637
FXUS65 KBOI 060331
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
831 PM MST FRI DEC 5 2025
DISCUSSION
LIGHT SHOWERS ARE CONTINUING ACROSS THE AREA THIS
AFTERNOON, ASSOCIATED WITH THE PASSAGE OF AN UPPER-LEVEL
SHORTWAVE TO THE NORTHWEST. OVERALL, BOTH PRECIPITATION AND
SNOWFALL AMOUNTS HAVE BEEN LIGHT THIS EVENING AS TEMPERATURES
HAVE WARMED ABOVE FREEZING UP TO 5,500 FEET. IN AREAS ABOVE
6,000 FEET, 1 TO 2 INCHES OF SNOW HAVE BEEN OBSERVED THIS
EVENING. SHOWERS ARE EXPECTED TO DIMINISH FOR THE LOWER VALLEYS
THROUGH MIDNIGHT BUT WILL CONTINUE IN THE CENTRAL IDAHO
MOUNTAINS THROUGH AT LEAST SUNRISE. OVERNIGHT, WEST-
NORTHWESTERLY WINDS WILL HELP PREVENT WIDESPREAD FOG OR STRATUS
FROM DEVELOPING, THOUGH THERE REMAINS A LOW CHANCE (AROUND 20%)
FOR ITS FORMATION IN MORE SHELTERED MOUNTAIN VALLEY AREAS. HIGH
CLOUDS ARE FORECAST TO KEEP OVERNIGHT TEMPERATURES NEAR FREEZING
IN THE MOUNTAINS BELOW 5,500 FEET AND IN THE MID-30S ACROSS THE
LOWER VALLEYS. THE CURRENT FORECAST IS HANDLING THESE
CONDITIONS WELL, AND NO SIGNIFICANT UPDATES ARE REQUIRED AT THIS
TIME.
AVIATION
PRECIPITATION DIMINISHING TONIGHT, EXCEPT SOME SNOW/RAIN
MIX AND POSSIBLE FREEZING RAIN OVER WEST-CENTRAL ID MOUNTAINS (NEAR
KMYL) THROUGH SATURDAY MORNING. MVFR/IFR CEILINGS EXPECTED TO
CONTINUE OVER MOST AREAS OVERNIGHT AND LIFTING BY SATURDAY EARLY
MORNING. STRONG LLWS 30-45 KT THROUGH SATURDAY MORNING, EXPECTED TO
SUBSIDE BY EARLY AFTERNOON. SNOW LEVELS BECOMING 4-5.5 KFT MSL
OVERNIGHT. SURFACE WINDS: MOSTLY VARIABLE UNDER 10 KTS, EXCEPT NEAR
KJER/KTWF WITH NW 10-20 KT GUSTING UP TO 35 KT, AND SE OR WITH W/SW
15-20 KT GUSTING TO 30 KT. WINDS AT 10KFT MSL: W/NW 30-55 KT.
KBOI...LIGHT RAIN SHOWERS ENDING AT AROUND 05Z. VFR/MVFR CEILINGS
LINGERING OVERNIGHT, WITH A 30% CHANCE OF LIFR INTO EARLY SATURDAY
MORNING. LLWS THREAT PERSISTING UNTIL SATURDAY AFTERNOON. SURFACE
WINDS: LIGHT AND VARIABLE, BECOMING W-NW 10-14 OVERNIGHT.
SUNDAY OUTLOOK...LIGHT SNOW SHOWERS OVER HIGHER TERRAIN THROUGH
EARLY HOURS SUNDAY, THEN MORE WIDESPREAD PRECIPITATION (RAIN IN
LOWER ELEVATIONS AND SNOW IN MOUNTAINS) THROUGH AFTERNOON/EVENING.
PATCHY FOG EXPECTED IN MOUNTAIN VALLEYS DURING MORNING HOURS. SNOW
LEVELS EXPECTED TO INCREASE FROM THE 4000-5000 FT RANGE TO THE 6000
FT RANGE LATER IN THE DAY. WINDS SE-SW 5-10 KT.
