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fxus63 kbis 210853 
afdbis 


Area forecast discussion 
National Weather Service Bismarck ND 
250 am CST Sat Nov 21 2009 


Short term...today through Monday night... 
the latest water vapor imagery shows our first in a series of 
shortwave troughs sliding into Idaho and the Great Basin region. 
Despite a 300mb 80kt jet and decent Omega/upward vertical motion 
in the right entrance region moving through North Dakota today...the 
overall column remains relatively dry resulting in a scattered cirrus 
shield to thin broken at times. The latest msas shows a surface cold 
front now moving through western Montana and eastern Idaho. 3hr 
pressure falls of 3mb to 4mb were observed over western and 
southwestern North Dakota indicative of ongoing warm air advection. 
The warm air advection will come to a halt across western North 
Dakota around sunrise and across central North Dakota during the 
afternoon. Using the 1000-500mb thickness packing for frontal 
passage/frontal passage placement and timing...models are in better agreement 
with frontal passage and onset of cold air advection. Should see 
this occur across the west between 15z-18z west 
(kisn/kdik)...21z-00z central (kmot/kbis)...and around 06z far 
eastern counties which includes kjms. Fully expect a continued dry 
frontal passage forecast and hence mostly sunny to partly cloudy 
skies today. Strong southerly winds out ahead of the front with 
mixing to around 900mb over our far eastern zones from Jamestown 
south will yield winds between 25 and 35 miles per hour. Contemplated a Wind 
Advisory but after collaborating with surrounding offices decided to 
highlight the gusty winds in the zones and severe weather potential statement. The day shift can 
issue a Nowcast or two if needed this afternoon. Afternoon highs 
will be maximized along and just ahead of the front today which 
places the warmest air from around Bismarck south and east. Cooler 
further west. 


Tonight and Sunday...the upper trough will slide through late 
tonight into Sunday morning followed by a transitory shortwave 
ridge Sunday afternoon. Overall afternoon high temperatures Sunday 
will be around 8 to 10 degrees cooler than today. Continued dry 
tonight and Sunday. 


Sunday night through Monday night...another upper trough will affect 
North Dakota. The GFS and Canadian gemglb are in close agreement 
with the track of the low. This solution is furthest north and has 
the highest impact for our County Warning Area with at least a slight chance of 
snow and rain. The NAM and European model (ecmwf) dig the low further south and 
hence removes the precipitation threat...with the exception of our 
far southeastern counties. Decided to make little or no change to 
ongoing pop/weather grids Sunday night through Monday night since 
current data is no more conclusive than last couple of model runs. 
Whichever model is correct...all concur on a colder regime...as 
the low moves south of North Dakota late Monday and Monday night. 
High temperatures on Monday will range from the upper 30s to 
around 40 which is still above average for this time of year. 


Long term...Tuesday through Saturday 
some differences in medium range models especialy at end of and past 
extended grid periods. At beginning of extended GFS and Gem slightly 
more progressive than European model (ecmwf) but majority of models have quantitative precipitation forecast east of 
forecast area by Tuesday daytime. 


Differences begin to appear Thursday night and Friday as closed 
Diggs over Great Lakes and ridging building in northern rockies and 
northern plains. European model (ecmwf) laggs more energy into a western Continental U.S. Trough 
while GFS is deep trough rebuilding Great Lakes region with much 
colder airmass farther west on GFS. 511 dm thickness on GFS and 524 
on European model (ecmwf) poised just north of border south of Lake Winnipeg at end 
of extended periods. Generally followed GFS for timing but 
ameliorated the cold temperatures of GFS with combo of European model (ecmwf) and GFS for 
day 8. 




&& 


Aviation... 
high clouds spreading from west to east will bring thin broken 
conditions to western and central North Dakota. Only concern will be 
strength of winds over eastern taf sites where gusts to 35 miles per hour are 
possible this afternoon. 




&& 


Bis watches/warnings/advisories... 
none. 
&& 


$$ 


Kansas/hw