332
FXUS65 KBOI 150413
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
913 PM MST SAT DEC 14 2024
DISCUSSION
PRECIPITATION WILL CONTINUE AS A LOW PRESSURE
SYSTEM MOVES THROUGH THE REGION. THE RAIN AND SNOW WILL TAPER
OFF FROM WEST TO EAST BEHIND A COLD FRONT OVERNIGHT WITH SNOW
LEVELS FALLING TO VALLEY FLOORS BY EARLY SUNDAY MORNING. SNOW
WILL CONTINUE TO ACCUMULATE, MAINLY IN CENTRAL IDAHO WHERE
SEVERAL MORE INCHES ARE EXPECTED. A WINTER WEATHER ADVISORY
REMAINS IN EFFECT TONIGHT. SNOW SHOWERS LINGER IN CENTRAL IDAHO
ON SUNDAY WITH ADDITIONAL LIGHT ACCUMULATIONS OF UP TO AN INCH
OR TWO. THE COLD FRONT MAY BRING A BRIEF PERIOD OF GUSTY WINDS
AS IT CROSSES THE REGION OVERNIGHT, ESPECIALLY EAST OF MOUNTAIN
HOME WITH GUSTS UP TO 40 MPH EARLY SUNDAY MORNING. NO UPDATES
PLANNED.
AVIATION
RAIN AND SNOW CREATING MVFR TO LIFR CONDITIONS AND
MOUNTAIN OBSCURATION WILL DECREASE FROM WEST TO EAST OVERNIGHT.
SNOW LEVELS WILL LOWER FROM 4000-5000 FT MSL THIS EVENING TO
3000-4000 FT OVERNIGHT BEHIND A COLD FRONT. SCATTERED SNOW
SHOWERS WILL CONTINUE IN THE CENTRAL IDAHO MOUNTAINS ON SUNDAY
WITH DRY CONDITIONS ELSEWHERE. SURFACE WINDS: W-NW 10-20 KT,
WITH BRIEF GUSTS 25-45 KT ALONG A COLD FRONT LATE THIS EVENING,
STRONGEST NEAR KGNG/KTWF/KJER. WINDS ALOFT AT 10KFT MSL: W-NW
25-35 KT.
KBOI...LOW VFR TO MVFR CIGS OVERNIGHT, IMPROVING BY SUNDAY
MORNING. RAIN SHOWERS WILL TAPER OFF OVERNIGHT, WITH A 30%
CHANCE OF MIXING WITH SNOW BEFORE ENDING. NO SNOW ACCUMULATION.
SURFACE WINDS: SE 5-15 KT BECOMING W-NW 5-15 KT BY SUN/06Z
ALONG A COLD FRONT, WITH BRIEF GUSTS 25-35 KT POSSIBLE.
PREV DISCUSSION
SHORT TERM...TONIGHT THROUGH MONDAY NIGHT...AN UPPER LOW
NEAR THE NV/CA BORDER THIS AFTERNOON WILL LIFT THROUGH IDAHO
OVERNIGHT BRINGING ANOTHER ROUND OF RAIN AND SNOW TO THE REGION.
SNOW LEVELS WILL FALL TO LOWER VALLEY FLOORS AS THE LOW EXITS
NORTHEASTWARD SUNDAY MORNING. A COLD FRONTAL PASSAGE THIS
EVENING WILL BRING WIND GUSTS OF 30-50 MPH WITH THE STRONGER
GUSTS (45-50MPH) MORE LIKELY IN THE FOOTHILLS OR HIGHER TERRAIN
OF THE WESTERN MAGIC VALLEY. SNOW LEVELS THIS AFTERNOON WILL
START OUT BETWEEN 4000-5500FT ACROSS SE OREGON AND 5-6KFT
ACROSS SW IDAHO, FALLING TO LOWER VALLEY FLOORS BEFORE SUNRISE
SUNDAY. THIS WILL BRING A RAIN/SNOW MIX OR CHANGEOVER TO SNOW
WHERE PRECIPITATION IS LINGERING, WHICH IS MOST LIKELY TO BE
EAST OF MOUNTAIN HOME TO THE TWIN/JEROME AREA. ANY MINOR
ACCUMULATION WILL BE LIMITED TO COLDER SURFACES SO LITTLE IF
ANY IMPACT IS EXPECTED. AS SNOW LEVELS FALL OVERNIGHT LOWER MTN
VALLEYS WILL BEGIN TO SEE ACCUMULATION, WITH MINOR AMOUNTS DOWN
TO 3500 FEET. STILL LOOKING AT SITES BETWEEN 4500-6000 FEET TO
GET AN ADDITIONAL 2 TO 4 INCHES, WHILE ELEVATIONS ABOVE 6000
FEET ADD 6-10 INCHES THROUGH SUNDAY MORNING.
