461
FXUS65 KBOI 061718
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1018 AM MST SAT DEC 6 2025
DISCUSSION
UNSEASONABLY WARM CONDITIONS CONTINUE THROUGH THE
EXTENDED PERIOD. TODAY, STRONG WESTERLY FLOW CONTINUES, BRINGING
SCATTERED SNOW SHOWERS OVER THE MOUNTAINS THROUGH THIS EVENING.
MINIMAL ACCUMULATIONS EXPECTED. VALLEY BASINS WILL SEE MAINLY
DRY CONDITIONS WITH PERIODS OF SUNSHINE. BREEZY WEST-NORTHWEST
WINDS EXPECTED THIS AFTERNOON AS WINDS ALOFT MIX DOWN TO THE
SURFACE. A WEAK WARM FRONT MOVES OVER THE AREA ON SUNDAY,
KEEPING TEMPERATURES SLIGHTLY COOLER THAN TODAY WITH
PRECIPITATION DURING THE DAYTIME HEATING HOURS. THEN
TEMPERATURES CONTINUE TO WARM ON MONDAY WITH ANOTHER WARM
FRONTAL PASSAGE. STRONG ZONAL FLOW PERSISTS THROUGH THE
EXTENDED PERIOD, SUPPORTING NEAR RECORD HIGH TEMPERATURES EARLY
NEXT WEEK WITH UNUSUAL VERTICAL MIXING AND A LACK OF INVERSION
DEVELOPMENT. CURRENT FORECAST ON TRACK WITH NO UPDATES.
AVIATION
LLWS ACROSS THE AREA THROUGH SAT/18Z. CONTINUING
RAIN/SNOW SHOWERS AND MVFR-IFR CEILINGS IN THE W-CENTRL MTNS.
SNOW LEVELS: 4.5-5.5 KFT MSL. SURFACE WINDS: W-NW 10-20 KT,
WITH GUSTS TO 20-30 KT IN OPEN AREAS AND RIDGES. WINDS ALOFT AT
10 KFT MSL: W-NW 25-40 KT.
KBOI...VFR. A SLIGHT CHANCE OF SHOWERS IN THE VICINITY THIS
EVENING. SURFACE WINDS: NW 8-12KT BECOMING SE LESS THAN 6 KT
THIS EVENING.
SUNDAY OUTLOOK...LIGHT SNOW SHOWERS OVER HIGHER TERRAIN THROUGH
EARLY HOURS SUNDAY, THEN MORE WIDESPREAD PRECIPITATION THROUGH
AFTERNOON/EVENING. PATCHY FOG IN MOUNTAIN VALLEYS SUNDAY
MORNING. SNOW LEVELS: 4-6 KFT MSL IN THE MORNING, INCREASING TO
5-7 KFT MSL IN THE AFTERNOON. SURFACE WINDS: SE-SW 5-15 KT.
PREV DISCUSSION
SHORT TERM...TODAY THROUGH MONDAY NIGHT...OUR REGION WILL
REMAIN JUST WITHIN THE ENVELOPE OF A BROAD PACIFIC HIGH THAT
WILL CONTINUE TO DIRECT SUB-TROPICAL MOISTURE ONTO THE OR/WA
COAST. THE BREEZY WINDS WE'VE SEEN OVERNIGHT, ESPECIALLY AT
HIGHER ELEVATIONS, WILL SUBSIDE THIS MORNING AS FLOW ALOFT
WEAKENS BEHIND YESTERDAY'S DEPARTING STORM SYSTEM. FOR TODAY,
MTNS WILL KEEP A 40-80% CHANCE OF SHOWERS. THAT SAID, THE AIR
MASS IS NOTABLY DRIER TODAY (PWS IN THE 50TH PERCENTILE
COMPARED TO 95+ PERCENTILE WE OBSERVED ON FRIDAY) SO RAIN/SNOW
AMOUNTS WILL BE LIGHT IN COMPARISON. LOOKING AT UP TO AN INCH IN
MOUNTAIN VALLEYS ABOVE 4500 FEET AND 2 TO 5 INCHES ABOVE VALLEY
FLOORS THROUGH SUNDAY MORNING. SNOW LEVELS THROUGH THE WEEKEND
ARE THE LOWEST THEY'LL REACH FOR A WHILE, SITTING BETWEEN
4500-5500 FEET MSL. SOUTHEAST OREGON AND SW IDAHO FROM THE SNAKE
PLAIN TO THE NV BORDER WILL SEE A BREAK FROM PRECIPITATION
TODAY.
A WARM FRONT WILL PUSH ANOTHER ROUND OF RAIN AND MTN SNOW INTO
THE REGION ON SUNDAY. LIGHT AMOUNTS WILL FALL ACROSS SE OREGON
TO THE SNAKE PLAIN, LIKELY JUST HUGGING THE FOOTHILLS EAST OF
MOUNTAIN HOME. MOUNTAINS WILL DO SLIGHTLY BETTER WITH 0.2-0.4"
OF RAIN/LIQUID EQUIVALENT FOR THE SUN/SUN NIGHT PERIOD. WITH
SNOW LEVELS REMAINING STEADY, UP TO 2 INCHES WILL FALL TO MTN
VALLEY FLOORS WITH 2-5 INCHES ABOVE 6KFT MSL.
