Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 272000

Area Forecast Discussion
National Weather Service La Crosse WI
300 PM CDT Thu Oct 27 2016

.SHORT TERM...(This evening through Friday)
Issued at 300 PM CDT Thu Oct 27 2016

Latest water vapor satellite imagery shows upper level ridge over
eastern Rockies and southern Canadian Prairies and upper level
trough over the eastern Great Lakes region. Upper level trough is
wrapping low stratus deck of clouds and sprinkles/drizzle across
much of the forecast area per latest visible satellite imagery
and mosaic radar.

Upper level ridge will build into the Upper Midwest tonight into
Friday. Strong southerly winds aloft are expected to slowly diminish
the clouds south to north across the forecast area.
However...winds near the surface remain light tonight...with moist
near surface boundary layer. Patchy to areas of fog is expected to
form across much of the forecast area tonight.

Pressure gradient tightens across the forecast area by 12z surface low pressure moves along the international
border. The 27.12z GFS/NAM indicate southerly winds increasing to
15 to 20 knots sustained with around 30 knot wind
gust...especially in higher and open areas west of the Mississippi
River. There is potential winds could gust a little higher up to
35 knots...if winds aloft mix down to the surface.

Another concern for Friday is potential of low stratus deck of
clouds redeveloping over the northern parts of the forecast area
Friday afternoon on nose of strong warm air advection. The 27.12z
NAM is more progressive than the GFS with this and the NAM produces
drizzle per bufkit soundings over north central Wisconsin. At this
time...the 27.12z NAM may be overdone with moisture at lower
levels...but have increased cloud cover over the far northern
parts of the forecast area Friday.

.LONG TERM...(Friday night through Thursday)
Issued at 300 PM CDT Thu Oct 27 2016

The 27.12z GFS/NAM/ECMWF are in better agreement in tracking
shortwave trough over central Minnesota/northern Wisconsin
Saturday afternoon into Saturday evening. The deterministic 27.12z
models continue to show 500-300mb pv advection and qg forcing in
association with the shortwave. This would result in light
precipitation across the northern half of the forecast area
Saturday afternoon into Saturday evening. Have increased
precipitation chances after 18z Saturday across the northern
portions of the forecast area.

Shortwave/surface ridge builds into the Upper Great Lakes Region
Sunday and provides dry weather/seasonable temperatures.

The GFS and ECMWF are in good agreement bringing a progressive
shortwave from northern California into northern Minnesota late
Sunday into Monday. Strong WAA associated with an 850 mb jet around
50-60 kts will keep temperatures much above average for Halloween.
The best forcing/moisture for precipitation remains to our north,
however, with the surface low tracking from the central Dakotas into
the Arrowhead of Minnesota. Could still see a few sprinkles, but
currently thinking Monday should remain dry for most areas, with the
best chance for any precipitation across our northern counties.
Cloud cover could limit temperatures on Monday, but should still see
widespread 60s. 70s are not out of the question if much of the day
turns out to be clear. Winds could also become an issue on Monday,
with GFS soundings showing mixing up to 825 mb. Quieter weather
should build in behind the departing low for Tuesday, with
temperatures returning closer to normal. The GFS and ECMWF begin to
diverge Wednesday and Thursday, but both hint at a return to
unsettled weather with longwave troughing developing over the
western CONUS. Temperatures should remain warm enough that winter
precipitation would not be a concern.


.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1240 PM CDT Thu Oct 27 2016

Widespread stratus continues to encompass much of the region, but
should slowly erode from the south and west into the evening and
early overnight hours as southerly flow increases. Current
ceilings in the IFR to MVFR range will very slowly rise through
early evening, with the expectation that lower stratus will
completely exit LSE and RST by 05Z, though ultimately that timing
could end up being a little slower. With moistening though the
boundary layer taking place overnight in advance of low pressure
over the northern Plains, the fog threat continues to increase,
especially for RST where skies will be clearest for longer.

Have really kicked the fog idea into high gear with a period of
LIFR conditions roughly 10-14Z, though the exact timing of that is
still a bit in question. Farther east for LSE, not entire sure
just how low visibility will go given the later clearing skies,
but there is some smaller risk for LIFR conditions for a time
centered on sunrise. Any fog (and maybe a little additional
stratus) should erode by mid morning, leaving gusty southerly
winds at 15-25 knots heading into midday Friday.


Issued at 300 PM CDT Thu Oct 27 2016

Due to the recent rainfall of 1 to 3 inches Tuesday night into
Wednesday morning...a few rivers...the Cedar and Trempealeau...
remain at or rise above flood stage over the next couple of days.
See the latest Flood Statements for the latest specific forecast.
Other rivers...streams and creeks will have rises and remain below
flood stage.




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