979
FXUS65 KBOI 181554
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
854 AM MST SUN JAN 18 2026
DISCUSSION
NO UPDATE TO THE FORECAST THIS MORNING. STRATUS
UNLIKELY TO SHOW MUCH BREAKAGE TODAY WITH LIGHT VARIABLE WINDS.
THIS WILL LIMIT THE AFTERNOON TEMPS, RESULTING IN VERY LITTLE
WARM UP DURING THE DAY. CONDITIONS IN THE SNAKE PLAIN AND BASINS
OF SE OR WILL REMAIN CLOUDY AND CHILLY. HIGHER ELEVATIONS ABOVE
ABOUT 5KFT MSL WILL GENERALLY BE ABOVE THE STRATUS DECK AND SEE
CLEAR CONDITIONS WITH WARMER TEMPS. THE MAGIC VALLEY AND AREAS
ALONG THE EDGE OF THE STRATUS MAY SEE BRIEF CLEARING.
AVIATION
MVFR-LIFR IN LOW STRATUS AND FOG IN THE SNAKE PLAIN
AND SE OR THIS MORNING EXPECTED TO LAST THROUGH THE DAY. IFR-
LIFR AREAS MAY SEE MARGINAL IMPROVEMENT TO MVFR IF THE FOG LIFTS
TO STRATUS ESPECIALLY IN THE MAGIC VALLEY. LOW CLOUDS WILL
OBSCURE MTNS BELOW APPROX 5KFT MSL, WHILE HIGHER ELEVATIONS
REMAIN CLEAR. SURFACE WINDS: VARIABLE LESS THAN 8 KT. WINDS
ALOFT AT 10KFT MSL: N 10-20 KT.
KBOI...LOW STRATUS WILL CONTINUE TO STRADDLE MVFR/IFR THIS
MORNING. STRATUS WILL LAST THROUGH THE DAY, POSSIBLY LOWERING TO
LIFR TONIGHT. SURFACE WINDS: VARIABLE UP TO 5 KT.
AIR STAGNATION
A STAGNANT AIR MASS WILL STAY IN PLACE OVER
THE REGION THROUGH THURSDAY BRINGING MINIMAL DAYTIME MIXING AND
LIGHT WINDS. THE TEMPERATURE INVERSION WILL CONTINUE TO TRAP
POLLUTANTS NEAR THE SURFACE WHILE LOW CLOUDS AND FOG REMAIN
ENTRENCHED ACROSS LOWER VALLEYS.
PREV DISCUSSION
SHORT TERM...TODAY THROUGH TUESDAY NIGHT...INTERESTING TO SEE
THE FOG AND STRATUS EXPAND ON SATELLITE IMAGERY TONIGHT,
ESPECIALLY THROUGH LOWER CANYONS OF SE OREGON. ANY MINOR
CHANGES TO THE UPPER LEVEL WEATHER PATTERN WILL HAVE LITTLE
IMPACT ON OUR WEATHER, SO THE NEXT SEVERAL DAYS WILL SEE THE
STRATUS AND PERIPHERAL FOG WILL HOLD IN PLACE. FOR MOST SITES
IT WILL REMAIN A BLANKET OF LOW CLOUDS WITH PATCHY FOG WHERE
IT LOWERS TO GROUND OR INTERSECTS THE HIGHER TERRAIN ON THE
EDGES. DO EXPECT SOME DIURNAL 'BREATHING', WITH THE FOG/CLOUDS
ERODING ALONG THE EDGES DURING THE DAYS, EXPANDING DURING THE
NIGHT. THE WESTERN MAGIC VALLEY IS ONE AREA THAT COULD BREAK
OUT OF THE FOG LATE TODAY AND AGAIN MONDAY. THE SUN WILL
CONTINUE TO SHINE BRIGHT OUTSIDE OF THE COLD/GREY VALLEYS. THE
TEMPERATURE INVERSION WILL KEEP SUBFREEZING HIGH TEMPERATURES IN
THE VALLEYS WITH ABOVE NORMAL TEMPERATURES IN THE MOUNTAINS.
LONG TERM...WEDNESDAY THROUGH SUNDAY...THE UPPER RIDGE IS STILL
FORECAST TO GIVE WAY TO TROUGHING AT THE END OF NEXT WEEK. THE
DETERMINISTIC GUIDANCE IS BACK TO DISAGREEING ON THE AMPLITUDE
AND LONGEVITY OF THE TROUGH OVER OUR REGION, BUT THE INITIAL
COLD FRONT AND INCREASED FLOW STILL ARRIVES LATE THURSDAY IN
BOTH THE GFS AND ECMWF. THE ENSEMBLE MEAN INCREASES THE CHANCE
OF PRECIPITATION FROM ~20% IN THE MTNS THURSDAY NIGHT TO 30-50%
ON SATURDAY AS MOISTURE IS INJECTED INTO THE REGION ON NW FLOW.
THIS BRINGS AN END (OR AT LEAST A BRIEF BREAK IN THE GFS) TO
OUR PROLONGED INVERSION EVENT WHILE ADDING THE CHANCE FOR
ACCUMULATING SNOW IN THE MOUNTAINS. THE INTRUSION OF COLDER AIR
ALOFT AND INCREASED MIXING WOULD HELP TO WARM THE VALLEYS AND
COOL THE MOUNTAINS HEADING INTO NEXT WEEKEND.
BOI WATCHES/WARNINGS/ADVISORIES
ID...AIR STAGNATION ADVISORY UNTIL 11 AM MST THURSDAY
IDZ011>014-016-028-033.
DENSE FOG ADVISORY UNTIL 11 AM MST THIS MORNING IDZ016.
OR...AIR STAGNATION ADVISORY UNTIL 11 AM MST /10 AM PST/ THURSDAY
ORZ061>064.
WWW.WEATHER.GOV/BOISE
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSBOISE
WWW.X.COM/NWSBOISE
DISCUSSION...JM
AVIATION.....JM
AIR STAGNATION...JM
SHORT TERM...DG
LONG TERM....DG
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