806
FXUS65 KBOI 171605
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
905 AM MST SAT JAN 17 2026
DISCUSSION
NO UPDATE TO THE FORECAST THIS MORNING. THE SNAKE
PLAIN REMAINS INUNDATED WITH FOG AND LOW STRATUS. SEEING A
TREND TOWARDS STRATUS AS SE WINDS CAUSE SOME SLIGHT DOWNSLOPING.
THIS TREND WILL CONTINUE AS WE ADD SOLAR HEATING TO THE MIX, THE
CLOUDS WILL PUSH TOWARDS ONTARIO, CLEARING FOR MOST OF THE SNAKE
PLAIN EAST OF MOUNTAIN HOME BY THIS AFTERNOON. THE UPPER
TREASURE VALLEY AND AREAS WEST OF MOUNTAIN HOME WILL SEE
CLEARING DURING THE AFTERNOON. HOWEVER, THE LOWER TREASURE
VALLEY IS LIKELY TO STAY FOGGED IN WITH PERSISTENT LOW CLOUDS.
THE CLEARING WON'T LAST LONG AS FOG AND LOW STRATUS REDEVELOPS
TONIGHT, WITH LIGHTER NORTHWEST WINDS BUILDING BACK IN. THE PUSH
TOWARDS ONTARIO MAY BRING SURFACE MOISTURE TO OTHER PARTS OF SE
OREGON, WITH A CHANCE FOR FOG TONIGHT AT ROME AND BURNS. HIGHER
TERRAIN WILL SEE FOG AND STRATUS MORE SPORADICALLY, BUT AS THE
RIDGE AXIS MOVES OVERHEAD SUNDAY AFTERNOON THE CHANCES INCREASE
IN THESE AREAS.
AVIATION
IFR-VLIFR IN THE SNAKE PLAIN EXPECTED TO IMPROVE TO
MVFR-VFR THIS AFTERNOON, WITH THE GREATEST CHANCE EAST OF KMUO.
SOUTHEAST WIND WILL PUSH THE FOG TOWARDS KONO, LEADING TO
EVENTUAL IMPROVEMENT IN THE UPPER TREASURE VALLEY. IFR CONTINUES
AT KONO THROUGH THE DAY WITH STRATUS BEFORE FOG/LOW STRATUS
REDEVELOPS TONIGHT. MTNS AND HIGH LANDS REMAIN MOSTLY CLEAR. SURFACE
WINDS: VARIABLE LESS THAN 8 KT. WINDS ALOFT AT 10KFT MSL:
VARIABLE 5-15 KT.
KBOI...IFR-LIFR IN STRATUS. CONDITIONS WILL IMPROVE TO MVFR
18-20Z AS STRATUS LIFTS/CLEARS. LIFR CONDITIONS RETURN WITH
FOG/LOW STRATUS 03-05Z TONIGHT AND COULD REMAIN IN PLACE WELL
INTO SUNDAY. SE WINDS BECOME LIGHT AND VARIABLE THIS AFTERNOON.
SUNDAY OUTLOOK...SNAKE PLAIN WILL REMAIN IFR WELL INTO THE DAY
SUNDAY WITH SOME IMPROVEMENT POSSIBLE IN THE TWF/JER AREA.
POSSIBLE INCREASE IN FOG/STRATUS AND IFR IN BASINS OF SE OREGON
TO INCLUDE THE KBNO TERMINAL. LIGHT SURFACE WINDS AND NW WINDS
ALOFT.
AIR STAGNATION
NO CHANGE TO THE FORECAST HERE. WE'RE IN THE
INVERSION/STAGNANT AIR MASS THROUGH AT LEAST TUESDAY AND
POSSIBLY THROUGH THURSDAY. THIS MEANS MIXING HEIGHTS OF LESS
THAN 2KFT MSL AND LIGHT WINDS. VALLEY LOCATIONS THAT HAVE SETUP
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). REDUCED AIR QUALITY IS POSSIBLE IN THE
STAGNANT AIR.
