Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 240807

Area Forecast Discussion
National Weather Service La Crosse WI
307 AM CDT Mon Oct 24 2016

.SHORT TERM...(Today and tonight)
Issued at 307 AM CDT Mon Oct 24 2016

Today will be mostly sunny with light northerly winds as a surface
ridge builds into the Upper MS River Valley. Temperatures will be
noticeably cooler in the wake of yesterday`s cold frontal passage
with afternoon highs in the lower to mid 50s. Mid-high clouds will
increase from southwest to northeast tonight ahead of the mid-week
system. Winds will be light from the east with lows dipping into
the 30s.

.LONG TERM...(Tuesday through Sunday)
Issued at 307 AM CDT Mon Oct 24 2016

General idea of rain returning late Tuesday and Wednesday still
on track, but some fine-tuning of the forecast will be needed as
24.00Z model suite continues to differ on some details. Namely,
the GFS is more aggressive with initial warm advective rain
showers Tuesday afternoon compared to the drier NAM/ECMWF/GEM
solutions. Given drier low-level easterly flow on the backside of
the departing ridge, the GFS may be overdone, so POPs were lowered
mainly into the chance category through Tuesday afternoon. In
addition, the NAM is now slower and weaker, showing an open wave
at 850 hPa moving across the region through Wednesday. This is in
contrast to the GFS/ECMWF/GEM which all show a closed low
developing near the tri-state border area by 12-18Z Wednesday.
This latter cluster of models is more consistent with previous
model runs, so will consider the NAM solution an outlier for now.

Keeping these model issues in mind, the best combination of
increased moisture (PWATs to around one inch) and strong forcing
along the track of the mid-level low is expected to result in
widespread showers mainly Tuesday night into Wednesday morning
across much of the forecast area. Latest model consensus lowered
rainfall totals through Wednesday with most areas seeing between
1 and 2 inches. Locally higher amounts still possible for areas
that see repeated moderate to heavy showers. Will continue with
isolated thunder mention Tuesday afternoon through Wednesday
afternoon mainly south of I-90 given the potential for strong
vertical motion through a deep column and MUCAPE values of a
couple hundred J/kg. Given the expected rainfall rates, lack of
widespread thunderstorms, and the drier antecedent soil moisture
conditions of the past month, not anticipating any hydro/flooding
issues through mid week.

Flow aloft shifts to the northwest Thursday into next weekend as a
500 hPa ridge builds across the western CONUS. A parade of short-
waves move through the region, but it appears the deepest moisture
remains north of the forecast area, limiting precipitation
potential. Timing and strength of individual waves also somewhat
uncertain between various model solutions, so will cover potential
with model consensus 20 POPs. Seasonal temperatures will be the
rule with highs generally in the 50s and lows in the 30s/40s.


.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1100 PM CDT Sun Oct 23 2016

An area of 1.5-3 kft clouds continue to sink southward across WI.
Some small diminishing trend via satellite imagery...with the
HRRR/RAP13/NAM12 all suggesting this will continue. The upshot is
that KRST should avoid a low cig threat...with KLSE on the western
fringe of seeing a couple hours of ~ 3kft. Going to opt with keeping
KLSE cig free for now, updating if necessary. Rest of Monday will be
VFR, with some increase in high clouds Monday night.

Light northerly winds will shift east Monday, staying light.




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