870
FXUS65 KBOI 200338
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
838 PM MST THU DEC 19 2024
DISCUSSION
HIGH PRESSURE CONTINUES TO DOMINATE, WITH INVERTED
CONDITIONS IN VALLEYS. LOWER ELEVATIONS WILL BE COLDER AND
FOGGY DUE TO THE INVERSION, WHILE HIGHER ELEVATIONS WILL BE
MOSTLY CLEAR WITH ABOVE NORMAL TEMPS. DENSE FOG HAS FORMED IN
PORTIONS OF THE LOWER TREASURE VALLEY, BASINS IN SE OREGON, AND
MOUNTAIN VALLEYS IN THE CENTRAL MOUNTAINS, SO THE DENSE FOG
ADVISORY WILL REMAIN. A TROUGH ON SATURDAY IS ON TRACK TO MIX
THINGS UP, NO UPDATES TO THE PREVIOUS FORECAST.
AVIATION
PATCHY IFR/LIFR FOG HAS RETURNED TONIGHT IN BASINS
AND VALLEYS AT/NEAR KBNO, KONO, KEUL, AND KMYL. HIGH CLOUDS
WILL INHIBIT FORMATION SOMEWHAT, KEEPING FOG PATCHY. SURFACE
WINDS: VARIABLE LESS THAN 10 KT, EXCEPT EASTERLY 15-25 KT NEAR
KJER. WINDS ALOFT AT 10KFT MSL: W-SW 15-25 KT.
KBOI...GENERALLY VFR. WE MAY STAY TOO DRY WITH DECENT HIGH
CLOUD COVER FOR FOG TO BE FAVORED, THOUGH WITH FOG STILL
EXPECTED TO FORM IN THE AREA A TEMPO GROUP REMAINS IN THE TAF.
SURFACE WINDS: SE UP TO 8 KT BECOMING LIGHT AND VARIABLE
TOMORROW.
WEEKEND OUTLOOK...VALLEY RAIN AND MOUNTAIN SNOW MOVING WEST TO
EAST SATURDAY AFTERNOON THROUGH EARLY SUNDAY AND RETURNING
SUNDAY NIGHT. MVFR TO LIFR IN PRECIPITATION AND SNOW LEVELS
AROUND 3500-5000 FT MSL DURING PRECIP. MOUNTAINS OBSCURED.
SURFACE WINDS: GENERALLY SW-SE 5-15 KT EACH DAY. LOW LEVEL WIND
SHEAR POSSIBLE SATURDAY.
PREV DISCUSSION
SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT...THE RIDGE WILL
CONTINUE TO BUILD OVER THE REGION TODAY THROUGH SATURDAY MORNING,
BRINGING INVERTED CONDITIONS TO THE VALLEYS. LOWER ELEVATION VALLEYS
WILL BE COLD AND FOGGY WHILE HIGHER ELEVATIONS WILL SEE MOSTLY CLEAR
CONDITIONS WITH ABOVE NORMAL TEMPERATURES THROUGH EARLY SATURDAY.
DENSE FOG WILL FORM IN LOCALIZED VALLEYS TONIGHT, CAUSING VISIBILITY
HAZARDS TO MOTORISTS. THEREFORE, A DENSE FOG ADVISORY HAS BEEN
ISSUED FOR THE LOWER TREASURE VALLEY, WEST CENTRAL MOUNTAINS, UPPER
WEISER BASIN, HARNEY AND MALHEUR COUNTIES FOR TONIGHT INTO TOMORROW
MORNING.
A SHORTWAVE TROUGH WILL MOVE INTO THE PACIFIC NORTHWEST ON SATURDAY
AFTERNOON BRINGING MOUNTAIN SNOW AND LIGHT VALLEY RAIN TO THE
REGION. SNOW LEVELS LOOK TO BE AROUND 5000-6000 FEET, ALTHOUGH
LINGERING COLD POOLS IN THE VALLEYS COULD ALLOW FOR POCKETS OF SNOW
LEVELS AROUND 3000-4000 FEET ON SATURDAY NIGHT. SNOW ACCUMULATIONS
WILL BE LIGHT, WITH LESS THAN AN INCH IN MOST POPULATION CENTERS IN
THE MOUNTAINS. THE HIGH SUMMITS WILL SEE ANYWHERE FROM 2-4 INCHES OF
SNOW, WITH LESS THAN A TENTH OF AN INCH OF RAIN LIKELY IN THE
VALLEYS. THE MAGIC VALLEY AND IDAHO- NEVADA BORDER WILL LIKELY
REMAIN DRY THROUGH THE SHORT TERM PERIOD.
LONG TERM...SUNDAY THROUGH THURSDAY...ACTIVE WEATHER IS EXPECTED
THROUGHOUT THE EXTENDED FORECAST PERIOD AS A SERIES OF TROUGHS MOVE
THROUGH THE REGION. THE TIMING OF THESE SYSTEMS REMAINS CONSISTENT,
WITH THE FIRST TROUGH ARRIVING LATE SUNDAY INTO MONDAY, THE SECOND
FROM TUESDAY INTO EARLY WEDNESDAY, AND ANOTHER ON THURSDAY. EACH
TROUGH BRINGS A HIGH LIKELIHOOD OF PRECIPITATION, WITH PROBABILITIES
RANGING BETWEEN 70% AND 90% FOR THE FORECAST AREA.
SNOW LEVELS ARE ANTICIPATED TO VARY BETWEEN 4500 AND 5500 FEET MSL
IN THE NORTHERN ZONES AND BETWEEN 4500 AND 7000 FEET MSL IN THE
SOUTHERN ZONES NEAR THE NEVADA BORDER DURING THE FIRST TWO TROUGHS.
VALLEY LOCATIONS COULD SEE OVER A TENTH OF AN INCH OF RAIN FROM EACH
OF THESE SYSTEMS. A COLDER AIR MASS IS EXPECTED WITH THE WEDNESDAY
TROUGH, LOWERING SNOW LEVELS TO 3500 TO 4500 FEET MSL ACROSS THE
ENTIRE AREA.
A STRONGER SYSTEM, POSSIBLY AN ATMOSPHERIC RIVER (AR) EVENT, IS
PROJECTED FOR THURSDAY INTO THE WEEKEND, POTENTIALLY BRINGING
SIGNIFICANT PRECIPITATION TOTALS. SNOW LEVELS BETWEEN 3000 TO 4000
FEET MSL WOULD KEEP THE VALLEY AS ALL RAIN WHILE THE MOUNTAINS COULD
SEE SIGNIFICANT SNOWFALL. BREEZY WINDS ARE LIKELY BEFORE AND AFTER
THE PASSAGE OF EACH TROUGH AND ASSOCIATED COLD FRONT. TEMPERATURES
WILL RUN 4 TO 7 DEGREES ABOVE NORMAL THROUGHOUT THE PERIOD.
BOI WATCHES/WARNINGS/ADVISORIES
ID...DENSE FOG ADVISORY UNTIL 11 AM MST FRIDAY IDZ011-012-033.
OR...DENSE FOG ADVISORY UNTIL 11 AM MST /10 AM PST/ FRIDAY
ORZ061-063-064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.TWITTER.COM/NWSBOISE
DISCUSSION...JM
AVIATION.....JM
SHORT TERM...SA
LONG TERM....JDS
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