900
FXUS65 KBOI 240356 CCA
AFDBOI
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE BOISE ID
856 PM MST TUE DEC 23 2025
DISCUSSION
THE WIND ADVISORY FOR WEDNESDAY HAS BEEN EXPANDED
TO INCLUDE ALL OF EASTERN OREGON EXCEPT THE LOWER TREASURE
VALLEY, AS NEWEST MET MOS HAS INCREASED SPEEDS IN BAKER COUNTY
FROM THE PREVIOUS VERSION. THE ADVISORY CONTINUES UNCHANGED ON
THE IDAHO SIDE, I.E., SOUTH OF THE SNAKE BASIN. AS NOTED IN THE
PREVIOUS AFD (BELOW) WEDNESDAY WILL BE MILD AGAIN BEFORE RAIN
MOVES IN FROM THE SOUTH-SOUTHWEST. MANY LOWER VALLEYS STAYED IN
THE 40S TODAY. BUT BOI REACHED 61F (NEW RECORD) AND MOUNTAIN
HOME, TWIN FALLS, AND ROME, OR ALSO GOT WARM. WITH STRONGER
SOUTHEAST WINDS AND BETTER MIXING EXPECTED WEDNESDAY, ALL VALLEYS
SHOULD BECOME MILD. RAIN WILL BE SIGNIFICANT ON THE IDAHO SIDE
WEDNESDAY NIGHT, HEAVIEST IN THE BOISE MOUNTAINS AND WEST-CENTRAL
IDAHO MOUNTAINS, BUT LIGHTER IN THE SNAKE BASIN DUE TO SHADOWING
FROM THE OWYHEE MOUNTAINS AND SOUTHERN SAWTOOTHS. EASTERN OR,
EXCEPT ALONG THE NV BORDER, WILL ALSO HAVE ONLY LIGHT AMOUNTS
AS THE MAIN MOIST SURGE STAYS ON THE IDAHO SIDE.
AVIATION
FOG/MIST AROUND KEUL-KONO AND KBKE SHOULD GRADUALLY
IMPROVE IN THE EARLY MORNING AS SURFACE WINDS INCREASE. OTHERWISE,
VFR TONIGHT. PRECIP ARRIVING WED/14Z IN SE OREGON, AND WED/16Z IN
SW IDAHO. SNOW LEVELS 6K-8K FEET MSL. GENERALLY VFR-MVFR IN RAIN,
IFR-LIFR IN MTN SNOW. MTNS BECOMING OBSCURED. AREAS OF LOW-LEVEL
WIND SHEAR THROUGH MORNING. SURFACE WINDS: SE-S 5-15 KT. WINDS
INCREASING IN AM HOURS TO 15-30 KT WITH 25-45 KT GUSTS. LOCALLY
HIGHER GUSTS TO 50-55 KT NEAR NV BORDER AND IN E-CENTRAL OREGON.
WINDS ALOFT AT 10KFT MSL: S-SW 25-40 KT, INCREASING TO 45-60 KT
LATE WED AM.
KBOI...CHANCE OF LIGHT RAIN LATE WED MORNING THROUGH WED NIGHT,
BUT SE WIND WILL BE LIMITING FACTOR FOR AMOUNT/INTENSITY. VFR
EXPECTED. SURFACE WINDS: SE-E 5-10 KT TONIGHT, WITH A LOW-LEVEL
WIND SHEAR THREAT PRIOR TO THE STRONGER WINDS ALOFT MIXING DOWN
TO THE SURFACE. SURFACE WINDS WILL THEN INCREASE EARLY WED
MORNING HOURS TO SE-E 15-22 KT WITH GUSTS 25-35 KT. BRIEF GUSTS
TO 40-45 KT POSSIBLE BETWEEN WED/15Z-19Z.
