645 
fxus65 kbyz 062120 
afdbyz 


Area forecast discussion 
National Weather Service Billings Montana 
320 PM MDT Monday Oct 6 2008 


Short term...valid for Tuesday and Wednesday... 


Fast zonal flow to be over the forecast area for the next couple 
of days before big changes arrive by the end of the week. 
Disturbance that brought the showers to the forecast area last 
night and this morning has moved well out into the Dakotas. Just 
a few lingering showers remain over the Southwest Mountains and 
Big Horn Mountains and this activity will diminish quickly by 
early evening. Gusty northwest winds will continue through the 
evening and these are expected to subside shortly after sunset. 


Next system quickly arrives by late in the day Tuesday. Fast 
zonal flow will be over the state as an upper level wave moves 
across southern Canada and the northern half of Montana. Lee-side 
troughing sets up during the afternoon bringing windy conditions 
to The Gap favored areas especially the Livingston area. 
Sustained winds around 30 miles per hour with gusts around 45 miles per hour will be 
likely. A cool front will move through the western zones by early 
evening and the east by midnight. This will destabilize the 
atmosphere allowing for the stronger gap flow winds to decrease. 
However...gusty northwest winds can be expected behind the front 
and continue through the night...especially across the eastern 
zones. Temperatures Tuesday will be the warmest of the week and 
possibly for quite some time as compressional warming ahead of 
the front will allow for readings to be around 70 degrees most 
locations. Bulk of energy looks to be just to our north so best 
chances for a shower will be across our northern zones. 
However...models showing a decent frontogenesis band to move from 
northwest to southeast Tuesday night. As a result...have added a 
slight pop chance across the western and central zones and 
stretched them south and east...but will leave the far southeast 
zones dry for now. Gusty northwest winds will continue behind the 
front for Wednesday with the windiest conditions across the east. 
Temperatures will be about 10 degrees cooler with readings back 
down into the upper 50s to lower 60s. Hooley 




Long term...valid for Thursday...Fri...Sat...sun...Mon... 


Will keep thinking with upcoming storm system the same as Main 
Point to get across now is that a turn to cold weather is in 
store. The chances of snow will also be in place...but weather it 
will be significant is still uncertain. 


Thursday...models in pretty good agreement to start off and begin 
digging a large trough into northwest U.S. This looks to set up 
some warm air advection lift across southern zones and have left 
probability of precipitation nearly the same as previous forecast. 


Friday through Saturday...models deepen upper storm system over 
the area and push a general trough axis across the area. Have 
raised probability of precipitation a bit as the feature moves through...but main 
difference is position of the feature by 00z Sunday. European model (ecmwf) 
continues to have a further west location with the upper low 
placing Billings forecast area in large upper diffluent flow as 
well as upslope flow from the surface to 700 mb. GFS position is 
further east placing Billings forecast area in drier northwest 
flow at low levels quicker. Either solutions looks to be cold and 
have kept with highs in the 40s and lows in the 20s to 30s. Still 
thinking that the GFS drier solution is the better solution as 
UKMET tends to be in the middle of these two models. 
Also...although a handful of GFS ensemble members have closed 
upper low solution...they are much further south and also further 
east with their position. With that in mind...did raise probability of precipitation a bit 
into low scattered range and isolated range for plains as European model (ecmwf) 
continues to stick with it's solution. Did raise probability of precipitation a bit in 
upslope areas mainly for Friday and Saturday as even a dry GFS 
solution would support some upslope flow into these areas. Rasch 


&& 


Aviation... 


Breezy and VFR conditions will prevail through early this 
evening. A cold front will move into the area tomorrow afternoon 
and night. It will bring more wind and a chance of light showers 
tomorrow night...otherwise VFR conditions are expected to prevail. Rasch 


&& 


Preliminary point temp/pops... 


Tuesday Wednesday Thursday Friday Sat sun Monday 
----------------------------------------------------------- 
bil 042/073 044/061 035/048 033/044 029/040 028/045 030/053 
00/b 20/u 22/r 23/o 33/o 22/west 21/b 
lvm 038/072 032/060 029/049 027/042 022/042 022/047 029/056 
00/north 20/b 24/o 44/o 43/o 22/west 21/north 
hdn 037/074 041/063 033/054 032/045 029/041 027/047 029/056 
00/b 20/u 23/r 23/o 23/o 22/west 11/b 
mls 038/074 042/061 034/052 032/048 031/044 029/046 031/058 
00/b 20/north 12/r 22/o 22/o 32/west 11/b 
4bq 036/072 041/059 034/053 029/048 030/042 029/046 030/058 
00/u 00/north 33/r 23/o 34/o 33/west 11/u 
bhk 033/073 038/057 030/051 026/048 027/043 027/046 029/055 
00/u 20/north 12/o 23/o 33/o 33/west 21/u 
shr 035/073 038/061 032/050 028/045 028/039 027/044 029/057 
00/b 00/north 34/r 34/o 44/o 32/west 21/b 


&& 


Byz watches/warnings/advisories... 
Montana...none. 
Wyoming...none. 


&& 


$$ 
Weather.Gov/Billings