Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 221737
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1037 AM MST MON DEC 22 2014

.DISCUSSION...NORTHWEST FLOW TODAY WILL KEEP SNOW SHOWERS GOING IN
THE MOUNTAINS...ESPECIALLY ALONG WEST FACING SLOPES...AND BRING
GUSTY WINDS TO THE SNAKE RIVER PLAIN. HAVE MADE UPDATES TO THE
FORECAST TO INCREASE POPS ACROSS THE WEST CENTRAL AND EASTERN
BOISE MTNS THROUGH THIS AFTERNOON...THOUGH PRECIPITATION AMOUNTS
WILL BE LIGHT. WINDS IN THE WESTERN MAGIC VALLEY ARE ALREADY
HIGHER THAN MOST MODEL GUIDANCE SO HAVE INCREASED SPEEDS THERE FOR
THIS AFTERNOON. THIS BRINGS THEM UP TO ADVISORY CRITERIA...AND
THERE IS NOW A WIND ADVISORY IN PLACE FOR THE WESTERN MAGIC AND
SOUTHERN TWIN FALLS COUNTY ZONES THROUGH EARLY EVENING. FOG
DEVELOPMENT TONIGHT WILL BE THE NEXT CONSIDERATION FOR THE
AFTERNOON PACKAGE.

&&

.AVIATION...MVFR CEILINGS IMPROVING TO VFR BY THIS AFTERNOON. EXPECT
IFR -SHSN TO CONTINUE IN CENTRAL IDAHO MTNS THRU 00Z TUES. MOUNTAINS
OBSCURED. AREAS OF MVFR-IFR FOG AND STRATUS OVERNIGHT. SURFACE WINDS
GENERALLY NW 5-15KT...STRONGER NW 15-25KT WITH GUSTS TO 35KT IN
UPPER TREASURE AND MAGIC VALLEYS. WINDS ALOFT AROUND 10K FEET
MSL...NW 30-45KT BECOMING NW 25-35KT.

&&

.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH TUESDAY...LONG FETCH OF DEEP PACIFIC
MOISTURE STREAMING INTO THE REGION WILL END BY MIDDAY AS AN UPPER
RIDGE AMPLIFIES OFF THE WEST COAST...THEREBY PINCHING OFF THE
MOIST NW FLOW. LATEST RADAR IMAGES CONTINUE TO SHOW LIGHT
PRECIPITATION IN THE MOIST NW FLOW MOVING THROUGH PORTIONS OF SE
OREGON AND SW IDAHO...INCLUDING THE TREASURE VALLEY...EARLY THIS
MORNING. THE PRECIP WILL GRADUALLY LESSEN THROUGH THE MORNING AND
BECOME SPOTTY THIS AFTERNOON. PRECIP WILL END THIS EVENING AS THE
AMPLIFYING RIDGE STARTS TO WORK EASTWARD TOWARD THE AREA. THE
RIDGE WILL MOVE INTO THE AREA ON TUESDAY FOR DRY WEATHER ACROSS
ALL OF SE OREGON AND SW IDAHO. CLEARING SKIES AND LIGHTER
WINDS...ALONG WITH MOISTURE FROM RECENT PRECIP...WILL LEAD TO
PATCHY VALLEY FOG LATE TONIGHT THROUGH TUESDAY MORNING.

WINDS WILL INCREASE AND BECOME WINDY ESPECIALLY IN THE WESTERN
MAGIC VALLEY LATER THIS AFTERNOON. WINDS WILL DIMINISH THIS
EVENING. LIGHT WINDS ARE EXPECTED ON TUESDAY AS HIGH PRESSURE
BUILDS INTO THE REGION. TEMPERATURES WILL REMAIN ABOVE
NORMAL...ALTHOUGH THE HIGHS ON TUESDAY WILL BE SLIGHTLY COOLER
THAN TODAY.

LONG TERM...TUESDAY NIGHT THROUGH MONDAY. DRIER CONDITIONS WILL
CONTINUE TUESDAY NIGHT THROUGH MID DAY WEDNESDAY AS THE HIGH
PRESSURE SITTING OFF OF THE CALIFORNIA COAST BEGINS TO FLATTEN
OUT. THE NEXT TROUGH AND ASSOCIATED COLD FRONT ARE SET TO MOVE
INTO THE AREA ON WEDNESDAY NIGHT/THURSDAY MORNING. MODELS ARE IN
DECENT AGREEMENT OF A COLD FRONT MOVING THROUGH FROM NW TO SE
BETWEEN 03Z AND 15Z THURSDAY MORNING. HOWEVER...THE ECMWF AND GFS
NOW AGREE ON BRINGING THE MAIN CENTER OF THE TROUGH TO OUR
SOUTH...WHICH DELAYS THE COLD FRONT SLIGHTLY...WHILE THE NAM IS A
BIT QUICKER WITH THIS SYSTEM. NONETHELESS...IT WILL BRING COLDER
TEMPERATURES AND DROP SNOW LEVELS TO OR NEAR VALLEY FLOORS BEHIND
THE FRONT...AND AFTER THE BULK OF MOISTURE. CONDITIONS WILL DRY
AND REMAIN COLD AS THE AREA TRANSITIONS INTO A NORTHWEST FLOW
LATER ON THURSDAY. YET ANOTHER TROUGH IS EXPECTED THIS WEEKEND
WITH A MUCH MORE NORTHERLY FETCH WHICH WILL BRING ANOTHER CHANCE
OF PRECIP...MAINLY SNOW...AND KEEP TEMPERATURES AT OR BELOW
NORMAL.

&&

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

&&

$$

WEATHER.GOV/BOISE

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


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