Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 130829

Area Forecast Discussion
National Weather Service Pocatello ID
229 AM MDT Wed Sep 13 2017

.DISCUSSION...Upper low continues to spin off the California coast
while an upper trough digs in from British Columbia. Diffluent
flow over the area is helping trigger some showers and early
morning thunderstorms. Expect much of this activity to increase
through the afternoon as the upper low begins to lift across the
Great Basin, and the upper trough in BC drops into WA/OR tonight.
Dynamics pick up tomorrow afternoon as the PAC NW trough deepens.
This will result in more widespread precipitation as well as the
lowering of snow levels. We`ve lowered snow levels from previous
forecasts based on 850 Tw projections, but snowfall amounts should
be confined to the Central Mountains Thursday night and Friday.
Areas 9000 ft and above may see 3 to 5 inches during this time.
As the upper trough deepens across the area, temperatures will
take a dive as well. High temperatures on Friday and Saturday
still look to be generally at or below 60 degrees. Models close
off an upper low over Idaho Friday night and Saturday with the
ECMWF a bit deeper than the GFS. Long-term models show a brief
period of clearing before re-developing deep upper trough over the
West by next Monday. Hinsberger

.AVIATION...A few showers continue this morning, with minimal impact
across the region. Expect to see some thunderstorms this afternoon,
primarily over higher elevations. Winds become locally breezy this
afternoon particularly across the Snake Plain and higher
elevations of the central mountains. Wind gusts could approach
25kts in these areas. The central mountains, including KSUN should
get a break in the precipitation overnight, but coverage of the
showers may increase over the southern and eastern highlands
overnight. Except under the influence of heavier precipitation
where MVFR ceilings may occur, widespread VFR is expected to
continue. DMH


.FIRE WEATHER...Precipitation has been slow to expand overnight but
there are a few light showers across the region. Mainly scattered
showers and isolated thunderstorms are expected to redevelop for the
day, and as moisture continues to increase across the region, so
does the chance for more areas to see wetting rains. Winds will also
be on the increase today with gusts approaching 25 mph through the
Snake Plain and higher elevations, but humidities should remain
above critical levels. This will also be the last "warm" day
of the week. Should see a significant ramp up in precipitation
coverage into Thursday ahead of cold front dropping toward the
region. Wetting rains are likely over most areas, and crews working
active fires and recent burn scars will want to stay vigilant for
flash flooding. The cloud cover and rainfall will help keep temps
down, but the cold front late in the day will usher in the truly
cooler temps and higher humidities for several days. Temps should be
cool enough to induce snow at higher elevations, but accumulations
will likely stay light as precipitation tries to shift out of the
region behind the front. There will still be some lingering
precipitation Friday and Saturday as the upper low lingers, but it
should be much lighter and not as widespread. DMH



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