924 
fxus65 kbyz 230929 
afdbyz 


Area forecast discussion 
National Weather Service Billings Montana 
229 am MST sun Nov 23 2008 


Short term...valid for today and Monday... 


Upper level short wave energy moving across the region early this 
morning. Initial dry airmass in place has taken some time to 
moisten but finally did so across much of the area with light 
precipitation noted in Livingston...Billings and Miles City 
overnight. Enough depth to low level warm layer to keep most of 
precipitation as rain. Best upper level forcing in areas from 
Billings southward into the mountains and this is where best radar 
returns showing up. As this system continues to shift southeast 
this morning...this area of precipitation will continue to shift 
into south central Montana and into the Big Horn Mountains where 
chances have been raised to likely in the foothills to 
categorical in the big horns during the early morning hours. Any 
measurable amounts will be light...although an additional couple 
inches of snowfall is still possible in the big horns. System 
quickly departs by afternoon for clearing skies most areas. 


Weather turns quiet into Monday as upper level ridging builds 
across the region for dry conditions. After a bit cooler 
temperatures today behind this mornings system...temperatures will 
rebound again into Monday with many lower elevations reaching back 
into the 50s. 


Frieders 




Long term...valid for Tuesday...Wed...Thu...Fri...Sat... 


Models continued to show upper ridging for Tuesday followed by a 
splitting Pacific trough that had main energy well to the S with a 
low cutting off over California by midweek. 00z WRF was outlier of the 
models Tuesday night with a 500 mb low over the Pacific northwest and energy 
streaming into the forecast area. GFS/European model (ecmwf) were not too impressive 
with moisture over western mountains Tuesday night...so lowered probability of precipitation to 
slight chance and took them out of the NE big horns. Latest models 
had a northern stream shortwave with associated cold front affecting 
the area on Wednesday. Previous runs did not show this feature. Will not 
latch onto the front yet...but with European model (ecmwf) consistently going drier 
for Wednesday and new GFS trending drier...will go a bit drier on Wednesday. 850 
mb temperatures will range from +6 NE to +10 degrees c central on Tuesday so 
raised temperatures toward the bias corrected European model (ecmwf). Wednesday will be 
cooler than Tuesday with more cloud cover. The going temperature 
forecast was reasonable. 850 thermal ridging moves east over eastern 
zones Tuesday night. Have raised temperatures toward the bias 
corrected NAM numbers. 


On Wednesday night...situation becomes more uncertain with GFS showing a 
ridge over the area and European model (ecmwf) a weak trough. GFS ensembles also 
reflected both solutions. The European model (ecmwf) solution was a bit wetter than 
GFS solution. Left going forecast with chance probability of precipitation over the west alone 
due to uncertainty. Model differences continued through Thursday 
night...then solutions appeared similar on Friday when an upper ridge 
was forecast to fold over the area north of another cutoff low over California. 
Despite some agreement for Friday...models differed in their moisture 
depictions. Thus will not make any changes to Wednesday night through the 
end of the period. Arthur 




&& 


Aviation... 


Areas of rain and snow will bring scattered MVFR conditions to the 
region this morning as well as mountain obscuration over the 
beartooths...absarokas and NE big horns. The precipitation will 
taper off from north to S late this morning. VFR will return to the 
region this afternoon...although areas of mountain obscuration will 
continue over the NE big horns. VFR will prevail over the entire 
region tonight. Arthur 


&& 


Preliminary point temp/pops... 


Today Monday Tuesday Wednesday Thursday Friday Sat 
------------------------------------------------------- 
bil 045 025/052 034/055 033/046 028/039 025/039 023/039 
1/b 00/u 00/u 01/b 33/o 22/S 10/b 
lvm 045 025/054 034/057 031/044 024/040 021/039 019/038 
1/b 00/north 00/b 02/o 44/S 32/S 20/b 
hdn 046 021/053 029/058 029/049 026/040 023/040 021/043 
2/west 00/u 00/u 01/b 23/S 22/S 10/b 
mls 044 022/048 024/052 030/044 025/038 022/038 020/041 
1/b 00/u 00/u 01/b 13/S 21/b 10/b 
4bq 044 021/050 026/055 029/046 025/036 022/036 020/040 
2/west 00/u 00/u 01/b 13/S 22/S 10/b 
bhk 040 018/046 025/047 026/042 024/035 021/035 019/039 
2/west 00/u 00/u 01/u 12/S 21/b 10/b 
shr 041 019/053 023/058 030/047 026/038 023/038 021/041 
5/west 00/u 00/u 01/b 24/S 32/S 20/b 


&& 


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


&& 


$$ 
Weather.Gov/Billings