355 
fxus63 karx 211910 
afdarx 


Area forecast discussion 
National Weather Service La Crosse WI 
210 PM CDT sun Mar 21 2010 


Short term...tonight through Wednesday night 


A closed upper level low will continue to stay well south of the 
area...churning from the lower Mississippi River valley eastward 
toward the middle atl states through Tuesday. This will leave the area of 
high pressure at the surface to continue its influence on the upper 
Mississippi River valley tonight and Monday...with clear and 
tranquil conditions expected. 


Both the 21.12z GFS and NAM point to some upper level shortwave 
energy moving west out of the Pacific northwest...sliding across the western 
Great Lakes on Tuesday. Some low level warming in the 850-700 mb layer 
ahead of this feature...along with isentropic upglide on the 285-300 
k sfcs. Most of this occurs out ahead of the shortwave...12-18z 
Tuesday. This thermodynamic forcing doesn/T have much saturation to 
work with...however...with condensation pressure deficits in the 
285-305 k layer relatively dry from 12-18z...as are the relative humidity fields. 
West-east running x-sections via the GFS and NAM continue the lack 
of moisture into Tuesday afternoon...building in some saturation below 
850 mb...but also below the potential lift from the upper level 
shortwave. Both models keep any quantitative precipitation forecast over northern Minnesota/WI and points 
north of there...where better forcing/moisture is expected. Will 
hold onto the small chances for the far northern parts of the 
forecast area...staying dry with perhaps some clouds elsewhere. 


A surface high looks to build back across the area on Wednesday while a 
stronger shortwave trough drops southeast over south central 
Canada...with this feature then slipping across the northern/eastern 
Great Lakes starting Wednesday night. NAM/GFS/ec all on the same track 
with the shortwave...which would keep its associated precipitation chances 
North/East of the forecast area. 


Overall...the dry trend should continue through at least Wednesday...with 
a weak shortwave probably bringing a few clouds Tuesday...but likely no 
precipitation. After a couple seasonable days...look for temperatures to 
become relatively mild again for late March...although the low-middle 
60 highs of last week are not expected. 


Long term...Thursday through Sunday 


GFS and European model (ecmwf) continue to favor a split flow through the later part 
of the week...with solutions persisting with sliding an upper level 
shortwave trough across the northern Great Lakes into the New 
England states Thursday-Friday and another shortwave trough eastward across 
the Southern Plains toward the atl states. Precipitation chances will likely 
split north and south of the local forecast area as a result...with 
a surface high being the greater influence. The GFS and ec then suggest 
that the split flow might give way to a more zonal setup...and would 
shove a shortwave trough across the plains into the region on 
Sat/sun. The GFS is much stronger compared to the ec...and there is 
quite a variety of solutions via the members of the 
ensembles...although all agree to the trough. So...precipitation chances are 
trending up for the region for next weekend. Temperature profiles 
would lean toward rain...although some snow can/T be ruled out. 


&& 


Aviation... 


VFR conditions will persist through Monday as a dry airmass 
associated with high pressure sits over the region. Winds will be 
light and generally variable but as the high begins to slide to the 
south on Monday...wind direction will switch to a southerly 
direction...while staying below 10kts. 


&& 


Arx watches/warnings/advisories... 


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


&& 


$$ 


Short/long term... rieck 
aviation.......... Brooks