Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 252342

Area Forecast Discussion
National Weather Service La Crosse WI
642 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 00Z TAFS through 00Z Sunday evening)
Issued at 642 PM CDT Sat Mar 25 2017

A band of light rain from KGRB to KAEL as of 25.2330Z will
continue to lift northwestward early this evening, impacting both
KLSE/KRST. However, greater impact to aviation operations will be
falling ceilings/visibility into the IFR range later this evening
and overnight. With widespread IFR ceilings currently across IA/
southern WI, it should only be a matter of a couple hours before
cloud bases drop below 1000 ft agl at TAF airfields. Also expect
MVFR/IFR reductions in visibility due to mist, especially
overnight into Sunday morning. KRST could drop below 1SM in fog
later tonight, but given what happened last night in the same air
mass, will keep visibility around 1 1/2SM for now. IFR/low MVFR
ceilings will then continue on Sunday with only a very gradual
improvement in visibility by late morning/afternoon.




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