Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 162115

Area Forecast Discussion
National Weather Service Pocatello ID
215 PM MST Mon Jan 16 2017

.SHORT TERM...Tonight through Friday.

Cold weather remains in place over the region. Fog, stratus, and
perhaps some light snow falling out of the cold stratus is possible
across the Magic Valley and parts of the Snake Plain. Will start to
see the area of high pressure break down on Tuesday as our next
storm system begins to move onshore. This system continues to slow
down with less precipitation amounts as the axis of the heaviest
precipitation shifts further west. The 12Z GFS is most notable
bringing snow into the Sawtooths Wednesday but very hesitant to
bring anything into the Magic Valley until Wednesday night and
doesn`t want to develop much elsewhere until Thursday. The NAM and
ECMWF are more consistent timing-wise but even the NAM is slower.
Then there`s the issue of mixed precip across the Magic Valley to
near American Falls. Freezing rain is possible on the initial front
part of this precipitation Wednesday evening. Expect it to change
over to all snow during the overnight hours going into Thursday
morning. Not expecting a ton of freezing rain, but could be enough
to create some travel problems. This system is still expected to
exit the region Thursday night. Snowfall amounts look to be in the 5
to 10 inch range from Bellevue to Stanley with locally up to a foot
possible on the peaks. Snowfall amounts across the Magic Valley are
highly problematic because of the possibility of rain or freezing
rain. But, 2 to 6 inches are possible there and down the I 84
corridor. Elsewhere amounts look relatively light...generally in the
1 to 3 inch range. Sheet flooding is still a bit of a concern in the
Magic Valley. However, pure rain accumulations look light, generally
less than 0.15 inches and temps will probably hold in the mid 30s.
So, not expecting a widespread problem at this time. However,
forecasts can change dramatically from model run to model run.


.LONG TERM...Fri through next Mon night. Very weak longwave upper
level ridge gradually transitions to an even lower amplitude coastal
trough during this period. So this means it has the potential to be
a little wetter in the second half as the trough moves towards the
coast. There are some weak shortwaves that break through the weak
ridge and generate a threat of light precipitation, and then by
Sunday night the most significant short wave enters the forecast
area, spreading the best chance of precipitation on Mon and Mon
night. Still, it appears to be light precipitation amounts compared
to the storm in the near term. Temperatures should be warmer, even
warmer than normal with no expected return to the arctic outbreaks
in the present and recent past. No real significant wind with the
main storm of this period either. Messick


.AVIATION...Decided to repeat the observed scenario of last night
for the onset of fog and stratus. Most of the IFR conditions will
occur during the late night, but it should return. KBYI and KIDA
again under threat of morning closures. With some of the moisture
taken out of the air with the light fluffy snow seen at the three
valley airdromes, do not think there is enough moisture for that to
happen again. Wind continues calm to light for everywhere except
KSUN. KSUN expected to be problem-free.



An Areal Flood Advisory for Cassia and southern Minidoka county
has been cancelled.

A Flood Warning continues at Antelope Creek in Darlington due to an ice
jam on this creek along with runoff from early-week rainfall and
snowmelt has resulted in some homes being flooded in Darlington.

The Flood Advisory for the Challis River Bridge south of Challis
will continue at the request of the BLM and local law enforcement.
Citizens are urged to avoid this area.

Dry conditions remain forecast through Tuesday. Frozen flooded areas
continue to pose a threat to drivers. Ice jams will remain a threat
with sub-zero lows in many areas through Tuesday morning, and ice
build-up already present in many river channels. Another storm
system arrives mid week. This system is expected to bring a warm-up
to near or just above freezing to Cassia, Minidoka, Power and Oneida
counties, where frozen flooded areas exist. At least partial melting
of these areas is possible, along with the added concerns of
additional precipitation which could fall as rain in lower
elevations. Current headlines are expected to be evaluated again
in consultation with emergency management officials.  DMH/JAM



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