Area Forecast Discussion
Issued by NWS La Crosse, WI

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000
FXUS63 KARX 051738
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1138 AM CST Tue Dec 5 2017

.SHORT TERM...(Today and tonight)
Issued at 315 AM CST Tue Dec 5 2017

Water vapor imagery early this morning showed an impressive
negatively tilted shortwave trough rotating towards Lake Superior
helping to deepen a surface low across southern Ontario. Lingering
light snow across north-central Wisconsin has been waning as the
surface low continues to pull away. Strong low-level cold advection
and mixing have really helped to boost winds overnight, with gusts
as high as around 50 to 55 mph overnight in a few spots.

For today, the surface low will continue to lift away. Although the
cold advection will level off, strong gradient flow and mixing will
lead to continued gusty winds. Mixed layer winds will be more on the
order of 30 to 35 kts, so although it will be a windy day, it`s not
looking quite as windy as early this morning. In collaboration with
surrounding offices, extended the Wind Advisory through the
afternoon across southwest Wisconsin and northeast Iowa and will
allow the remaining portion of the advisory to expire this morning.
Temps today will be a far cry from yesterday, with temps some 30
degrees colder than yesterday. A bit of snow shower/flurry
activity may occur especially across north central Wisconsin under
the stratus deck, with more sun farther south.

Tonight will be a much more typical December night, as temps fall
into the teens. The gradient will stay up enough to keep winds
breezy through the night, allowing wind chills to fall to near zero
or even below in spots overnight. A few flurries/snow showers are
possible once again, especially across north central Wisconsin.

.LONG TERM...(Wednesday through Monday)
Issued at 315 AM CST Tue Dec 5 2017

A very stable upper flow pattern will then remain in place through
the rest of this forecast cycle with a deep eastern US trough and
western ridge. A series of upper level disturbances will drop
southward within the flow which will help reinforce the seasonably
cold air mass through late week. There are indications among the
deterministic and ensemble models that some modest temperature
recovery may occur towards Sunday/Monday as the upper flow pattern
temporarily relaxes. Even then, highs would still remain seasonable
in the 20s and 30s.

As for precip chances, the pattern isn`t conducive for any
significant precip events with very dry northerly flow persisting.
However, any weak disturbance in the flow could set off some light
snow/flurries at times. For the most part, confidence is low with
timing and placement of these systems. The strongest signal for
light snow remains on Friday when a more prominent upper trough is
expected to sink south across the western Great Lakes. Very light
accumulations are possible with the stronger waves, but with overall
minor impacts.

&&

.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1138 AM CST Tue Dec 5 2017

Cold, cyclonic flow will prove tricky with ceilings, winds, and
occasional snow into Wednesday. Seeing more cloud development
upstream with MVFR ceilings but they will be in-out at times with
brief reductions in visibility due to snow showers. Winds also
remain strong, out of the west, and gusts in the 30 to 40 kt range.

Short term models still hint at some airmass drying except closer to
Interstate 94 so banking on a VFR period tonight before cyclonic
flow drives low clouds back into area on Wednesday. With that could
see more snow flurries and widespread MVFR conditions. Detail will
need to be added later but introduced more clouds and occasional
snow threat.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...Wind Advisory until 6 PM CST this evening for WIZ054-055-061.

     Wind Advisory until 6 AM CST early this morning for WIZ017-029-
     032>034-041>044-053.

MN...None.
IA...Wind Advisory until 6 PM CST this evening for IAZ008>011-018-019-
     029-030.

&&

$$

SHORT TERM...JM
LONG TERM...JM
AVIATION...Shea



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