203
FXUS65 KBOI 271000
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
300 AM MST SAT DEC 27 2025
SHORT TERM...TODAY THROUGH MONDAY NIGHT
A COLD FRONT IS
MOVING ACROSS SOUTHWEST IDAHO THIS MORNING, ACCOMPANIED BY
ISOLATED SNOW SHOWERS AND GUSTY NORTHWEST WINDS. SNOW LEVELS
WILL DROP TO VALLEY FLOORS BEHIND THE FRONT. THE MOUNTAINS,
PARTICULARLY THE WEST CENTRAL AND BOISE MOUNTAINS, WILL SEE
ADDITIONAL LIGHT SNOWFALL ACCUMULATIONS BEFORE PRECIPITATION
TAPERS OFF FROM WEST TO EAST THIS AFTERNOON. A FEW SNOW SHOWERS
ARE POSSIBLE IN THE SNAKE RIVER PLAIN, PARTICULARLY THIS
AFTERNOON AS CONVECTIVE SHOWERS DEVELOP, THOUGH NO ACCUMULATION
IS EXPECTED. GUSTY NORTHWEST WINDS WILL CONTINUE THROUGH THE DAY
WITH GUSTS TO 40 MPH, ESPECIALLY ACROSS OPEN TERRAIN, BEFORE
DIMINISHING THIS EVENING AS THE PRESSURE GRADIENT RELAXES.
THE PATTERN SHIFTS QUICKLY TONIGHT AS AN UPPER LEVEL RIDGE
BEGINS TO BUILD OVER THE REGION. THIS TRANSITION WILL BRING AN
END TO PRECIPITATION AND LEAD TO CLEARING SKIES. HOWEVER, THE
CLEARING SKIES AND LIGHT WINDS WILL SET THE STAGE FOR STRONG
RADIATIONAL COOLING AND THE DEVELOPMENT OF VALLEY INVERSIONS.
PATCHY FOG AND LOW STRATUS ARE EXPECTED TO FORM IN THE SHELTERED
VALLEYS OF SOUTHEAST OREGON AND SOUTHWEST IDAHO LATE TONIGHT
INTO SUNDAY MORNING. THE CENTRAL MOUNTAINS WILL SEE SOME OF THE
COLDEST TEMPERATURES SO FAR THIS WINTER, WITH READINGS DROPPING
BELOW ZERO ABOVE 6500 FEET. THE RIDGE WILL STRENGTHEN SUNDAY AND
MONDAY, FIRMLY ESTABLISHING STRONG TEMPERATURE INVERSIONS. THIS
WILL LEAD TO DRY CONDITIONS BUT PERSISTENT LOW CLOUDS AND FOG IN
THE VALLEYS, WHICH WILL SUPPRESS DAYTIME HIGH TEMPERATURES.
CONVERSELY, MOUNTAIN LOCATIONS WILL EXPERIENCE MOSTLY SUNNY
SKIES AND MODERATING TEMPERATURES. WITH LIMITED MIXING EXPECTED
UNDER THE RIDGE, AIR STAGNATION COULD START TO BECOME A CONCERN
BY MONDAY.
LONG TERM...TUESDAY THROUGH SATURDAY
PRONOUNCED UPPER RIDGING
WILL CHARACTERIZE THE START OF THE PERIOD, BRINGING DRY CONDITIONS
WITH TEMPERATURES NEAR SEASONAL NORMALS. THIS PATTERN WILL ALSO
PROMOTE INVERSION CONDITIONS IN THE VALLEYS, RESULTING IN HIGHER
PROBABILITIES OF FOG/LOW STRATUS EACH DAY AND REDUCED AIR QUALITY.
STILL A SIGNIFICANT AMOUNT OF UNCERTAINTY IN EXACTLY HOW THE UPPER
RIDGE BREAKDOWN PROCESS WILL UNFOLD, WITH ECMWF AI MEMBERS SHOWING A
MORE AGGRESSIVE SUPPRESSION OF HEIGHTS OVER THE NORTHWEST COMPARED
TO OTHER DETERMINISTIC MODEL SOLUTIONS. HOWEVER, MODEL CONSENSUS IS
STILL RELATIVELY HIGH THAT AN ANOMALOUS AREA OF MOISTURE CURRENTLY
OVER THE SOUTHWEST WILL ADVECT NORTHWARD INTO THE REGION AND BRING
HIGHER CHANCES OF PRECIPITATION (GENERALLY 20-50%) FROM LATE
THURSDAY THROUGH SATURDAY. SNOW LEVELS WILL GENERALLY REMAIN BELOW
5000 FEET AS WELL, RESULTING IN PERIODS OF MOUNTAIN SNOW.
AVIATION
SCATTERED SNOW SHOWERS MAINLY OVER THE HIGHER TERRAIN
THROUGH THIS AFTERNOON. IFR/LIFR IN SNOW. MOUNTAINS OBSCURED. SNOW
LEVELS NEAR VALLEY FLOORS. SURFACE WINDS: NW 5-15 KT INCREASING TO
NW-W 10-20 KT WITH 20-35 KT GUSTS LATE THIS AM. WINDS ALOFT AT 10KFT
MSL: NW 20-35 KT.
KBOI...VFR. SHOWERS IN VICINITY OVER BOISE FOOTHILLS, CREATING
OBSCURATION. POTENTIAL FOR BRIEF SNOW SHOWER AND DEGRADED VISIBILITY
AT KBOI SATURDAY MID MORNING THROUGH EARLY AFTERNOON. HOWEVER,
FORECAST CONFIDENCE IS VERY LOW AS SHOWER ACTIVITY WILL BE FAVORING
HIGHER TERRAIN. PRECIPITATION CHANCES END AFTER 22Z. SURFACE WINDS:
W-NW 8-18 KT WITH GUSTS AROUND 25 KT, DECREASING THIS EVENING.
SUNDAY OUTLOOK....VFR, COLD, AND DRY. SURFACE WINDS LIGHT AND
VARIABLE, EXCEPT W-NW 10-15 KT WITH A FEW STRONGER GUSTS SUN AM IN
SOUTH-CENTRAL IDAHO (KTWF-KJER).
AIR STAGNATION
STAGNANT CONDITIONS DEVELOP SUNDAY AS A RIDGE
OF HIGH PRESSURE BEGINS TO BUILD OVER THE AREA. POOR MIXING
HEIGHTS WITH LIGHT WINDS EXPECTED MONDAY THROUGH THURSDAY. A
TEMPERATURE INVERSION WILL STRENGTHEN MONDAY THROUGH WEDNESDAY
OF NEXT WEEK AS THE RIDGE MOVES OVERHEAD WITH WARMER
TEMPERATURES ALOFT. AN ADVISORY WILL LIKELY BE NEEDED FOR NEXT
WEEK.
BOI WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY UNTIL 5 AM MST EARLY THIS MORNING
IDZ011-013.
OR...NONE.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
SHORT TERM...JDS
LONG TERM....JR
AVIATION.....JR
AIR STAGNATION...JDS
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