114
FXUS65 KBOI 282126
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
226 PM MST SUN DEC 28 2025
SHORT TERM...TONIGHT 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
FAR WESTERN IDAHO WHERE THE INVERSION WILL BE STRONGEST. HIGHS
BY WEDNESDAY WILL BE 5-10 DEGREES ABOVE NORMAL IN MOST AREAS,
EXCEPT NEAR NORMAL IN THE LOWER TREASURE VALLEY DUE TO THE
INVERSION. OVERNIGHT LOWS WILL BE COLD (10S AND 20S) WITH MOSTLY
CLEAR SKIES AND A COOL AIRMASS IN PLACE. THIS WILL ALSO ALLOW
PATCHY VALLEY FOG TO DEVELOP, ALTHOUGH DRY AIR WILL LIMIT
POTENTIAL. WINDS WILL REMAIN LIGHT UNDER THIS PATTERN.
LONG TERM...THURSDAY THROUGH SUNDAY
A MUCH MORE ACTIVE
PATTERN WILL REDEVELOP DURING THE EXTENDED. 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/SNOW CHANCES WILL INCREASE FROM
THE SOUTH ON NEW YEAR'S DAY, REACHING 40-70% THURSDAY NIGHT AND
FRIDAY. THIS MOIST AIRMASS, DUE TO ITS ORIGIN IN THE
SUBTROPICS, WILL BE MILD AND SNOW LEVELS WILL RISE 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 30-50% CHANCE OF RAIN AND HIGH ELEVATION SNOW. THESE
IMPULSES SHOULD GRADUALLY BRING COOLER AIR ALOFT INTO OUR AREA
WITH SNOW LEVELS LOWERING TO 3500-5500 FEET. MODERATE
PRECIPITATION TOTALS ARE EXPECTED THURSDAY THROUGH SUNDAY WITH
SIGNIFICANT SNOW ACCUMULATIONS LIMITED TO HIGHER PEAKS. WINDS
WILL MOSTLY BE LIGHT, BUT COULD TICK UP OVER THE WEEKEND AS THE
SHORTWAVES MOVE THROUGH. TEMPERATURES THROUGH THE PERIOD WILL
AVERAGE 5-10 DEGREES ABOVE NORMAL.
AVIATION
MAINLY VFR. PATCHY FOG DEVELOPING OVERNIGHT IN
MOUNTAIN VALLEYS. SURFACE WINDS: VARIABLE LESS THAN 10 KT.
WINDS ALOFT AT 10KFT MSL: N-NE 5-15 KT, BECOMING NW 10-20 KT
AFTER MON/06Z.
KBOI...VFR. SURFACE WINDS NW LESS THAN 10 KT THIS AFTERNOON,
BECOMING SE BY MID EVENING.
AIR STAGNATION
AN UPPER LEVEL RIDGE WILL BUILD OVER THE
REGION MONDAY 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.
CONDITIONS MAY IMPROVE LATE THURSDAY OR FRIDAY AS AN APPROACHING
PACIFIC SYSTEM BRINGS PRECIPITATION AND INCREASES MIXING.
BOI WATCHES/WARNINGS/ADVISORIES
ID...AIR STAGNATION ADVISORY FROM 6 PM THIS EVENING TO 10 AM MST
THURSDAY IDZ012-014-016-028-033.
OR...AIR STAGNATION ADVISORY FROM 6 PM MST /5 PM PST/ THIS EVENING
TO 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
SHORT TERM...ST
LONG TERM....ST
AVIATION.....ST
AIR STAGNATION...ST
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