588
FXUS65 KBOI 280340
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
840 PM MST SAT DEC 27 2025
DISCUSSION
UPPER TROUGH OVER NORTHERN MONTANA WILL CONTINUE
STEERING OUT EAST TONIGHT, SUSTAINING NORTHWEST FLOW THAT WILL
DROP NIGHTTIME TEMPERATURES INTO THE UPPER 20S FOR LOWER
ELEVATIONS AND INTO THE SINGLE DIGITS FOR MOUNTAIN AREAS. COLDER
DAYTIME TEMPERATURES WILL BE EXPECTED SUNDAY, WITH PEAK VALLEY
TEMPERATURES IN THE UPPER 30S AND PEAK MOUNTAIN TEMPERATURES IN
THE UPPER 20S. HIGH PRESSURE WILL BUILD INTO THE AREA LATE
SUNDAY, CONTINUING DRY CONDITIONS. STAGNANT CONDITIONS AND WEAK
WINDS UNDER 10 MPH ARE STILL EXPECTED LATE SUNDAY THROUGH
MONDAY.
AVIATION
MAINLY VFR. BRIEF MOUNTAIN OBSCURATION AND MVFR/IFR
CONDITIONS IN SNOW SHOWERS NEAR KBKE SUNDAY MORNING. SURFACE
WINDS: SW- NW 5-15 KT, STRONGEST IN THE MAGIC VALLEY. WINDS
ALOFT AT 10KFT MSL:
NW 20-35 KT.
KBOI...VFR WITH HIGH CLOUDS TOMORROW. SURFACE WINDS: W-NW 4-7
KT.
AIR STAGNATION
STAGNANT CONDITIONS DEVELOP SUNDAY AS A RIDGE
OF HIGH PRESSURE BEGINS TO BUILD OVER THE AREA. POOR MIXING
HEIGHTS, LIGHT WINDS, AND A TEMPERATURE INVERSION EXPECTED
MONDAY THROUGH THURSDAY. TEMPERATURE INVERSION WILL LIKELY TRAP
POLLUTANTS, CREATING HAZE AND PATCHY FOG ESPECIALLY OVER
SHELTERED VALLEY AREAS.
PREV DISCUSSION
SHORT TERM...TONIGHT THROUGH MONDAY NIGHT...A TROUGH CONTINUES
TO MOVE EAST OVER MONTANA THIS AFTERNOON. WEST TO NORTHWEST
SURFACE WINDS 10-20 MPH ACROSS THE AREA THIS AFTERNOON EXCEPT
30-40 MPH IN THE MAGIC VALLEY. WINDS EASE AFTER SUNSET WITH
COOL TEMPERATURES TONIGHT. SUNDAY AND MONDAY WILL BE PARTLY
SUNNY AND DRY WITH STAGNANT CONDITIONS DEVELOPING AS UPPER LEVEL
WINDS WEAKEN AND A RIDGE BUILDS INTO THE AREA. TEMPERATURES
WILL BE NEAR NORMAL SUNDAY WITH SLIGHT WARMING ON MONDAY.
LONG TERM...TUESDAY THROUGH SATURDAY...AN UPPER LEVEL RIDGE
WILL BRING DRY AND STABLE CONDITIONS TO THE AREA TUESDAY
THROUGH EARLY THURSDAY. WARMING ALOFT COMBINED WITH COLD AIR
TRAPPED NEAR THE SURFACE WILL CREATE A TEMPERATURE INVERSION. AS
A RESULT, MOST MID TO HIGH ELEVATION SITES WILL SEE
TEMPERATURES 5-10 DEGREES ABOVE NORMAL, WHILE THE LOWEST VALLEYS
WILL BE NEAR TO SLIGHTLY BELOW NORMAL.
A RETURN TO MORE ACTIVE CONDITIONS IS EXPECTED LATE THURSDAY
THROUGH SATURDAY AS AN UPPER LEVEL TROUGH ALONG THE COAST
HELPS TO DIRECT SUBTROPICAL MOISTURE FROM THE SOUTHWEST
NORTHWARD. THE TROUGH IS EXPECTED TO MOVE INLAND FRIDAY OR
SATURDAY. AHEAD OF THE TROUGH, PRECIPITATION CHANCES WILL
INCREASE WITH MILD TEMPERATURES AND SNOW LEVELS AROUND 4000-6000
FEET, POSSIBLY RISING TO AS HIGH AS 7000 FEET IF THE TROUGH IS
DELAYED AND THE FLOW ALOFT BECOMES MORE SOUTHERLY. COOLER AIR
ACCOMPANYING THE TROUGH SHOULD LOWER SNOW LEVELS, POSSIBLY TO
NEAR VALLEY FLOORS BY SATURDAY. IF THE TROUGH CAN DIRECT DEEPER
MOISTURE INTO OUR AREA, AS IS DEPICTED IN A MAJORITY OF
GLOBAL/AI ENSEMBLE MEMBERS, ANOTHER ROUND OF WIDESPREAD
PRECIPITATION WITH MODERATE TOTALS AND MILD TEMPERATURES ARE
EXPECTED. HOWEVER, IF THE TROUGH IS FASTER AS IS FAVORED BY THE
GEFS, THEN LESS PRECIPITATION AND COOLER TEMPERATURES ARE MORE
LIKELY. OVERALL, THE UNCERTAINTY RESULTS IN PRECIPITATION
CHANCES RISING TO AROUND 40-70% BY FRIDAY MORNING, THEN
GRADUALLY DECREASING ON SATURDAY, WITH TEMPERATURES AVERAGING
5-10 DEGREES ABOVE NORMAL.
BOI WATCHES/WARNINGS/ADVISORIES
ID...AIR STAGNATION ADVISORY FROM 6 PM SUNDAY TO 10 AM MST THURSDAY
IDZ012-014-016-028-033.
OR...AIR STAGNATION ADVISORY FROM 6 PM MST /5 PM PST/ SUNDAY TO 10
AM MST /9 AM PST/ THURSDAY ORZ061>064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
DISCUSSION...JY
AVIATION.....SA
AIR STAGNATION...JY
SHORT TERM...KA
LONG TERM....ST
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