Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 260403
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
903 PM MST THU DEC 25 2014

.DISCUSSION...NORTH-NORTHWEST FLOW KEEPING ISOLATED SHOWER
ACTIVITY ALONG WINDWARD SLOPES...OTHERWISE SNOW SHOWERS HAVE
DISSIPATED AND THUS HAVE REMOVED MENTION OF SNOW IN WESTERN MAGIC
VALLEY FOR REST OF TONIGHT. STILL QUITE A BIT OF CLOUD COVER OVER
SE OREGON AND UPSTREAM OVER EASTERN WA AND THE IDAHO PANHANDLE
WHICH LOOKS TO BE ASSOCIATED WITH WEAK UPPER LEVEL FEATURE. EXPECT
THIS TO HANG ON OVER THE WEST CENTRAL ID MTNS AND SE OREGON INTO
EARLY FRIDAY MORNING. SURFACE PRESSURE GRADIENT WILL CONTINUE TO
WEAKEN OVERNIGHT RELAXING WINDS AS IT GOES. THE PASSING CLOUD
COVER...DRY AIRMASS AND LIGHT W-NW WIND WILL PROHIBIT FOG
DEVELOPMENT ACROSS THE FORECAST AREA. HAVE MADE MINOR UPDATES TO
THE FORECAST TO REFLECT THESE DEVELOPMENTS.

&&

.AVIATION...AREAS OF LOW VFR CEILINGS IN EASTERN OREGON AND THE
CENTRAL IDAHO MOUNTAINS THIS EVENING MAY PERSIST THROUGH TONIGHT.
OTHERWISE EXPECT VFR CONDITIONS UNDER MOSTLY CLEAR SKIES. SURFACE
WINDS...WEST TO NORTHWEST 10-20 KTS DECREASING TO 5-15 KTS AFTER
06Z. WINDS ALOFT...NORTH AROUND 25 KTS UP THROUGH 10K FT MSL.

WEEKEND OUTLOOK...VFR CONDITIONS WILL CONTINUE THROUGH SATURDAY
MORNING. SNOW WILL SPREAD INTO BAKER COUNTY OREGON AND THE WEST
CENTRAL MOUNTAINS SATURDAY AFTERNOON. SATURDAY NIGHT EXPECT
WIDESPREAD SNOW WITH TERRAIN OBSCURATION AND LOCAL IFR/LIFR
CONDITIONS...CONTINUING OVER THE MOUNTAINS ON SUNDAY. VALLEY
CONDITIONS WILL GRADUALLY IMPROVE ON SUNDAY WITH SNOW BECOMING
SCATTERED BY AFTERNOON.

&&

.PREV DISCUSSION...
SHORT TERM...TONIGHT THROUGH SATURDAY...STRONG SURFACE WINDS
EARLY THIS EVENING SHOULD DIMINISH AS NORTHERLY FLOW ALOFT WEAKENS
AND THE TIGHT SURFACE PRESSURE GRADIENT PUSHES OFF TO THE EAST.
NORTHERLY FLOW ALOFT WILL CONTINUE THROUGH FRIDAY NIGHT. STILL
ENOUGH MOISTURE IN THE EASTERN PART OF THE FORECAST AREA THAT
UPSLOPE SNOW SHOWERS COULD CONTINUE IN THE HIGHLANDS SOUTH OF TWIN
FALLS THROUGH TONIGHT...AS WELL AS IN THE CENTRAL IDAHO MOUNTAINS
WHERE A WEAK SHORTWAVE PASSES BY IN THE FLOW ON FRIDAY
MORNING...BUT ANY SNOW ACCUMULATIONS SHOULD REMAIN LIGHT.
TEMPERATURES TONIGHT WILL BE MUCH COLDER WITH MOSTLY CLEAR SKIES
IN THE WESTERN TWO-THIRDS OF THE FORECAST AREA. HOWEVER...SOME
HIGHER CLOUDS SHOULD MOVE IN FROM THE NORTH AFTER MIDNIGHT TO HELP
MODERATE THE TEMPERATURES A BIT. BY SATURDAY MORNING...CLOUDS ARE
INCREASING AS ANOTHER STORM APPROACHES FROM THE NORTHWEST...WITH
SNOW PROBABLY STARTING IN THE NORTHERN PARTS OF THE FORECAST AREA
BY SATURDAY AFTERNOON.

LONG TERM...SATURDAY NIGHT THROUGH THURSDAY.  WEAK RIDGE OF
HIGH PRESSURE OVER THE REGION SATURDAY WILL BE PUSHED WEST AS THE
NEXT UPPER LEVEL TROUGH DIGS SOUTH ALONG THE CANADIAN WEST COAST.
THIS TROUGH WILL MOVE INTO THE PACIFIC NORTHWEST SATURDAY NIGHT THEN
OVER IDAHO SUNDAY.  THIS SYSTEM IS COLD ENOUGH FOR ANY
PRECIPITATION TO FALL AS SNOW...EVEN IN THE LOWEST ELEVATIONS.  BEST
CHANCE FOR PRECIPITATION WILL BE LATE SATURDAY NIGHT THROUGH SUNDAY
MORNING WITH LINGERING SHOWERS THROUGH SUNDAY AFTERNOON.  SNOWFALL
AMOUNTS AT THIS TIME WILL BE 4 TO 6 INCHES IN THE MOUNTAINS WITH UP
TO 2 INCHES IN THE SNAKE RIVER VALLEY AND AN INCH OVER SOUTHEAST
OREGON.  SUNDAY NIGHT AND MONDAY THE UPPER LEVEL TROUGH WILL SLOWLY
SHIFT TO THE SOUTHEAST WITH ENOUGH LINGERING MOISTURE TO KEEP SLIGHT
CHANCE POPS OVER THE FORECAST AREA.  MONDAY NIGHT A NORTHERLY FLOW
ALOFT WILL DEVELOP OVER THE FORECAST AREA AS A RIDGE OF HIGH
PRESSURE BUILDS NORTH INTO THE GULF OF ALASKA.  THIS NORTHERLY FLOW
WILL BRING COLD AIR TO THE REGION FROM CANADA FOR DRY CONDITIONS AND
COLD TEMPERATURES THROUGH THURSDAY.  AT THIS TIME THE COLDEST
TEMPERATURES LOOK TO BE TUESDAY AFTERNOON AND TUESDAY NIGHT WITH
HIGHS ON TUESDAY IN THE 20S IN THE LOWEST VALLEYS AND TEENS IN THE
MOUNTAINS.  LOWS TUESDAY NIGHT WILL BE IN THE SINGLE DIGITS ABOVE
ZERO WITH BELOW ZERO READINGS IN THE MOUNTAINS.  TEMPERATURES WILL
SLOWLY WARM FOR WEDNESDAY AND THURSDAY AS THE RIDGE FLATTENS DUE THE
NEXT APPROACHING WEATHER SYSTEM AND THE FLOW ALOFT SHIFTING TO THE
NORTHWEST.
&&

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

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...DG
AVIATION.....JT
PREV SHORT TERM...TB
PREV LONG TERM....JA/WH



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