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Office: BOI

FXUS65 KBOI 171603

Area Forecast Discussion
National Weather Service Boise ID
1003 AM MDT Sat Mar 17 2018

.DISCUSSION...National Weather Service radar, web cams, surface
observations and spotter reports show areas of light to moderate
snow this morning across much of southeastern Oregon and
southwestern Idaho. However, temperatures in lower valley
locations along the I-84 corridor from Baker City to Ontario to
Boise to Twin Falls are in the mid 30s. So...snow will be mixed
with rain at times in these lower valleys, and any accumulation
of snow is expected to be limited to grassy areas. Roads in these
lower valley areas should just be wet today. the
mountains above 3500 feet, expect periods of accumulating snow,
especially in Boise Mountains and West Central Mountains of Idaho,
where snow should be heavy enough and temperatures cold enough
for several inches of new snow. Motorists traveling into the
mountains, including along highway 95 north of council, and along
highway 55 from Horseshoe Bend to Mccall will likely experience
winter driving conditions today and tonight.

.AVIATION...MVFR/IFR continues through Monday in rain and show
showers, otherwise low VFR. Snow levels are 3000-4000 ft.  Mountains
obscured. Surface winds: west/northwest 10 kts or less.  Winds aloft
near 10 KFT MSL: west 10-15 kts.


SHORT TERM...Today through Sunday...Band of precipitation near a
surface trough extends NW-SE across southern Idaho early this
morning. The band will shift to the northeast with snow ending
across south-central Idaho from the Western Magic Valley to the
ID/NV border in a couple hours. A Winter Weather Advisory is in
effect for areas along the ID/NV border, which will be cancelled
once the band of snow lifts north. The snow will continue in the
Boise/West Central Mountains today where a Winter Weather Advisory
is also in effect. The upper low centered in Oregon will continue
to move eastward, reaching southwest Idaho this afternoon.
Showers and isolated afternoon thunderstorms will accompany the
upper low. A cold front will move in behind the low tonight
through Sunday morning. Another round of snow showers is expected
along the front, mixing with rain in the lower valleys. Snow
accumulations will be light, except enhanced amounts are expected
in the higher elevations of southwest Idaho. A Winter Weather
Advisory will remain in effect for the Owyhees and Southwest
Idaho Highlands tonight through Sunday morning, along with the
Boise/West Central Mountains. Drier conditions will arrive behind
the front on Sunday. Temperatures will remain below normal through
the weekend.

LONG TERM...Sunday night through Saturday...An upper level
trough swings in from off the Oregon coastline at the beginning of
the period bringing a slight chance of showers for our northern
zones. By Wednesday a much deeper upper level trough sitting off
the California coastline starts to impact our area. We remain in
the warm sector through early Friday morning which means
widespread precipitation. Snow levels climb up to near 6000 feet
MSL for much of the area so snowfall limited for the highest peaks
only. The cold front is still on track to push through Friday
morning dropping snow levels back down to valley floors. Models
diverge after the main frontal band moves through leaving low
confidence in the forecast to start the weekend.


ID...Winter Weather Advisory until noon MDT Sunday IDZ011-013.
     Winter Weather Advisory from 6 PM this evening to noon MDT
     Sunday IDZ015-029.




Office: PIH FXUS65 KPIH 171538 AFDPIH Area Forecast Discussion National Weather Service Pocatello ID 938 AM MDT Sat Mar 17 2018 .UPDATE...We updated the forecast to reflect higher snow numbers with the band currently working across areas east of a Burley to Rexburg line. This is the band associated with the front. This will continue to work north and east the rest of the day. We are seeing accumulations, even on the roads during periods of heavier snow creating a mix of wet and snowy/slushy roads. Also, snow continues to work northwest through the central mountains. Although, we might be a bit heavy on snowfall totals in the central mountains...the warning is still warranted since this is a heavier wet snow for some. That could cause impacts alone, along with some blowing/drifting where the winds are gusting at this hour. The advisory for areas from Lone Pine to near Island Park also looks good. We should see showers and possibly a few thunderstorms developing behind the front and areas where we try to clear up a bit. Keyes && .PREV DISCUSSION... /issued 200 AM MDT Sat Mar 17 2018/ SHORT TERM...Today through Monday night. A cold front will slowly progress across the area today while an upper level low moves in from the west. Cool air aloft being drawn in by the upper low will create instability which makes the threat of thunder possible once again this afternoon. Headlines continue to hit the Central Mountain zones and the Upper Snake Highlands for snowfall today. An additional 7 to 10 inches of new snow will be possible today across the Central Mountains, and an additional 5 to 7 inches over the Island Park area west to Monida Pass. Model guidance is split this afternoon across the Snake plain and southern zones. NAM is much drier in the post- frontal airmass than the GFS. Both models generally in agreement in drying those zones this evening while wrap-around moisture remains over the Central Mountains through Sunday. More settled conditions will return Sunday night and Monday while the upper low exits the region. O'Hinsberger LONG TERM...Tuesday through next Saturday. The GFS and to a lesser extent the ECMWF show a weak disturbance shifting east through the region Tuesday resulting in light precipitation across the region. Two upstream Pacific disturbances were also noted converging on the NW coastal waters. These systems will merge producing an extended period of warm and moist SW flow across SRN Idaho Thursday and Friday. The parent storm appears to reload along the coast Friday night before advancing inland Saturday and Sunday for another round of snowfall. Temps look to be on the warm side of climatology Tuesday and Wednesday and then cool slightly with the incoming low Thursday through Saturday. No wild deviations from that idea planned on this forecast cycle. O'Huston AVIATION...Early morning satellite imagery was showing a closed upper low over SW oregon with a very moist southerly flow into SRN Idaho. Model time sections suggest lowering CIGS this morning with LIFR anticipated at KSUN and MVFR with occasional IFR CIGS and VIS at KBYI, KPIH, and KIDA throughout the day as the low fills and lifts NE toward Montana. The models suggest saturated conditions at KSUN through 03z this evening and thus will have to look closely at adjusting the current forecast trend there after getting sense of the trend. Valley terminals should see improving CIGS mid to late afternoon. O'Huston && .PIH WATCHES/WARNINGS/ADVISORIES... Winter Storm Warning until 6 PM MDT this evening for IDZ018-031- 032. Winter Weather Advisory until 6 PM MDT this evening for IDZ019. && $$