086 
fxus63 karx 200720 
afdarx 


Area forecast discussion 
National Weather Service La Crosse WI 
220 am CDT Sat Mar 20 2010 


Short term...today through Monday night 


Focus this morning is on the departing snow...cloud trends today and 
tonight...and then mainly temperatures. 


07z surface analysis shows a low pressure area over the Ozarks... 
with a frontal boundary reaching northeast into the eastern Great 
Lakes region. High pressure was centered over Montana and the western 
Dakotas. Northerly winds across our area was sending cold air in 
from Canada...and where this cold air was meeting the warm and moist 
air riding up and over the front...a potent band of snow had set up. 
The snow ran from the Kansas City area...up across Iowa and into 
northern Illinois and far southern WI. Several inches of accumulation seen 
to our south...but only a light dusting on grassy areas reported so 
far in our zones. 


For today...the area of deep frontogenesis responsible for the upward 
motions for snow production will slowly sag southward as the front 
and storm system shift toward the Ohio River valley. Will hang onto 
small snow chances over the far southern zones this morning...but 
that is it. In fact...dry air also invading from the north should 
result in clearing skies. Ample sunshine today should help offset 
the cold advection...so anticipate highs from the middle 30s to middle 40s. 


Model solutions remain in rather good agreement through the remainder 
of the short term period...with above average forecast confidence. 


A ridge of high pressure will remain across the area from tonight 
all the way through Monday...with an overall slow-moving weather 
pattern. The overall pattern will remain in place...with the main 
jet up across Canada...and periodic short wave trough energy hitting 
the West Coast and digging into a slow moving closed circulation. 
This next cycle looks to set up again by the middle of next week. 
A short wave trough in the northern stream will bring the next 
cold front and threat for precipitation late Tuesday. 


But before that gets here...look for temperatures to begin to rebound 
back above normal Sunday into Monday as low level warm air starts to 
advect back in under the ridging. 


One last thing to consider. With light winds under the ridging...and 
dry air around to allow for maximum radiational cooling...thought 
about the need to add some fog to the forecast for both tonight and 
Sunday night. Available moisture looks pretty shallow...so not sold 
on it completely. Will leave out...but will alert later shifts to 
consider this possibility. 


Long term...Tuesday through Friday 


As alluded to above...we look to have a repeat performance of a 
northern stream disturbance bringing a front into the area...as a 
piece of energy again digs into the southwestern states and closes 
off. The timing of this remains in question...but the first small 
chances from the northern stream look to be late Tuesday into 
Wednesday. Currently...the southern piece looks to pass south of 
our region...so no precipitation in the forecast yet. But will 
have to monitor the eventual track of this for late next week. 
No changes to the long term yet until this becomes more clear. 


&& 


Aviation... 


Post-cold frontal MVFR clouds will be scoured out at the beginning 
of the taf period as drier air moves into the area. A strong storm 
over the central U.S. Will keep some middle-level clouds over the taf 
sites until full clearing occurs. VFR through the remainder of 
weekend. However...will be monitoring Sunday morning for the lower 
probability that some radiational fog may form at klse. It appears 
moisture will be a limiting factor at this time. 


&& 


Arx watches/warnings/advisories... 
WI...none. 
Minnesota...none. 
Iowa...none. 
&& 


$$ 


Short/long term...mw 
aviation...baumgardt/das