723
FXUS65 KBOI 192121
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
221 PM MST THU DEC 19 2024
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.
AVIATION
GENERALLY VFR. PATCHY IFR/LIFR FOG RETURNING TONIGHT IN
BASINS AND VALLEYS AT/NEAR KBNO, KONO, KEUL, AND KMYL. SURFACE
WINDS: VARIABLE LESS THAN 10 KT. WINDS ALOFT AT 10KFT MSL: W TO SW
10-25 KT.
KBOI...VFR. BASED ON FOG DEVELOPMENT THIS MORNING, THERE IS A 60%
CHANCE OF FOG AT KBOI BEGINNING LATE TONIGHT LASTING THROUGH
AT LEAST 16Z. SURFACE WINDS: SE UP TO 10 KT BECOMING LIGHT.
WEEKEND OUTLOOK...AREAS OF VALLEY FOG FRIDAY MORNING, OTHERWISE VFR.
PRECIPITATION SPREADING FROM WEST TO EAST BY SATURDAY AFTERNOON
THROUGH EARLY SUNDAY, THEN RETURNING AGAIN SUNDAY NIGHT. MVFR TO
LIFR IN PRECIPITATION EXPECTED, WITH SNOW LEVELS ROUGHLY 3500-5000
FT MSL DURING PRECIP. MOUNTAINS OBSCURED. SURFACE WINDS: GENERALLY
SW-SE 5-15 KT EACH DAY. LOW LEVEL WIND SHEAR POSSIBLE SAT NIGHT.
BOI WATCHES/WARNINGS/ADVISORIES
ID...DENSE FOG ADVISORY FROM 11 PM THIS EVENING TO 11 AM MST FRIDAY
IDZ011-012-033.
OR...DENSE FOG ADVISORY FROM 11 PM MST /10 PM PST/ THIS EVENING TO
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
SHORT TERM...SA
LONG TERM....JDS
AVIATION.....JDS
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