Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 200832
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
330 AM CDT Fri Oct 20 2017

.SHORT TERM...(Today through Sunday)
Issued at 330 AM CDT Fri Oct 20 2017

Great end to the work week...stormy (severe?) start to the weekend.

1) Warmth: 850 mb temps +15 C today with NAEFS anomalies around +2.
Highs in the mid to upper 70s should result, with a few locations
flirting with 80. Gusty southerly winds will also play a part in the
mild end to the work week. Get out and enjoy the warmth while you
can - cooler, more seasonable air returns Sunday.

2) Storms: The models have been consistent with tracking a 500 mb
trough from the west coast eastward...sliding it across the
upper/mid mississippi river valley sat night/sun morning. A cold
front leads the trough into the region, centered north-south across
the local forecast area Sat night. Decent low level moisture return
for late Oct ahead of the front, pushed along by a 40-45 kt 850 mb
jet.

Some instability to play with, around 500-1000 J/kg of MUCAPE along
and ahead of the cold front. Bufkit CAPE profiles are long and
skinny though, not supportive of strong updrafts. Shear is strong,
albeit mostly along and west of the front. About 40 kts 0-3 km and
50 kts 0-6 km. There is enough instability/shear overlap though that
there will be a strong, potentially severe risk Sat evening. Strong
to damaging winds would be the main threat.

.LONG TERM...(Monday thru Thursday)
Issued at 330 AM CDT Fri Oct 20 2017

A return to reality - at least for temperatures - as the models move
from the ridging/mild pattern of the current week to more
troughing/northwest flow a loft for next week. So, say goodbye to
the 70s and hello to more seasonable 50s.

The GFS and EC drop a 500 mb tough southwest out of Canada and
through the region Mon/Tue with another trough taking a similar path
for Thu/Fri. Both bringing cold air, but moisture looks meager at
this time - which will be a limiting factor for shower chances. That
said, plenty of upper level energy and low/mid level cold air that
there should be at least small chances for showers. Will let the
consensus solution detail that.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 1036 PM CDT Thu Oct 19 2017

VFR conditions set to continue into Friday evening, with a gradual
increase and thickening of high and eventually mid level clouds the
next 24 hours. Low level wind shear remains an issue for most
locations through the early morning hours, before surface winds
become gusty in the 20-25+ knot range toward midday. Stronger winds
will continue into tonight with a pretty good pressure gradient in
place, though very strong flow (50+ knots) just off the surface will
again lead to the development of low level wind shear for all areas.

&&

.FIRE WEATHER...(Today)
Issued at 330 AM CDT Fri Oct 20 2017

Drying crops/fuel with natural maturity and progression of fall
raises some concern for heightened fire weather conditions today.
Gusty south winds 15 to 20 mph gusting 25-30 mph will be seen for
many locations by this afternoon along with minimum relative
humidities values in the 30-40 percent range.

&&

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

$$

SHORT TERM.....Rieck
LONG TERM......Rieck
AVIATION...Lawrence
FIRE WEATHER...DAS



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