Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 261739
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1139 AM CST Sat Nov 26 2016

.SHORT TERM...(Today and tonight)
Issued at 325 AM CST Sat Nov 26 2016

Challenges today into tonight include cloud trends and possible
fog development. Surface ridge axis across central WI will move
eastward today, resulting in increasing southerly return flow
across the forecast area. Stratus deck early this morning across
much or northeast MN into WI will slowly lift northeastward as
low level west-southwest flow increases, only to be replaced by
cirrus for much of the day. Some forecast guidance suggests re-
development of low level cumulus later this afternoon, so
something to watch as well. Despite a mix of sun and clouds,
expect warm conditions today as 925 hPa temperatures rise to
between +2 and +5 Celsius by 00Z tonight. Afternoon highs likely
to top out in the mid 40s to near 50 degrees.

26.03Z SREF probabilities are rather bullish (greater than 60
percent) concerning fog development tonight across much of the
forecast area. Do expect some degree of clearing with light east-
southeast surface wind, but light wind layer is quite shallow.
Best chance for fog appears to be farther north across central MN
into northern WI over the established snow pack. With the vast
majority of the forecast area snow free, think fog will be mainly
confined to areas north of I-94 so will add patchy wording for
this potential. Lows tonight will range from mid 20s to lower 30s.

.LONG TERM...(Sunday through Friday)
Issued at 325 AM CST Sat Nov 26 2016

Still watching an impressive lee surface cyclone eject from
northeast CO and into the Northern Plains on Sunday. At the same
time, a sharp short-wave with strong 500 to 300 hPa potential
vorticity advection swings across the forecast area late in the
day, interacting with the mid-level warm frontal boundary. While
much of Sunday will be dry with increasing cloud cover, expect a
band of rain to rapidly lift northeastward late Sunday afternoon
and evening, bringing a quick quarter to half inch of rain by
Monday morning. Additional rain is possible later on Monday as
the cold front moves into and through the forecast area. The GFS
is still the most optimistic with instability, showing roughly 250
J/kg of MUCAPE in the vicinity of the front. As such, will
continue with isolated thunder potential late Sunday night through
Monday, moving from west to east with the front. Prior to cold
frontal passage, very warm air gets wrapped into the system and
across the region with 925 hPa temperatures soaring to between +7
and +10 Celsius, resulting in Monday afternoon highs into the 50s
for most areas.

Tuesday through Thursday, the occluding low pressure system
weakens and stalls across the Upper Midwest. Primary impact to
sensible weather will be a prolonged period of cloudy skies and
cooler (near normal) temperatures with highs in the 30s to lower
40s. Preciptiation signals are not well organized, but given
broad cyclonic flow over a large depth of the atmosphere,
periodic rain or snow showers are possible each day, especially
for areas north of I-90.

An Eastern Pacific kicker short-wave crashes onto the west coast
late Wednesday into Thursday, helping to move the stubborn low
into the Great Lakes by late Thursday into Friday for a return to
dry conditions to end the week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1138 AM CST Sat Nov 26 2016

With diurnal mixing, the stronger winds from aloft will mix to the
surface. The sustained south winds will be in the 10 to 20 knot
range. These winds will decrease to less than 10 knots tonight...
and then once again increase into the 10 to 20 knot range after
27.15z.

While some of the guidance suggests the development of widespread
fog overnight and Sunday morning, thinking that the boundary layer
will remain mixed enough that this will not occur.

&&

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

$$

SHORT TERM...Rogers
LONG TERM....Rogers
AVIATION...Boyne



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