Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 231555

Area Forecast Discussion
National Weather Service Boise ID
955 AM MDT Wed Aug 23 2017

.DISCUSSION...Seeing lingering cloud cover this morning across
the region with embedded isolated showers. Afternoon heating and
mid-level dynamics will increase shower coverage and support
thunderstorm development. Focus of activity will be across higher
terrain. There`s a slight chance that activity gets into the
Snake Plain, though it does look more favorable for the Western
Magic Valley. With precipitable water values around an inch storms
will be wet. Gusty outflow winds to 45 mph are also possible with
the afternoon showers and storms. No updates to the forecast for
this morning.


.AVIATION...VFR. Smoke layers. BKN-OVC mid and high level clouds.
Scattered thunderstorms developing mainly over the higher terrain
this afternoon, with isolated thunderstorms in the Snake Plain.
Surface winds generally SW-SE 5-15kt except gusty outflow winds up
to 40kt in the vicinity of thunderstorms. Winds aloft at 10kft MSL:
SW 5-15kt.


SHORT TERM...Today through Friday...The stars are aligning for a
relatively active weather period across SE Oregon and SW Idaho
through late Thursday. Radar and satellite imagery indicate that
moist and unstable air, associated with an area of low pressure
over California, has moved as far north as central OR/ID this
morning. Ridging remains in place further to the north, with a
strong Pacific trough of low pressure approaching the area from
the Gulf of Alaska. Hi-resolution model data is indicating a moist
and unstable airmass in place for today and the threat of showers
and thunderstorms. Observational data confirms the presence of a
meso-low pressure center over north central Nevada. This is
depicted in model data migrating into the area throughout the day.
This meso-low will act as a trigger for convection along with
daytime heating and terrain interactions. The limiting factor
today will be cloud cover that may inhibit surface heating enough
to discourage convection in some areas. Storms that develop will
have gusty winds along with brief periods of moderate to heavy
rainfall near their cores. Storms will linger into the evening
hours and will remain active in response to an approaching front
into Thursday.

The frontal band associated with the approaching Pacific trough
will begin impacting the area tomorrow, with lingering affects
into Friday. Precipitation will favor northern areas as the front
moves through, including the Blues and central Idaho mountains.
Temperatures will be above normal today and close to normal both
Thursday and Friday.

LONG TERM...Friday night through Wednesday...Zonal flow aloft
Friday night into Saturday will transition to a building ridge Sat
night into Sun. This ridge will hold fairly strong Monday before
likely weakening Tue into Wed. This will lead to increasing
temperatures. Thickness forecasts indicate the hottest temps will be
Tue, and MOS agrees. Smoke from fires in Oregon could easily trim a
few degrees off the upper 90s temps given to the lower elevations on
the latest runs for Mon and Tue, so went a little below the highest
guidance. However, if the smoke is not thick, then this latest
forecast may need to be tweaked upward on later forecasts. Based on
the locations of the fires and the wind direction throughout the
extended, smoke will likely be with us the entire period. Precip
will be severely limited by the ridge, and numbers were kept below
mentionable values throughout the extended.


ID...Red Flag Warning from 3 PM this afternoon to 3 AM MDT Thursday
OR...Red Flag Warning from 3 PM MDT /2 PM PDT/ this afternoon to 3 AM
     MDT /2 AM PDT/ Thursday ORZ636-637-646.



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