Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 181656
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1150 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
teens.

.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 18Z TAFS through 18Z Sunday afternoon)
Issued at 1150 AM CDT Sat Mar 18 2017

Cigs: persistent mvfr deck across the area. Satellite imagery
showing some holes starting to develop with only a small push east
with the backedge. Probably need to get into axis of ridge/high
pressure over the Plains to clear the clouds east of KRST/KLSE,
which looks closer to 00z. That said, more holes could develop and
expand - so will monitor and update as needed. For now, hung onto
the mvfr cigs a bit longer.

The ridge quickly shifts east of the area Sunday morning, with
models pointing to an increase in low level rh for the afternoon -
and a likely return to mvfr cigs.

VSBY/wx: no concerns anticipated until later Sunday afternoon-night.
Sfc front/low level warm advection looks to move west-east across
the region during this time, and with that increase in low level RH,
a few showers look likely. Could be more scattered in nature though,
so impacts at the taf sites isn`t assured.

Winds: winds will go light vrb/southeast tonight, but increase
quickly Sunday morning as the ridge leaves and the pressure gradient
tightens. Temp inversion (thanks to warming a loft) could keep most
of the potential gustiness in check Sunday afternoon.

&&

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

Drying weather Monday-Wednesday, Fire Weather Concerns Possible.

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
range.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...Wetenkamp
LONG TERM...Wetenkamp
AVIATION...Rieck
FIRE WEATHER...Wetenkamp



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