Area Forecast Discussion
Issued by NWS La Crosse, WI

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471
FXUS63 KARX 231952
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
252 PM CDT Sat Sep 23 2017

.SHORT TERM...(This evening through Sunday)
Issued at 211 PM CDT Sat Sep 23 2017

(This Afternoon through Sunday)

Upper air analysis continues to show a large ridge in place over the
eastern US with a deep trough over the west. Surface analysis
indicates an area of low pressure in southwest Ontario with a cold
front extending through Minnesota and into Nebraska.

Showers and storms continued today in northwest Minnesota and into
the Dakotas behind the surface front, as it remained nearly
stationary. Warm air aloft remained over the forecast area today,
with 925 mb temperatures in the 25-26C range. While this is not
quite as warm as Friday, high temperatures were still able to climb
to around 90 throughout the area, with heat indices getting into
the upper 90s in many locations. Cumulus has developed throughout
the area and even a few showers moved through parts of southeast
Minnesota. The HRRR has been consistently showing these showers,
and with 1500-2000 J/kg of MLCAPE, have added an isolated
thunderstorm mention for areas west and north of Rochester through
the afternoon.

The upper level ridging will remain in place on Sunday with the
front/precip remaining well west of the area. 925 mb temperatures
will be 1-2C cooler than Saturday, indicating highs in the mid 80s
to lower 90s.

.LONG TERM...(Sunday night through Saturday)
Issued at 211 PM CDT Sat Sep 23 2017

From Sunday night into Monday, the 23.12z models are continuing to
slow the eastward progress of the cold front. With much of the
forcing and low condensation deficits in the wake of the front,
removed the rain chances on Sunday night and delayed the eastward
progress of the rain chances on Monday. 0-1 km mixed layer CAPES
will climb in the 500 to 1000 J/kg during the afternoon. However,
with weak shear, not anticipating any of these storms to become
severe.

With the cold front moving through the region later, raised the
high temperatures some. The greatest increase was along and east
of the Mississippi River where the high temperatures were raised
anywhere from 3 to 5F.

From Monday night into Tuesday, the cold front will move slowly
east through the region. With limited instability and convergence
along with the best synoptic forcing moving northeast into
Ontario, concerned that the rain chances and amounts will continue
to decrease. The ECMWF ensemble even hints at a possibility that
the front could be even slower. There is a 20 degree difference at
KLSE for the high temperatures on Tuesday. The coldest member has
a high of 63 and the warmest member has a high of 83. The current
forecast high is right down the middle.

From Wednesday through Friday...

Models are in good agreement with surface high pressure building
into the region on Wednesday as the upper-level shortwave departs to
the northeast. There is some suggestion in the 23.12Z GFS of a weak
upper-level disturbance passing through Wednesday evening. But given
the dry air mass associated with the surface high and little to no
moisture transport, will maintain a dry forecast. Both the GFS and
ECMWF then bring a stronger shortwave down from southern Canada late
Thursday into Friday, which should provide enough forcing for a
chance of showers. This shortwave will also usher in the coolest air
of the season. With 850 mb temperatures falling to 0-2C on Friday,
highs should be limited to near 60F. Canadian high pressure is then
forecast to build in for the weekend, which would lead to chilly
nights and potentially the first frost of the season for our typical
cooler spots in Wisconsin.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1206 PM CDT Sat Sep 23 2017

VFR conditions expected throughout the period. Southerly winds in
the 10-15 kt range will be seen through the afternoon, with gusts
up to 20 kts possible. Scattered cumulus will also be present
through the afternoon. Some guidance does hint at the development
of showers in southeast Minnesota, but chances of this occurring
look to be quite low. Additionally, if they were to develop, the
best chances look to be northwest of RST. Lighter southerly winds
will be seen at both sites overnight before gustiness returns
to at least RST on Sunday.

&&

.CLIMATE...Tonight through Sunday
Issued at 211 PM CDT Sat Sep 23 2017

It continues to look like some more record high and warmest low
temperatures could be in jeopardy from tonight in Sunday.

The following are record low temperatures for Saturday (September
23)...

Austin MN - 64F in 1940
Charles City IA - 67F in 1930
Decorah IA - 67F in 1937
La Crosse WI - 69F in 1937
Mauston WI - 62F in 1908
Medford WI - 64F in 1968
Neillsville WI - 65F in 1920
Prairie du Chien, WI - 67F in 1968
Rochester MN - 66F in 1920
Sparta WI - 65F in 1937
Winona MN - 64F in 2016

The following are record high temperatures for Sunday (September
24)...

Austin MN - 84F in 2007
Charles City IA - 86F in 1935
Decorah IA - 90F in 1937
La Crosse WI - 92F in 1891
Mauston WI - 85F in 1984
Medford WI - 89F in 1908
Neillsville WI - 86F in 1908
Prairie du Chien, WI - 92F in 1984
Rochester MN - 88F in 1937
Sparta WI - 84F in 2008
Winona MN - 89F in 1935

The following are record low temperatures for Sunday (September
24)...

Austin MN - 63F in 2016
Charles City IA - 68F in 2007
Decorah IA - 65F in 1958
La Crosse WI - 71F in 1891
Mauston WI - 63F in 1958
Medford WI - 64F in 1920
Neillsville WI - 69F in 1930
Prairie du Chien, WI - 72F in 1930
Rochester MN - 67F in 1886
Sparta WI - 64F in 1958
Winona MN - 64F in 2015

&&

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

$$

SHORT TERM...CA
LONG TERM...Boyne/MAH
AVIATION...CA
CLIMATE...Boyne



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