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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Saturday
• 
• High: 73 °
• Low: 52 °
• Partly Cloudy

• Sunday
• 
• High: 72 °
• Low: 48 °
• Chance of T-Storms

• Monday
• 
• High: 70 °
• Low: 50 °
• Chance of Rain

• Tuesday
• 
• High: 73 °
• Low: 45 °
• Chance of Rain

• Wednesday
• 
• High: 73 °
• Low: 45 °
• Partly Cloudy

Area forecast discussion 
National Weather Service Boise Idaho 
831 PM MDT Friday may 24 2013 


Discussion...asymmetric upper low over Washington was shifting north 
after rotating a lobe cyclonically across our northern zones earlier 
today. A new lobe was moving eastward across Oregon this evening 
and it also is prognosticated across our northern zones overnight and 
Saturday morning with another chance of showers. Our southern and 
eastern zones will stay dry. A much stronger lobe will come into our 
Oregon zones Sunday and then into our northern Idaho zones Sunday 
night/Monday with more showers...and general troughing and 
chance of showers will continue into at least the middle of 
next week. In the short term...current forecast has highest 
probability of precipitation Sunday afternoon but latest models from 18z say Sunday 
night will be at least as wet. We await 00z models for new information 
beyond Sunday. No updates for now. 


&& 


Aviation...VFR with areas of high and middle level clouds. Surface 
winds...west to northwest around 10 kts. Winds aloft...southwest up 
to 20 kts at 10k feet mean sea level. 


Weekend outlook...VFR Saturday. Scattered showers and isolated 
thunderstorms developing Saturday afternoon over the higher terrain 
of eastern Oregon and the west central Idaho mountains...spreading 
over most of southeast Oregon and southwest Idaho by Sunday 
afternoon. Snow levels 7500-8500 feet mean sea level rising to 8000-9000 feet 
mean sea level Sunday afternoon. 


&& 


Previous discussion... 
short term...tonight through Sunday...the Memorial Day weekend will 
start off dry as the upper low that has been parked over Washington 
state lifts into Canada. Showers and isolated thunderstorms over 
east-central Oregon and SW Idaho this afternoon will dissipate by 
sunset. Air mass modifies into Saturday on strengthening SW flow. 
Only a slight chance of showers or thunderstorms over mountains on 
Saturday as large scale forcing is absent so development is 
dependent on afternoon instability which is marginal. Clouds 
increase Sunday ahead of a short wave trough moving into the Pacific northwest. 
There are some differences on timing the feature. It becomes 
negatively tilted as it moves inland which will likely slow it down 
which would follow the GFS and European model (ecmwf) solutions. Height falls and 
increased dynamical forcing will favor shower and thunderstorm 
development over southeast Oregon and much of SW Idaho by late Sunday 
afternoon. Cloud cover could cap development in the Snake River 
Valley of Idaho so have only slight chance there. Raised the chance 
of precipitation elsewhere across southeast Oregon and mountains of SW Idaho for 
Sunday afternoon where confidence is higher. More clouds and some 
cooling aloft will take 3-7f degrees off of high temperatures from 
Saturday to Sunday. 


Long term...Sunday night through Friday...the Pacific northwest 
remains under a broad upper trough through the extended period. 
Monday looks to be the driest and warmest day next week as region 
will be between low pressure systems. Increased moisture associated 
with the next upper trough on Tuesday will bring precipitation 
across the entire area. At the moment...this looks like the best day 
for widespread precipitation. Latest model guidance is trending this 
system further north across the forecast area Tuesday. Models are 
not in total agreement with this idea as a few GFS ensemble members 
and the 12z European model (ecmwf) continue to show the trough closing over central 
Nevada as it moves east. However...more solutions are trending 
towards the GFS open wave across the forecast area and thus have 
trended the forecast in this direction. This system lingers over the 
region through Wednesday and is followed quickly by another system 
Thursday/Friday. These systems will continue the chance of showers 
and thunderstorms through Friday. Temperatures will remain below 
normal throughout the extended period. 


&& 


Boi watches/warnings/advisories... 
Idaho...none. 
Or...none. 


&& 


$$ 


Weather.Gov/Boise 


Discussion...lc 
aviation.....Jt 
previous short term...dg 
previous long term....js/wh