnesota, and should impact RST with a brief
shower/t-storm through 13Z. Some of that activity could approach
LSE by mid to late morning as well, but overall conditions should
remain VFR. Winds will pick up from the south to southeast today,
gusting at 20-25 knots into the afternoon (perhaps briefly higher
at RST), but with low level wind shear expected into tonight as
very strong flow develops just off the surface. After
precipitation exits this morning, dry weather and VFR conditions
are expected through this evening, with just a very low end risk
for additional storms very late tonight. Given low confidence,
have opted to keep a dry forecast going for now.


.HYDROLOGY...through Wednesday night
Issued at 341 AM CDT Tue Jul 25 2017

Flood Warnings continue along the Kickapoo River from Soldiers
Grove to Steuben and along the Trempealeau River at Dodge. Despite
some rain through early this afternoon, these levels will
continue to slowly fall.

From tonight into Wednesday night, additional rain is expected
across the region. Some of these storms may produce locally heavy
rainfall that could result in some additional river rises and
perhaps minor flooding.

Thursday into the weekend will be dry.




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