Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 190923

Area Forecast Discussion
National Weather Service Pocatello ID
323 AM MDT Mon Mar 19 2018

.SHORT TERM...Today through Wednesday night. Weak high pressure
ridging builds in today bringing light northwest flow over the
area. Patchy freezing fog is possible for the Snake river plain,
Caribou Highlands, and Bear Lake region briefly this morning. A
weak wave will move through the high pressure ridge bringing
light, mostly mountain, snow showers in northwest flow impacting
mainly the northern central mountains and the eastern highlands
today and Tuesday. Tuesday night high pressure ridging moves east
allowing for southwest flow across the area on Wednesday. Moisture
starts to move into the area in southwest flow bringing light
snow showers across mainly the mountains on Wednesday. With
Southwest flow expect breezy winds and above normal temperatures
by Wednesday. With higher snow levels and warmer temperatures
expect rain on snow in some areas. Warmer temperatures, breezy
winds, and rain on snow will bring back snow melt and higher
runoffs. Wyatt &&

.LONG TERM...Thursday through next Monday. The GFS and ECMWF remain
consistent with the idea that a fairly significant disturbance will
eject from the Pacific NW low across SRN Idaho in a vary warm SW
flow aloft Thursday with colder temperatures trailing across the
region Friday in the wake of the exiting wave. Thus have once again
boosted the precipitation potential upwards to account for the
fairly strong confidence. With the elevated snow levels Thursday and
threat of a decent rain event it will be interesting to see how low
level snowmelt responds. Nothing actionable yet but we will be
monitoring the National Operational Hydrologic Remote Sensing Center
snowmelt model for clues. Beyond Friday, both the GFS and ECMWF
shear the remainder of the Pacific NW low inland over the weekend
but with varying strengths and trajectories...enough variability to
really preclude any type of detail. Mainly tried to maintain the
going forecast through Monday which had some mention of snow
throughout the period. Did not stray too far from the statistical
guidance which featured seasonably warm conditions Thursday and then
turning colder over the weekend. Huston

.AVIATION...Lingering moisture and VFR CIGS with mountain top
obscurations were evident in early morning satellite imagery NE of a
Challis to Preston line. Numerical models suggest improving
conditions through the morning except near KDIJ where the low level
moisture will likely remain. A weak disturbance shearing east
through the region this afternoon coupled with diurnal heating
should be enough to support SCT showers favoring the CNTRL and ERN
mountains this afternoon and early evening impacting mainly KDIJ.
Mid-level CIGS will overspread the valley terminals this afternoon
with perhaps temporary low level VFR CIGS in VCNTY showers at KPIH
and KIDA. Huston



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