Area Forecast Discussion
Issued by NWS Boise, ID

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000
FXUS65 KBOI 211627
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
927 AM MST SUN DEC 21 2014

.DISCUSSION...RAIN AND SNOW CONTINUE IN IDAHO ZONES NORTH OF THE
SNAKE BASIN THIS MORNING BUT IT HAS DECREASED IN OREGON AND SWRN
IDAHO.  MORE PCPN UPSTREAM WHICH MODELS BRING IN MID-DAY THROUGH
TONIGHT. SNOW CHANGED TO RAIN AT MCCALL AROUND 330 AM MST AND
OUR ENTIRE CWA BELOW 6000 FEET WILL HAVE RAIN RATHER THAN SNOW
THROUGH MID-AFTERNOON.  SNOW LEVEL WILL SLOWLY LOWER THS AFTERNOON
AND TONIGHT AS UPPER WINDS CHANGE FROM WESTERLY TO NWLY.  TEMPS
WILL COOL DOWN WITH HIGHS MONDAY ABOUT 10F LOWER THAN TODAY.  WIND
ADVISORY WILL CONTINUE IN OUR SRN ZONES THROUGH THE DAY.  12Z BOI
RAOB HAD VERY STRONG WESTERLY WINDS ALOFT.  AVALANCHE WARNING
STILL IN EFFECT IN THE SAWTOOTH RECREATION AREA THROUGH AT LEAST
700 AM MONDAY.  GENERAL TREND THROUGHOUT OUR CWA IS COOLER AND
DRIER TONIGHT THROUGH MONDAY.  DRY THROUGH WEDNESDAY THEN COLDER
WITH A CHANCE OF SNOW WEDNESDAY NIGHT.  CHANCE OF LIGHT SNOW C
RISTMAS DAY...THEN DRY AND COLD THROUGH SATURDAY.  NO UPDATES AT
THIS TIME.

&&

.AVIATION...WIDESPREAD MVFR-IFR CONDITIONS WITH PRECIPITATION.
MOUNTAINS OBSCURED. SNOW LEVELS AT THE SURFACE IN CENTRAL IDAHO
MOUNTAINS RANGING UP TO 10K FEET MSL SW OF THE SNAKE RIVER PLAIN.
SNOW LEVELS WILL SLOWLY FALL FROM NORTH TO SOUTH AS PRECIPITATION
BAND MOVES SOUTHWARD TODAY AND TONIGHT. VFR CONDITIONS SOUTH AND
WEST OF A LINE FROM KBNO-KREO IN SE OREGON. SURFACE WINDS WESTERLY
15-25KT WITH GUSTS TO 45KT THIS AFTERNOON IN SE OREGON AND EASTERN
MAGIC VALLEY EAST OF KJER...NORTHWESTERLY SURFACE WINDS UP TO 15KT
ELSEWHERE. WINDS ALOFT AROUND 10K FT MSL...NW 50-75KT DIMINISHING TO
NW 35-50KT BY 12Z MON.

&&

.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH MONDAY...THE WARM FRONT IS FINALLY
SHOWING SIGNS OF PUNCHING NORTHWARD AS THE MODELS HAVE PROMISED.
BOGUS BASIN IS ABOVE FREEZING AND THE WEB CAM INDICATES RAIN. KMYL
IS STILL SNOWING...BUT SHOULD CHANGE TO RAIN SHORTLY. THE WSW WILL
BE ALLOWED TO EXPIRE AT 3 AM WITH THE MORNING FORECAST PACKAGE.
LIGHT TO MODERATE RAIN IS STILL FALLING OVER MOST OF THE REGION...
AND WE EXPECT IT TO CONTINUE FOR MUCH OF TODAY AS A WARM MOIST
FLOW REMAINS ENTRENCHED ALOFT. LATEST HRRR MODEL INDICATES A BREAK
THIS MORNING IN THE LOWER TREASURE VALLEY AND WESTERN PORTIONS OF
THE UPPER TREASURE VALLEY...INCLUDING BOISE. BUT THEN PRECIP
SPREADS BACK INTO THESE AREAS THIS AFTERNOON. THIS WILL HAVE A
STRONG IMPACT ON TEMPERATURES TODAY. WE HAVE LOWERED THE FORECAST
FOR THESE AREAS DUE TO HIGH-RESOLUTION MODEL DATA INDICATING
LESS WARMING THAN PREVIOUSLY EXPECTED TODAY. AS WE MOVE INTO
TONIGHT...SNOW LEVELS MOVE BACK DOWN AND MOISTURE WILL FINALLY
BEGIN TO DECREASE. THE CHANCE OF PRECIP DECREASES SHARPLY MONDAY
AND TEMPS WILL COOL FURTHER. WINDS WILL BE STRONG TODAY IN SE
OREGON...THE SOUTHWEST HIGHLANDS OF IDAHO...AND THE HIGHER TERRAIN
OF SRN TWIN FALLS COUNTY. THE WIND ADVISORY IS STILL ON TRACK TO GO
INTO EFFECT AT 8 AM MST AND RUN UNTIL 5 PM MST.

LONG TERM...MONDAY NIGHT THROUGH SATURDAY...CONDITIONS ARE
EXPECTED TO CONTINUE TO DRY OUT MONDAY NIGHT AND TUESDAY AS A
RIDGE OFF OF THE CALIFORNIA COAST AMPLIFIES. THIS WILL KEEP
TEMPERATURES ABOVE NORMAL. MODELS ARE IN GOOD AGREEMENT OF THE
RIDGE STARTING TO FLATTEN OUT ON WEDNESDAY AHEAD OF A TROUGH
MOVING IN FROM COASTAL BRITISH COLUMBIA. THE LATEST GFS AND ECMWF
RUNS HAVE BEGUN TO AGREE ON TIMING OF THIS TROUGH AND ASSOCIATED
COLD FRONT. PRECIP CHANCES WILL SPREAD FROM NW TO SE LATE WED
NIGHT WITH SNOW LEVELS AROUND 5000 FT DROPPING TO 2000 FT BY
EARLY CHRISTMAS MORNING. HOWEVER...THIS SYSTEM WILL LIKELY MOVE
OUT OF THE AREA QUITE QUICKLY SO CONDITIONS SHOULD DRY OUT ONCE
AGAIN CHRISTMAS AFTERNOON/EVENING. THE ASSOCIATED COLD FRONT WILL
BRING TEMPERATURES BACK TO NEAR NORMAL FOR THE REST OF THE PERIOD.
A COOLER NORTHWEST FLOW WILL SET IN FOR FRIDAY AND BEYOND.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...WIND ADVISORY UNTIL 5 PM MST THIS AFTERNOON IDZ015-029-030.
     AVALANCHE WARNING IN THE SAWTOOTH RECREATION AREA UNTIL 730 AM
        MST MONDAY.
OR...WIND ADVISORY UNTIL 5 PM MST /4 PM PST/ THIS AFTERNOON ORZ061-063.

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...LC
AVIATION.....KA
PREV SHORT TERM...SP
PREV LONG TERM....EP


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