724
FXUS65 KBOI 161701
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
1001 AM MST FRI JAN 16 2026
DISCUSSION
EASTERLY TO SOUTHEASTERLY SURFACE WINDS HAVE
INCREASED THIS MORNING AS EXPECTED THROUGH THE SNAKE BASIN.
THIS HAS HELPED TO LIFT FOG INTO A LOW CLOUD DECK ACROSS MOST
LOWER ELEVATION SITES. FOG WILL TAKE LONGER TO ERODE IN THE
LOWER TREASURE VALLEY NEAR THE IDAHO/OREGON BORDER, AND
THEREFORE HAVE CONTINUED THE DENSE FOG ADVISORY IN THESE AREAS
WHILE CANCELING IT ELSEWHERE. HOWEVER, AREAS OF LOW CLOUDS WILL
PERSIST THROUGH THE AFTERNOON. WINDS WILL DECREASE THIS
EVENING, AND HI-RES MODELS SHOW HIGH POTENTIAL FOR FOG
REDEVELOPING TONIGHT ACROSS THE TREASURE AND MAGIC VALLEYS.
ANOTHER DENSE FOG ADVISORY MAY BE NEEDED, BUT WILL ASSESS THIS
FOR THE AFTERNOON PACKAGE.
AVIATION
WIDESPREAD IFR-VLIFR IN THE SNAKE PLAIN AND LOCAL
MTN VALLEYS THROUGH 18Z THIS MORNING. IMPROVEMENT TO VFR IS
EXPECTED THIS AFTERNOON, WITH LOCAL IFR PERSISTING ALONG THE
SNAKE RIVER. OTHERWISE VFR CONDITIONS IN THE MTNS AND ACROSS SE
OREGON TODAY UNDER MOSTLY CLEAR SKIES. SURFACE WINDS: VARIABLE 5
KT OR LESS, BECOMING EASTERLY 5-15 KT IN THE SNAKE PLAIN AFTER
18Z. WINDS ALOFT AT 10KFT MSL: N 15-30 KT.
KBOI...IFR-LIFR CONDITIONS WILL BE SPORADIC UNTIL 18Z, WHEN
HIGH CONFIDENCE (80%) OF CONDITIONS BECOMING PREDOMINANT MVFR OR
VFR. FOG AND IFR-VLIFR CONDITIONS WILL RETURN FRIDAY NIGHT,
THOUGH EXPECT A DELAYED START UNTIL AFTER 06Z, WITH 60% CHANCE
BY 07Z. SURFACE WINDS: SE 9-14 WITH GUSTS 15-20 KTS THIS
AFTERNOON, BECOMING LIGHT AND VARIABLE AFTER SUNSET.
WEEKEND OUTLOOK...AREAS OF IFR-LIFR IN VALLEY FOG/CLOUDS WITH
BREAKS DURING THE AFTERNOONS. SOME AREAS OF SE OREGON (INCLUDING
KONO) COULD SEE AN EXTENDED PERIOD OF IFR IN FOG/CLOUDS. LOCAL
MTN VALLEY FOG, WITH VFR ABOVE VALLEY FLOORS. LIGHT SURFACE
WINDS AND NORTHERLY WINDS AT 10KFT MSL.
AIR STAGNATION
SOME COOLING ALOFT TODAY, BUT NOT ENOUGH TO
REMOVE THE SURFACE BASED TEMPERATURE INVERSION. ALSO EASTERLY
WINDS TODAY WILL STIR UP THE AIR MASS AND HELP ERODE MUCH OF
FOG/CLOUDS IN THE SNAKE PLAIN. SOME SITES EAST OF MOUNTAIN HOME
COULD SEE MIXING HEIGHTS REACH 2KFT AGL, BUT TODAY LOOKS TO BE
THE ONLY DAY FOR THAT HOPE. WE'LL SEE A CONTINUATION OF LIGHT
WINDS AND SUB 2KFT MIXING HEIGHTS THROUGH AT LEAST WEDNESDAY OF
NEXT WEEK.
