Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 282333
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
633 PM CDT SUN AUG 28 2016

.SHORT TERM...(This evening through Tuesday night)
Issued at 254 PM CDT Sun Aug 28 2016

Water vapor satellite this afternoon shows an upper level ridge
along the East Coast into the Great Lakes Region. This ridge is
expected to gradually reform farther to the west and be centered
near the Rockies by Tuesday into Tuesday night. This will keep the
Upper Midwest on the norhtern periphery of this ridge through the
period. A couple of weak short wave troughs are expected to top
the ridge and move across northern Minnesota and Wisconsin. The
first of these should come across the region from late tonight
into Monday with the second coming through Monday night into
Tuesday. Both of these waves look to be rather flat with the weak
pv advection from them staying north of the local area. The first
short wave trough will help to push a weak cold front, currently
across Montana, toward the area with the second wave sweeping it
through the region. Given the upper air pattern, if there are to
be any showers and storms, the cold front will be the focus of
development. The 28.12Z GFS indicates there should be a band of
weak frontogenesis in the 1000-700 mb layer that comes across with
the front. The warm air advection ahead of the front should result
in about 2 ubar/s of up glide on the 310K isentropic surface into
Tuesday morning. With the short wave troughs being rather weak,
the moisture transport also looks to be weak and focused north of
the area ahead of the waves. The deterministic models show some
rain occurring along the front as it comes through but the 28.12Z
hi-res meso scale models show little to nothing along it for the
area through Monday night and the CR-NAMNest continues this trend
through Tuesday. Given the lack of forcing along the front,
believe it has a pretty good chance of coming through with very
little activity along it and will only show up to 30 percent rain
chances.

.LONG TERM...(Wednesday through Sunday)
Issued at 254 PM CDT Sun Aug 28 2016

High pressure continues to build in Wednesday night leading to a
couple more cool nights in the lower to mid 50s. Fog could be
possible Thursday or Friday morning, pending location of the high.
The GFS and ECMWF then show better agreement today on moving the
ridge axis over the area Friday afternoon and pushing the surface
high to the east. Southerly surface flow then picks up, bringing a
decent moisture plume in ahead of another cold front. While the
signal for developing precipitation along this front is consistent
between models, timing discrepancies show up again. The GFS has
somewhat consistently brought the precipitation into the area
Saturday night, while the 28.00Z ECMWF kept the ridge over the area
for a bit longer, holding off on precipitation until Sunday
afternoon. However, the 28.12Z ECMWF was in agreement with the GFS,
bringing the showers and storms in Saturday night as well.

&&

.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 634 PM CDT Sun Aug 28 2016

High pressure centered over northern Michigan will continue to
influence the local weather overnight, with moist conditions but
light winds once again. That should set the stage for some
redevelopment of fog and/or stratus, though the exact degree of
coverage remains in question. At the moment, it appears the
greatest risk for dense fog will wrap from southwest Wisconsin
back into parts of northeast Iowa in an axis of higher low level
moisture, though given light flow through the column, should also
see at least some patches of dense fog throughout the river
valleys. Whether or not that impacts the LSE terminal remains
lower confidence, especially with hints of a 12-17 knot wind field
just above the inversion (like last night). Regardless of whether
it fogs or not, do still expect a period of IFR conditions in some
stratus, with some IFR fog also likely for a time out at RST.
Improvement should come faster into Monday morning than seen this
past morning, with just some diurnal cumulus development into the
afternoon on Monday with winds under 10 knots.

&&

.ARX Watches/Warnings/Advisories...
WI...None.
MN...None.
IA...None.
&&

$$

SHORT TERM...04
LONG TERM...CA
AVIATION...Lawrence



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