Flood Watch 1, NWS Pocatello, ID

Area Forecast Discussion
National Weather Service Pocatello ID
210 PM MST Fri Jan 6 2017

.SHORT TERM...Tonight through Monday. Dry conditions continue
through Saturday morning while the next Pacific storm system
advances toward the NW coast. We should see a quick burst of
moderate snowfall across the Magic Valley, Sawtooths and South-
Central Highlands Saturday afternoon through midnight in the initial
volley of moisture moving inland with the incoming storm. Thus I
have issued a Winter Weather Advisory to cover this event with a
brief break in the action anticipated late Saturday night/early
Sunday morning. The main onslaught begins in earnest Sunday morning
with warm moist sub-tropical moisture spreading inland through the
day and continuing through Monday afternoon/eve. The critical issue
here is the snow levels and how quickly we scour out the arctic
airmass from the lower elevations. For now, the models suggest that
the process will begin in the ERN Magic Valley late Sunday morning
with Snow mixed with or changing over to rain with the possibility
of freezing rain complicating matters. By late afternoon and evening
this threat spreads NE into the Lower and Upper Snake River Plain
with periods of moderate snow and/or rain to further complicate the
picture. Meanwhile, in the mountains above 6000 feet MSL, heavy
snowfall is expected throughout the period. Thus we have issued a
Winter Storm Watch for all zones to cover the heavy snow in the
mountains and the wintry mix down in the valleys with areas of
moderate snow accumulation. In addition, we may see some areal
flooding (locally referred to as sheet flooding) in some of the
lower reaches like the Portneuf, Goose Creek, Lower portion of the
Wood river, etc. The picture is a bit unclear here as it is
critically dependent on snow levels and the amount and duration of
rain on snow. For now we have posted an Areal Flood Watch Sunday
night through Monday to cover this potential event.

.LONG TERM...Tuesday through Friday. Expect a continued active
period particularly Tuesday through Thursday. Tuesday will start
with continued upslope mountain snow for mainly the Western Central
mountains and the Eastern highlands. Late Tuesday afternoon into the
Wednesday another strong system will move through the area bringing
moderate to heavy mountain snow and moderate valley snow. Also,
expect moderate to strong winds, which will bring blowing and
drifting snow. Models are showing snow for all areas late Tuesday
afternoon through the evening. They are showing areas below
approximately 4500 feet receiving a rain and snow mix on Wednesday.
By early Wednesday evening the snow tapers off. However, starting on
Thursday morning and continuing through Thursday early evening
models are indicating moderate and heavy snow across the Southern
and Caribou highlands. At this point, there is low confidence on the
placement of this snow for Thursdays storm. Friday look for drier
Northwest flow to move into the area with just lingering snow across
the Eastern highlands. Wyatt
&&

.AVIATION...Conditions will remain mostly VFR through the period.
There will be brief period early in the morning where KPIH and KIDA
and to an lesser extent KBYI could see IFR CIGS and VIS. Otherwise
expect VFR conditions until Saturday evening when the next system
starts to move across the area. Wyatt
&&

.PIH WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from noon Saturday through 11 PM MST
Saturday evening for IDZ017-018-022-031.

Winter Storm Watch from Sunday morning through Monday afternoon
for IDZ017-018-022-031.

Winter Storm Watch from Sunday morning through Monday afternoon for
IDZ020-021.

Winter Storm Watch from noon Sunday through Monday afternoon for
IDZ032.

Winter Storm Watch from noon Sunday through Monday evening for
IDZ019-023-024-025

Flood Watch Sunday night through Monday for IDZ017-021-022-023-024.
&&