Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 281113

Area Forecast Discussion
National Weather Service La Crosse WI
613 AM CDT Fri Oct 28 2016

.SHORT TERM...(Today and tonight)
Issued at 309 AM CDT Fri Oct 28 2016

The main impactful weather concerns for today are on breezy
southerly winds that could gust to around 35 mph at times in open
areas. Focus then turns to rain chances late Saturday afternoon into
Saturday night.

Breezy south to southwest winds develop across the region today in
response to a tightening pressure gradient ahead of an approaching
cold front. The main question for today is how deeply will we mix.
This will have a direct impact on how windy and warm we may get
today. RAP and NAM Forecast soundings across southeast Minnesota,
northeast Iowa, and portions of southwest Wisconsin suggest we will
mix to just above 950 mb, maybe as deep as 925 mb. This should
result in high temperatures climbing into the mid to upper 60s, and
possibly to around 70 in southern areas. It will really depend on
how much sunshine is seen today. It appears areas along and west of
the Mississippi River will see some filtered sunshine at times
through high clouds. Sustained winds today will likely be in the 18
to 23 mph range, with gusts to around 35 mph possible in the open
areas of southeast Minnesota and northeast Iowa. If we mix just a
little deeper, closer to 925 mb, we could see a few gusts closer to
40 mph.  Further to the northeast across central into northern
Wisconsin, thicker cloud cover should limit mixing and keep high
temperatures in the lower 60s, still very pleasant for this time of

The surface front edges across the area late tonight into Saturday
morning and looks to stall out across portions of central Iowa
through northern Illinois. Winds will switch to the north in the
wake of the front but will be on the light side. Considerable
cloudiness will linger across the area in the wake of the front.

.LONG TERM...(Saturday through Thursday)
Issued at 309 AM CDT Fri Oct 28 2016

A shortwave trough will slide through the region late Saturday
afternoon into Saturday night and interact with the front.
Frontogenesis looks to increase across the region mainly in the 900 to
600 mb layer. This will result in a period of light rain, but the
concern is exactly where. Forecast models paint light rain across
much of the forecast area.  The NAM is showing more concentrated
area of light rain positioned mainly along and south of the
Interstate 90 corridor. The GFS shows a broader swath of rain and
meanders it south across the region. The bottom line is that all of
the models are indicating rain across much of the area, it`s really
a matter of where the best frontogenesis zone sets up for a more
concentrated band of light rain. Forecast models have slowed the
arrival of the rain down slightly and has shifted the axis of rain
slightly south. Will lean toward a model consensus blend for rain
chances but if trends continue we will likely need to increase these
chances along and south of Interstate 90.

After a quiet day on Sunday, another windy and potentially milder
day is in store for the region on Monday. Again, cloud cover and how
deeply we can mix will be a big player in wind speeds and high
temperatures. There is the potential for some light rain across far
northern Wisconsin on Monday as a shortwave trough moves in from the
northern plains. Temperatures then remain on the milder side for
early November as we go through next week with west to southwest
flow aloft in place with highs in the 50s to around 60. The next
chance for rain arrives late Tuesday into Wednesday as a weak
boundary sets up across the region. Considerable uncertainty in
the forecast models regarding these rain chances so it`s difficult
to nail down any specific details on timing and rainfall amounts
at this time. Weak upper level ridging looks to remain in place
across much of the conus through the end of next week with no
major cool downs on the immediate horizon.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 613 AM CDT Fri Oct 28 2016

Increasing SW winds in the 1K-3K above ground level have finally
advected the bulk of the IFR/MVFR cloud deck north and east of the
TAF sites. Sfc winds to increase thru the morning with diurnal
warming, with the patchy/areas of MVFR BR dissipating by mid
morning. With the stronger winds aloft this morning, added a mention
of LLWS to both KRST/KLSE thru 15z-16z as a headed up to pilots.
Generally good VFR expected after 15z-16z with the southwest
gradient flow for mixing and a dry airmass progged over the area in
the 925-500mb layer. Gradient winds increase into the 15-25kt G25-
35kt range for the late morning/afternoon hours, then diminish
rather quickly near/after 23z as the gradient relaxes and diurnal
cooling starts to stabilize the boundary layer. Weak cold front
slides thru the area later tonight, with sfc winds shifting NW and N
by 12z Sat.




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