Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 202017

Area Forecast Discussion
National Weather Service Pocatello ID
217 PM MDT Fri Apr 20 2018

.SHORT TERM...Tonight through Monday. A ridge of high
pressure was building into the region this afternoon ahead of an
approaching Pacific trough. The models show the trough sweeping east
through Canada Saturday resulting in enhanced wind speeds across SE
Idaho and seasonably warm temps. A second modest looking disturbance
trails into the NW states Sunday and across SE Idaho Monday with
mixed results among the models. The GFS is showing fairly enhanced
convective precipitation returns while the NAM has been somewhat
more reserved. The operational GFS falls on the stronger end of the
ensemble spectrum so we may yet see a weaker solution from this
model suite as the event plays out. For now, have tried to play the
field between the drier NAM and wetter GFS solutions while blending
with forecast neighbors to the north and south. Seasonably warm
temps continue Sunday before falling to normal with the trough
passage Monday. Huston

.LONG TERM...Monday night through next Friday night. Look for
lingering precipitation and breezy to moderate winds early Monday
evening from an exiting system. High pressure gradually begins
building in Tuesday bringing overall dry conditions and gradually
warming. Wednesday and Thursday models continued to be in good
agreement with mostly dry conditions under high pressure. Have
removed most precipitation for Wednesday and Thursday. Have still
kept breezy winds as both models show a mostly, dry wave dropping
south out of Montana into Wyoming Wednesday night into Thursday
grazing our eastern areas. Both models show a system on Friday
though they are off on timing and precipitation amounts.  The ECMWF
is drier and slower holding onto the high pressure ridging longer.
Temperatures will be around normal Tuesday morning before gradually
rising to 10 to 15 degrees above normal by the end of the period.
Models are showing low to mid 70s for most the Eastern Magic valley,
Snake River plain, Southern Highlands and Cache valley by Thursday
and Friday. Wyatt

.AVIATION...Expect VFR conditions through the period under high
pressure ridging. A weak wave will move through the area tomorrow
morning into tomorrow afternoon. However, only morning mid-level
clouds and mostly afternoon breezy winds are expected tomorrow.

.HYDROLOGY...The Snake River at Lorenzo and Menan continue to be
above flood stage, although barely. This is mainly driven by
optimizing releases from Palisades Dam for ongoing snow melt.
High flows continue all along the Snake until it reaches American
Falls Reservoir. This is creating a hazard for recreational
interests for this stretch of the river with the strong and high
flows. Messick


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