Weather

349 
fxus65 kbyz 280311 
afdbyz 


Area forecast discussion 
National Weather Service Billings Montana 
911 PM MDT Wednesday Aug 27 2008 


Short term...valid for Thursday and Friday... 


Somewhat gusty winds continue but are decreasing across the area. 
Humidities actually took a jump with the passage of the cold front 
earlier this afternoon. Humidities are well above 20 percent 
across most of the area as of 9 PM...so along with the decreasing 
winds have let the red flag warning expire. Would be surprised if 
humidities do not fall into the upper teens again Thursday 
afternoon...and west winds will be gusty but not nearly to the 
extent as today. Will keep this highlighted in the fire weather 
forecast. 


Otherwise a few showers trying to make it to eastern parts as 
shortwave drops through northeast Montana. Will keep isolated 
showers going east of Rosebud County...but any precipitation will be very 
light. Otherwise will be dry/cool for the remainder of the night. 


Updated zones/fire weather forecast coming now. 


Jkl 


Long term...valid for Sat...sun...Mon...Tue...Wed... 


Made significant changes toward a much colder and wetter forecast 
for the Sunday through Tuesday period. Models have been trending 
in this direction for a couple days now with guidance trending 
temperatures for Monday (labor day) down about 5 degrees with each 
forecast cycle. 


A deepening upper low Diggs into the Great Basin Sunday bringing a 
due southerly wind field aloft. This tends to bring good 
divergence to the area resulting in increasing precipitation 
potential through the day. An initial cold front pushes into 
the area during the day Sunday resulting in temperatures in the 
70s west while the east keeps highs in the upper 80s to lower 90s. 
As the upper system pushes slowly northeast Sunday night a surface low 
develops over northeast Wyoming which will help to pull colder air 
into the area and begin to generate isentropic lift over central 
areas. Combined with energy and Pacific moisture ejecting 
northeast from the upper low...should see increasing precipitation 
chances overnight. Strong cold push enters western zones late 
Sunday night and pushes through the eastern zones by middle day 
Monday. Latest run of the GFS and European model (ecmwf) shows highs in the 40s 
from Billings west...with 50s and lower 60s east for Monday (labor day). 
With cloud cover/precipitation and 850 temperatures around +4c this doesn't 
seem unreasonable. Given the extend period though only dropped 
highs part of the way...into the 50s for the western half of the 
area...with 60s east to get foot in the door. But if trends 
continue...Labor Day could see highs in the 40s across a large 
portion of the forecast area...with 30s in the mountains. 
Northerly winds of 10 to 20 miles per hour combined with the precipitation 
would only add to the chill across the region. The system will 
shift across northern Wyoming Monday night into early Tuesday 
keeping precipitation chances going. Mountain areas look prone to 
seeing some snow accumulation. Hard to pinpoint what elevation and 
how much just yet...but accumulating snow above 7000 feet seems 
reasonable at this point. Model quantitative precipitation forecast indicating three quarters to 
an inch and a half type amounts will be possible with this system 
Sunday night through Tuesday. 


Should see warmer temperatures on Tuesday...although that depends 
on how fast the system moves out. Previous forecast warmed 
temperatures and dried out the middle to late week period...but 
latest GFS showing a second system for late Wednesday through 
early Friday. European model (ecmwf) not showing this yet so will hold off on 
further changes to late periods. Chambers 


&& 


Aviation... 


Gusty west to northwest winds will decrease tonight. Stronger 
winds aloft will gradually decrease overnight too...but will 
provide a choppy flight as the night wears on. Middle level clouds 
will work through the area but conditions will remain VFR. 
Humphrey 


&& 


Preliminary point temp/pops... 


Thursday Friday Sat sun Monday Tuesday Wednesday 
----------------------------------------------------------- 
bil 051/079 055/085 057/093 061/074 046/059 042/071 047/079 
10/u 00/u 00/u 22/T 55/r 52/r 00/b 
lvm 042/079 047/084 048/087 053/068 041/056 036/069 045/075 
10/north 00/u 00/u 23/T 55/r 41/u 00/b 
hdn 049/080 052/085 054/096 060/078 047/063 043/071 045/080 
10/u 00/u 00/u 22/T 45/r 52/r 00/b 
mls 050/079 055/083 058/096 063/080 050/065 045/068 048/078 
20/u 00/u 00/u 12/T 44/r 53/r 00/u 
4bq 049/077 051/084 056/095 061/082 051/066 044/068 046/080 
20/u 00/u 00/u 12/T 34/r 52/r 00/u 
bhk 047/078 050/083 056/095 059/085 047/066 042/064 044/075 
20/north 00/u 00/u 12/T 34/r 53/r 00/u 
shr 045/079 048/083 050/092 056/077 047/063 041/068 043/079 
10/u 00/u 00/u 22/T 45/r 52/r 00/b 


&& 


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


&& 


$$ 
Weather.Gov/Billings