Area Forecast Discussion
Issued by NWS La Crosse, WI

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315
FXUS63 KARX 121130
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
530 AM CST Fri Jan 12 2018

.SHORT TERM...(Today through Saturday Night)
Issued at 237 AM CST Fri Jan 12 2018

High Impact Weather Potential: Wind chills of -20F or colder
expected at various times through Saturday night.

Well...it was a fun 36 hours of respite, but reality has returned
with temps early this morning centered either size of zero degrees.
We can thank a return to broad upper troughing along the northern
tier, in place behind quite the impressive Arctic cold front that
marched through the area roughly 18 hours ago. That troughing will
be in no hurry to leave as we head into the weekend (and beyond),
with a few additional reinforcing shortwaves dropping through the
region and helping lock in another bout of well below normal
temperatures. At the surface, broad and rather strong low level
ridging centered across southern Alberta/Saskatchewan early this
morning will gradually drift southeast across the local area by
Saturday night, with the coldest air of this round arriving for
Saturday into Saturday night.

Prior to that time, enough of a gradient in place to maintain some
wind chill issues, with the current advisory for western areas
looking good through midday, and likely another one needed for more
of the area tonight as wind chill values dip into the -20 to -30F
range. However, not much in the way of any sensible weather
expected the next few days, with early lower stratus in some spots
connected to Lake Superior this morning giving way to nothing
worse than a little cirrus at times, particularly later Saturday
and Saturday night in advance of our next incoming better
shortwave.

.LONG TERM...(Sunday through Thursday)
Issued at 237 AM CST Fri Jan 12 2018

Main focus remains the better "clipper" system advertised for quite
a few days now toward later Sunday and Sunday night, with that
system increasingly looking to deliver measurable snowfall for much
of the area. Surprisingly low spread among both ensemble and
operational guidance for that system too, with not a lot of
available moisture given its source region from northern Canada but
a deep dendritic growth region taking advantage of what precip is
there to maximize snowfall potential. Based on current trends,
looking at a 2-3" accumulation forecast but with some wiggle room
for higher values pending placement of any localized heavier QPF.

Another surge of quite cold air on track to arrive behind that wave
for the early work week, with additional wind chill issues likely to
arise as well as potentially some blowing snow problems with
current hints of 25-30 knots of flow through the mixed layer
working over fresh fluffy snow. Could also see some additional
light snow or flurries into Monday beneath the main trough axis as
an upper low tries to cut off overhead, with the better chances
for that near/east of the Mississippi River. Thereafter, looking
like a gradual warmup is in the cards through the mid/late work
week as we again dig energy into the western CONUS while
flattening the flow regime over the central states. At some point,
that setup may allow for some drizzle concerns with warmer air
running up over cold ground once again, but plenty of time to
watch those details unfold over the coming days.

&&

.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 530 AM CST Fri Jan 12 2018

Battling Lake Superior origin MVFR stratocumulus early this
morning along and east of the Mississippi River. Model soundings
have this cloud thinning/pushing east out of KLSE by 14z.
Otherwise, VFR conditions then expected through the rest of the
period as high pressure builds in from the Northern Plains.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...None.
MN...Wind Chill Advisory until 10 AM CST this morning for MNZ079-086-
     087-094-095.

IA...Wind Chill Advisory until 10 AM CST this morning for IAZ008-009-
     018-019.

&&

$$

SHORT TERM...Lawrence
LONG TERM...Lawrence
AVIATION...DAS



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