Area Forecast Discussion
Issued by NWS Boise, ID

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000
FXUS65 KBOI 290359
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
859 PM MST FRI NOV 28 2014

.DISCUSSION...FORECAST ESSENTIALLY UNCHANGED SINCE YESTERDAY EXCEPT
THAT THE ARCTIC FRONT EXPECTED SATURDAY SHOULD ARRIVE ABOUT 3 HOURS
LATER THAN FORECAST YESTERDAY.  AT 03Z FRONT COULD BE SEEN ON I/R
SATELLITE IMAGERY EXTENDING FROM NE WASHINGTON THROUGH NWRN OREGON.
HEAVY SNOW IS STILL EXPECTED IN HIGHER IDAHO MOUNTAINS ABOVE 7000
FEET SATURDAY...WITH RAIN OR SNOW CHANGING TO SNOW SHOWERS AT LOWER
ELEVATIONS SHORTLY AFTER FROPA.  THE LATER ARRIVAL OF THE FRONT
MEANS THAT SHOWERS WILL CONTINUE INTO EARLY SATURDAY EVENING IN THE
SNAKE BASIN...AND LAST LONGER INTO SATURDAY NIGHT NEAR THE NEVADA
BORDER.  LITTLE IF ANY SNOW ACCUMULATION IS EXPECTED IN THE TREASURE
AND MAGIC VALLEYS.  YESTERDAY THE HIGH TEMPERATURE FORECASTS FOR
SATURDAY VARIED GREATLY AMONG THE MODELS.  THE GFS AND MAV GUIDANCE
WERE MUCH WARMER THAN THE NAM AND MET GUIDANCE FOR EXAMPLE.  THE
DIFFERENCES HAVE BEEN LARGELY RESOLVED TODAY TO ABOUT MID-WAY
BETWEEN THEM BUT SLIGHTLY FAVORING THE COOLER NAM/MET FORECASTS.
CURRENT FORECAST LOOKS GOOD AT THE MOMENT...NO UPDATES PLANNED.

&&

.AVIATION...GENERALLY VFR CONDITIONS AND MID-HIGH CLOUDS...WITH THE
EXCEPTION OF FRONTAL PASSAGE WHERE MVFR/IFR CEILINGS ARE POSSIBLE.
FRONTAL PASSAGE WILL MOVE FROM NW TO SE SATURDAY MORNING THROUGH
SATURDAY EVENING...PRODUCING RAIN IN THE VALLEYS AND SNOW IN THE
HIGHER MOUNTAINS...AS WELL AS MOUNTAIN OBSCURATION. SURFACE WINDS
WILL SHIFT AND BE GUSTY WITH THE FRONT. WINDS ALOFT NEAR 10K FT
MSL...WESTERLY AT 45-60 KTS.

&&

.PREV DISCUSSION...
SHORT TERM...TONIGHT THROUGH SUNDAY...THE PAC NW WILL UNDERGO A
PATTERN CHANGE OVER THE NEXT 24 HOURS AS AN UPPER TROUGH AND
ACCOMPANYING COLD FRONT DROP IN FROM CANADA. A WEAK BAND OF
SHOWERS ALONG THE NORTHERN PERIPHERY OF THE EXITING UPPER RIDGE
WILL WORK THROUGH SE OREGON AND SW IDAHO THIS EVENING. BY EARLY
SATURDAY MORNING PRECIPITATION INTENSITY WILL INCREASE ACROSS THE
EAST-CENTRAL OREGON AND WEST-CENTRAL IDAHO MOUNTAINS...AHEAD OF
THE UPPER TROUGH AXIS AND ACCOMPANYING COLD FRONT. SNOW LEVELS ARE
5-6K FEET AHEAD OF THE FRONT. HIGHER PEAKS AND MOUNTAIN PASSES
/INCLUDING THE BANNER SUMMIT AREA ALONG HIGHWAY 21/ COULD SEE UP
TO A FOOT OF SNOW BY SATURDAY NIGHT. MOUNTAIN VALLEY LOCATIONS
AROUND 5K FEET WILL SEE A FEW INCHES OF WET SNOW WITH ELEVATIONS
BELOW 5K FEET SEEING MOSTLY RAIN BEFORE CHANGING OVER TO SNOW AS
THE PRECIPITATION ENDS. WITH A SHARP BACK EDGE TO THE PRECIPITATION
DON/T EXPECT THE COLD AIR TO MAKE IT INTO THE LOWER VALLEYS IN TIME
FOR A CHANGEOVER TO SNOW. TEMPERATURES SATURDAY WILL BE 10-15 DEGREES
COOLER THAN TODAY. SUNDAY IS COLD AND DRY AS THE COLD FRONT STALLS
ALONG THE ID/NV BORDER. TEMPERATURES WILL DROP ANOTHER 15-20 DEGREES
FROM SATURDAY TO SUNDAY.

LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...WARM-FRONTAL OVERRUNNING
WILL OCCUR LATE SUNDAY NIGHT INTO MONDAY MORNING AS A CUTOFF LOW OFF
THE CALIFORNIA COAST PUSHES MOISTURE UP OVER THE COLD AIR IN PLACE
FROM THE ARCTIC COLD FRONT. WE EXPECT PRECIPITATION TO START OFF AS
SNOW AT ALL LOCATIONS BEFORE CHANGING TO RAIN IN THE LOWER VALLEYS BY
TUESDAY AFTERNOON...THOUGH CONFIDENCE IS LOW IN THESE SITUATIONS AS
THE COLD AIR TENDS TO TAKE LONGER TO ERODE IN THE VALLEY LOCATIONS.
PRECIPITATION WILL CONTINUE ESPECIALLY OVER THE HIGHER TERRAIN
THROUGH THURSDAY AS THE CUTOFF LOW OFF THE CALIFORNIA COAST SLOWLY
MOVES INLAND AND WEAKENS. AS THE LOW WEAKENS THE UPPER LEVEL FLOW
WILL TURN ZONAL KEEPING THE PRECIPITATION OVER THE HIGHER TERRAIN
GOING THROUGH THE EXTENDED PERIOD. TEMPERATURES WILL RISE TO AROUND
5 DEGREES ABOVE NORMAL FROM TUESDAY THROUGH THE EXTENDED PERIOD.

&&

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

&&

$$

WEATHER.GOV/BOISE

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


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