PREV DISCUSSION
SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT...MILD TEMPERATURES
AND DRIER CONDITIONS HAVE MOVED INTO THE AREA SOUTH OF A WARM
FRONT WHICH HAS NOW MOVED WELL TO THE NORTH OF BAKER CITY AND
MCCALL. CLOUDS ARE ALSO DIMINISHING ACROSS SOUTHEASTERN OREGON
THIS AFTERNOON WITH CLEARING EXPECTED ACROSS PORTIONS OF
SOUTHWESTERN IDAHO EARLY THIS EVENING. TEMPERATURES ARE RUNNING
15 TO 20 DEGREES ABOVE SEASONAL NORMALS. THE MILD WEATHER WILL
CONTINUE TOMORROW BUT CLOUDS WILL MOVE BACK INTO THE AREA ALONG
WITH AN INCREASING CHANCE OR RAIN. A STRONG PRESSURE GRADIENT
WILL ALSO DEVELOP ACROSS SOUTHERN OREGON AND SOUTHERN IDAHO
TOMORROW. THIS WILL BRING STRONG SOUTHERLY WINDS TO THE
HIGHLANDS OF SOUTHERN IDAHO NEAR THE NEVADA BOARDER AND TO
PORTIONS OF HARNEY AND MALHEUR COUNTIES IN SOUTHERN OREGON
WHERE A WIND ADVISORY HAS BEEN ISSUED FOR TOMORROW. THE MILD
WEATHER IS EXPECTED TO CONTINUE THROUGH CHRISTMAS DAY WITH
WINDS SLACKENING. THERE IS A 70 PERCENT CHANCE OF RAIN ON
CHRISTMAS DAY ACROSS MUCH OF THE CENTRAL IDAHO MOUNTAINS WHERE
SNOW LEVELS WILL REMAIN ABOVE 7000 FEET. LESSER CHANCES OF RAIN
(20 TO 40 PERCENT CHANCE) ARE FORECAST ON CHRISTMAS DAY ACROSS
THE REST OF SOUTHWESTERN IDAHO AND SOUTHEASTERN OREGON.
LONG TERM...FRIDAY THROUGH TUESDAY...PRECIPITATION CHANCES
REMAIN ELEVATED AREA-WIDE FRIDAY AS THE UPPER-LEVEL TROUGH
MAKES ITS WAY ONSHORE. PRECIPITATION CHANCES FRIDAY MORNING
WILL START OUT AT 70-100% NORTH AND EAST OF THE SNAKE PLAIN,
WITH A 50-69% CHANCE IN AND SOUTHWEST OF THE SNAKE PLAIN.
PRECIPITATION CHANCES DECREASE THROUGHOUT THE DAY FRIDAY AS
WE BEGIN TO LOSE THE MOISTURE AND SYNOPTIC FORCING ONCE
PROVIDED BY THE AFOREMENTIONED TROUGH. PRECIPITATION WILL
CONTINUE OVER THE MOUNTAINS, HOWEVER, AS LOCALIZED OROGRAPHIC
LIFT WILL PERSIST. THE COLDER AIRMASS MOVING IN SATURDAY WILL
DROP SNOW LEVELS DOWN TO VALLEY FLOORS COME SATURDAY. HOWEVER,
AT THAT POINT PRECIPITATION CHANCES WILL BE CONFINED TO HIGHER
TERRAIN, AND THEN TAPER OFF ENTIRELY BY SATURDAY EVENING.
A SIGNIFICANT PATTERN CHANGE IS IN STORE FOR NEXT WEEK AS THE
TROUGH CLOSES OFF INTO A LOW OVER THE PACIFIC. WITH RIDGING
BUILDING IN OVER THIS LOW, OUR AREA WILL BE IN THE DRY PORTION
OF A REX BLOCK. THIS BLOCKING PATTERN WILL BRING WITH IT DRY
CONDITIONS, LIGHT WINDS, AND CLEAR SKIES. WHILE THAT SOUNDS
LIKE REALLY NICE WEATHER, THE STRONG SUBSIDENCE PAIRED WITH
THE LOW SUN ANGLE WILL KEEP MIXING HEIGHTS LOW AND VALLEYS
INVERTED. AIR STAGNATION IS LIKELY FROM SUNDAY THROUGH THE
FORECAST PERIOD. WITH THE AMOUNT OF ADDED MOISTURE RECEIVED
ACROSS THE AREA AS OF LATE, AND RELATIVELY WARM TEMPERATURES,
CONDITIONS ARE FAVORED FOR LONG LASTING FOG/STRATUS. THIS ALSO
LEADS TO CONSIDERABLE UNCERTAINTY REGARDING THE MAX TEMPERATURES
IN THE WEEK TO COME, COLD AIR TRAPPED IN THE VALLEYS PAIRED
WITH DECREASED SURFACE HEATING (AS A RESULT OF FOG/STRATUS)
COULD PUT A DAMPER ON THE FORECAST HIGHS AND KEEP TEMPERATURES
LOWER.
BOI WATCHES/WARNINGS/ADVISORIES
ID...WIND ADVISORY FROM 6 AM TO 4 PM MST WEDNESDAY IDZ015-029-030.
OR...WIND ADVISORY FROM 6 AM MST /5 AM PST/ TO 4 PM MST /3 PM PST/
WEDNESDAY ORZ061>063.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
DISCUSSION...LC
AVIATION.....SH
SHORT TERM...JB
LONG TERM....NF
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