903
FXUS65 KBOI 252113
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
213 PM MST THU DEC 25 2025
SHORT TERM...TONIGHT THROUGH SATURDAY NIGHT
THE TEMPERATURE,
AS OF WRITING THIS, HAS REACHED 58 DEGREES IN BOISE. THIS PUTS
THIS CHRISTMAS AS THE SECOND WARMEST ON RECORD. SHOWER COVERAGE
WILL INCREASE THROUGHOUT THE AFTERNOON AS AN UPPER-LEVEL JET
CONTINUES TO OVERSPREAD ACROSS OUR AREA. WITH INCREASING
DYNAMICS, MOISTURE, INSTABILITY, AND STEEPENING LAPSE RATES,
ADDITIONAL SHOWERS WILL TAKE ON MORE OF A CONVECTIVE NATURE.
LIGHTNING FLASHES HAVE ALREADY BEEN OBSERVED IN EASTERN IDAHO
AND NORTHERN NEVADA. CURRENT MESOSCALE ANALYSIS HAS SHEAR VALUES
OF 45-55 KTS OVER OUR AREA, THESE VALUES WILL CONTINUE TO
INCREASE AS THE JET MAX MOVES OVER. WHILE THIS STRONG SHEAR MAY
WORK TO TEAR APART UPDRAFTS THAT TRY DEVELOPING WITH WEAK CAPE,
LOCALLY HEAVIER PRECIP, GUSTY WINDS, AND LIGHTNING WILL BE PLAY
WITH THE STRONGEST SHOWERS. THIS THREAT WILL STICK AROUND IN
THE WEST CENTRAL/IDAHO MOUNTAIN ZONES THROUGH FRIDAY MORNING.
PRECIPITATION WILL CONTINUE COME FRIDAY, AS THE MAIN UPPER
LEVEL TROUGH AND SURFACE COLD FRONT WILL MOVE ACROSS THE AREA.
THIS FRONT WILL LOWER DAYTIME HIGH TEMPERATURES BY 5-10
DEGREES. SNOW LEVELS WILL ALSO DROP TO 3.5-5 KFT MSL BY FRIDAY
AFTERNOON. HAVE EXPANDED THE WINTER WEATHER ADVISORY TO INCLUDE
THE BOISE MOUNTAIN ZONE IN COLLABORATION WITH NEIGHBORING
OFFICES. HIGHER ELEVATION MOUNTAIN VALLEYS WILL SEE 4-7 INCHES
OF SNOWFALL THROUGH FRIDAY THROUGH SATURDAY MORNING, WITH UP TO
19 INCHES AT BANNER SUMMIT.
SNOW LEVELS WILL DROP TO VALLEY FLOORS BY SATURDAY AFTERNOON;
ALTHOUGH WITH DECREASING UPPER-LEVEL SUPPORT AS THE TROUGH MOVES
EAST, PRECIPITATION CHANCES WILL BE ON THE DECLINE THROUGHOUT
THE DAY SATURDAY. ANY ADDITIONAL PRECIPITATION IN LOWER
ELEVATIONS WILL BE SNOW OR WINTRY MIX, HOWEVER NO ACCUMULATION
IS EXPECTED. ADDITIONAL SNOW ACCUMULATIONS IN THE MOUNTAINS WILL
BE LIMITED TO UP TO 1.5 INCHES. COME SATURDAY NIGHT,
PRECIPITATION CHANCES WILL TAPER OFF ENTIRELY AS RIDGING BEGINS
TO BUILD IN. THIS WILL MAKE WAY FOR A MORE STAGNANT, STABLE
PATTERN IN THE LONG TERM PERIOD.
LONG TERM...SUNDAY THROUGH THURSDAY
A BROAD RIDGE OF HIGH
PRESSURE WILL BUILD OVER THE WESTERN US ON SUNDAY, BRINGING AIR
STAGNATION CONCERNS AND DRY CONDITIONS THROUGH THE MIDDLE OF NEXT
WEEK. COLD POOLS AND PATCHY FOG WITH LOW STRATUS CLOUDS WILL LIKELY
DEVELOP IN AREA VALLEYS DUE TO LIMITED DAYTIME MIXING, WITH ABOVE
NORMAL TEMPERATURES MIDSLOPE AND ON RIDGETOPS. MODEL AGREEMENT
REMAINS CONSISTENT ON THE DEVELOPMENT OF THE RIDGE AND THE DRY
PATTERN FOR EARLY NEXT WEEK, WITH SOME DISCREPANCIES IN THE PATH OF
A TROUGH BY THE END OF THE LONG TERM PERIOD (THURSDAY). SOME MEMBERS
ARE DIGGING THE TROUGH INTO THE REGION, BRINGING COLD AIR AND THE
POTENTIAL FOR SNOW ON VALLEY FLOORS, WHILE OTHERS KEEP THE COLDEST
AIR TO OUR NORTH AND WEST, KEEPING US IN WARM SOUTHWEST FLOW WHICH
WOULD KEEP SNOW LEVELS HIGHER AROUND 5000-6000 FEET MSL. AT THIS
POINT, AGREEMENT EXISTS ON THE PATTERN SHIFT BACK TO WET WEATHER,
BUT THE TRACK OF THE COLDEST AIR REMAINS UNCERTAIN. THE CLIMATE
PREDICTION CENTER 6-10 DAY OUTLOOK FAVORS ABOVE NORMAL TEMPERATURES
CONTINUING (60% CHANCE) WITH ABOVE NORMAL PRECIPITATION.
