Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 210358 AAA
AFDBOI

Area Forecast Discussion...UPDATED
National Weather Service Boise ID
858 PM MST Mon Feb 20 2017

.DISCUSSION...No changes to forecast at this time. A moist
southwest flow aloft will continue through Tuesday. The strong
winds aloft will support the heavier precip in the mountains and
lighter amounts in the valleys. Snow levels generally 6-7k feet
will lower to around 5k feet on Tuesday. Winds will increase,
becoming windy on Tuesday, especially in portions of SE Oregon and
in the Owyhees where a Wind Advisory is in effect. Instability
ahead of a cold front will support a slight chance of thunderstorms
Tuesday afternoon. Temperatures will be a little warmer on
Tuesday, possibly reaching 60F in Boise (record is 63F set in
1991).

&&

.AVIATION...Scattered showers becoming widespread by 06z, with
areas of low VFR/MVFR ceilings in rain in the valleys. IFR
conditions in snow above 5500 ft msl, continuing in the central
Idaho mountains through Tuesday. After 12z conditions improving to
mainly VFR in the Snake River Valley and lower elevations of
eastern Oregon, with scattered rain showers. Isolated afternoon
thunderstorms. Surface winds southeast to south 10-20 kts,
becoming southwest to west 20-30 kts after 18z, with gusts
exceeding 40 kts over the higher terrain of southeast Oregon.
Winds aloft near 10k ft msl southwest to west 30-50 kts.

&&

.HYDROLOGY...Mild and breezy conditions will accelerate snowmelt
across lower elevations over the next 24-36 hours. Coupled with
overnight precipitation, expect to see an increase in runoff
through Tuesday afternoon. Those in lowland areas with remaining
snow cover or located along small streams and rivers should
continue to monitor the weather conditions closely. Flood warnings
remain in effect for the Malheur River near Vale and the Weiser
River near Weiser. The Malhuer River at Vale is expected to reach
flood state Tuesday night. The Weiser River near Weiser has
shown a dramatic rise over the past few hours and based on the
current trends, could reach flood stage by late tonight or early
Tuesday morning.

&&

.PREV DISCUSSION...
SHORT TERM...Tonight through Wednesday...Moist southwest flow
will continue to feed precipitation into the mountains of
southeast Oregon and southwest Idaho tonight and Tuesday. Lower
elevations will see a period of rain tonight as an upper wave
lifts north across the region. Strong winds aloft will focus
precipitation in the mountains on Tuesday, while valleys are
mostly dry. Snow levels are 6-7k feet through Tuesday morning,
dropping to around 5k feet by Tuesday afternoon. Sites at or above
7k feet could see an additional 6-10 inches of snow through
Tuesday afternoon as qpf in the higher terrain approaches an inch
of liquid. Windy conditions will prevail through Tuesday with the
strongest winds across southeast Oregon and highlands of southwest
Idaho. The wind advisory for these areas remains well supported,
though the strongest winds aloft (700 mb) are during the early
morning, before the surface inversion breaks. A deeper trough
moves into the Pac NW on Wednesday, pinching off the feed of
Pacific moisture and refocusing precipitation over far southeast
Oregon. Snow levels drop to valley floors, but temperatures will
remain too warm at lowest elevations to see any accumulations.
Temperatures are about 10 degrees above normal Tuesday, dropping
to around 5 degrees below normal on Wednesday.

LONG TERM...Wednesday night through Monday...A deep trough along
the Pacific Northwest coastline through the period helps push
feature after feature through the CWA. Snow levels are at the
valley floors throughout the extended. Most of the precipitation
with the waves passing through look to be convectively driven,
meaning they will be most active during the afternoon periods.
Snow showers expected to occur during the afternoon periods
throughout the extended period, however with the daytime high
temperatures forecast to go above freezing for most valley
locations, accumulations are not expected to be of much impact.
Temperatures stay below normal the entire period.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...Wind Advisory from 11 AM to 8 PM MST Tuesday IDZ029.
OR...Wind Advisory from 11 AM MST /10 AM PST/ to 8 PM MST /7 PM PST/
     Tuesday ORZ061-063.

&&

$$

www.weather.gov/Boise
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DISCUSSION...BW
AVIATION.....JT
HYDROLOGY....DG/BW
PREV SHORT TERM...DG
PREV LONG TERM....JC



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