Area Forecast Discussion
Issued by NWS Boise, ID

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000
FXUS65 KBOI 261717
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1017 AM MST WED NOV 26 2014

.DISCUSSION...PARTLY TO MOSTLY CLOUDY SKIES /EXCEPT THE MAGIC
VALLEY/ TODAY ARE ON TRACK AS AN UPPER LEVEL RIDGE AXIS SHIFTS
INLAND. NAM/GFS AND 00Z EC AGREE ON MEASUREABLE PRECIP AND WARM
SNOW LEVELS ACROSS THE NORTHERN TIER /BAKER TO MCCALL/
THANKSGIVING. ACROSS CENTRAL IDAHO SIGNIFICANT /1 TO 2 FEET/ HIGH
MOUNTAINS SNOW IS STILL EXPECTED MAINLY THURSDAY NIGHT THROUGH
FRIDAY AND SATURDAY. THE MAIN IMPACT IS EXPECTED TO BE ON HIGHWAY
21 FROM GRANDJEAN ROAD THROUGH BANNER SUMMIT WHERE A FEW INCHES OF
SNOW EVERY 6 TO 12 HOURS IS EXPECTED. A ROUND OF MODERATE SNOW IS
POSSIBLE WITH STRONG MOIST SOUTHWEST FLOW FRIDAY NIGHT THROUGH
SATURDAY MORNING...BOTH THE 12Z GFS AND NAM RUNS AGREE WITH THIS
TIMING. AT THIS TIME SNOW LEVELS LOOK TO REMAIN ABOVE 6K UNTIL THE
ARCTIC FRONT AND COLD UPPER TROUGH AFFECT THE AREA SATURDAY. BIG
CHANGE FROM SATURDAY WITH HIGHS NEAR 50 FROM BOISE TO TWIN
FALLS...TO SUNDAY WHEN HIGHS IN THE 30S /20S MTNS/ ARE EXPECTED.

&&

.AVIATION....VFR CONDITIONS WITH SCT TO BKN CLOUD COVER AND MOUNTIAN
OBSCURATION. SURFACE WINDS GENERALLY LIGHT AND BELOW 15KTS. WINDS
ALOFT THROUGH 10K FT MSL...NORTHWEST AT 35 TO 50 KTS

&&

.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH THURSDAY...UPPER RIDGE NEAR THE WEST
COAST WILL SLIDE EAST AND REACH SE OREGON AND SW IDAHO THIS
AFTERNOON. THIS WILL BRING AN END TO THE LIGHT PRECIPITATION BY
THIS AFTERNOON WHICH WILL LINGER ACROSS THE FAR NORTH THIS
MORNING. CLOUDS HAVE BEEN EXTENSIVE ACROSS THE AREA OVERNIGHT
THEREBY LIMITING THE FOG. THERE MAY STILL BE ENOUGH BREAKS IN THE
CLOUDS /AND WITH THE RECENT VALLEY RAIN/MOUNTAIN SNOW/ FOR PATCHY
FOG THIS MORNING IN MCCALL AND ONTARIO. UPPER RIDGE WILL SLIDE
EAST TONIGHT FOLLOWED BY ZONAL FLOW ON THURSDAY. MOISTURE WILL
START TO MOVE IN OFF THE PACIFIC IN THE ZONAL FLOW AND BRING A
SLIGHT CHANCE OF VALLEY RAIN AND MOUNTAIN SNOW ACROSS THE NORTH ON
THANKSGIVING DAY. ELSEWHERE...EXPECT DRY WEATHER WITH PARTLY TO
MOSTLY CLOUDY SKIES. TEMPERATURES WILL REMAIN ABOVE NORMAL...WITH
HIGHS IN THE 40S ACROSS THE NORTH AND 50S ACROSS THE SOUTH
/INCLUDING THE TREASURE VALLEY AND WESTERN MAGIC VALLEY/. NO
SIGNIFICANT WINDS ARE EXPECTED.

LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY...THE UPPER LEVEL
RIDGE WHICH HAS BEEN OVER THE AREA BREAKS DOWN THURSDAY NIGHT
ALLOWING A SUBTROPICAL MOISTURE PLUME WHICH HAS BEEN NORTH OF THE
RIDGE TO SLOWLY MOVE SOUTHWARD OVER THE FORECAST AREA. THIS PLUME
WILL BRING SUBSTANTIAL PRECIPITATION TO THE MOUNTAINS FRIDAY NIGHT
INTO SUNDAY...WITH SIGNIFICANT SNOW ABOVE 6500 FEET. A RIDGE OVER
THE GULF OF ALASKA WILL ALLOW A TROUGH TO DIG SOUTHWARD ALONG THE
BRITISH COLUMBIA COAST. THIS IS A FAVORABLE SETUP TO BRING COLD
ARCTIC AIR INTO THE REGION WITH THE UPPER LEVEL FORCING. THE
TIMING OF THE ARCTIC COLD FRONT WILL BE SOMETIME SATURDAY NIGHT
INTO SUNDAY MORNING IN BOISE. THE ARCTIC FRONT WILL STALL NEAR THE
NEVADA BORDER THROUGH MONDAY BEFORE SOUTHERLY FLOW DEVELOPS AHEAD
OF A DEEP UPPER LEVEL LOW OFF THE CALIFORNIA COAST MONDAY
AFTERNOON. FORECAST CONFIDENCE BEYOND MONDAY IS LOW WITH THE
DETAILS OF THIS SYSTEM AS MODELS HAVE DIFFERENT SOLUTIONS WITH THE
HANDLING OF THE SYSTEM NEAR THE CALIFORNIA COAST.

&&

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

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...VM
AVIATION.....EP
PREV SHORT TERM...BW
PREV LONG TERM....KA


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