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Area forecast discussion 
National Weather Service La Crosse WI
1210 PM CDT Tuesday Jul 29 2014

Short term...(today and tonight)
issued at 321 am CDT Tuesday Jul 29 2014

Main forecast concerns are how far west showers and thunderstorms
develop this afternoon across the forecast area.

Latest water vapor satellite imagery and upper air analysis
showing upper level low over Ontario and Quebec Canada. Shortwave
trough embedded in the northerly flow aloft was producing showers
over north central Wisconsin and now have weakened due to the
showers moving into a more stable airmass over central Wisconsin.

The latest 29.00z GFS/NAM and 29.03z rap are in good agreement in
keeping upper level low closed off over Ontario and Quebec Canada
today. The models show a couple of shortwave troughs embedded in
the northerly flow to move over the area today. BUFKIT soundings
mainly along and east of the Mississippi River continue to show
steep lapse rates and a few hundred surface base cape today. With
the latest hi resolution models...hrrr/arw/NAM 4km...indicate
showers to develop and increase in coverage along and east of the
Mississippi River late this morning into the afternoon hours.
Have increase probability of precipitation slightly over the north central Wisconsin. The
latest 29.00z GFS/NAM/ECMWF linger rain showers/thunderstorms and rain activity into the
evening hours. Have kept small precipitation chances into the
evening hours. No severe thunderstorms are expected across the
forecast area the latest 29.03z rap/29.00z NAM show
0-3km shear less than 20 knots over central Wisconsin...however
small hail will be possible with some of the stronger thunderstorms.

Long term...(wednesday through monday)
issued at 321 am CDT Tuesday Jul 29 2014

Main forecast concerns are small precipitation chances
through much of the period.

The 29.00z GFS/NAM/ECMWF rotate several shortwave troughs into the
upper Great Lakes region Wednesday into Thursday. The 29.00z
NAM/GFS BUFKIT soundings over central Wisconsin show some cape
less than 100 j/kg Wednesday and a couple of hundred j/kg cape
Thursday. With the combination of shortwave troughs providing lift
and steepening lapse rates due daytime heating Wednesday and
Thursday. Will continue with small chances of precipitation mainly
along east of the Mississippi River...with slightly higher chances
Thursday afternoon.

Thursday night into Monday...upper level low/trough over the eastern
United States and Canada breaks down and shortwave ridging builds
into the upper greats lakes region Sunday. A couple of shortwave
troughs will track over the forecast area Friday into Saturday
and provide chances of showers and isolated thunderstorms per
latest 29.00z GFS/Gem/ECMWF. Sunday looks 500mb heights
rise with shortwave ridge building into the forecast area. Focus
turns to next shortwave trough/surface cold front to push across
the forecast area Monday. The 29.00z GFS/European model (ecmwf) are in a
disagreement with timing and placement with this feature. The
29.00z GFS/European model (ecmwf) are in agreement there will be decent lift and
moisture convergence in association with shortwave trough/surface
front to warrant chances of precipitation across much of the
forecast area Monday.


Aviation...(for the 18z tafs through 18z Wednesday afternoon)
issued at 1210 PM CDT Tuesday Jul 29 2014

A weak shortwave rippling southeast through the northwest flow aloft is
expected to produce scattered -shra and isolated -tsra mainly along and
east of the MS river during the middle afternoon into early evening
hours. With the scattered coverage...continued with a vcsh at klse in the
20-01z time-frame. The -shra or any -tsra could produce some brief/
local MVFR visibilities in the rain cores...otherwise VFR conditions to
prevail this taf period. Scattered-broken cumulus in the 4k-6k feet range this
afternoon/early this evening to dissipate after sunset. Northwest
winds of 4-8kt should keep the boundary layer stirred tonight and
any late night/early morning br in the valleys to a minimum.


Arx watches/warnings/advisories...


Short term...dtj
long term....dtj

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