Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 252018

Area Forecast Discussion
National Weather Service La Crosse WI
318 PM CDT Sat Mar 25 2017

.SHORT TERM...(This evening through Sunday)
Issued at 315 PM CDT Sat Mar 25 2017

At 3 PM, a vertically stacked low was centered over central
Missouri. KARX radar show a narrow band of rain located across
northeast Iowa and southwest Wisconsin. The northern of this
extent in near the Interstate 90 corridor. This rain is associated
with a deformation band on the northern edge of the low pressure
system. The GOES 16 7.34 channel (low-level water vapor IR band)
shows good drying north and south of this band.

The 25.12z models are in good agreement that this band will pivot
north and northwest across the forecast area this evening and then
additional bands of precipitation will move across the area late
tonight and Sunday. Like the past several days, soundings
continue to show that the temperatures aloft will warm enough
that the precipitation will be in the form of rain. There was some
initial concern that due to the temperatures and dew points near
freezing that there may be some light freezing rain in Taylor and
northern Clark counties late tonight. However, the 25.12z data
came in slightly warmer and as a result it is all rain event for
even these counties.

With strong warm air advection and abundant cloud cover,
temperatures will remain steady tonight. On Sunday, the NAM MOS
temperatures seemed too cold when considering the temperatures
that are currently underneath the low pressure area, so went
closer to the GFS MOS temperatures.

.LONG TERM...(Sunday night through Saturday)
Issued at 315 PM CDT Sat Mar 25 2017

On Sunday night and Monday, the low pressure area will move move
slowly east across the Great Lakes. Meanwhile, another short wave
trough will be moving to the south of the forecast area. These 2
systems will likely keep the skies cloudy across the region. For
Monday, the NAM MOS seemed too cold with its temperatures and the
GFS MOS seemed too warm, so split the difference.

From Thursday into Saturday, the GFS has a Hudson Bay high
suppressing an upper level low to our south. This keeps the Upper
Mississippi River Valley dry.  Meanwhile, both the GEM and ECMWF
have precipitation moving across the region as a low pressure
system either moves northeast across either Mid or Upper
Mississippi River Valley. The GEM`s track is slightly further
north and west than the ECMWF. Overall felt that the GFS was too
deep with its trough over eastern Canada, so trended more toward
the GEM and ECMWF.  With the 925 and 850 mb temperatures much
cooler with this system than they were with this current system,
allowed for a light wintry mix of rain and snow to occur on both
Thursday night and Friday night.


.AVIATION...(For the 18Z TAFS through 18Z Sunday afternoon)
Issued at 1213 PM CDT Sat Mar 25 2017

The rain has been slow to move in today and remains well south of
both airports late early this afternoon. Still expecting this to
work its way north through the evening as the surface low over
Missouri moves northeast. The rain should be pretty light and not
expecting much, if any, visibility restrictions from the rain. The
rain should begin to move off to the east and be away from both
airports by late evening. Ceilings will not improve during this
period as the low level boundary layer remains saturated and look
for these to be IFR through the period. This saturated boundary
layer will likely lead to some fog formation overnight as the
surface winds drop to under 10 knots. Plan to show this going down
to IFR for both airports but with winds just above the surface
remaining around 15 knots, not expecting this to drop to go below
2 miles.




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