Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 280603
AFDARX

Area Forecast Discussion
National Weather Service La Crosse WI
1159 PM CST Sun Nov 27 2016

.SHORT TERM...(This evening through Monday)
Issued at 243 PM CST Sun Nov 27 2016

At 3 PM, a negatively tilted short wave trough was moving
northeast into southwest Iowa. Strong moisture transport ahead of
this trough has resulted in showers and isolated thunderstorm
development across western and southern Iowa. In addition, strong
600 to 500 mb frontogenesis has resulted in some scattered shower
developing in northeast Iowa and southwest Wisconsin.

For tonight, the 27.12z and 27.18z models are in very good
agreement that a negatively tilted short wave trough will move
northeast through the region. With 0-3 km most unstable climbing
up to 300 J/kg ahead of this wave and isolated thunderstorms
already reported, kept isolated thunderstorms in the forecast.
The only real changes to them was to fine tune the timing of their
passage through the region. With the passage of the warm front
west of the Mississippi River, expect that temperatures will
slowly rise as we approach day break Monday. Rainfall totals
tonight look like they will range from a 0.33 to 0.75 inches.

On Monday morning, it looks like much of the area will be located
in the dry slot of the upper level low. Soundings show that this
area will be subsident, so was tempted to follow the CAMS and go
dry for much of the morning. However with many of the 27.12z
deterministic models still showing light rain across the area
opted to keep a 20 to 60 percent chance in the forecast.

On Monday afternoon, the 850 mb moisture transport will be
increasing ahead of a short wave trough moving northeast out of
the mid-Mississippi River Valley. With 0-3 km most unstable CAPES
climbing up to 350 J/kg, kept isolated thunderstorm chances in the
forecast.

.LONG TERM...(Monday night through Sunday)
Issued at 243 PM CST Sun Nov 27 2016

On Monday night, a short wave trough will move northeast through
southern Wisconsin, northern Illinois, and Lower Michigan. This
system will bring another round of rain for the counties along and
east of the Mississippi River. Additional rainfall totals will be
up to 0.15 inches.

On Wednesday night, the stacked low pressure system will finally
start to move off to the east leaving in its wake a highly
positively-tilted longwave troughing. Long-range guidance
indicates a piece of energy swinging around the western side of
the departing low on Thursday. This should allow extensive cloud
cover and areas of light precipitation to continue through
Thursday. A quick glance at GFS thermal profiles suggest that
surface temperatures will work well for a precipitation type
discriminator.

By Friday night, the GFS becomes more progressive than the ECMWF,
while the ECMWF contains a more amplified synoptic pattern. The
GFS quickly brings a shortwave ridge through the region late
Friday followed by a series of shortwave troughs through the
weekend. Meanwhile, the ECMWF is slower to bring deeper ridging
through the region on Saturday, followed by a stronger shortwave
on Sunday. Weak upper-level dynamics and low-level moisture leads
to lower confidence that these disturbances will produce any QPF,
so kept the forecast dry for this weekend except across our
southern counties on Sunday to account for the stronger ECMWF
shortwave.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 1159 PM CST Sun Nov 27 2016

WX/Cigs: most cigs sub 1 kft across the region...and expect this to
hold across the area into Mon afternoon. Should start to get some
bump upward in heights by late afternoon/evening.

While the main shield of -ra has moved northeast...radar pointing
out some scattered light showers while sfc obs suggest there may be
some drizzle around too. Infact, soundings support drizzle potential
thru Monday afternoon, with 3-4kft of low level saturation coupled
with thermodynamic lift through that layer. If this occurs, mvfr
vsbys are likely. For the moment, will go with vcsh. Will continue
to evaluate and update as needed.

Wind: tight pressure gradient will keep relatively strong/gusty
southeast winds for the ovenight hours, persisting into the
early/middle part of Monday afternoon. &&

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

$$

SHORT TERM...Boyne
LONG TERM...Boyne/Hollan
AVIATION...Rieck



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