Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 180440
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1140 PM CDT TUE MAY 17 2016

.SHORT TERM...(This evening through Wednesday)
Issued at 238 PM CDT Tue May 17 2016

At 2 PM...a 1028 mb surface high was located over northern
Minnesota. With diurnal heating...a scattered to broken deck of
fair weather cumulus clouds had developed across the Upper
Mississippi River Valley. With loss of daytime heating...the
17.12z models are in good agreement that these clouds will quickly
dissipate late this afternoon and evening.

The combination of clear skies and light winds will allow for
temperatures to cool rapidly tonight. Temperatures will cool
into the 20s and 30s across western Wisconsin and around 40
in southeast Minnesota and northeast Iowa. The coolest
temperatures will be found in central Wisconsin where
they will be in the upper 20s. Due to these cold temperatures... a
Frost Freeze Advisory will be issued from 1 AM to 8 AM Wednesday
morning.

As we reach the convective temperature /in the lower 60s/ late
Wednesday morning and early afternoon...a scattered deck of
fair weather cumulus will develop across the Upper Mississippi
River Valley.  The greatest concentration of these clouds will
be south of Interstate 90.

As diurnal mixing increases on Wednesday afternoon...surface
dew points will likely drop into the lower and mid-30s /about 5F
lower than the MOS values/.  This will lower the afternoon
relative humidities into 25 to 35 percent range.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 238 PM CDT Tue May 17 2016

Like Wednesday afternoon...the 17.12z models look a bit too high
on the surface dew points. Due to this...used the GFE dew point
mix down tool to lower them to around 40F. This will lower the
afternoon relative humidities into 30 to 40 percent range.

On Friday afternoon and evening...a weakening surface cold front
and upper level short wave will move southeast through the Upper
Mississippi River Valley. Like the past couple of days...it
continues to look like there will be limited moisture and
convergence along this front. Despite this...both the GFS and
ECMWF generate a few showers along and just ahead of this front.
Meanwhile the NAM and GEM have this front moving through the
region dry. With the signal for any rain chances being rather
weak...opted to keep the forecast dry.

As we head toward early next week...the models show that the winds
aloft will become more southerly. This will bring more moisture
into the region...and as a result our chances of showers and
thunderstorms will increase. The only question is whether this is
a bit too fast due to the models generating a stronger equatorial
Rossby wave than what the actual data shows at this time. Due to
this uncertainty...opted to stay with the model blends for now.

&&

.AVIATION...(For the 06Z TAFS through 06Z Wednesday night)
Issued at 1140 PM CDT Tue May 17 2016

VFR conditions will prevail at both TAF airfields through the
period. Clear skies overnight will give way to some cumulus in
the 5000 to 6000 ft agl layer Wednesday afternoon before clearing
back out again late in the period. With surface high pressure
moving overhead, light and variable winds will be the rule,
perhaps taking on a more southerly preference at KRST after
18.23Z.

&&

.ARX Watches/Warnings/Advisories...
WI...Frost Advisory until 8 AM CDT Wednesday for WIZ017-029-032>034-
     041>044-053>055-061.

MN...None.
IA...None.
&&

$$

SHORT TERM...BOYNE
LONG TERM...BOYNE
AVIATION...ROGERS



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