150
FXUS65 KBOI 180354
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
854 PM MST SAT JAN 17 2026
DISCUSSION
AN EXTENSIVE AREA OF LOW CLOUDS AND PATCHY FOG
EXTENDS ACROSS LOWER ELEVATIONS FROM BAKER COUNTY OR SOUTHEAST
THROUGH THE SNAKE BASIN, AND IS ADVANCING INTO THE MAGIC VALLEY
THIS EVENING. STABLE CONDITIONS UNDER A TEMPERATURE INVERSION
WILL KEEP THESE CONDITIONS IN PLACE TONIGHT, WITH FOG BECOMING
MORE COMMON AS TEMPERATURES COOL AND WINDS REMAIN LIGHT. FOG IS
MOST LIKELY TO DEVELOP IN THE MAGIC VALLEY AND IN THE FOOTHILLS
WHERE THE LOW CLOUDS INTERSECT THE GROUND. LITTLE DAY-TO-DAY
CHANGE IS EXPECTED OVER THE NEXT SEVERAL DAYS AS HIGH PRESSURE
REMAINS OVERHEAD. NO UPDATES THIS EVENING.
AVIATION
FOR VALLEYS AND LOW BASINS, AREAS OF MVFR-LIFR FROM
LOW STRATUS AND FOG THROUGH SUNDAY MORNING. FOG LIFTING TO
STRATUS FOR MOST BY SUNDAY AFTERNOON. MOUNTAIN OBSCURATION BELOW
APPROX 5000FT MSL, WHILE HIGHER ELEVATIONS REMAIN CLEAR.
SURFACE WINDS: VARIABLE LESS THAN 8 KT. WINDS ALOFT AT 10KFT
MSL: TRANSITIONING FROM W TO NW- N OVERNIGHT, 10-25 KT.
KBOI...GENERALLY MVFR/IFR IN PERSISTENT LOW STRATUS. BEST
CHANCE FOR LIFR CEILINGS WITH REDUCED VISIBILITY BETWEEN
SUN/08Z-17Z. SURFACE WINDS: VARIABLE UP TO 5 KT.
AIR STAGNATION
THE INVERSION AND STAGNANT AIR IS EXPECTED TO
LAST THROUGH THURSDAY. THIS MEANS MIXING HEIGHTS OF LESS THAN
2KFT MSL, LIGHT WINDS, AND REDUCED AIR QUALITY. VALLEY
LOCATIONS THAT HAVE SET UP UNDER FOG/CLOUDS WILL LIKELY KEEP
THESE CONDITIONS THROUGH THE TUE-THUR TIME PERIOD (SOME DAYTIME
EROSION AND THUS GLIMPSES OF THE SUN ARE POSSIBLE).
PREV DISCUSSION
SHORT TERM...TONIGHT THROUGH MONDAY NIGHT...THE PATTERN REMAINS
DRY AND STABLE AS AN UPPER RIDGE REMAINS OVER THE REGION,
BLOCKING THE STORM TRACK. THE RIDGE IS SLOWLY MOVING DIRECTLY
OVERHEAD BRINGING WARMER AIR AND STRENGTHENING THE INVERSION.
THIS WILL BRING CONTINUED FOG, LOW CLOUDS, COLDER TEMPS, AND
REDUCED AIR QUALITY FOR LOWER ELEVATIONS. HIGHER TERRAIN WILL
SEE TEMPS AT OR ABOVE NORMAL WITH CLEAR SKIES. FOG HAS MOSTLY
LIFTED TO STRATUS TODAY, AND WILL LIKELY REPEAT THIS PATTERN IN
THE FOLLOWING AFTERNOONS WITH SOME BRIEF CLEARING POSSIBLE.
OVERNIGHT, STRATUS WILL SETTLE AND DENSE FOG WILL REDEVELOP EACH
MORNING. ALTHOUGH, THE SOUTHEAST WINDS WE SAW TODAY SHOULD HAVE
DISSIPATED MORE OF THE STRATUS DECK THAN IT DID, WHICH BRINGS
SOME CONCERN FOR IF THE CLOUDS WILL SHOW ANY CLEARING IN THE
FOLLOWING DAYS WHERE SOUTHEAST WINDS ARE NOT FORECAST.
LONG TERM...TUESDAY THROUGH SATURDAY...THE RIDGE REMAINS
OVERHEAD WITH NORTHWESTERLY FLOW THROUGH THURSDAY MORNING. THIS
PERIOD WILL SEE CONTINUED LOW ELEVATION STAGNANT AIR, FOG,
COLDER TEMPERATURES, AND REDUCED AIR QUALITY AS THE INVERSION
BREATHES WHAT ARE HOPEFULLY ITS FINAL BREATHES. THURSDAY AND
ESPECIALLY FRIDAY THE PATTERN BEGINS TO CHANGE SIGNIFICANTLY AS
A DEEP HUDSON BAY LOW BRINGS ARCTIC AIR OVER MUCH OF THE US, AND
WE MOVE INTO IT'S WESTERN INFLUENCE. THIS PATTERN CHANGE WILL
OPEN THE DOOR FOR SHORTWAVES AND MOISTURE TO FINALLY BRING SOME
PRECIPITATION AND MIXING TO THE STAGNANT AND DRY CONDITIONS.
RIGHT NOW THIS FORECAST HINGES ON A SHORTWAVE AND THE POSITION
OF THE LOW, WHICH HAVE YET TO BE SOLIDIFIED AMONGST MODELS.
ENSEMBLE CLUSTERS STILL SHOW SOME POTENTIAL FOR THE
LOW'S INFLUENCE TO MISS US. HOWEVER, THE STRENGTH OF THE LOW
SHOULD AT LEAST BRING WINDS TO HELP MIX OUT THE INVERSION OR
WEAKEN IT EVEN IF THE PRECIP MISSES US.
BOI WATCHES/WARNINGS/ADVISORIES
ID...AIR STAGNATION ADVISORY UNTIL 11 AM MST THURSDAY
IDZ011>014-016-028-033.
OR...AIR STAGNATION ADVISORY UNTIL 11 AM MST /10 AM PST/ THURSDAY
ORZ061>064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
DISCUSSION...ST
AVIATION.....SH
AIR STAGNATION...JM
SHORT TERM...JM
LONG TERM....JM
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