Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 180839

Area Forecast Discussion
National Weather Service Pocatello ID
239 AM MDT Fri Mar 17 2017

.SHORT TERM...Today through Monday night. Early morning satellite
imagery was showing an elongated PAC trough with two distinct
circulations embedded in the flow advancing toward the coast with
attending high level moisture lifting NE through the WRN Great Basin
toward SE Idaho. Both the GFS and NAM show increasing clouds today
with the leading edge of enhanced precipitation associated with the
NRN most circulation advancing into the CNTRL mountains late this
afternoon and continuing through the night. The SRN most circulation
rotates NE into the area this evening with attending showers and
perhaps even a thunderstorm developing over the Snake River Plain
and SE mountains...showers should also continue through the night
across the SE before diminishing early Sunday morning. The models
continue to maintain scattered showers across the region Sunday and
Sunday night under a dirty (moist) SW flow aloft. The next PAC
trough rotates into the NW coastal waters Monday afternoon with
increasing instability showers across the region continuing into
Monday evening before gradually diminishing late Monday night as the
main circulation lifts further north along the coast. Still enough
moisture embedded in the SW flow aloft to support a chance mention
of showers. Statistical guidance continues to advertise a fairly
warm day today even under the advancing cloud shield with record or
near record highs across a good portion of the Snake River Plain.
Some cooling is anticipated Sunday and Monday but with daytime temps
remaining well above normal. Huston

.LONG TERM...Tuesday through Saturday. GFS and ECMWF start to
swing low pressure northeast towards Washington State on Tuesday
bringing a piece of energy through our area.  Based on previous
model runs and trends, snow levels to remain fairly high with a
modest amount of instability for a chance of afternoon
thunderstorms.  Tonight`s model runs show a second lob of energy
pushing into the central great basin region by Wednesday evening
into Thursday with hints of splitting with ECMWF further south while
GFS brings center more towards SW Wyoming.  If GFS turns out the
solution winner, there may be cold enough air in the wrap around
moisture feature to lower snow levels down to the valley floor over
a portion of southeast Idaho with possible accumulations.  We will
need to see more runs to build confidence level in this happening.
Either way, it will be wet through most of central and eastern Idaho
with snow accumulating in the higher mountain peaks. A brief respite
on Friday with short wave ridge in place transitioning to the next
storm entering our area on Saturday and Sunday.  Main impacts
through this period will be rain on mid-level snow pack and
additional high mountain snow accumulations. Flooding at lower level
stream, creeks and rivers to continue. Preston

.AVIATION...Increasing cloud cover today as next storm system moves
in from the west.  Breezy conditions anticipated in the Snake River
Plain airport locations midday through early evening. Their is a
chance for an isolated thunderstorm late this afternoon but not
enough chance to place in the airport TAF forecast at this time.
Saturday evening through Sunday anticipate a chance for rain showers
over the region with the best opportunity in the central mountains
affecting KSUN with mvfr ceiling conditions.  Preston

.HYDROLOGY...After discussions with area Emergency Managers, have
made a few minor adjustments to flood advisories across the area.
Main changes were to allow the Advisory for Minidoka to quietly
expire as trend is for rapid decrease in water levels. Have
adjusted Advisory for Bear Lake to the northwest in anticipation
of additional snow melt running into the basin. Remainder of the
Advisories were allowed to stand. The Flood Watch was extended
until Monday to account for additional snow melt and anticipated
rainfall over the weekend. The areal extent of the Watch was not
adjusted at this time. Lastly, the Flood Warning for the Portneuf
River was extended as well with the river a few inches short of
flood stage and continuing to rise. Latest river forecast
maintains the gage at Pocatello above flood stage for the
foreseeable future. DMH

Flood Watch through Monday morning for IDZ017-019-021>025-031.

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