Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 181635
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
935 AM MST THU DEC 18 2014

.DISCUSSION...SKIES ARE MOSTLY CLOUDY THIS MORNING. ISOLATED
SHOWERS ARE MOVING NE ACROSS THE LOWER TREASURE VALLEY...AND AS
FAR EAST INTO THE UPPER TREASURE VALLEY AS MOUNTAIN HOME. THESE
SHOWERS WILL PROGRESS INTO THE WEST-CENTRAL AND BOISE MOUNTAINS
THIS AFTERNOON AS THE VALLEY DRIES OUT. THESE SHOWERS ARE
ASSOCIATED WITH A DEPARTING SHORT WAVE TROUGH. AS THIS WEAK WAVE
DEPARTS...A SMALL UPPER LEVEL RIDGE WILL BRIEFLY PASS OVER THE
REGION TONIGHT. HOWEVER...UNLIKE MOST RIDGES...THIS ONE WILL BE
TOO WEAK TO CLEAR OUR SKIES AND DRY US OUT. A STRONGER AND WETTER
SYSTEM IS STILL ON THE WAY FOR TOMORROW. NO CHANGES AT THIS TIME.

&&

.AVIATION...SCATTERED MVFR SNOW SHOWERS OVER THE MOUNTAINS OF BAKER
COUNTY OREGON AND CENTRAL IDAHO WILL DECREASE TO ISOLATED BY 00Z.
AREAS OF SNOW WITH RAIN BELOW 4K FT MSL WILL SPREAD ACROSS EASTERN
OREGON INTO THE CENTRAL IDAHO MOUNTAINS AFTER 06Z AND ALL OF
SOUTHWEST IDAHO AFTER 12Z. ON FRIDAY EXPECT MOUNTAIN OBSCURATION...
AREAS OF MVFR CEILINGS...AND LOCAL IFR CONDITIONS ACROSS THE ENTIRE
AREA WITH SNOW LEVELS AROUND 4K FT MSL. SURFACE WINDS...EAST TO
SOUTHWEST 5-10 KTS. WINDS ALOFT...SOUTHWEST AROUND 15 KNOTS UP
THROUGH 10K FEET MSL.

&&

.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH FRIDAY...THE NORTHERN PORTION OF A
SPLIT TROUGH WILL CONTINUE TO MOVE THROUGH THE AREA TODAY. LIGHT
SHOWERS WILL ACCOMPANY THE TROUGH...WITH THE BULK OF THE ACTIVITY
RESIDING TO THE WEST AND NORTH OF BOISE. THE SHOWERS WILL DECREASE
IN COVERAGE THIS AFTERNOON AND EVENING AS THE SYSTEM MOVES EAST.
SNOW LEVELS BETWEEN 3000 AND 3500 FEET WILL RISE TO NEAR 4000 FEET
THIS AFTERNOON. LIGHT SNOW ACCUMULATIONS OF AN INCH OR LESS ARE
POSSIBLE IN THE WEST CENTRAL MOUNTAINS. AN UPPER RIDGE AXIS WILL
BRING A BRIEF DRY PERIOD TO MUCH OF THE AREA THIS EVENING WHILE A
MORE VIGOROUS TROUGH MOVES INTO THE PACIFIC NORTHWEST. THIS TROUGH
HAS AMPLE MOISTURE WITH IT TO DELIVER PRECIPITATION TO ALL OF SE
OREGON AND SW IDAHO ON FRIDAY. HOWEVER...MODEL QPF AND SNOW
AMOUNTS ARE NOT IMPRESSIVE. LOOKING FOR AN INCH OR TWO OF SNOW
ABOVE 3500 FEET AND 2-4 INCHES IN THE MOUNTAINS. SNOW LEVELS WILL
REMAIN GENERALLY ABOVE 3500 FEET ALTHOUGH ELEVATIONS BETWEEN 3000
AND 3500 FEET COULD SEE A RAIN/SNOW MIX. HIGH TEMPERATURES WILL BE
4-8 DEGREES ABOVE NORMAL.

LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...MODELS REMAIN IN
RELATIVELY GOOD AGREEMENT THROUGH THE EXTENDED PERIOD.  ZONAL FLOW
WILL SET UP OVER THE PACIFIC NORTHWEST OVER THE WEEKEND WITH A RIDGE
OF HIGH PRESSURE TRYING TO BUILD JUST OFF THE COAST THAT WILL SHIFT
THE FLOW FROM WESTERLY FRIDAY NIGHT TO NORTHWESTERLY BY SUNDAY.
DECREASING POPS FRIDAY NIGHT AS A WEAK TROUGH SHIFTS TO THE EAST BUT
THE NEXT ROUND OF PRECIPITATION WILL SPREAD OVER THE FORECAST AREA
SATURDAY.  SNOW LEVELS AROUND 4000 FEET FRIDAY NIGHT AND SATURDAY.
SATURDAY NIGHT AND SUNDAY AS THE FLOW ALOFT SHIFTS TO THE NORTHWEST
WILL SEE THE BEST CHANCE OF PRECIPITATION OVER THE REGION WITH SNOW
LEVEL RISING TO AROUND 6000 FEET.  PRECIPITATION WILL SLOW DECREASE
OVER THE REGION FROM WEST TO EAST SUNDAY NIGHT THROUGH MONDAY.
TUESDAY THROUGH WEDNESDAY THE FORECAST AREA WILL REMAIN UNDER A
NORTHWESTERLY FLOW WITH ENOUGH MOISTURE FOR CHANCE POPS IN THE WEST
CENTRAL AND BOISE MOUNTAINS AND BAKER COUNTY OREGON WITH THE REST OF
THE FORECAST AREA BEING MOSTLY DRY.  TEMPERATURES OVER THE WEEKEND
WILL BE A FEW DEGREES ABOVE NORMAL BUT FOR NEXT WEEK TEMPERATURES
WILL WARM TO AROUND 10 DEGREES ABOVE NORMAL.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...SP
AVIATION.....JT
PREV SHORT TERM...BW
PREV LONG TERM....JA


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