SUNDAY WILL SEE A BRIEF BREAK FROM THE RAIN/SNOW FOR MOST AREAS.
THE W-CENTRAL IDAHO MTNS ARE THE EXCEPTION, HOLDING ONTO A
20-40% CHANCE OF SNOW SHOWERS THROUGH THE AFTERNOON. MOUNTAIN
VALLEYS WILL ADD LESS THAN AN INCH OF SNOW WITH UP TO 2 INCHES
ACROSS HIGHER ELEVATIONS.
THE NEXT STORM SYSTEM IS ON TRACK TO PUSH PRECIPITATION INTO
THE REGION LATE SUNDAY NIGHT ON A SOUTHWEST FLOW ALOFT. LIGHT
SNOWFALL WILL INITIALLY BE FOCUSED ACROSS SE OREGON, THE LOWER
SNAKE PLAIN/WEISER BASIN AND W-CENTRAL IDAHO MTNS, WHILE THE
SOUTHWEST WINDS ALOFT SHADOW PORTIONS OF THE SNAKE PLAIN FROM
ROUGHLY BOISE EASTWARD. PRECIPITATION SPREADS EASTWARD ON MONDAY
TRACKING WITH THE UPPER LOW AS IT SWINGS INTO SE OREGON. SNOW
LEVELS REMAIN LOW ENOUGH ACROSS SE OREGON AND THE WEISER BASIN
ON MONDAY THAT MODERATE ACCUMULATIONS ARE POSSIBLE DOWN TO
VALLEY FLOORS. OTHERWISE EXPECT MOST LOWER ELEVATION SITES TO
SEE LITTLE ACCUMULATION. FOR NOW THE NBM HAS A 40-60% CHANCE OF
MEASURABLE SNOWFALL IN THE LOWER SNAKE PLAIN (ONTARIO TO BOISE)
BUT LESS THAN A 10% CHANCE OF AN INCH OR MORE THROUGH MONDAY
AFTERNOON. THE MOUNTAINS ARE IN LINE FOR A WIDESPREAD MODERATE
SNOWFALL WITH THIS SYSTEM WITH A BROAD 5-10 INCHES POSSIBLE FOR
MON/MON NIGHT. THE CHANCE FOR SHOWERS WILL CONTINUE THROUGH
MONDAY NIGHT AS ANOTHER SYSTEM APPROACHES FROM THE WEST.
LONG TERM...TUESDAY THROUGH SATURDAY...DETERMINISTIC MODELS
REMAIN QUITE VARIED ON THE EVOLUTION OF THE SHORTWAVE TROUGH
PASSAGE ON TUESDAY. THE GFS/NAM SOLUTIONS SHOW HIGHER CONFIDENCE
IN WIDESPREAD COOLER TEMPERATURES AND PRECIPITATION WITH THE
TROUGH DIGGING TOWARDS THE WEST. THIS WOULD BRING MORE
PRECIPITATION TO SOUTHEAST OREGON AND OVER THE SNAKE RIVER
VALLEY, WITH THE POTENTIAL FOR SNOW IN THE BOISE METRO AREA (10%
CHANCE). THE ALTERNATIVE SCENARIO IS WITH THE ECMWF/CANADIAN
SOLUTIONS, WHICH SHOW A MUCH QUICKER PROGRESSION OF THE TROUGH,
WITH A RIDGE SWIFTLY BUILDING IN AFTER, BRINGING HIGHER SNOW
LEVELS AND PRECIPITATION OVER THE NORTHEASTERN PORTION OF OUR
CWA (CENTRAL ID MOUNTAINS). THE CURRENT FORECAST STRIKES A
BALANCE BETWEEN THESE TWO TRACKS, WITH HIGHER PRECIPITATION
CHANCES OVER THE ID MOUNTAINS.
