Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 180720

Area Forecast Discussion
National Weather Service La Crosse WI
220 AM CDT Sat Mar 18 2017

.SHORT TERM...(Today and tonight)
Issued at 220 AM CDT Sat Mar 18 2017

Main forecast concerns today will be on cloud cover and high
temperatures. An upper level trough will gradually edge east today
as surface high pressure builds in from the west. We will see a slow
decrease in cloudiness this afternoon from west to east. It will be
cooler today with high temperatures ranging from the upper 30s to
lower 40s. Also, persistent northwest winds of 10 to 20 mph
making it feel a little cooler. High pressure slides over the
region tonight providing quiet weather and cool overnight low
temperatures. Plan on lows falling into the 20s at most locations.
A few locations over central Wisconsin may drop into the upper

.LONG TERM...(Sunday through Friday)
Issued at 220 AM CDT Sat Mar 18 2017

A cold front approaches from the northern plains on Sunday with
tight pressure gradient setting up across the region. Strong
southerly winds will help temperatures warm well into the 50s
across much of the local area Sunday. In fact, we may see a few
locations hit 60 along the Mississippi and Wisconsin River
Valleys. Plan on south winds increasing to 15 to 20 mph with gusts
to around 30 mph in open areas. Clouds will be on the increase
ahead of an approaching shortwave and the cold front so will have
to keep a close eye on cloud trends. More cloud cover would lead
to cooler temperatures and a little less wind since mixing would
limit how strong the winds get.

A few light rain showers are possible as the front slides through
Sunday night but the warm sub cloud layer will likely win out with
only sprinkles. It`s interesting to note that the NAM shows some
fairly robust elevated CAPE along the front when lifting a parcel
from just above 800 MB. This would yield CAPE values of nearly
1200 J/kg across portions of northeast Iowa and far southwest
Wisconsin. Feel that this is overdone and the dry lower levels
will win out.

The next concern is dry air moving in behind the front Monday night
into Tuesday. There may be some fire weather concerns Monday with
minimum relative humidity values falling into the 20 to 25 percent
range across much of western into central Wisconsin. Winds won`t be
too strong but will hover in the 10 to 15 mph range out of the
northwest through much of the day. Plan on high temperatures edging
into the lower 50s.

The humidity recovery Monday night won`t be all that great with
maximum relative humidity values getting to around 60 percent.
Tuesday will be another dry day across the area but a little bit
cooler. Afternoon relative humidity values will drop into the 20s
again across much of western into central Wisconsin.  Winds will
once again be out of the northwest at 10 to 15 mph. The high
slides overhead on Wednesday with another very dry day across the
area. We could see afternoon relative humidity values once again
fall into the 20s and possibly the teens over central Wisconsin.

Precipitation chances return Wednesday night and continue into the
weekend as low pressure moves out of the southwest CONUS and lifts
northeast toward the Upper Mississippi River Valley. That
precipitation could be in the form of rain or snow early Thursday
then transitioning to mainly rain Friday into the weekend and we
could even hear some thunder at times. However, there is
considerable uncertainty on the track of the low pressure system and
how much warm or cold air would move into the region.  Keep a close
eye on this timeframe as we continue to refine the forecast.

.AVIATION...(For the 06Z TAFS through 06Z Saturday night)
Issued at 1141 PM CDT Fri Mar 17 2017

Satellite imagery continues to show a large expanse of clouds
caught up in the low level cyclonic flow around the surface over
southwest Ontario. With the slow southeast movement of the surface
low, the cyclonic flow and clouds will remain through Saturday
morning before scattering out early in the afternoon as high
pressure builds in from the west. Ceilings are expected to remain
MVFR until the clouds break up. The winds have become gusty as
cold air advection in the cyclonic flow as allowed some steep low
level lapse rates to form. There will be enough wind in the mixed
layer for the gusts to continue through the night before
diminishing late Saturday morning.


.FIRE WEATHER...Monday Through Wednesday
Issued at 220 AM CDT Sat Mar 18 2017

...Drying weather Monday-Wednesday, Fire Weather Concerns

Low minimum relative humidities are expected across much of
western into central Wisconsin Monday through Wednesday as a dry
canadian airmass settles over the region. Monday and Tuesday
afternoon relative humidity values could fall into the 20s with
teens possible by Wednesday. Plan on persistent northwest winds of
10 to 15 mph Monday and again on Tuesday. Winds look to be a
little lighter for Wednesday as high pressure slides overhead.

Across southeast Minnesota and northeast Iowa, conditions won`t be
as dry but we will still see afternoon relative humidity values
bottom out in the 30 to 35 percent range on Monday and Tuesday,
with drier conditions expected on Wednesday when afternoon
relative humidity values will fall into the 25 to 35 percent




SHORT TERM...Wetenkamp
LONG TERM...Wetenkamp
FIRE WEATHER...Wetenkamp is the U.S. government's official web portal to all federal, state and local government web resources and services.