Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 210400
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
900 PM MST SAT DEC 20 2014

.DISCUSSION...STRONG MOIST FLOW OFF THE PACIFIC CONTINUES TO HELP
PRODUCE LARGE PRECIP AMOUNTS IN THE AREA. MODERATE TO HEAVY PRECIP
IS EXPECTED TO CONTINUE OVER MUCH OF THE AREA TONIGHT AND MOST OF
TOMORROW. OVERNIGHT LOWS HAVE ALREADY DROPPED BELOW OUR FORECAST
OVER MUCH OF THE CWA...AS THE WARM FRONT HAS BEEN SLOWER TO BRING
WARM TEMPS THAN EXPECTED. TEMPS ARE EXPECTED TO WARM THROUGH THE
NIGHT...CLOSE TO THE FORECAST...SO IT WILL NOT BE UPDATED AT THIS
TIME. WINTER WEATHER ADVISORY REMAINS IN EFFECT FOR THE WEST-
CENTRAL MTNS UNTIL 11 PM MST. IS THE WARM FRONT CONTINUES TO BE
SLOW TO PROGRESS...WE MAY NEED TO EXTEND THE ADVISORY A FEW MORE
HOURS.

&&

.AVIATION...WIDESPREAD MVFR CONDITIONS WITH RAIN AND SCATTERED IFR
WITH SNOW. MOUNTAINS OBSCURED. SNOW LEVELS AROUND 5000 FT THIS
EVENING RISING TO 9000 FT IN SE OREGON AND 6500 FT IN CENTRAL IDAHO
MOUNTAINS LATE TONIGHT INTO SUNDAY. SURFACE WINDS...SE TO SW 10-20
KTS. WINDS WILL INCREASE SUNDAY AFTERNOON IN SE OREGON AND SOUTHERN
IDAHO TO WESTERLY 15-25 KTS WITH GUSTS TO 35 KTS DURING THE
AFTERNOON. WINDS ALOFT AT 10K FT MSL...NORTHWEST 50-70 KT.

&&

.PREV DISCUSSION...
SHORT TERM...STRONG PACIFIC STORM WILL BRING HEAVY PCPN AND RISING
TEMPERATURES THROUGH SUNDAY.  VALLEY RAIN AND MOUNTAINS SNOW WILL
BECOME ALL RAIN LATE TONIGHT BELOW 7000 FEET MSL.  VERY STRONG
WESTERLY WINDS ALOFT WILL CAUSE SURFACE WINDS TO INCREASE TO
ADVISORY SPEEDS SUNDAY IN ALL SOUTHERN ZONES...INCLUDING SRN PARTS
OF HARNEY AND MALHEUR COUNTIES IN OREGON...AND OWYHEE AND TWIN
FALLS COUNTIES IN IDAHO. ALSO...AVALANCHE DANGER WILL BECOME HIGH
SUNDAY IN THE SAWTOOTH RECREATION AREA. PCPN WILL DECREASE SUNDAY
NIGHT AS UPPER WINDS CHANGE TO NORTHWESTERLY WHILE AN UPPER RIDGE
AMPLIFIES OFF THE COAST. SUNDAY WILL BE QUITE WARM AND MONDAY WILL
BE ABOUT 10 DEGREES COOLER BUT STILL ABOUT 5 DEGREES ABOVE NORMAL
FOR THE FIRST DAY OF WINTER. WINTER BEGINS AT 403 PM MST SUNDAY.

LONG TERM...MONDAY NIGHT THROUGH THURSDAY...MOIST NORTHWESTERLY
FLOW WILL TURN NORTHERLY TUESDAY MORNING AS AN UPPER LEVEL RIDGE OFF
THE WEST COAST AMPLIFIES BRINGING DRIER CONDITIONS TO OUR REGION.
THIS SETUP ALLOWS AN ARCTIC COLD FRONT TO SLIDE SOUTHWARD ALONG THE
FRONT RANGE OF THE ROCKY MOUNTAINS INTO THE GREAT PLAINS...WELL EAST
OF THE AREA. TROUGH MOVING SOUTHWARD ALONG THE BRITISH COLUMBIA
COAST WILL TEMPORARILY DEFLECT THE RIDGE OVER THE AREA WEDNESDAY
BEFORE A STRONG COLD FRONT ARRIVES LATE WEDNESDAY NIGHT INTO
CHRISTMAS MORNING. TEMPERATURES WEDNESDAY WILL BE WELL ABOVE NORMAL
BEFORE DROPPING CHRISTMAS DAY. EXPECT SNOW LEVELS TO DROP TO THE
VALLEY FLOORS WITH THIS COLD FRONT...WITH A CHANCE OF A WHITE
CHRISTMAS.

THURSDAY NIGHT THROUGH SATURDAY...A COLD NORTHWESTERLY FLOW WILL
AFFECT THE REGION FOR THE MAJORITY OF THIS PERIOD IN THE WAKE OF THE
PREVIOUS COLD FRONT. THIS WILL KEEP TEMPERATURES DANCING AROUND
NORMAL. BEST CHANCE FOR PRECIPITATION WILL BE IN THE WEST CENTRAL
AND BOISE MOUNTAINS THURSDAY NIGHT. SNOW LEVELS WILL BE LOW...
PRECIPITATION SHOULD COME IN THE FORM OF SNOW. TIMING OF THE
NEXT SHORT WAVE TROUGH AND HOW MUCH MOISTURE IT WILL BRING ARE STILL
UNCLEAR...BUT THERE IS A CHANCE OF PRECIPITATION IN THE MOUNTAINS
AGAIN FOR SATURDAY NIGHT.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...WIND ADVISORY FROM 8 AM TO 5 PM MST SUNDAY IDZ015-029-030.
     WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING IDZ011.
OR...WIND ADVISORY FROM 8 AM MST /7 AM PST/ TO 5 PM MST /4 PM PST/
     SUNDAY ORZ061-063.

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...SP
AVIATION.....JS
PREV SHORT TERM...LC
PREV LONG TERM....KA/AB



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