Area Forecast Discussion
Issued by NWS Boise, ID

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000
FXUS65 KBOI 222158
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
258 PM MST MON DEC 22 2014

.SHORT TERM...TONIGHT THROUGH WEDNESDAY...SHARP NORTHWEST FLOW
WILL WEAKEN OVERNIGHT AS AN UPPER RIDGE BUILDS IN ALOFT. THIS WILL
CUT OFF PRECIPITATION IN THE MTNS AND GUSTY WINDS IN THE
VALLEYS. AS WINDS DIMINISH FOG WILL FORM ACROSS THE VALLEYS.
HIGHEST CONFIDENCE IN FOG FORMATION IS IN MTN VALLEYS...INCLUDING
THE BAKER VALLEY AND LONG VALLEY. LESS CONFIDENT IN FOG FORMATION
IN THE SNAKE VALLEY AND BURNS OREGON AREA. NORTHWEST WINDS EARLY
TONIGHT SHOULD BE ENOUGH TO KEEP CONDITIONS MIXED IN THE TREASURE
VALLEY UNTIL 09Z...AFTER WHICH THE WINDS RECEDE AND FOG SHOULD
FORM. THE SW WIND IN THE WESTERN MAGIC VALLEY MIGHT BE ENOUGH
UPSLOPE FOR AREAS NORTH OF THE SNAKE TO SEE A LOW STRATUS OR FOG
TONIGHT...BUT WILL BE TOO MUCH OF A DOWNSLOPE COMPONENT TO
SUPPORT FOG SOUTH OF THE RIVER. INVERSION STRENGTHENS INTO
TUESDAY NIGHT WITH THE UPPER RIDGE AXIS SHIFTING EAST OF THE AREA
ON WEDNESDAY. CLOUDS AND EASTERLY WINDS IN THE VALLEYS WILL
INCREASE WEDNESDAY MORNING. BY AFTERNOON RAIN AND MTN SNOW WILL
DEVELOP OVER THE EAST-CENTRAL OREGON AND WEST-CENTRAL ID MTNS
AHEAD OF A VIGOROUS SHORTWAVE TROUGH. SNOW LEVELS WILL START
BETWEEN 4-5K FEET.

.LONG TERM...WEDNESDAY NIGHT THROUGH MONDAY...WINTRY CONDITIONS
EXPECTED IN THE LONG TERM AS THE NAM/GFS BOTH COMING INTO
AGREEMENT WITH THE ECMWF. A STRONG COLD FRONT WILL IMPACT THE
REGION LATE WEDNESDAY NIGHT INTO CHRISTMAS MORNING. PRECIPITATION
WILL START OUT AS RAIN AHEAD OF THE FRONT IN THE LOWER VALLEYS
BELOW 5000 FEET MSL AND FALL TO THE VALLEY FLOORS BEHIND THE
FRONT. DO NOT EXPECT MUCH SNOW ACCUMULATION IN THE LOWER VALLEYS
AS THE PRECIPITATION WILL SUBSIDE WITH THE COOLER AIR...BUT
NONETHELESS A GOOD CHANCE OF SEEING SNOWFLAKES ON CHRISTMAS DAY.
MOUNTAINS COULD SEE ANYWHERE FROM 6-12 INCHES WITH THIS SYSTEM
ABOVE 7000 FEET...WITH HAZARDOUS TRAVEL THROUGH THE MOUNTAIN
PASSES. EXPECT TEMPERATURES FALLING TO NEAR NORMAL WITH THIS FRONT
AS COOL NORTHWESTERLY FLOW DEVELOPS IN WAKE OF THE COLD FRONT.
ANOTHER SYSTEM FROM THE GULF OF ALASKA WILL PUSH SOUTHEASTWARD
INTO INTO THE PACIFIC NORTHWEST OVER THE WEEKEND BRINGING ANOTHER
REINFORCEMENT OF COLD AIR...MORE PRECIPITATION...MAINLY IN THE
FORM OF SNOW...IS EXPECTED FOR THE REGION SATURDAY NIGHT INTO
SUNDAY NIGHT WITH THE PASSING OF THIS SYSTEM.

.AVIATION...MAINLY VFR. MOUNTAINS OBSCURED WITH SCATTERED SNOW
SHOWERS OVER HIGHER TERRAIN...ENDING AFTER SUNSET. AREAS OF MVFR-IFR
FOG AND STRATUS OVERNIGHT IN VALLEY LOCATIONS. SURFACE WINDS
GENERALLY NW 5-15KT...STRONGER NW 15-25KT WITH GUSTS TO 35KT IN
MAGIC VALLEY THIS AFTERNOON...SURFACE WINDS BECOMING LIGHT AFTER
SUNSET. WINDS ALOFT AROUND 10K FEET MSL...NW 35-45KT BECOMING NW 25-
35KT BY 06Z TUES.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...WIND ADVISORY UNTIL 5 PM MST THIS AFTERNOON IDZ016-030.
OR...NONE.

&&

$$

WEATHER.GOV/BOISE

SHORT TERM...DG
LONG TERM....KA/AB
AVIATION.....KA



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