628
FXUS65 KBOI 171056
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
356 AM MST SAT JAN 17 2026
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.
AVIATION
WIDESPREAD IFR-VLIFR IN THE SNAKE PLAIN. IMPROVEMENT
TO VFR IS EXPECTED THIS AFTERNOON MOSTLY EAST OF KMUO. EXPECT
IFR TO HOLD ON ALONG ID/OR BORDER (ROUGHLY KONO TO VICINITY OF
KEUL) WITH LIKELY IMPROVEMENT TO MVFR BETWEEN KBOI-KMUO AFTER
18Z. OTHERWISE VFR CONDITIONS IN THE MTNS AND ACROSS SE OREGON
TODAY UNDER MOSTLY CLEAR SKIES. SURFACE WINDS: VARIABLE
GENERALLY LESS THAN 8 KT. WINDS ALOFT AT 10KFT MSL: NLY 10-20
KT.
KBOI...SHOULD HOLD AT LIFR CEILINGS WITH A 30% CHANCE OF
DROPPING TO VLIFR THROUGH 15Z. CONDITIONS WILL STEP UP TO IFR
AROUND 18Z WITH IMPROVEMENT TO MVFR 18-20Z. LIFR CONDITIONS
RETURN 03-05Z TONIGHT AND COULD REMAIN IN PLACE WELL INTO
SUNDAY. LIGHT SURFACE WINDS BECOME EASTERLY 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 IT
(THE INVERSION/STAGNANT AIR MASS) THROUGH AT LEAST TUE 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).
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
SHORT TERM...DG
LONG TERM....DG
AVIATION.....DG
AIR STAGNATION...DG
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