Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 180921

Area Forecast Discussion
National Weather Service Pocatello ID
321 AM MDT Sun Mar 18 2018

.SHORT TERM...Today through Tuesday night.  A cold front has exited
the area leaving an broad upper level low over our area. Expect
light snow showers particularly this afternoon mainly over the
mountains, especially the Central mountains.  Expect 1 to 3 inches
of snow for the Central mountains and around 1 inch for other
areas, mainly mountains, elsewhere. Due to the convective nature
this afternoon there could be local areas receiving brief,
moderate to heavy snow with amounts of 2 to 3 inches possible.
High pressure ridging starts to build in Monday bringing weak
northwest flow over the area. Patchy fog is possible Monday
morning. However, low level clouds or stratus is most likely.
Expect light, mostly mountain, showers in northwest flow Monday
impacting mainly the northern central mountains and the eastern
highlands. Tuesday high pressure builds even more into the area
but quickly starts to break down as moisture ahead of the next
system starts to move into the area. These light to moderate
showers will impact the Western Central mountains by Tuesday
afternoon and start to spread into the rest of our area by Tuesday
evening. Wyatt


.LONG TERM...Wednesday through next Sunday. The GFS and ECMWF are in
good agreement early on in the forecast cycle as two Pacific lows
converge on the NW coastal waters Wednesday with the SRN most
circulation getting swept inland across the Great Basin in a warm,
moist SW flow aloft ahead of the main upper low setting up off the
NW coast. The best day for precipitation appears to be Thursday and
thus have boosted the precipitation potential to account for the
increasing confidence. By Friday, the ejecting wave shears into the
Dakotas while the main low remains positioned off the NW coast with
an unsettled WSW flow over SRN Idaho. Both the GFS and ECMWF were
showing lower snow levels over the region Friday and Saturday and
thus have nudged the going forecast colder again this morning. The
previous run of the ECMWF was a bit more progressive in sweeping the
low inland but both current runs seem to favor a good portion of the
low ejecting east Saturday afternoon and Sunday resulting in a good
chance of snow across the region next weekend. Not straying too far
from statistical guidance which suggests warming temps ahead of the
storm Wednesday followed by cooler temps heading into the weekend.


.AVIATION...Early morning satellite imagery was showing a broad
upper low over the region with three well defined circulations
embedded in the cyclonic flow. The proximity of the upper low will
provide support for instability showers this afternoon favoring the
mountains. Any showers passing over the terminals will likely
produce temporary IFR/MVFR CIGS in snow showers. Partial clearing
follows after sunset with the loss of surface heating. Huston



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