CLUSTER AND DETERMINISTIC MODELS REMAIN MUCH MORE CLOSELY
ALIGNED BY LATE WEDNESDAY-FRIDAY. AN ANOMALOUS RIDGE IS
PROJECTED TO BUILD OVER THE REGION, WHICH WILL LEAD TO ABOVE
NORMAL TEMPERATURES AND DRY CONDITIONS. THIS STABLE PATTERN WILL
ALSO LEAD TO INVERTED CONDITIONS AND HIGH CONFIDENCE IN A
RETURN TO STAGNANT CONDITIONS DUE TO LIGHT WINDS AND LOW MIXING
HEIGHTS. VALLEY TEMPERATURES WILL BE BELOW NORMAL, PRIMARILY IN
THE SNAKE RIVER VALLEY WHILE HIGHER ELEVATIONS ABOVE THE TOP OF
THE INVERSION WILL SEE ABOVE NORMAL TEMPERATURES.
THERE IS SOME HINT AT A SHORTWAVE TROUGH MOVING INTO THE REGION
LATE SATURDAY BRINGING VALLEY RAIN AND MOUNTAIN SNOW, BUT THE
EVOLUTION OF THIS STORM THROUGH FUTURE MODEL RUNS WILL LIKELY
WEAKEN AS IT ADVANCES INLAND. THIS IS MAINLY DUE TO THE STRENGTH
OF THE UPPER LEVEL RIDGE. CLUSTER SOLUTIONS WIDELY SUPPORT THE
RIDGE STAYING IN PLACE THROUGH THE WEEKEND, WHILE DETERMINISTIC
SOLUTIONS ARE MORE OPTIMISTIC WITH EXTENT AND LOCATION OF THE
TROUGH. THEREFORE, FORECAST UNCERTAINTY IS FAIRLY HIGH WITH THE
CHANCE OF PRECIPITATION NEXT SATURDAY.
AVIATION...PERIODS OF RAIN/SNOW CREATING MVFR TO LIFR
CONDITIONS AND MOUNTAIN OBSCURATION. SNOW LEVELS 4000-6000 FT
MSL, DROPPING TO 3000-4000 FEET MSL LATER TONIGHT. BRIEF SNOW AT
VALLEY FLOORS EARLY TOMORROW MORNING, WITH PRECIPITATION ENDING
BY SUN/16Z. SURFACE WINDS: E-S 10-20 KT, WITH GUSTS 20-30 KT.
SHIFTING TO W-NW 10-20 KT TONIGHT, WITH A PERIOD OF GUSTS TO
25-45 KT DURING COLD FRONT PASSAGE SUN/05Z-09Z, STRONGEST WINDS
NEAR KGNG/KTWF/KJER. WINDS ALOFT AT 10KFT MSL: W 20-35KT.
KBOI...MOSTLY VFR. LIGHT TO MODERATE RAIN THIS AFTERNOON, WITH
PERIODS OF MVFR/IFR EXPECTED. TRANSITION TO RAIN SNOW/MIX AS
SHOWERS END SUN/09Z. MOUNTAINS OBSCURED IN PRECIPITATION AND
LOW CLOUDS. SURFACE WINDS: SE 10-20 KT BECOMING W-NW 5-15 KT
WITH GUSTS 20-25 KT AROUND SUN/05Z. BRIEF PERIOD OF W-NW 15-25
KT WITH GUSTS 30-45 KT POSSIBLE SUN/05Z-07Z WITH COLD FRONT
PASSAGE.
BOI WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY UNTIL 5 AM MST SUNDAY IDZ011-013-028.
OR...NONE.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.TWITTER.COM/NWSBOISE
DISCUSSION...BW
AVIATION.....ST
SHORT TERM...DG
LONG TERM....SA
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