Weather

417 
fxus65 kboi 110839 
afdboi 


Area forecast discussion 
National Weather Service Boise Idaho 
235 am MDT Sat Oct 11 2008 


Short term...since 06z sapix suggested upper low was re-forming 
in southeastern Nevada as prognosticated and should begin to turn northeastward again after 
12z...to near Wendover/Utah by 00z Sunday. From there both GFS and 
NAM forecast the low to drift slowly eastward to the Great Salt Lake by 12z 
Sunday...then accelerate northeastward after 12z Sunday to southeastern Montana by 
00z Monday. This track is favorable for snow in and near Twin Falls 
County today and tonight...and our Winter Storm Warning will 
continue there. See wswboi for more information. Highest probability of precipitation will be in 
that area today...decreasing northward and westward...to less than 10 percent 
in Harney County/or. Probability of precipitation will gradually decrease west to east 
tonight and Sunday. Throughout the weekend Idaho zones will have 
higher probability of precipitation than Oregon zones. But Oregon zones will have 
considerably more wind...as that/S where the greatest surface 
pressure gradient will be. Met MOS wind speeds at bke bno and Ono 
are much too high however...especially at bke where met forecasts 
sustained 60 miles per hour this afternoon. Met MOS winds at those sites 
yesterday were also about 50 percent too strong. Expect similar 
errors today. Even so...northwest winds will still reach advisory speeds 
in all parts of southeastern Oregon from about noon today until early this 
evening. We discontinued the Wind Advisory for the west central 
Idaho mountains and Idaho lower Treasure valley. Note that the 
western Magic Valley and southern Twin Falls County are not within any 
wind advisories this weekend as those areas will be too close to the 
passing upper low. Lack of wind and the wetness of the expected 
snow will prevent or at least limit blowing and drifting. Fog has 
formed tonight in the snake basin after Friday/S precipitation and relatively 
light winds. Winds should increase enough this morning to dissipate 
the fog by 15z. Other areas which usually have fog when the snake 
basin has fog...such as bke myl and Ono...already have too much wind 
to support fog formation. Maximum temperatures today will only be in the middle 
30s to near 50...or 10-15 degrees below normal. Lows tonight will 
range from 20 to near 32 under cloud cover. Highs Sunday will be 2 
to 5f warmer than today in Idaho zones and 4 to 8f warmer than today 
in Oregon zones. 


Long term...Sunday night through Saturday...brief ridging on Monday 
will be followed by a progressive pattern for the remainder of the 
long term. This leads to increasing uncertainty in timing shortwave 
features. For this reason we are weighting probability of precipitation toward climatology 
after Tuesday. Model consensus has relatively high heights over US 
toward the end of the week so we are trending temperatures to 
slightly above normal starting Thursday. No significant changes were 
needed. 


&& 


Aviation...conditions will be mainly VFR on the Oregon side of the 
border. On the Idaho side scattered MVFR and isolated IFR ceilings 
and visibilities due to valley fog and stratus will persist until 
about 15z. At about that time snow is expected to increase from the 
Nevada border to east of kmuo...east portions of the Boise 
Mountains...and eastward. The Camas Prairie...Magic Valley...and 
southern Twin Falls County can expect locally heavy snow today 
through tonight. Expect widespread mountain obscuration and IFR/LIFR 
conditions in those areas. West of kmuo conditions will be mainly 
VFR although surface winds will be strong...30-45 kts across much of 
eastern Oregon and southwestern Idaho through this evening. Winds 
aloft will be moderate from the northeast. 


&& 


Boi watches/warnings/advisories... 
Idaho...Winter Storm Warning from 6 am MDT today to 6 am MDT Sunday for 
idz016 idz030. 
Or...Wind Advisory from noon MDT /11 am PDT/ today to 9 PM MDT /8 PM 
PDT/ tonight for all Oregon zones. 
&& 


$$ 


Weather.Gov/Boise 


Short term...lc 
long term....jt 
aviation.....Jt