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fxus63 kbis 022131 
afdbis 


Area forecast discussion 
National Weather Service Bismarck ND 
331 PM CST Tuesday Dec 2 2008 


Short term...tonight through Friday night... 
two concerns this evening. Snow falling across the extreme 
southwest counties of Bowman and Adams. Will keep a period of snow 
for this area this evening. Snow accumulations around an inch 
associated in a preferred area of orographic upslope beneath 
divergence aloft associated with jet stream proximity. Snow will 
diminish lated this evening with just flurries expected after 
midnight. I have canceled the Wind Advisory north central as 
wind gusts have diminished to generally 30 kts or less late this 
afternoon and expected to diminish further. 


Cold cyclonic flow aloft remains over the region through Wednesday 
night with next shortwave Wednesday night bringing next chance 
for accumulating snow. At this time amounts should be around an 
inch or two across the central by Thursday morning. On Thursday 
and Friday the cyclonic inflection point moves east and rising 
heights should signal dry weather for the region. 


Long term...Saturday through Tuesday... 
models/ensembles continue to depict strong negative height anomalous 
across the Hudson Bay region southward across much of the eastern 
half of the Continental U.S.. this supports a rather amplified upper level long 
wave pattern across North America...featuring an eastern 
Pacific/West Coast ridge...and anomalies troughing across the 
eastern Continental U.S.. this pattern will keep North Dakota under persistent 
northwest flow aloft...at least through the first half of the long 
term period. The main forecast challenges in this type of flow 
pattern will be timing and exact placement of numerous shortwave 
disturbances to transition across the eastern Pacific/West Coast 
ridge and eventually across the northern plains. 


Initially...it appears that cold Canadian high pressure will 
dominate the region on Saturday...likely keeping temperatures cold. 
However...by Sunday it appears a short wave disturbance...emanating 
from the northeast Pacific...will lead to the development of surface 
low pressure across the Front Range of the northern rockies. Decent 
isentropic ascent appears to set up across the region late Sunday 
night ahead of this feature. Thus a slight chance of snow is 
warranted. I decided to leave the mention of all snow in the grids 
at this time. However...the models are hinting at some warmer middle 
level temperatures advecting across the southern half of the state. 
Later shifts may have to add a winter mix...depending on the exact 
track of the surface low. The chance of snow looks to continue into 
Monday as the upper short wave transitions across the area. 


A second system then looks to affect the region by the middle of 
next week. Again the exact track of this system will make all the 
difference in the world for US. Behind this second system we may see 
much colder air spill in across the northern plains. 




&& 


Aviation... 
low pressure across western Ontario pushed a cold front across the 
state. Behind this front...winds have become gusty out of the 
northwest at up to 40 miles per hour. Expect these winds to continue into the 
evening hours. In addition to the winds...middle level forcing will 
produce some snow this afternoon...mainly across the southwest 
portions of the state. Low VFR to MVFR ceilings can be expected across 
central and eastern sections of the area late this afternoon into 
Wednesday. 


&& 


Bis watches/warnings/advisories... 
none. 


&& 


$$ 


Warm air advection/kb