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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Thursday
• 
• High: 84 °
• Low: 55 °
• T-Storms

• Friday
• 
• High: 75 °
• Low: 55 °
• Chance of T-Storms

• Saturday
• 
• High: 79 °
• Low: 59 °
• Chance of T-Storms

• Sunday
• 
• High: 95 °
• Low: 64 °
• Partly Cloudy

• Monday
• 
• High: 79 °
• Low: 50 °
• Chance of T-Storms

Area forecast discussion 
National Weather Service La Crosse WI 
1100 PM CDT Wednesday may 23 2012 


Short term...through Friday night 
321 PM CDT Wednesday may 23 2012 


Main forecast concern is with the rain chances tonight through 
Thursday night and the associated severe weather threat. 


Surface analysis this afternoon shows a cold front extending from 
eastern North Dakota to an area of low pressure over central Kansas. 
Regional radars showing showers and thunderstorms along and ahead 
of the front from northern Minnesota into eastern South Dakota. 


The rain chances through Thursday night appear to be tied to two 
short wave troughs. The first is coming into the Dakotas this 
afternoon and is driving the on going convection across the 
Dakotas and Minnesota. This wave will continue to lift to the 
northeast and is expected to take most of the forcing past the 
area. At the same time...the cold front will make slow eastward 
progress and by late tonight should extend from northeast 
Minnesota into eastern Kansas as the surface low moves north along 
the front. As the low moves north...warm air aloft will be working 
north as well and is expected to start capping off the warm 
sector. The 23.12z NAM BUFKIT sounding for Kalo shows this cap 
developing late tonight between 800 and 700 mb. This developing 
cap...along with the best forcing behind to the north is expected 
to keep the bulk of the rain out of the forecast area tonight. 
However...with the isentropic up Glide north of the surface low 
and the frontogenesis along the front...can not totally rule out 
the possibility of some of this activity sneaking into the 
northwest sections of the forecast area. 


The second short wave trough will become the main player for 
Thursday. This wave is currently coming across the Great Basin and 
is expected to strengthen as it turns the corner in the base of 
the trough and starts to lift to the northeast. This is expected 
to cause the trough to take on a slight negative tilt with the 
bulk of the pv advection in the 500-300 mb layer moving from 
southern South Dakota into northwest Wisconsin with about 12 to 16 
pvu/S brushing the northwest part of the forecast area Thursday 
afternoon. The NAM suggests the left exit region of the upper 
level jet will provide some additional lift during the afternoon 
while the 23.12z GFS places this farther to the west. As the front 
comes into the area...the cap is expected to hold through the 
morning keeping the rain chances confined to the northwest half of 
the area. By afternoon...the front will be moving into the 
forecast area with increasing frontogenesis and fn vector 
convergence along the front. The ml cape is expected to build to 
around 1200 j/kg during the afternoon ahead of the front and by 
late afternoon...the 0-6 km shear of 50 knots will start to 
overrun the cape axis ahead of the front. The forcing from the 
wave and upper level jet is expected to be enough to cause the cap 
to break over northwest Wisconsin/eastern Minnesota. Once the cap 
breaks...storms are expected to develop farther south along the 
front in the moisture transport axis and the zone of best 
frontogenesis and fn vector convergence. These storms will have 
the potential to be severe with damaging winds the main threat. 
However...if any of these storms can remain discrete along the 
front...there will be the potential for a tornado. However...not 
sure how great this threat is as most of the shear is in the low 
levels with 45 to 50 knots of shear in the 0-3 km layer. The 
threat for storms/severe weather will continue into the early 
evening before everything pushes off to the east. 


The front is expected to become stationary south of the area 
Friday and then start to return back as a warm front Friday night. 
There is no consensus among the 23.12z models as to how far north 
the warm front will be and thus where the overrunning rains will 
set up. The NAM is the farthest north with the front across 
northern Iowa into southern Wisconsin with the main area of 
overrunning rains well to the north of this. The GFS and European model (ecmwf) are 
similar in placing the front across southern Iowa into northern or 
central Indiana. The GFS keeps the rain along and just north of the 
front and south of the forecast area while the European model (ecmwf) has the band 
of rain right across the forecast area. With so much 
uncertainty...hedged the forecast toward the European model (ecmwf) solution but 
kept the rain chances in the 30 to 50 percent range. 


Long term...Saturday through Wednesday 
321 PM CDT Wednesday may 23 2012 


The rain chances tied to the warm front will continue Saturday and 
Saturday night as the front moves north. The possibility for 
severe exists for Friday night into Saturday as elevated cape 
starts to push north over the front with good shear in the 0-6km 
layer north of the front. Additional rain chances will occur 
Sunday night into Memorial Day as a cold front moves quickly 
across the region. The current set of models suggests this front 
will move across late Sunday night into Monday morning limiting 
the chances for severe weather. However...this will have to be 
watch closely as any slowing of this system could put the front 
over the forecast area Monday afternoon. Additional storms are 
expected to fire along the front Monday afternoon and there will 
will be the potential for severe weather...but it will all depend 
on where the front is located. 


&& 


Aviation... 
1100 PM CDT Wednesday may 23 2012 


Winds remain a concern through the overnight and into Thursday evening as 
tight pressure gradient and hefty low level jet remains in place. 
BUFKIT soundings point to wind gusts in excess of 30 kts late Thursday 
morning/afternoon. In addition...latest rap/nam12 continue to show 
upwards of 50 kts at 2 kft overnight...making low level wind shear a concern for 
krst and klse. Will continue mention for krst/klse overnight/early 
morning. 


Broad line of rain showers/ts continue to move northeast across northwest Iowa 
into northeast Minnesota...mostly along and west of a cold front...in a 
region of higher instability/moisture. East of there...it dries out 
rapidly...evidenced by the 00z dvn sounding and surface observation. Precipitation is 
going to have a hard time moving off the front and into the area. 


There is more confidence for a period of rain showers/ts Thursday 
afternoon/evening as the front moves in from the west. Expect mostly 
VFR conditions...with some MVFR with any thunderstorm on Thursday. The 
atmosphere could support some severe weather Thursday 
afternoon/evening...with winds being the main threat. 


The front looks to track east of krst between 22-01z and klse 
between 00-03z. 


&& 


Arx watches/warnings/advisories... 
645 PM CDT Wednesday may 23 2012 


WI...none. 
Minnesota...none. 
Iowa...none. 


&& 


$$ 


Short term...04 
long term....04 
aviation.....Rieck