665
FXUS65 KBOI 182057
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
157 PM MST SUN JAN 18 2026
SHORT TERM...TONIGHT THROUGH TUESDAY NIGHT
STRATUS HELD ON
REALLY STRONG TODAY, IN LINE WITH THINKING FROM YESTERDAY, BUT
SHOWING ALMOST NO SIGNS OF DISSIPATION. IT'LL LIKELY STICK
AROUND THROUGH TONIGHT, WITH SLIGHT LOWERING TO BRING FOG BACK
TO SOME RELATIVE HIGH POINTS AROUND THE SNAKE PLAIN AND
SURROUNDING BASINS, ESPECIALLY NEAR THE EDGE OF THE STRATUS SUCH
AS IN THE MAGIC VALLEY. THIS MORNING'S DENSE FOG ADVISORY WAS
EXPIRED AFTER AN EXTENSION, AND WE ANTICIPATE MORE DENSE FOG TO
FORM TONIGHT. THE OVERALL PATTERN REMAINS THE SAME, A RIDGE SITS
OVER US, KEEPING CONDITIONS DRY AND INVERTED. STAGNANT AIR IS
PRESENT IN MANY OF OUR VALLEYS. WE EXPECT THE VALLEY FOG/STRATUS
TO CONTINUE THROUGH THE SHORT TERM WITH DAILY HIGH TEMPERATURES
5-10 DEGREES COLDER THAN NORMAL UNDER THE STRATUS.
LONG TERM...WEDNESDAY THROUGH SUNDAY
THE UPPER LEVEL RIDGE
WILL REMAIN OVERHEAD THROUGH THURSDAY MORNING. THE PATTERN GETS
A LITTLE TRICKY AS THE UPSTREAM WAVE BREAKS INTO A CUT OFF LOW
OFF THE CALIFORNIAN COAST. AMONGST MOST GUIDANCE THIS INCREASES
CLOUD COVER FOR OUR AREA BRINGIN A WEAK TROUGH AXIS THROUGH FROM
A DEEP HUDSON BAY LOW. HOWEVER, COMPARED TO PREVIOUS RUNS THIS
IS A LESS SIGNIFICANT SET UP FOR OUR AREA. THE CUT OFF LOW WOULD
CARRY MOST OF ITS ENERGY AWAY FROM OUR AREA, PREVENTING
PRECIPITATION THURSDAY-FRIDAY MORNING. BY FRIDAY EVENING THE CUT
OFF LOW BEGINS MAKING LANDFALL IN SOCAL AS IT REJOINS THE
PRIMARY LOW, TOO FAR EAST TO CARRY PRECIP THROUGH THE AREA
AGAIN. DETERMINISTIC GUIDANCE FOR SATURDAY-SUNDAY HAS TRENDED
TOWARDS A SLIGHT RIDGE. WHILE THIS SEEMS TO BE THE MEAN
OUTCOME, THERE IS STILL A STRONG CONTINGENT OF GUIDANCE SHOWING
A MORE UNSETTLED PATTERN WITH ZONAL FLOW ALOFT. IF WE DON'T GET
A PRECIPITATION EVENT OR A DECENT WAVE THROUGH THE AREA, WE
COULD SEE THE INVERSION HANG ON FOR A FEW MORE DAYS.
AVIATION
MVFR-LIFR IN LOW STRATUS AND FOG IN THE SNAKE PLAIN
AND SURROUNDING BASINS. STRATUS WILL LOWER SLIGHTLY TONIGHT TO
FAVOR IFR-LIFR, ESPECIALLY IN THE MAGIC VALLEY. MOUNTAINS BELOW
5KFT MSL OBSCURED, HIGHER ELEVATIONS CLEAR. SURFACE WINDS:
VARIABLE LESS THAN 8 KT. WINDS ALOFT AT 10KFT MSL: N-NW 10-20
KT.
KBOI...LOW STRATUS CONTINUES THIS AFTERNOON AND LIKELY THROUGH
THE NIGHT. MVFR-IFR TODAY WITH LOWERING TO IFR-LIFR OVERNIGHT.
SURFACE WINDS ARE LIGHT OUT OF THE NW, BECOMING SE EARLY
TOMORROW MORNING.
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.
BOI WATCHES/WARNINGS/ADVISORIES
ID...AIR STAGNATION ADVISORY UNTIL 11 AM MST THURSDAY
IDZ011>014-016-028-033.
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
SHORT TERM...JM
LONG TERM....JM
AVIATION.....JM
AIR STAGNATION...JM
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