Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 201116

Area Forecast Discussion
National Weather Service La Crosse WI
616 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

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 12Z TAFS through 12Z Saturday morning)
Issued at 616 AM CDT Fri Oct 20 2017

Gusty south winds today and wind shear tonight will be the main
concern. Otherwise, VFR conditions expected through the period.

Some cirrus today will thicken up into broken altocumulus tonight
with cloud bases expected to be above 8kft through the night.
These clouds are in advance of a cold front moving through the
Northern Plains. There is also a slight chance a few -shra toward
Saturday morning but opted to keep them out at this point since
these will be very isolated in nature.

Otherwise, plan on south winds today sustained in the 10-20kt
range, gusting 20-30kt by late this morning/early afternoon. Some
low level wind shear is expected tonight as south winds not too
far off the surface increase ahead of the approaching cold front.
Will likely see south winds of 45-50kt at 1-2kft off the ground.


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.




SHORT TERM.....Rieck
LONG TERM......Rieck
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