718 
fxus65 kbyz 221638 aaa 
afdbyz 


Area forecast discussion...updated 
National Weather Service Billings Montana 
938 am MST Sat Nov 22 2008 


Short term...valid for today and sun... 


Winds at Livingston have been below advisory criteria the last 
couple of hours...but close on both gusts and sustained. 
Gradients remain snug from Idaho Falls to Lewistown...in fact 
have tightened up even more the last several hours. The Lee 
trough that is playing a large role in wind production there will 
be sliding east the rest of the day...as evident by surface 
pressure falls over Saskatchewan and eastern Montana. Guidance 
continues to hit winds hard at Livingston up till noon. Would 
expect winds to back off steadily this afternoon as gap flow 
decreases with heating and the Lee trough pulls away. Will let 
advisory ride out. Temperatures over western and central zones 
ahead of guidance pace...and have raised a bit more with 
downslope today. Clouds will roll through the area and keep 
heating down...but should be able to reach upper 40s to lower 
50s. Will have to take a close look at system for tonight as 
models generating some strong qc forcing with decent moisture 
over western and southern zones. Will cover that on the afternoon 
package. Humphrey 


Long term...valid for Monday...Tue...Wed...Thu...Fri... 


High confidence to start the extended period as models had good 
agreement with upper ridging and a dry air mass over the area...then 
confidence decreases due to differences in handling of next Pacific 
trough. No changes to the dry forecast Monday through Tuesday. Will have 
Lee troughing with downslope flow over the area which will result in 
above normal temperatures. Did trend higher than guidance on low 
temperatures from kbil west to klvm Monday night with Lee troughing over 
area and fairly strong 850 mb thermal ridge. SW flow ahead of 
Pacific trough will bring high level moisture to mountains Tuesday night so 
confined precipitation chances to high terrain. 


Concerning the remainder of the forecast...possible unsettled period 
will occur into late in the week due to a Pacific system. 
However...confidence not high as forecast area will not be under any 
well-defined features. Model consensus was splitting the approaching 
Pacific trough on Wednesday. Jet energy was confined to the southern 
portion of the system...well to the S of the forecast area through 
Thursday. The GFS brought more moisture into the area around a 700 mb 
upper low over Idaho on Wednesday than the European model (ecmwf). Both models were fairly 
similar from run-to-run with their moisture depictions. Saw no 
reason to change inherited probability of precipitation which were over the western zones 
and NE big horns. The model differences in handling moisture 
continued Wednesday night through Thursday night. Will not change going probability of precipitation 
which looked reasonable for now. An upper low over California becomes the 
system/S dominant feature on Friday. Bulk of moisture was forecast to 
shift to the S of the region Friday night. The slight chance probability of precipitation over 
the area looked fine. 


In addition to the model differences in handling the moisture during 
the period...there were also differences in handling the forecast 
temperature profiles between the GFS and European model (ecmwf). Thus...made no 
changes to temperatures which reflected a cooling trend late in the 
week. Arthur 


&& 


Aviation... 


VFR conditions will prevail through the day today. Areas of 
patchy fog in the east...around kbhk...having previously reduced 
visibility to IFR/LIFR conditions this morning...continue to 
improve rapidly and should be cleared out by middle morning. 


Strong gusty southwest winds continue in and near klvm...with 
gusts around 55 miles per hour...are expected to drop off by this 
afternoon/evening with the passage of the cold front. 


Additionally...a cold front is expected to impact the area late 
this afternoon...crossing the region throughout the evening and 
overnight. Associated scattered rain and snow showers will likely 
cause localized MVFR/IFR conditions as the system traverses the 
area. Mountain obscurations will increase through the afternoon 
and overnight. Gilstad 






&& 


Preliminary point temp/pops... 


Today sun Monday Tuesday Wednesday Thursday Friday 
------------------------------------------------------- 
bil 052 030/046 026/053 035/053 032/048 028/041 025/039 
0/north 31/b 00/u 00/u 01/b 33/o 32/S 
lvm 051 028/045 025/055 035/055 030/046 024/041 021/039 
1/north 41/b 00/u 00/b 03/o 44/S 42/S 
hdn 052 028/048 021/054 031/056 031/051 026/042 023/040 
0/b 31/b 00/u 00/u 01/b 22/o 22/S 
mls 047 026/043 021/049 025/050 027/046 025/040 022/038 
0/b 21/north 00/u 00/u 01/b 22/S 22/S 
4bq 047 027/044 019/050 026/053 025/048 025/038 022/036 
0/b 22/j 00/u 00/u 01/b 22/S 22/S 
bhk 041 023/038 018/048 027/049 025/044 024/037 021/035 
0/b 11/north 00/u 00/u 01/u 22/S 22/S 
shr 051 026/045 018/053 023/054 027/048 026/040 023/038 
0/b 22/j 00/u 00/b 01/b 22/S 22/S 


&& 


Byz watches/warnings/advisories... 
Montana...Wind Advisory in effect until noon MST today for zones 65-66. 
Wyoming...none. 


&& 


$$ 
Weather.Gov/Billings