PREV DISCUSSION
SHORT TERM...TODAY THROUGH MONDAY NIGHT...OVERALL THERE IS NO
CHANGE TO THE DRY AND STABLE PATTERN THROUGH THE PERIOD AS AN
UPPER RIDGE AXIS REMAINS POSITIONED OFF THE WEST COAST. THE
WEEKEND WILL SEE THE RIDGE EXPAND EASTWARD BRINGING WARMER AIR
ALOFT WHICH WILL STRENGTHEN THE TEMPERATURE INVERSION OVER THE
REGION. MONDAY WILL BRING SLIGHT COOLING ALOFT IN RESPONSE TO A
PASSING TROUGH WELL EAST OF THE AREA. HIGHER TERRAIN OF SE
OREGON AND MOUNTAINS OF SW IDAHO WILL SEE TEMPERATURES AT OR
ABOVE NORMAL UNDER MOSTLY CLEAR SKIES.
IN THE SNAKE PLAIN THE INVERSION HAS ENTERED ITS STRATUS PHASE
WITH MOST LOCATIONS NO LONGER SEEING DENSE FOG. FOR TODAY, A
RETURN OF EASTERLY WINDS WILL ERODE THE CLOUD COVER BACK TO
AROUND THE CANYON/ADA COUNTY LINE BY LATE AFTERNOON WHILE LIKELY
EXPANDING CLOUD COVER FURTHER INTO BASINS OF MALHEUR AND HARNEY
COUNTIES. TO SOME DEGREE, WE'LL SEE A REPEAT OF THIS EBB AND
FLOW SUNDAY AND MONDAY, THOUGH WE DO LOSE THE EASTERLY WINDS ON
SUNDAY WHICH WOULD LIKELY REDUCE THE EXTENT OF DAYTIME EROSION.
TEMPERATURES IN LOWER VALLEYS WILL REMAIN AT OR BELOW NORMAL
WITH A NOTABLE GRADIENT BETWEEN THE AFTERNOON STRATUS/SUN LINE.
LONG TERM...TUESDAY THROUGH SATURDAY...WE REMAIN UNDER A RIDGE
OR WEAK NORTHWESTERLY FLOW THROUGH THURSDAY. HEADING INTO NEXT
WEEKEND WE'RE LOOKING AT A SHORTWAVE TROUGH DROPPING OUT OF
CANADA ALONG THE WESTERN EDGE OF THE POLAR VORTEX THAT HAS SO
FAR SPENT ITS WINTER OVER HUDSON BAY AND AREAS EAST OF THE
C-DIVIDE. TONIGHT'S MODEL RUNS BRING BETTER AGREEMENT ON THE
EVOLUTION OF THE PATTERN FOR FRI/SAT WITH THE UPPER TROUGH
BRINGING LIGHT PRECIPITATION TO E-CENTRAL OREGON AND THE
W-CENTRAL IDAHO MTNS. THE DETERMINISTIC SOLUTIONS ARE WETTER
ACROSS THESE AREAS. THE ENSEMBLE MEAN IS LAGGING IN THIS
FORECAST SHIFT, BUT DOES PAINT THE MOUNTAINS WITH A 30-40%
CHANCE OF 2+ INCHES OF SNOW BY SATURDAY. ITS NOT A LOT, BUT ITS
SOMETHING AND THE RECENT TREND IS POSITIVE.
BOI WATCHES/WARNINGS/ADVISORIES
ID...AIR STAGNATION ADVISORY UNTIL 5 PM MST TUESDAY
IDZ011>014-016-028-033.
OR...AIR STAGNATION ADVISORY UNTIL 5 PM MST /4 PM PST/ TUESDAY
ORZ061>064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
DISCUSSION...JM
AVIATION.....JM
AIR STAGNATION...JM
SHORT TERM...DG
LONG TERM....DG
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page