Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 182057

Area Forecast Discussion
National Weather Service La Crosse WI
257 PM CST Sat Feb 18 2017

.SHORT TERM...(This evening through Sunday)
Issued at 257 PM CST Sat Feb 18 2017

Even behind the weak front, temps this afternoon were similar to
yesterday, with much of the area in the 50s to low 60s, 20 to 30
degrees above average. Quiet and unseasonably mild weather will
continue to be the story through the rest of the weekend. A weak
surface ridge will be centered over the area tonight with light
winds. Confidence in any fog is very low right now with very dry
air just off the surface and trend of high res models to overdo
surface moisture over the past several days.

Southerly flow will develop on Sunday ahead of the developing
surface low out to the west. 925 mb temps will be a few degrees
warmer on Sunday, in the 10-13C range by Sunday afternoon. There
likely will be more in the way of high cloud cover with both the
GFS/ECMWF indicating plenty of high level moisture at 300 mb.
All in all, though, another day with highs in the 50s and 60s is
expected, near record territory again.

.LONG TERM...(Sunday night through Friday)
Issued at 257 PM CST Sat Feb 18 2017

18.12Z guidances remains consistent lifting an upper shortwave
trough across the Upper Midwest Monday and Monday night with an
associated weak front pushing through Monday night. A strong surge
of low-level moisture ahead of the system will bring a plume of
high precipitable water values northward, possibly nearing 1.25
inches, highly anomalous for February. Low clouds will increase
as this occurs later Sunday night into Monday. Consensus guidance
supports a general 0.25 to 0.75 inch rainfall as the frontal
system passes. There may be a ribbon of weak instability ahead of
the front, giving at least a risk for a few storms on Monday. If
thunderstorms do occur, some locally higher rainfall amounts are
possible, but the system continues to look quite progressive,
helping to mitigate a greater threat for excessive rainfall. With
frozen/saturated ground, runoff from the rain likely would aid in
some rises on area rivers/streams, but greater impacts likely
would be dependent on whether we get any higher rainfall amounts.

Temps Monday and Tuesday will remain unseasonably mild with highs
in the 50s to low 60s.

After yet another day of near record high temperatures on Wednesday,
attention will then be focused on a strong upper-level trough moving
from the Rockies toward the Upper Midwest Thursday into Friday.
Surface cyclogenesis is forecast over the Central High Plains early
Thursday, with the surface low tracking northeastward toward the
Great Lakes by late Friday. Confidence is increasing that a winter
storm will impact the region, but details are far from certain as
we are still 5-6 days out. The GFS and ECMWF are coming into
better agreement on the track of the low, with the GFS being a
slightly quicker solution. Precip types could be very challenging
for our CWA. Model soundings are suggesting rain in the warm
sector and snow on the back side of the low, with a potentially
messy transition zone in between. Given the current consensus
track of the surface low, our CWA would experience precipitation
starting as mostly rain, then changing to all snow on Friday.
Several inches of snow may be possible, especially if the low
takes a more southerly/easterly track. If accumulating snow does
occur, blowing snow will be a concern given the strong pressure
gradient on the back side of the low.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1136 AM CST Sat Feb 18 2017

High pressure, currently centered over eastern Nebraska, will
drift east/northeast through Sunday morning. Other than some high
level clouds starting to arrive from the large upper level low
over the southwest, little in the way of cloud cover is expected.
There is a slowly increasing threat for some fog at night, but not
anticipating this to be much of a problem tonight as the forecast
soundings continue to show very dry air just above the surface.
The fog may become more of a concern for Sunday night as higher
dew point will start to move in and spread over the cold ground.


Issued at 257 PM CST Sat Feb 18 2017

Unseasonably warm February temperatures will continue through
next Wednesday with highs in the 50s to low 60s and lows in the
30s and 40s. These temperatures will be near record levels.

Below are the records for La Crosse and Rochester through
Wednesday February 22nd:

                          Record Highs

             La Crosse                     Rochester
            -----------                   -----------

Sat (18th)    64/1981        Sat (18th)     60/1981
Sun (19th)    59/1930        Sun (19th)     59/1930
Mon (20th)    61/1930        Mon (20th)     60/1930
Tue (21st)    64/1930        Tue (21st)     60/1930
Wed (22nd)    62/1984        Wed (22nd)     59/1930

                         Record High Lows

Sat (18th)    38/1981        Sat (18th)     37/1954
Sun (19th)    38/2002        Sun (19th)     36/2002
Mon (20th)    41/1930        Mon (20th)     34/1954
Tue (21st)    48/1930        Tue (21st)     39/1930
Wed (22nd)    39/1930        Wed (22nd)     42/1930




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