Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 262303

Area Forecast Discussion
National Weather Service La Crosse WI
603 PM CDT Wed Oct 26 2016

.SHORT TERM...(This evening through Thursday)
Issued at 246 PM CDT Wed Oct 26 2016

Latest water vapor satellite imagery indicates shortwave trough over
the Great Lakes Region and shortwave ridging over the Rocky
Mountains. Light rain and drizzle in association with the
shortwave trough were seen across much of eastern Minnesota and
much of Wisconsin per latest mosaic radar.

An inverted trough will linger across the area through this evening
and then move southeast out of the area as the parent low pressure
system moves east through the lower Great Lakes.  This system will
provide enough lift to keep the drizzle/light rain going through
early evening, and then this precipitation will quickly come to an
end.  While the precipitation will be ending, the overcast skies
will linger through the night.  With the clouds and neutral
temperature advection aloft, kept the minimum temperatures for
tonight either near to a couple of degrees above the GFS MOS

The forecast area will remain under cyclonic flow Thursday morning
and linger clouds. As surface ridge builds into eastern Iowa and
central Iowa Thursday afternoon. Clouds are expected to slowly
diminish from west to east across the forecast area.

.LONG TERM...(Thursday night through Wednesday)
Issued at 246 PM CDT Wed Oct 26 2016

Shortwave/surface ridge builds into the Ohio River Valley and west
to east zonal flow develops aloft Thursday night into Friday. Weak
shortwave trough moves into northern Minnesota Friday. Out ahead of
the surface front in association with the shortwave
trough...pressure gradient tightens across the forecast area. The
26.12z GFS/NAM show slight differences on how far aloft the
atmosphere mixes Friday afternoon per bufkit GFS
is slightly higher in mixing aloft than the NAM. With the GFS
mixing aloft higher...wind speeds near the surface would be
slightly higher. For now...have kept blend of the models for wind
speeds Friday and forecast area should be breezy and warmer.

Next shortwave trough embedded in the west to east zonal flow moves
into northern Wisconsin Saturday. The 26.12z GFS/NAM suggest 500-
300mb pv advection and 850-700mb moisture convergence in association
with the shortwave trough. The 26.12z deterministic models
indicate slight differences in placement of the shortwave
trough...however with enough upper level forcing/lift/moisture.
Showers can be expected Saturday afternoon into Saturday night.

Main forecast concerns Saturday night into Wednesday are
precipitation chances Monday into Monday night and Wednesday. The
26.12z GFS/ECMWF/GEM are in okay agreement in developing west to
southwest zonal flow across the northern tier United States through
the period. However...the deterministic models are in disagreement
in timing/placement of the shortwave troughs/ridges embedded in the
west to southwest flow aloft through the period. This will result in
differences of location and timing of precipitation chances across
the forecast area Monday into Monday night and Wednesday. First
shortwave trough tracks across Minnesota and northern Wisconsin
Monday/Monday night and provides the possibility of showers across
the northern half of the forecast area. The 26.12z GFS/ECMWF
indicate significant differences on timing of the next impulse to
impact the forecast area the GFS is more progressive.
The 26.12z GFS suggest lift/moisture convergence and produces the
possibility of scattered showers across the forecast area.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 603 PM CDT Wed Oct 26 2016

An area of low pressure was over western Illinois late this
afternoon with an inverted trough of low pressure extending north
into western Wisconsin. Still some light rain/drizzle occurring
over Wisconsin with this feature, but the radar returns have been
decreasing and with nothing reported at either airport, do not
plan to include this in the forecast. Lots of low clouds over the
area from these two features and satellite imagery shows these
extending well back into eastern South Dakota and western Iowa.
Forecast soundings from the 26.18Z NAM do not show this low level
moisture getting scoured out until possible Thursday evening and
plan to show the IFR/MVFR ceilings remaining through this entire
forecast period.


Issued at 246 PM CDT Wed Oct 26 2016

Overnight rainfall amounts of 1 to 3 inches fell across the forecast
area has caused minor flooding along the Cedar and Trempealeau
Rivers. See the latest Flood Statements for the specific river
forecast. Other rivers...streams and creeks will have rises and
remain below flood stage.




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