PREV DISCUSSION
SHORT TERM...TODAY THROUGH SUNDAY NIGHT...WITH THE UPPER RIDGE
AXIS NOW POSITIONED OFFSHORE, NORTHERLY FLOW HAS INCREASED OVER
THE AREA AND BROUGHT A FRESH ROUND OF COLD AIR EAST OF THE
CONTINENTAL DIVIDE. THE ACCOMPANYING SURFACE HIGH WILL ACT TO
INCREASE EASTERLY WINDS ACROSS THE AREA TODAY. THIS WILL BE MOST
PRONOUNCED IN THE SNAKE PLAIN AND AID IN BREAKING UP THE
FOG/STRATUS THAT HAS TAKEN HOLD. AREAS OF GREATER UNCERTAINTY
WITH REGARDS TO CLEARING THIS AFTERNOON WOULD BE ALONG THE
SNAKE RIVER, FROM BRUNEAU TO ONTARIO. SIMILAR TO YESTERDAY,
AREAS THAT KEEP THE FOG/STRATUS WILL STRUGGLE TO WARM ABOVE
FREEZING. THE EASTERLY WIND PUSH IS BRIEF, AND EXPECT THE
FOG/CLOUDS TO GET REESTABLISHED IN THE SNAKE PLAIN OVER THE
WEEKEND. THERE ARE ALSO SIGNS COVERAGE COULD EXPAND ACROSS SE
OREGON (MAINLY MALHEUR AND BAKER COUNTIES) AS A RESULT OF
TODAY'S EASTERLY WINDS.
FOR AREAS OUTSIDE OF THE FOG/STRATUS, EXPECT MOSTLY CLEAR
SKIES. TEMPERATURES IN THE MTNS WILL COOL TO NEAR NORMAL TODAY,
WARMING SOME OVER THE WEEKEND AS THE RIDGE EXPANDS BACK OVER THE
AREA.
LONG TERM...MONDAY THROUGH FRIDAY...THE UPPER RIDGE BEGINS TO
FLATTEN OUT NEXT WEEK IN RESPONSE TO THE WESTWARD EXPANSION OF
THE POLAR VORTEX THAT'S BEEN LOCKED UP OVER THE HUDSON BAY. THE
RECENT STRETCH OF DRY AND STABLE CONDITIONS WILL CONTINUE
THROUGH WEDNESDAY AS THE INCREASING FLOW AND GRADUALLY COOLING
TEMPERATURES ALOFT DON'T LOOK TO BE ENOUGH TO BREAK THROUGH
UNTIL THURSDAY. DETERMINISTIC AND ENSEMBLE MEAN SOLUTIONS SHOW
THE RIDGE ISN'T READY TO GO QUIETLY AND FOR NOW IS STRONG ENOUGH
TO DEFLECT THE COLDEST AIR TO OUR EAST. THOUGH A 20-30% CHANCE
OF SHOWERS SHOWS UP IN THE MTNS FOR THUR/FRI, THE DEEPEST
MOISTURE WILL CONTINUE TO BE ROUTED AROUND US (NORTH AND SOUTH)
THROUGH NEXT WEEK (AND LIKELY NEXT WEEKEND). TEMPERATURES WILL
FLIP AS THE INVERSION BREAKS, WARMING ACROSS THE LOWEST
ELEVATIONS, WHILE COOLING IN THE MOUNTAINS.
BOI WATCHES/WARNINGS/ADVISORIES
ID...AIR STAGNATION ADVISORY UNTIL 5 AM MST MONDAY
IDZ011>014-016-028-033.
DENSE FOG ADVISORY UNTIL 1 PM MST THIS AFTERNOON IDZ012.
OR...AIR STAGNATION ADVISORY UNTIL 5 AM MST /4 AM PST/ MONDAY
ORZ061>064.
DENSE FOG ADVISORY UNTIL 1 PM MST /NOON PST/ THIS AFTERNOON
ORZ064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
DISCUSSION...ST
AVIATION.....CH
AIR STAGNATION...DG
SHORT TERM...DG
LONG TERM....DG
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