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FXUS63 KARX 261131

Area Forecast Discussion
National Weather Service La Crosse WI
631 AM CDT Tue Sep 26 2017

.SHORT TERM...(Today through Wednesday Night) 
Issued at 314 AM CDT Tue Sep 26 2017

Water Vapor imagery this morning showing longwave troughing 
extending from eastern MT through the 4-corners area in the 
southwest US. An embedded mid-level shortwave trough was ejecting 
northeast out of the Central Plains. Lift ahead of this wave was 
fueling scattered showers and an occasional isolated thunderstorm 
from WI and MN southward through IA. This wave will continue moving 
northeast, spinning up a surface low over WI this morning. Scattered 
showers will continue through this morning as the wave and surface 
low move northeast across the area. Surface low will accelerate a 
cold front eastward through the area by early afternoon as MUCAPE 
builds slightly into the 500-1000J/kg range over central WI and 
points east. Expecting a few thunderstorms to result across central 
WI while the showers will be diminishing at least west of the 
Mississippi River behind the cold front. Otherwise, look for winds 
to increase from the northwest this afternoon in cold air advection 
with highs topping off in the middle 60s to middle 70s. 

Look for skies to gradually clear from west to east overnight as 
high pressure builds in from the Plains. Overnight lows are expected 
to drop into the middle 40s to lower 50s.

Wednesday shaping up to be more typical of late September as highs 
top off in the 60s under mostly sunny skies. High pressure slides 
across the area Wednesday night with mostly clear skies and cool 
temperatures. Look for lows in the lower to middle 40s. Am concerned 
about some river valley fog with good radiational cooling but winds 
just off the surface are still at 10-15kt. Also not sure how much 
decoupling will take place down in the valleys. Will leave out of 
the forecast for now but will continue monitoring. 

.LONG TERM...(Thursday through Monday)
Issued at 314 AM CDT Tue Sep 26 2017

On Thursday, a mid-level trough and surface cold front drop 
southeast across northern WI for a chance of showers. Confined 
shower chances across Clark and Taylor counties for now. Looks like 
a fairly nice day otherwise across the area with mostly sunny/partly 
cloudy skies and highs in the 60s/lower 70s.

Continued more typical of early fall weather expected for Friday 
into Saturday as a strong ridge of high pressure drifts over the 
area. Look for highs in the upper 50s to the upper 60s. Friday night 
is looking chilly as the high drifts overhead. Right now, going for 
lows in the upper 30s to the middle 40s. Could see the potential for 
some frost over the sand/cranberry bog areas of central WI. Will keep 
an eye on this over the next few days.

Slight warming takes place Saturday into Sunday as the high slides 
east and deepening low pressure works east into the Northern Plains. 
Plan on highs in the 60s and lower 70s.

Shower chances move in Sunday night, lasting through Monday as that 
area of low pressure and cold front rack east out of the Northern 
Plains into the Upper Mississippi River Valley region.  


.AVIATION...(For the 12Z TAFS through 12Z Wednesday morning)
Issued at 631 AM CDT Tue Sep 26 2017

A large area of IFR/MVFR conditions behind the cold front this
morning and this will be over both airports for a good share of
the day. Initial IFR conditions will show some improvement as the
showers end and the winds pick up out of the northwest but then
look for the MVFR ceilings to persist well into the afternoon. As
drier air works in late this afternoon, these ceilings should go
up to VFR for the evening and then scatter out overnight as high
pressure builds in over the region.



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