292
FXUS65 KBOI 021621
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
921 AM MST FRI JAN 2 2026
DISCUSSION
SCATTERED SHOWERS CONTINUE THIS MORNING
ASSOCIATED WITH A WARM FRONTAL PASSAGE, GENERALLY FOCUSED NORTH
OF A BURNS TO BOISE TO FAIRFIELD LINE. FREEZING RAIN REMAINS A
PRIMARY CONCERN FOR PORTIONS OF BAKER COUNTY AND THE UPPER
WEISER RIVER VALLEY, WHERE THE WINTER WEATHER ADVISORY REMAINS
IN EFFECT UNTIL 11 AM MST. TEMPERATURES ARE EXPECTED TO RISE
LATER THIS MORNING AS SHOWERS TAPER OFF OVER THE NEXT FEW HOURS.
DRIER CONDITIONS WILL TAKE HOLD THIS AFTERNOON AS PRECIPITATION
DECREASES FROM SOUTHWEST TO NORTHEAST. BEHIND THE EXITING WARM
FRONT, TEMPERATURES WILL BE SEVERAL DEGREES MILDER THAN
YESTERDAY. THE EXCEPTION WILL BE SHELTERED VALLEYS WHERE STRATUS
AND FOG ARE LIKELY TO PERSIST, SIGNIFICANTLY LIMITING WARMING
POTENTIAL. SPECIFICALLY, THE LOWER TREASURE VALLEY, BAKER
VALLEY, AND LONG VALLEY WILL LIKELY REMAIN UNDER STRATUS THROUGH
THE DAY. STRATUS AND FOG ARE EXPECTED TO EXPAND IN COVERAGE
TONIGHT, PARTICULARLY FOR THE UPPER TREASURE VALLEY, UPPER
WEISER RIVER VALLEY, AND MANY LOWER VALLEYS ACROSS SOUTHEAST
OREGON. A DENSE FOG ADVISORY MAY BE REQUIRED FOR THE SATURDAY
MORNING COMMUTE. OVERALL, THE CURRENT FORECAST REMAINS ON TRACK
AND NO UPDATES ARE NEEDED AT THIS TIME.
AVIATION
PRECIPITATION TAPERING OFF THROUGH THE MORNING,
SCATTERED SHOWERS CONTINUING OVER THE W-CNTRL/BOISE MOUNTAINS
THROUGH THE AFTERNOON. AREAS OF FOG/LOW STRATUS THIS MORNING
RESULTING IN MVFR/LIFR CONDITIONS. SOME IMPROVEMENT TO VFR BY MID-
DAY, ALTHOUGH LOW ELEVATION AND SHELTERED VALLEYS WILL HOLD ON TO
MVFR/IFR CEILINGS IN LOW STRATUS. MTNS OBSCURED. AREAS OF FOG
RETURNING OVERNIGHT TONIGHT. SURFACE WINDS: VARIABLE UP TO 10KT,
EXCEPT W-SW 5-15 KT WITH GUSTS TO 20KT NEAR THE MAGIC VALLEY AND
ID/NV BORDER. WINDS ALOFT AT 10KFT MSL: BECOMING W-SW 10-25 KT.
KBOI...IFR/LIFR THIS MORNING IN FOG/LOW STRATUS, IMPROVING TO VFR BY
AROUND 18Z. FOOTHILLS OBSCURED. A 25% CHANCE OF FOG/LOW STRATUS
REDEVELOPMENT TONIGHT BRINGING MVFR/LIFR CONDITIONS. ALTHOUGH SE
WINDS ADD UNCERTAINTY, ACTING TO MITIGATE DEVELOPMENT. SURFACE
WINDS: LIGHT AND VARIABLE, BECOMING SE 8-12 KT AFTER SAT/00Z.
WEEKEND OUTLOOK...LOW IFR/LIFR IN CLOUDS AND FOG ON SATURDAY IN THE
VALLEYS, WITH IMPROVEMENT TO VFR MIDDAY. AREAS OF MOUNTAIN
OBSCURATION. SHOWERS RETURN LATE SATURDAY THROUGH SUNDAY WITH
WIDESPREAD MOUNTAIN OBSCURATION AND MVFR-IFR CONDITIONS.
