163
FXUS65 KBOI 212105
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
305 PM MDT TUE OCT 21 2025
SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT
WEAK UPPER-LEVEL RIDGING
IS IN PLACE ACROSS THE REGION TODAY. THE RIDGING WILL CONTINUE TO BE
WEAK THROUGH THE PERIOD, AS AN UPPER-LEVEL CUTOFF LOW WILL MOVE
INLAND FROM THE CALIFORNIA COAST INTO THE DESERT SOUTHWEST. MODELS
KEEP IT FAR ENOUGH SOUTH OF THE REGION TO LIMIT IMPACTS, WITH A
TRANSITION TO WEAK UPPER-LEVEL FLOW WEDNESDAY AND ANOTHER SHORTWAVE
UPPER-LEVEL RIDGE BUILDING IN THURSDAY. AS THE UPPER-LEVEL LOW MOVES
INTO THE FOUR CORNERS REGION THURSDAY, THE SURFACE WINDS BETWEEN
MOUNTAIN HOME AND THE WESTERN MAGIC VALLEY WILL INCREASE OUT OF THE
W/NW WITH AN INCREASED PRESSURE GRADIENT.
THIS PATTERN IS PLACING THE AREA IN A WARMING TREND WITH HIGH
TEMPERATURES RISING FROM NEAR NORMAL TODAY TO 5 DEGREES ABOVE NORMAL
BY THURSDAY. DAILY LOW TEMPERATURES WILL ALSO RISE OVER THE PERIOD,
GOING FROM NEAR NORMAL TODAY TO 5 DEGREES ABOVE NORMAL BY THURSDAY
NIGHT. WHILE THIS WILL CAUSE LOWER ELEVATION VALLEY MINIMUM
TEMPERATURES TO HOVER IN THE MID-TO-HIGH 30S, NO ADDITIONAL FROST OR
FREEZE WARNINGS WILL BE ISSUED IN 2025.
LONG TERM...FRIDAY THROUGH TUESDAY
ON FRIDAY, THE AREA WILL START
UNDER A SHORTWAVE RIDGE PATTERN WITH AN IMPINGING UPPER-LEVEL
LONGWAVE TROUGH SYSTEM AND ASSOCIATED ATMOSPHERIC RIVER. WHILE THIS
INTENSE UPPER-LEVEL LOW SPINS IN GULF OF ALASKA (AND SLOWLY MOVES
ONSHORE INTO BRITISH COLUMBIA), MULTIPLE EMBEDDED SHORTWAVES IN THE
SOUTHWESTERLY FLOW ALOFT WILL CREATED ENHANCED CONDITIONS FOR
PRECIPITATION THROUGH THE WEEKEND. AN ASSOCIATED COLD FRONT WILL
MOVE THROUGH THE AREA WITH THESE EMBEDDED SHORTWAVES, HOWEVER EXACT
TIMING ON THIS SEEMS TO KEEP GETTING PUSHED LATER AND LATER.
PRECIPITATION CHANCES INCREASE WEST-TO-EAST FRIDAY NIGHT, EVENTUALLY
BECOMING WIDESPREAD 50% CHANCE OR GREATER SATURDAY NIGHT THROUGH
SUNDAY NIGHT. AREAS OF 75% CHANCE OR GREATER WILL EXIST DURING THIS
SAME PERIOD FOR HIGHER ELEVATION AREAS. PRECIPITATION CHANCES
CONTINUE INTO MONDAY, HOWEVER, LONG RANGE MODELS CURRENTLY DISAGREE
ON WHEN THE ROUNDS OF EMBEDDED SHORTWAVES AND ASSOCIATED MOISTURE
MAKE THEIR WAY FULLY THROUGH THE AREA.
WARM SOUTHWEST FLOW AHEAD OF THE MAIN COLD AIR MASS WILL KEEP
TEMPERATURES ABOVE NORMAL ON FRIDAY AND SATURDAY. TEMPERATURES WILL
THEN PLUMMET 10 TO 15 DEGREES ON SUNDAY AS COLD AIR, GUSTY WINDS,
AND SIGNIFICANT MOISTURE MOVES INTO THE REGION. SNOW LEVELS WILL BE
AROUND 7000-8000 FEET MSL THROUGH MIDDAY SATURDAY, DROPPING TO 4000-
5000 FEET MSL ON SUNDAY AND MONDAY. WIDESPREAD VALLEY RAIN AND HEAVY
MOUNTAIN SNOW IS ANTICIPATED, WITH 2 DAY SNOWFALL TOTALS REACHING UP
TO 8 TO 12 INCHES FOR HIGHER SUMMITS WITH 1-3 INCHES FOR MOUNTAIN
VALLEYS BY MONDAY MORNING.
BY LATE MONDAY, SOME LINGERING MOISTURE WILL MOVE THROUGH THE REGION
AND NORTHWESTERLY FLOW WILL SET IN. TEMPERATURES WILL REMAIN COOL
AND WILL BEGIN TO DRY OUT LATE MONDAY. ON TUESDAY, AN UPPER-LEVEL
RIDGE WILL START TO BUILD IN, STARTING TO RISE TEMPERATURES ONCE
AGAIN.
AVIATION
VFR. PATCHY MOUNTAIN VALLEY FOG WEDNESDAY MORNING.
SURFACE WINDS: VARIABLE LESS THAN 10 KT. WINDS ALOFT AT 10KFT MSL:
SW-W 5-15 KT.
KBOI...VFR. SURFACE WINDS: LIGHT AND VARIABLE, AFTER SUNSET BECOMING
SE 4-9 KT.
BOI WATCHES/WARNINGS/ADVISORIES
ID...NONE.
OR...NONE.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
SHORT TERM...CH
LONG TERM....CH
AVIATION.....CH
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