.AVIATION..MOSTLY VFR. SCATTERED RAIN/SNOW SHOWERS TODAY THROUGH
TOMORROW BRINGING PERIODS OF MVFR/IFR AND LOCALIZED LIFR CONDITIONS.
SNOW LEVELS: 5K-7KFT MSL DROPPING TO 3K-6KFT MSL OVERNIGHT. LOW
CONFIDENCE IN LIGHTNING (20% CHANCE) AND GUSTY OUTFLOW WINDS UP TO
40 KT, PRIMARILY OVER HIGH TERRAIN IN BOISE MTNS. MTNS OBSCURED.
AREAS OF LLWS TOMORROW MORNING, PRIMARILY OVER SNAKE RIVER VALLEY.
SURFACE WINDS: SE-SW 15-25 KT WITH 25-45 KT GUSTS. STRONGEST GUSTS
UP TO 55 KT WILL BE NEAR THE NV BORDER. WINDS ALOFT AT 10KFT MSL: SW
35-60 KT.
KBOI...GENERALLY VFR. BRIEF MVFR/IFR CONDITIONS IN CONVECTIVE
SHOWERS DEVELOPING LATE THIS AFTERNOON/EVENING. LOW CONFIDENCE IN
LIGHTNING AND GUSTY OUTFLOW WINDS UP TO 40 KT (20% CHANCE) WITH
STRONGER SHOWERS THIS EVENING. SURFACE WINDS: SE-E 5-15 KT. GUSTS TO
20-30 KT, TAPERING OFF AFTER SUNSET.
WEEKEND OUTLOOK...WIDESPREAD SNOW SHOWERS IN HIGH TERRAIN FRI THRU
SAT AFTERNOON, WITH IFR-LIFR CONDITIONS IN SNOW. SNOW LEVELS 3-4 KFT
MSL DROP TO VALLEY FLOORS SAT MORNING. SCATTERED SHOWERS IN LOWER
ELEVATIONS DURING THIS TIME. PRECIP CLEARS BY SAT NIGHT WITH PATCHY
FOG/STRATUS THAT MORNING AS AN INVERSION BUILDS. SURFACE WINDS: SE-
SE 15-20 KT WITH GUSTS TO 40 KT ON RIDGES FRI, BECOMING W 15-25 KT
SATURDAY, AND FINALLY LIGHT AND VARIABLE SUNDAY.
AIR STAGNATION
HIGH PRESSURE IS FORECAST TO BUILD OVER THE
REGION BEGINNING SATURDAY NIGHT AND WILL STRENGTHEN THROUGH THE
EARLY PART OF NEXT WEEK. THIS PATTERN WILL FAVOR THE DEVELOPMENT
OF A STRONG AND PERSISTENT SURFACE BASED TEMPERATURE INVERSION
FROM SUNDAY THROUGH AT LEAST NEXT TUESDAY. WITH LIGHT WINDS AND
LOW MIXING HEIGHTS (1000-2000 FEET) EXPECTED UNDER THE RIDGE,
THERE IS INCREASING CONCERN FOR DETERIORATING AIR QUALITY AND
POOR VENTILATION IN THE SHELTERED VALLEYS OF SOUTHEAST OREGON
AND SOUTHWEST IDAHO. WHILE IT MAY BE TOO EARLY FOR A FORMAL
ADVISORY, CONDITIONS WILL BE MONITORED CLOSELY AS THE STAGNANT
AIR MASS BECOMES ESTABLISHED.
BOI WATCHES/WARNINGS/ADVISORIES
ID...WINTER WEATHER ADVISORY FROM 5 AM FRIDAY TO 5 AM MST SATURDAY
IDZ011-013.
OR...NONE.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
SHORT TERM...NF
LONG TERM....SA
AVIATION.....SA
AIR STAGNATION...JDS
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