Area Forecast Discussion
Issued by NWS Pocatello, ID

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FXUS65 KPIH 240946

Area Forecast Discussion
National Weather Service Pocatello ID
246 AM MST Fri Feb 24 2017

.SHORT TERM...Today through Saturday night. Low pressure centered
over the Upper Snake Plain this morning remains nearly stationary
through much of the day while gradually weakening. Broad, moist
westerly upslope flow in place across the southern portion of our
area. Northerly flow on the back side of the low pressure system
meets westerly flow over southern sections of our area over the
Arco Desert and Upper Snake Plain this morning, and this is where
snowfall will be locally heavy through the morning. This band
gradually shifts eastward across the Interstate 15 corridor this
afternoon and then migrates to the Eastern Highlands and Island
Park area this evening. Strong, gusty winds to continue through
much of the day from the Snake Plain south to the Utah border
before weakening this evening. Given the above factors, have
extended Winter Storm Warnings through 6 PM, and have extended
Winter Weather Advisory for upper Snake Plain and Eastern
Highlands through the same time period given continuing snow and
wind. Many roads icy and snow-packed across SE Idaho this morning.
May have some improvement during the daytime hours but have
continued re-freeze potential after sunset tonight. Additional
snow accumulations for most areas through this evening a broad 1
to 4 inches, highest Southern Highlands, East bench areas east of
Interstate 15 and for the Sawtooths/Central Mountains.

Light snow showers expected to linger along the Divide/Island Park
region through Saturday. A wave of low pressure sliding through
northern NV and UT will promote snow showers over the Southern
Highlands Saturday afternoon, which could be locally heavy. Dry
conditions should finally build into the region Saturday Night.
May see some patchy fog before cloud cover ahead of our next
winter weather system approaches. AD/RS

.LONG TERM...Sunday through next Thursday. The ECMWF model has come
around to the GFS idea of moving inland at a faster pace,
precipitation develops in the Central Mountains about mid day Sunday
and does not exit to the east until Wednesday. Despite the roughly 3
days of unsettled weather, the overland path may be partly
responsible for less precipiation from this disturbance. Estimate the
mountains will see 3 to 7 inches of snow over a 2 1/2 to 3 day
period, the Snake Plain 1 to 2 inches and most of that should be
Sunday night and Monday. A cold front comes through late Monday
afternoon or evening with breezy winds following Monday night and
Tuesday for some drifting of snow. By Wednesday and Thursday, models
are in disagreement on the strength of any high pressure ridge
coming in. The models seem to be favoring a little flatter flow
pattern. Afternoon temperatures gradually warm to near 40F around
Wednesday or Thursday for portions of the Eastern Magic Valley and
Lower Snake Plain, providing a chance for melting of snow to resume.


.AVIATION...Very slow moving surface low is bringing IFR conditions
at least intermittently to KPIH, KBYI, and KIDA. Moisture extends
over the mountains to the west where snow has developed at KSUN and
that may not break off until about noon today. Snow over the Snake
Plain is showing a decreasing trend in intensity. Snow should end at
KBYI about 18-19Z, and for KPIH and KIDA 00-03Z. RS


.HYDROLOGY...Have trimmed out the lava fields of Blaine and Minidoka
counties, but otherwise the Flood Warnings and Advisories are
unchanged. Widespread flood damage continues in Lincoln, Minidoka
counties, while the Goose Creek drainage and the Raft River valley
continue to have problems in Cassia County, although the Raft River
only rises to Advisory status. Rural areas north and west of the
American Fall Reservoir continue to have major problems, as does the
stretch of the Bear River from Grace southward to the Utah border in
Caribou and Franklin counties. The upper Snake River plain continues
under Advisory with some partial receding due to sub-freezing
temperatures returning. Messick


Winter Storm Warning until 6 PM MST this evening for IDZ017-021-

Winter Weather Advisory until 6 PM MST this evening for IDZ020-

Winter Weather Advisory until 6 AM MST Saturday for IDZ018-019-


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