PREV DISCUSSION
SHORT TERM...TODAY THROUGH SUNDAY NIGHT...WARM-FRONTAL PCPN
HAS GENERALLY ENDED IN HARNEY AND WESTERN MALHEUR COUNTIES IN
OREGON BUT CONTINUES IN THE REST OF OUR CWA EARLY THIS MORNING.
FREEZING RAIN CONTINUES IN WESTERN BAKER COUNTY, AND PROBABLY
ALSO IN THE UPPER WEISER RIVER VALLEY, SO WE HAVE EXTENDED THE
WINTER WEATHER ADVISORY IN THOSE AREAS UNTIL 11 AM MST. IN THE
LOWER TREASURE VALLEY ONTARIO WAS REPORTING LIGHT RAIN AND 33
DEGREES AT 3 AM MST. THERE MAY BE FREEZING RAIN NEARBY BUT ROAD
TEMPS ARE ABOVE FREEZING AND WITH PCPN EXPECTED TO END SOON WE
WILL ALLOW THE WINTER WEATHER ADVISORY TO EXPIRE ON SCHEDULE
THERE AT 5 AM MST. PCPN WILL DECREASE FROM SW TO NE IN THE REST
OF OUR CWA THROUGH THE DAY AND TEMPS WILL END UP SEVERAL
DEGREES MILDER THAN YESTERDAY BEHIND THE EXITING WARM FRONT.
NO PCPN IS EXPECTED TONIGHT BUT AREAS OF FOG WILL DEVELOP IN
THE VALLEYS, ESPECIALLY IN THE LOWER TREASURE VALLEY AND UPPER
WEISER RIVER VALLEY. THE NEXT PACIFIC FRONTAL SYSTEM, ALONG
130W AT 3 AM MST, WILL BRING MORE PCPN TO OUR CWA SATURDAY,
WITH RAIN BELOW 5000 FEET MSL NORTH TO 6500 FEET SOUTH. ON
SUNDAY, A DEEPENING UPPER TROUGH OFF THE COAST WILL INCREASE
SOUTHWEST WINDS IN OUR OREGON ZONES, POSSIBLY TO ADVISORY
SPEEDS SUNDAY AFTERNOON. ON THE PLUS SIDE THE WINDS SHOULD
ALSO COMPLETELY MIX OUT ANY RESIDUAL COLD AIR IN THE VALLEYS.
LONG TERM...MONDAY THROUGH FRIDAY...THERE IS STRONG AGREEMENT
AMONGST BOTH THE DETERMINISTIC AND ENSEMBLE GUIDANCE THAT A
SHORTWAVE TROUGH WILL DIG FROM THE NORTHWEST COAST MONDAY.
THIS PATTERN WILL SET THE STAGE FOR SIGNIFICANT SNOWFALL
ACCUMULATIONS IN THE MOUNTAINS, WITH A 90+% CHANCE OF TOTALS
EXCEEDING A FOOT BY MID-WEEK IN CENTRAL IDAHO. A GRADUAL
COOLING TREND WILL BE EXPECTED THROUGH THE WEEK, WITH VALLEY
HIGH TEMPERATURES EXPECTED TO DROP FROM THE UPPER 40S MONDAY
INTO THE UPPER 30S BY FRIDAY. THOUGH WITH SOME UNCERTAINTY,
GUIDANCES GENERALLY FAVOR A LARGER LONGWAVE TROUGH DIGGING INTO
THE REGION MIDWEEK, BRINGING A POSSIBLE RAIN-SNOW MIX IN THE
VALLEYS AND HIGH FAVORABILITY FOR SNOWFALL OVER THE MOUNTAINS
WEDNESDAY THROUGH THURSDAY. A LARGE RIDGE WILL THEN BUILD INTO
THE AREA THROUGH FRIDAY, RETURNING DRIER BUT COLDER CONDITIONS
WITH A STRONG NORTHWEST FLOW.
BOI WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY UNTIL 11 AM MST THIS MORNING IDZ033.
OR...WINTER WEATHER ADVISORY UNTIL 10 AM PST THIS MORNING ORZ062.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
DISCUSSION...JDS
AVIATION.....NF
SHORT TERM...LC
LONG TERM....JY
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