715
FXUS65 KBOI 291622
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
922 AM MST MON DEC 29 2025
DISCUSSION
SEEING THIN HIGH CLOUDS OVER THE AREA THIS
MORNING, MOVING FROM NORTH TO SOUTH AS WE REMAIN ON THE EAST
SIDE OF AN UPPER RIDGE. WEBCAMS ARE SHOWING A FEW SPOTS OF LOWER
CLOUDS IN THE LONG VALLEY NEAR CASCADE, BUT OTHERWISE NOT SEEING
MUCH FOG/STRATUS THIS MORNING. THE INVERSION WILL STRENGTHEN
TODAY WITH WARMING ALOFT ACCOMPANYING THE BUILDING UPPER RIDGE.
LOWEST ELEVATIONS OF THE SNAKE PLAIN WILL SEE LITTLE CHANGE IN
HIGH TEMPERATURES FROM YESTERDAY, WITH MORE NOTABLE WARMING IN
THE MOUNTAINS (4-8 DEGREES). FORECAST IS ON TRACK FOR TODAY AND
AIR STAGNATION ADVISORY REMAINS IN PLACE THROUGH THURSDAY.
AVIATION
VFR TODAY. PATCHY LOW CLOUD NEAR CASCADE (U70) AND
OTHER CENTRAL ID MTN VALLEYS THROUGH 18Z. SIMILAR DEVELOPMENT
EXPECTED AGAIN TONIGHT AFTER 10Z. SURFACE WINDS: E-SE 5-15 KT.
WINDS ALOFT AT 10KFT MSL: W 10-15 KT.
KBOI...VFR. SE SURFACE WINDS THROUGH THE DAY.
AIR STAGNATION
AN UPPER LEVEL RIDGE WILL BUILD OVER THE
REGION TODAY AND REMAIN OVERHEAD THROUGH WEDNESDAY. THIS PATTERN
WILL CREATE STAGNANT CONDITIONS IN THE VALLEYS WITH POOR MIXING
AND LIGHT WINDS AS A TEMPERATURE INVERSION STRENGTHENS. DAYTIME
MIXING HEIGHTS WILL BE BELOW 2000 FEET AGL THROUGH AT LEAST
THURSDAY. AN AIR STAGNATION ADVISORY IS IN EFFECT FOR MOST
VALLEY LOCATIONS THROUGH EARLY THURSDAY.
PREV DISCUSSION
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT...AN UPPER LEVEL
RIDGE BUILDING ALONG THE COAST WILL MOVE OVERHEAD MONDAY THROUGH
WEDNESDAY. THIS WILL BRING DRY AND STABLE CONDITIONS WITH A
TEMPERATURE INVERSION THAT STRENGTHENS THROUGH MIDWEEK.
TEMPERATURES WILL GRADUALLY WARM THROUGH WEDNESDAY, ESPECIALLY
AT HIGHER ELEVATIONS THAT ARE ABOVE THE INVERSION, BUT WILL SEE
LITTLE CHANGE IN THE LOWEST VALLEYS ACROSS SOUTHEAST OREGON AND
SOUTHWEST IDAHO WHERE THE INVERSION WILL BE STRONGEST. PATCHY
VALLEY FOG AND STRATUS IS POSSIBLE, ALTHOUGH DRY AIR WILL LIMIT
POTENTIAL. HIGHS BY WEDNESDAY WILL BE 5 TO 10 DEGREES ABOVE
NORMAL IN MOST AREAS, EXCEPT NEAR NORMAL IN THE LOWER TREASURE
VALLEY DUE TO THE INVERSION.
LONG TERM...THURSDAY THROUGH SUNDAY... A RETURN TO AN ACTIVE
PATTERN EXPECTED THROUGH THE EXTENDED PERIOD. A DEEP TROUGH OFF
THE COAST WILL HELP TO STEER A WEAKER TROUGH NEAR THE CALIFORNIA
COAST NORTHWARD. THIS WEAKER TROUGH WILL BE ACCOMPANIED BY
SUBTROPICAL MOISTURE, AND RAIN OR SNOW CHANCES WILL INCREASE
FROM THE SOUTH ON NEW YEARS DAY, REACHING 40 TO 70 PERCENT
THURSDAY NIGHT AND FRIDAY. GIVEN THE AIR MASSES ORIGINATING FROM
THE SUBTROPICS, CONDITIONS WILL BE MILDER WITH SNOW LEVELS
INCREASING TO 5000-6500 FEET (POSSIBLY AS HIGH AS 7500 FEET).
THE DEEP TROUGH OFF THE COAST WILL SEND SHORTWAVE IMPULSES
INLAND OVER THE WEEKEND, BRINGING A 30 TO 50 PERCENT CHANCE OF
RAIN AND HIGH ELEVATION SNOW. THESE WILL BRING COOLER AIR WITH
SNOW LEVELS GRADUALLY LOWERING TO 3500-5500 FEET BY SATURDAY.
MODERATE PRECIPITATION TOTALS ARE EXPECTED THURSDAY THROUGH
SUNDAY WITH SIGNIFICANT SNOW ACCUMULATIONS LIMITED TO HIGHER
PEAKS. TEMPERATURES THROUGH THE PERIOD WILL AVERAGE 5-10 DEGREES
ABOVE NORMAL.
BOI WATCHES/WARNINGS/ADVISORIES
ID...AIR STAGNATION ADVISORY UNTIL 10 AM MST THURSDAY
IDZ012-014-016-028-033.
OR...AIR STAGNATION ADVISORY UNTIL 10 AM MST /9 AM PST/ THURSDAY
ORZ061>064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
DISCUSSION...DG
AVIATION.....DG
AIR STAGNATION...JDS
SHORT TERM...JDS
LONG TERM....JDS
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