FXUS65 KPIH 222006
Area Forecast Discussion
National Weather Service Pocatello ID
206 PM MDT Sat Sep 22 2018
.DISCUSSION...Pleasant Saturday continues across SE Idaho under
influence of weak ridging. Some higher elevation locations seeing
some breezy conditions, with implications for fire weather
concerns. Red Flag continues into early evening before winds
decouple. Upper trough continues to push toward the region, with
isolated to scattered showers arriving by mid morning. 12Z models
beginning to be more generous with the precipitation, spreading
the QPF further south but keeping it isolated to thin line of
convection associated with the shortwave axis. Kept thunder
isolated and closer to MT border as trough works east to WY border
by mid evening. Winds likely the greater concern for most of the
area. Guidance has weakened slightly, but still in the 15-25mph
range sustained for most areas, especially in the afternoon with
peak mixing. Temperature drop the next impact as ridge builds
along West coast and stronger northwest flow settles into the
region. May be close to necessitating a frost advisory for some
valley locations Sunday night and Monday night. A widespread
freeze is not anticipated at this time, either Monday morning or
Tuesday morning. For the Monday night through Thursday night
periods, the northwest flow remains entrenched, with multiple
shortwaves dropping through the Canadian Rockies into Montana.
Both the GFS and ECMWF keep these shortwaves north of the region,
so little impact expected at this time for SE Idaho. Beginning
Friday, stronger feature drops out of Canada toward Idaho while
cut off low in eastern Pacific begins to lift NE. Upper ridge axis
shifts toward the northern Rockies, amplifying temps across the
region. There is still not a lot of confidence headed into the
weekend regarding the track and timing of a potentially merged
western US trough will have on the region. Stuck with guidance
blend, which begins to introduce some precipitation to northern
zones and another uptick in winds to most of the region Saturday.
.AVIATION...VFR conditions will prevail through the period with some
high clouds moving through the area today. Winds will generally be
light, but some afternoon gusts to 25 kts are possible across the
Snake Plain. Increasing mid-level clouds will be moving in along a
cold front tomorrow, passing through KSUN tomorrow afternoon.
.FIRE WEATHER...Critical fire concerns today revolve around the
combination of gusty winds and low humidity. A Red Flag Warning
remains in effect for the Central Mountains above 7500 ft and the
Southeastern Highlands above 6500 ft. Wind gusts to 25 mph are
possible in those areas where humidity is expected to bottom out at
10 to 15 percent. Tomorrow, a cold front will push in from the
northwest, bringing temperatures down and humidity up while also
bringing increased winds due to the tightening pressure gradient.
Precipitation along the front will be confined to the Central
Mountains while much of the region will receive gusty winds.
Isolated thunderstorms will likely develop in the afternoon and
shift eastward into the Island Park area as the front progresses.
Red Flag Warning until 8 PM MDT this evening for IDZ413-422-476.
Back to Main Forecast Discussion Page