462
FXUS65 KBOI 191049
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
349 AM MST MON JAN 19 2026
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT
OVERNIGHT
SATELLITE IMAGERY SHOWING THE INLAND NW BLANKETED IN LOW
CLOUDS/FOG. WEBCAMS AND OBSERVATIONS REVEALING THE DENSE FOG IN
THE WESTERN MAGIC VALLEY IS STARTING TO LIFT INTO A LOW
OVERCAST SO WILL SEE IF TREND HOLDS IN REGARDS TO KEEPING THE
DENSE FOG ADV. HIGH-RES MODELS SHOW A FAIR AMOUNT OF
MIXING/EROSION EAST/SOUTH OF MOUNTAIN HOME-GLENNS FERRY TODAY AS
DRIER AIR WORKS IN ALOFT. FOR NOW HAVE LEANED ON PERSISTENCE
GIVEN THE EXTENTS OF STRATUS IN THE SNAKE PLAIN BUT THERE IS A
CHANCE THAT THESE AREAS BREAK INTO THE SUN. HAVE COUPLED THE
TEMPERATURE FORECAST WITH THE EXPECTED CLOUD COVER SO CERTAINLY
COULD BE WARMER IF THESE AREAS BREAK OUT INTO THE SUN. OTHERWISE
KEPT EXTENSIVE VALLEY CLOUD COVER IN THE FORECAST THROUGH
TUESDAY, WITH SOME IMPROVEMENT STARTING ON WEDNESDAY. BELIEVE
THE CORE OF IT (TREASURE VALLEY) COULD REMAIN INTACT BEYOND
THAT TIME. BY WEDNESDAY MORNING THE LOWER TREASURE VALLEY
(ONTARIO AREA) WOULD BE AT 7 DAYS OF CONTINUOUS LOW CLOUD/FOG
WHICH IF IT HOLDS WOULD BE ONE OF THE LONGER EVENTS ON RECORD
(THE ~12 STRAIGHT DAYS AT THE END OF JANUARY 2014 IS THE
LONGEST OR SECOND LONGEST ON RECORD FOR ONTARIO, CALDWELL AND
BOISE). MOUNTAINS STAY IN THE SUN AND RELATIVELY WARMER
TEMPERATURES THROUGH WED.
LONG TERM...THURSDAY THROUGH MONDAY
THE UPPER RIDGING WILL
GIVE SOME GROUND LATE IN THE WEEK AS A SHORT WAVE TROUGH AND
ACCOMPANYING COLD FRONT SWING THROUGH THE PAC NW. OVERALL THE
MODELS HAVE SHIFTED EAST WITH THE EXTENT OF COLD AIR AND
PRECIPITATION CHANCES LATE IN THE PERIOD (A COMMON THEME THIS
WINTER). FOR NOW IT STILL LOOKS TO GET COLD ENOUGH ALOFT TO AT
LEAST BRIEFLY BREAK THE INVERSION (FRI/SAT) BEFORE THE POTENTIAL
RETURN OF UPPER RIDGING. THE CHANCE FOR SNOW HAS RETRACTED TO
AROUND 20% THROUGH SATURDAY IN THE E-CENTRAL OREGON AND
W-CENTRAL ID MTNS AND NO MORE THAN 30% THROUGH MONDAY. THE SNAKE
PLAIN AND SE OREGON ARE LIKELY TO REMAIN DRY THROUGH THE
WEEKEND, THOUGH WARMER THAN RECENT DAYS.
AVIATION
WIDESPREAD IFR/LIFR BELOW 5000FT MSL ACROSS SE
OREGON AND SW IDAHO. MOUNTAIN OBSCURATION BELOW APPROX 5000FT
MSL, WHILE HIGHER ELEVATIONS REMAIN CLEAR. SURFACE WINDS:
VARIABLE LESS THAN 6 KT. WINDS ALOFT AT 10KFT MSL: N-NW 5-15
KT.
KBOI...IFR/LIFR IN PERSISTENT LOW STRATUS ALONG WITH VISIBILITY
RESTRICTIONS AT TIMES DUE TO MIST. BEST CHANCE FOR LIFR
CEILINGS WITH REDUCED VISIBILITY THROUGH 17Z MONDAY LIKELY
LIFTING TO MVFR AFTER 18Z. SURFACE WINDS: VARIABLE UP TO 5 KT.
AIR STAGNATION
HIGH PRESSURE AND STAGNANT CONDITIONS ARE IN
PLACE OVER THE REGION THROUGH THURSDAY. THE LIMITED MIXING AND
LIGHT WINDS WILL TRAP POLLUTANTS NEAR THE SURFACE AND KEEP LOWER
VALLEYS IN FOG/CLOUDS. COLDER AIR ON FRIDAY LOOKS LIKE BEST
CHANCE TO BREAK THE TEMPERATURE INVERSION BEFORE A POSSIBLE
RETURN OF STAGNANT CONDITIONS NEXT WEEKEND.
BOI WATCHES/WARNINGS/ADVISORIES
ID...AIR STAGNATION ADVISORY UNTIL 11 AM MST THURSDAY
IDZ011>014-016-028-033.
DENSE FOG ADVISORY UNTIL 11 AM MST THIS MORNING IDZ016.
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
SHORT TERM...DG
LONG TERM....DG
AVIATION.....DG
AIR STAGNATION...DG
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