Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 280300

Area Forecast Discussion
National Weather Service Boise ID
900 PM MDT Thu Oct 27 2016

.DISCUSSION...Evening water vapor satellite pics showing a
narrowing band of moisture stretching northeastward from the
central CA coast into central ID. This will be the focus of
precipitation development through the night and into Friday. The
precipitation forecast has continued to edge eastward in response
to drier air accompanying an upper wave approaching the Oregon
coast. For tonight showers will fill in across far southwest Idaho
with development transitioning toward s-central Idaho through the
night. The NV/ID border region, Snake River Plain (from Mountain
Home eastward), and Boise mountains will see the best chance for
overnight precipitation, with scattered showers westward to the
OR/ID border. Drier conditions will develop over much of southeast
Oregon after 06Z tonight. Have made updates to lower the chance of
precipitation and precipitation amounts for the lower Snake Plain
(Boise to Ontario) and points to the north and west for tonight.
Also updated winds for tonight.


.AVIATION...Generally VFR tonight with isolated showers. Clearing
NW of KBKE-KBNO with patchy fog possible overnight. Showers
becoming widespread after 09z/Fri south of a line from KREO-KBOI-
KSNT with mountains becoming obscured and MVFR to IFR conditions
near KJER and KTWF. Generally VFR northwest of a line from KREO-
KBOI-KMYL on Friday. Surface winds generally variable 10kt or
less. Winds aloft at 10k feet MSL: SW 35-45kt becoming variable
5-15kt by 18z/Fri.


SHORT TERM...Tonight through Saturday Morning...Persistent upper
low off the Northwest coast will be sending in a shortwave and
cold front through the area as this evening and overnight
continues. At the same time, a shortwave low off of the Southern
California coast will be moving Northeast and eventually get
absorbed into this flow over the CWA. As the front moves through
much of the area will see a some precip, especially the mountains.
As the california shortwave moves in, it will more or less meet
the front on Friday morning along the ID/NV border, and stall the
front into a stationary front. The biggest forecast challenge is
the location of where that front will stall, which will heavily
dictate the location and amount of precip. Models show the
shortwave`s axis moving over the area early Saturday morning which
will progress the front and precip out of the area and bring a
short lived break in precipitation. Confidence is high that areas
south and east of a line from Mountain Home, ID to Rome, OR will
see rainfall, with totals from now to Saturday morning approaching
one inch.

LONG TERM...Saturday night through Thursday...Upper trough off
the west coast will move inland, accompanied by showers in SE Oregon
and SW Idaho this weekend. Snow levels of around 8000-9000 feet
Saturday will lower to around 7000 feet on Sunday behind a cold
front. A couple more upper level troughs are progged to move through
the west Monday-Thursday. Confidence is low as models disagree on
timing and track of these systems, but they tend to agree that the
systems will weaken as they move into the region. Thus, will
maintain the slight chance of (mainly mountain) showers through the
period. Saturday will be the warmest day, with temperatures
averaging slightly above normal through next week.





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