068 
fxus65 kbyz 070856 
afdbyz 


Area forecast discussion 
National Weather Service Billings Montana 
256 am MDT sun Sep 7 2008 


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


This amazing run of unseasonably cooler weather will continue for 
another couple of days. The coolest day will be today with a 
small moderation in temperatures Monday before the main warm up 
of Tuesday. Today should be a wet one for western and central 
sections. Rain already falling from Harlowton to Billings to 
Lodge Grass as energy digs over southwest Montana. Precipitation 
being caused by a number of things. Vorticity advection and q 
vector forcing ahead of the wave moving toward Bozeman...along 
with warm air advection lift on the front side of the shortwave. 
Models have finally grabbed onto this feature...but still having 
a hard time placing quantitative precipitation forecast accurately. Raised probability of precipitation today as 
precipitation spreads across. Upper trough will dig southeast 
through the day and edge the rain southward. Enough instability 
for more showers to develop in the afternoon however...so will 
keep probability of precipitation high. 700mb temperatures fall to around -2c this 
afternoon. Kblx radar indicating some bright banding around 7 
thousand feet. Observations support snow level at around 8 
thousand feet at this hour. Will put light accumulations in the 
mountains today as will be working against early September day 
light. Cooled things down today with clouds and showers along 
with 850mb temperatures around 8c. 


The system lingers over the south this evening...then works 
southeast out of the area overnight. Tapered probability of precipitation from north to 
south in this process. Could see some evening accumulation of 
snow over the big horns...but kept amounts low as snow should be 
wet. Wet ground and decreasing clouds should lend to the 
possibility of fog formation. Low level winds should turn 
southwest late tonight over the Yellowstone valley...which is a 
favorable pattern for fog around here. Drier northwest flow 
should dissipate the fog quickly in the morning and lead to 
warmer temperatures. Highs will still be below normal with wet 
ground and a slow 850mb temperature response. Will keep highs in 
the 60s another day. Winds back Monday night and will provide 
flat ridging. Some energy moves into the mountains but moisture 
looks lacking so will keep probability of precipitation out for now. Humphrey 


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


Pretty extensive changes to the long term forecast this morning. 
Models still in pretty good agreement overall...however the upper 
trough appears to be moving more slowly and digging further south 
than previously prognosticated. Tuesday still looks dry and warm but 
slower progression of the trough will allow for warmer temperatures on 
Wednesday and Thursday as system eases into the area and slightly 
cooler temperatures later in the period as clouds and precipitation hang 
around. System now appears to take majority of the extended to 
work its way past keeping a slight to chance probability of precipitation each 
day...lingering in the east beginning Friday afternoon until 
finally clears out late Saturday night as slows down even further 
partially due in part to forecast movement of Hurricane Ike. 
Adjusted temperatures in an attempt to account for extended 
period of potential precipitation and associated cloud 
cover...especially for highs Friday which appears will now see 
precipitation crossing the area while previous indications were for 
rapidly clearing conditions with strong warm air advection. Warm 
up is still expected for Friday...though to a lesser degree 
followed by slight cool down for Saturday and Sunday as northwest 
flow sets up again. Gilstad 




&& 


Aviation... 


Showers activity will continue through the morning...spreading 
slowly eastward but staying west of a line from kmls to 
Broadus...with best chances extending in a northwest/southeast 
line through Billings. VFR condition will prevail today...but 
instances of isolated MVFR to IFR conditions will be possible 
with heavier Showers. Mountain obscuration are again expect 
throughout much of the day today. Gilstad 






&& 


Preliminary point temp/pops... 


Today Monday Tuesday Wednesday Thursday Friday Sat 
------------------------------------------------------- 
bil 055 042/066 046/080 052/069 043/072 047/074 049/067 
7/west 40/u 00/u 12/T 33/west 22/west 01/b 
lvm 055 037/070 040/080 043/068 038/069 039/072 041/071 
7/west 20/u 01/b 22/T 23/west 22/west 01/u 
hdn 058 040/069 044/081 050/076 043/075 044/076 045/075 
7/west 40/b 00/u 12/T 33/west 32/west 01/b 
mls 061 039/068 044/079 053/073 042/073 047/076 048/070 
3/west 20/b 00/u 02/T 23/west 22/west 22/r 
4bq 059 040/066 042/078 051/075 042/073 045/077 047/074 
4/west 30/b 00/u 12/T 22/west 32/west 12/r 
bhk 058 034/066 039/076 048/074 042/073 043/074 044/072 
2/west 20/b 00/u 02/T 22/west 32/west 22/r 
shr 054 036/064 038/080 047/070 039/071 041/072 042/067 
7/west 60/b 00/u 12/T 33/west 33/west 02/r 


&& 


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


&& 


$$ 
Weather.Gov/Billings