HEAVIER PRECIPITATION ARRIVES IN THE MOUNTAINS LATE MONDAY AND
MONDAY NIGHT AS AN IMPRESSIVE ATMOSPHERIC RIVER PUSHES IN FROM
THE COAST. THE PRECIPITABLE WATER VALUES ARE FORECAST TO EXCEED
THE 95TH PERCENTILE, APPROACHING RECORD VALUES AT KBOI BY 12Z
TUESDAY MORNING. MILD AIR WILL ACCOMPANY THE DEEP PACIFIC
MOISTURE, RAISING SNOW LEVELS TO 7500-8500 FEET MONDAY NIGHT.
IN TURN, THE HEAVIER ACCUMULATING SNOW WILL BE RELEGATED TO THE
HIGHER PEAKS. BEING MAINLY AN OROGRAPHIC EVENT, MUCH OF SE
OREGON AND SW IDAHO FROM THE SNAKE PLAIN TO NV BORDER WILL SEE
LITTLE IF ANY PRECIPITATION FROM THIS ROUND. IN THE E-CENTRAL
OREGON AND W-CENTRAL IDAHO MOUNTAINS CURRENT LIQUID TOTALS FOR
MON/MON NIGHT ARE IN THE RANGE OF 0.4-0.8" WITH LOCALLY UP TO AN
INCH. SITES ABOVE 7500 FEET THAT STAY ALL SNOW WILL SEE 5 TO 10
INCHES OF WET CONCRETE BY TUESDAY MORNING. GUSTY WINDS TO 40
MPH WILL ACCOMPANY THE RAIN/SNOW AT HIGHER ELEVATIONS MONDAY
NIGHT. TEMPERATURES THROUGH THE PERIOD ARE WILL BE 5-10 DEGREES
ABOVE NORMAL.
LONG TERM...TUESDAY THROUGH SATURDAY...UNSETTLED WEATHER
CONTINUES TO START OUT THE PERIOD. HIGH PRESSURE SITUATED OFF OF
THE WEST COAST WILL CONTINUE TO SHUTTLE PACIFIC MOISTURE OVER
THE REGION, WITH MID-LEVEL WINDS OF AROUND 50-70 KNOTS OVERHEAD.
THIS MOISTURE FLUX WILL ALLOW FOR A 80-100% CHANCE OF
PRECIPITATION NORTH AND EAST OF A LINE ROUGHLY FROM MALHEUR CITY
TO ANDERSON DAM, WITH THE HIGHEST PROBABILITY IN THE WEST
CENTRAL MOUNTAINS. SOUTH AND WEST OF THAT LINE WILL SEE A 30-65%
CHANCE OF PRECIPITATION TUESDAY MORNING. ENSEMBLES AND CLUSTER
ANALYSIS GENERALLY AGREE ON THE RIDGE PUSHING IN OVER OUR AREA
THROUGHOUT THE WEEK. THIS WOULD SHIFT THE JET STREAM AND FLOW OF
MOISTURE NORTH. AS A RESULT, PRECIPITATION CHANCES DECREASE AND
SHIFT NORTH THROUGHOUT THE WEEK, WITH A 20-40% CHANCE HANGING
ON NORTH OF THE SNAKE PLAIN COME FRIDAY MORNING. THE AREA
GENERALLY BECOMES DRY FRIDAY AFTERNOON/SATURDAY. WITH RIDGING
OVERHEAD, LOW STRATUS AND FOG COULD BE IN PLAY LATE THIS COMING
WEEK WITH INVERTED CONDITIONS. SOME UNCERTAINTY REMAINS IN THE
MAGNITUDE OF THE BUILDING RIDGE AND HOW LONG IT'LL STICK AROUND.
HOWEVER, 63% OF GRAND ENSEMBLE MEMBERS FAVOR A UNSEASONABLY
STRONG RIDGE BUILDING OVERHEAD.
WITH BUILDING HEIGHTS OVERHEAD, TEMPERATURES WILL BE WELL ABOVE
NORMAL (10-15 DEGREES ABOVE) THROUGHOUT THE LONG-TERM. ONE
CAVEAT TO THIS LATE NEXT WEEK WOULD BE THE POTENTIAL FOR LOW
STRATUS DEVELOPMENT WITH INVERTED CONDITIONS. IF STRATUS
DEVELOPS IT COULD HELP BUMP DOWN DAYTIME HIGH TEMPS ACROSS THE
AREA, BUT THE SET-UP WOULD STILL FAVOR ABOVE NORMAL TEMPS. A
RESULT OF THE WARM TEMPS WILL BE SNOW LEVELS FLUCTUATING AROUND
THE 6.5-9 KFT MSL RANGE (LOWEST IN THE NORTHEAST), LIMITING ANY
ADDITIONAL SNOW ACCUMULATIONS THROUGHOUT THE WEEK TO ABOVE 6.5
KFT MSL.
BOI WATCHES/WARNINGS/ADVISORIES
ID...NONE.
OR...NONE.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
DISCUSSION...KA
AVIATION.....JM
SHORT TERM...DG
LONG TERM....NF
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