PREV DISCUSSION
SHORT TERM...TONIGHT THROUGH SUNDAY NIGHT...AN ATMOSPHERIC
RIVER IN THE PACIFIC IS BRINGING ANOMOUSLY HIGH MOISTURE TO THE
AREA THIS AFTERNOON AND EVENING, AND WILL CONTINUE TO DRIVE THE
FORECAST THROUGH THE SHORT TERM. THIS AFTERNOON AND TONIGHT SNOW
LEVELS HAVE RISING TO 5-6 KFT MSL IN CENTRAL IDAHO AND 7-8 KFT
MSL IN SW IDAHO AND SE OREGON. WHILE THIS WILL BRING 4-8 EXTRA
INCHES OF SNOW TO MOUNTAINS AND HIGH PASSES, MOST MOUNTAIN TOWNS
IN IDAHO WILL BE WITHIN 800 FT OF THE SNOW LEVEL. THOSE JUST
ABOVE THE SNOW LEVEL COULD SEE 1-2 INCHES OF WET SNOW, COMPARED
TO 0.3-0.6 INCHES OF RAINFALL BELOW THE SNOW LEVEL. LOWER
ELEVATIONS AND LOW LANDS WELL BELOW THE SNOW LEVEL, ESPECIALLY
SE OREGON AND SW IDAHO WILL SEE 0.1-0.4 INCHES OF RAIN THROUGH
THIS EVENING. VISIBILITIES WILL BE REDUCED WITHIN PRECIPITATION
AS CLOUDS STAY LOW AND PRECIP RATES BECOME MODERATE. THE RISING
SNOW LEVELS AND WETTER SNOW WILL HELP TO IMPROVE ROAD
CONDITIONS AT THE TAIL END OF THE PRECIPITATION, SO THE WINTER
WEATHER ADVISORY WILL BE ALLOWED TO END AT THE SCHEDULED TIME
AROUND MIDNIGHT.
THIS EVENING THROUGH SATURDAY, IN HIGHLANDS, RIDGES, AND OPEN
AREAS GUST TO 25-40 MPH AS PRECIPITATION CLEARS OUT. THIS IS
DRIVEN BY VERY STRONG WINDS ALOFT OF 50-70 MPH AROUND 700 MB. A
SIGNIFICANT 130 MPH FLOW IS EXPECTED NEAR THE TROPOPAUSE. THE
FLOW REMAINS SOMEWHAT MOIST, ALLOWING A PERSISTENT 50-70% CHANCE
OF PRECIPITATION IN CENTRAL IDAHO MOUNTAINS THROUGH THE WEEKEND.
EXTRA SNOW ACCUMULATION OF 1-3 INCHES IS POSSIBLE ABOVE 4.5 KFT
MSL. A FEW CAMS SHOW FREEZING RAIN IN THESE SHOWERS, THOUGH THE
WINDS ON SATURDAY WILL HELP MIX THE ATMOSPHERE REDUCING THE RISK
TO LESS THAN A 10% CHANCE. ON SUNDAY THE FLOW BRIEFLY SOURCES
FROM THE NORTH, DROPPING SNOW LEVELS TO 4-5 KFT MSL. TEMPS ON
SUNDAY DROP A FEW DEGREES FROM SATURDAY. THIS BRIEF FLOW SWITCH
ALSO BRINGS ANOTHER POCKET OF MOISTURE RAISING PRECIP CHANCES IN
LOWER ELEVATIONS TO 40% AND HIGHER ELEVATIONS TO 80% SUNDAY
NIGHT.
LONG TERM...MONDAY THROUGH FRIDAY...FORECASTED TO BE MUCH OF THE
SAME FROM THE SHORT TERM. THE UPPER-LEVEL RIDGE IS STILL CEMENTED IN
THE EASTERN PACIFIC, WITH MOISTURE RIDING OVERTOP. HIGHER POPS (60-
90%) ARE MOSTLY LIMITED TO OUR NORTHERN ZONES, WITH LOWER CHANCES
(20-50%) FOR LOWER ELEVATIONS. BEGINNING THURSDAY, THE UPPER-LEVEL
RIDGE AXIS LOOKS TO BUILD FURTHER NORTH/NORTHWEST, BRINGING HIGHER
HEIGHTS OVERHEAD AND PUSHING THE MOISTURE FLUX FURTHER NORTH.
CURRENT LONG RANGE MODELS DISAGREE TO WHAT EXTENT THE MOISTURE MAY
STILL EXIST ALONG THE NORTHERN HIGHER ELEVATION ZONES, THUS THEY
RETAIN 20-40% POPS THURSDAY. THERE IS GOOD AGREEMENT THAT BY
AFTERNOON INTO EVENING FRIDAY, OUR NORTHERN MOUNTAIN ZONES WILL
FINALLY RECEIVE SOME RESPITE.
WITH THE UNSEASONABLE, STRONG UPPER-LEVEL RIDGE IN THE EASTERN
PACIFIC, WELL ABOVE AVERAGE TEMPERATURES (10-15 DEGREES) ARE
EXPECTED DURING THE LONG TERM. A CONSEQUENCE OF THE ABOVE AVERAGE
TEMPS WILL BE HIGHER SNOW LEVELS. SNOW LEVELS WILL FLUCTUATE WITH
EACH PASSING SHORTWAVE, BUT GENERALLY STAY IN THE 6.5-8KFT RANGE
(HIGHEST IN SE OR, LOWEST IN CENTRAL ID). THIS LIMITS ANY ADDITIONAL
SNOW ACCUMULATIONS THROUGHOUT THE LONG TERM TO BE ABOVE 6.5KFT, WITH
LOCATIONS BELOW THAT ELEVATION GENERALLY JUST SEEING RAIN.
BOI WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING
IDZ011-013.
OR...NONE.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
DISCUSSION...JDS
AVIATION.....JY
SHORT TERM...JM
LONG TERM....CH
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