Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 040737

Area Forecast Discussion
National Weather Service Pocatello ID
137 AM MDT Tue Oct 4 2022

.SHORT TERM...Today and Wednesday.
High pressure will dominant through the period. Expect clear to
mostly clear skies as well as overall light winds. No
precipitation is expected. Some very patchy fog is still possible
this morning in the Island Park area. Temperatures will gradually
increase each day. Temperatures will be in 70s to 80s in valleys
and 50s to 60s in mountains running around 5 to 10 degrees above
normal by Wednesday.

.LONG TERM...Thursday through next Tuesday.
Under the continued influence of a high pressure ridge overhead, no
significant weather is expected through the weekend as temperatures
remain steady in the 50s and 60s in the mountains and 70s to low 80s
across all lower elevations. Thursday is looking to be the warmest
day of the period approaching record highs in the Central Mountains
in places like Stanley and Challis where records for this time of
year are in the upper 70s to low 80s however breaking records
outside of this area remains unfavored as records remain in the low
to mid 80s for the Snake Plain climate sites. Morning lows will
remain seasonable for this time of year in the upper teens to low
30s in the mountains and valleys surrounding the Snake Plain and 30s
and 40s on the Plain itself as skies remain clear underneath the
ridge, supporting efficient radiative cooling processes each night.
For Saturday, the weight up a broad upper level trough descending
across the eastern United States will add weight to the upper level
ridge feature on its eastern extent supporting the closer passage of
shortwaves tracking up and over the ridge. This will bring increased
clouds across eastern Idaho with a limited uptick in winds. Winds
this week will remain less than 20 mph as a weak pressure gradient
force supports weaker diurnal influences during the afternoon.

By Monday, the upper level ridge that brought quiet weather
throughout the previous week will lose its influence over the region
and flatten as temperatures continue to represent a cooling trend
headed into midweek next week. Long range deterministic models and
ensemble cluster solutions are moving into better agreement on the
existence of a large scale upper level trough descending from Canada
across the Contiguous United States however the exact placement and
magnitude still remains the main area of disagreement. Scenario 1
from the latest ECMWF run has a cutoff low descending off of the
main trough directly overhead for next Tuesday and Wednesday with
scattered chances for rain and high elevation snow, cooler
temperatures, and an increase in winds before and during the event
in excess of 20 to 30 mph. Scenario 2 from the latest GFS run keeps
the trough and its associated energy well east of our area with no
precipitation expected and winds in excess of 15 to 25 mph likely
under a less of a cooling trend. The current forecast will have
winds increasing for next week with precipitation chances especially
further north and east of the Snake Plain returning Tuesday night
into Wednesday. A slight change in the track of this trough could
mean more precipitation with a further westerly track and
significantly less with an easterly track. We will continue to
monitor this system for next week but in the meantime, make sure to
get outside and enjoy this beautiful warm fall week ahead.


.AVIATION...High pressure will dominate for the foreseeable
future. Expect VFR conditions with clear to mostly clear skies
throughout the area the next couple of days. Additionally, look
for overall light winds.


.FIRE WEATHER...High pressure will bring continued warm and dry
conditions across eastern Idaho through the remainder of the week
as morning temperatures remain seasonably cool with afternoon
highs in the 50s and 60s in the mountains and 70s to low 80s
across lower elevations. Afternoon humidities yesterday were in
the 20s and 30s across lower elevations with a warming and drying
trend continuing through Friday, falling into the teens to low 20s
for much of the forecast area. Humidities will remain highest
across northern and eastern higher elevations zones generally
falling into the the 30s and 40s during the afternoon.

A series of shortwave troughs riding up and over this high pressure
ridge for this upcoming weekend will support very isolated shower
activity further north and east towards Montana and Wyoming with
increased cloud cover and cooling temperatures supporting daily
improvements to regional humidities. The high pressure ridge
flattens early next week with our next system arriving around that
Tuesday/Wednesday timeframe. The exact magnitude, locations, and
depth of the upper level trough descending over the western United
States will continue to be monitored for next week with the
consensus remaining around an increase in winds before and during
the event with the anticipated arrival of moisture around that
Tuesday/Wednesday timeframe.



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