Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 140736

Area Forecast Discussion
National Weather Service La Crosse WI
236 AM CDT Tue Aug 14 2018

.SHORT TERM...(Today and tonight)
Issued at 236 AM CDT Tue Aug 14 2018

Early this morning, a mid-level ridge axis was positioned over the
upper MS Valley in between closed lows over central Kansas and over
the eastern Great Lakes. A weak cold front was oriented from
northern Minnesota southwest into the Dakotas associated with an
upper trough over Ontario.

Today the cold front will make slow progress to the south. However,
upper support looks negligible with forcing from the northern stream
wave displaced across Canada, while stronger forcing with the upper
low remains to the south. As a result, not impressed by
convective chances today given weak boundary layer convergence
along the front. However a few storms are possible near the
boundary/instability axis this afternoon/early evening, primarily
from SE MN into N WI. With little vertical shear, expect
any storms to be diurnally driven and non-severe. Most areas
likely will be dry, though. There will be increasing high clouds
ahead of the central plains upper low, but with otherwise similar
thermal profiles to Monday, highs once again will be back up into
the 80s to near 90.

After any storms dissipate, much of tonight should be dry.
However, some showers may move into NE IA/SW WI overnight tonight
ahead of the approaching upper low.

.LONG TERM...(Wednesday through Monday)
Issued at 236 AM CDT Tue Aug 14 2018

The upper low will weaken as it lifts towards the southern Great
Lakes on Wednesday. With the strongest forcing and moisture
transport focused south and east of the area, widespread precip
looks unlikely. However, given proximity to the wave and only a
weakly capped environment, potential exists for scattered

Another upper level shortwave trough on the heels of the initial
wave across the southern Great Lakes will approach Thursday into
Friday. Within broad troughing on Thursday, isolated to scattered
showers/storms may develop. May see some showers linger into
Friday, especially south, although the 14.00Z GFS/ECMWF have the
trough southeast of the area by 18Z. All in all, for most areas,
rain chances should be pretty spotty through this week in this

After the wave passes, much of the weekend looks dry with
northwest flow aloft and surface ridging. Although details
differ among models, there is general agreement that troughing
will develop over the region early next week with increased precip

Temps should remain near to above normal through the weekend with
highs in the upper 70s to mid 80s Wed-Fri rising into the 80s for
most spots over the weekend.


.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 1151 PM CDT Mon Aug 13 2018

The signals for valley fog remain about as unclear as earlier in
the evening. The forecast soundings from both the 14.00Z NAM and
14.03Z RAP have trended toward having surface saturation and
extending this vertically for a couple hundred feet. At the same
time, they have also increased the winds just above the surface.
The temp/dew point spread through the evening has remained just
above the preferred values for having fog form but not high enough
to rule it out and there is also a light breeze at the office on
top of the ridge. Without a clear signal, will continue with some
visibility reduction at KLSE but not go for a LIFR event. The new
models continue to suggest there will be very little convective
activity along the approaching front Tuesday afternoon and will
continue to keep both forecasts dry through the evening.




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