Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 182308

Area Forecast Discussion
National Weather Service La Crosse WI
610 PM CDT Tue Oct 18 2016

.SHORT TERM...(This evening through Friday)
Issued at 207 PM CDT Tue Oct 18 2016

Pretty quiet stretch of weather coming up. A short wave trough
coming out of the central Rockies today is expected to amplify
Wednesday and Wednesday night over the Plains. This amplification
looks like it will cause the wave to dip south across the central
Mississippi River Valley Thursday as it heads east toward the
Appalachians. Both the 18.12Z NAM and GFS show the best forcing
from this system missing the area, but there should be some weak
pv advection in the 500-300 mb layer that comes across to cause
skies to become mostly cloudy for Wednesday afternoon and evening
for the southern half of the area. Not anticipating any rain from
this system and will have a dry forecast for the rest of the week.

Once this wave moves past the area, high pressure at the surface
will settle in over the Upper Midwest. The ridge axis should be
right over the area Thursday night. Skies should be mostly clear
under the high and with light winds, temperatures should drop into
the lower to middle 30s allowing frost to form again. Will likely
need an advisory for the portions of the area that have not seen
the growing season already come to an end.

.LONG TERM...(Friday night through Tuesday)
Issued at 207 PM CDT Tue Oct 18 2016

Warm air advection taking place over the region will lead to a
slight warming trend into the weekend, as well as a slight chance
for some precipitation Friday night into Saturday morning. Though
both the GFS and ECMWF show this warm air advection, the GFS has
kept the precipitation well to the north, while the ECMWF has
consistently moved precipitation through the forecast area. At
this point, have left a mix of rain and snow in areas near freezing
on Saturday morning, though 18.00Z ECMWF soundings show saturation
only to -7C or so, indicating that ice introduction, and therefore
snow, is rather unlikely. It should also be noted that the 18.12Z
ECMWF comes into agreement with the GFS and keeps the area mainly
dry. These details will be worked out as we get closer to the
weekend. Beyond Saturday, models stay in agreement with a ridge axis
to the west, leaving the region under northwest flow until Tuesday
when a shortwave and precipitation are progged to move through. The
ECMWF is quite aggressive with this feature and cuts off a low over
the area. It is much too early to get into details, but current
thinking is the region could see widespread precipitation by the
middle of next week.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 610 PM CDT Tue Oct 18 2016

Scattered mid level/diurnally driven clouds could move across the
TAF sites this evening, otherwise expect SKC conditions into Wed
morning. More high based VFR moves in ahead of an upper level
shortwave...lingering into the evening. For winds...more southwest
and light tonight...back to west/northwest with a slight uptick late
wed morning.




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