Area Forecast Discussion
Issued by NWS Boise, ID

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327
FXUS65 KBOI 091001
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
301 AM MST TUE FEB 9 2016

.SHORT TERM...FOG AND STRATUS HAVE BECOME MORE EXTENSIVE SINCE
YESTERDAY AS LOW-LEVEL INVERSION INTENSIFIES.  FOG/STRATUS HAVE
EXPANDED FROM THE MAGIC VALLEY DOWN THE SNAKE RIVER TOWARD
MOUNTAIN HOME DURING THE NIGHT.  A SECOND LARGER AREA WAS IN THE
LOWER TREASURE VALLEY AND GEM COUNTY.  THE FOG AND STRATUS
SHOULD REACH MAXIMUM EXTENT THIS MORNING THEN DECREASE LATE
MORNING THROUGH THIS EVENING BEFORE INCREASING AGAIN TONIGHT.
HIGH TEMPERATURES TODAY WILL BE LOWER THAN YESTERDAY IN THE LOWER
TREASURE VALLEY AND MOST OF EASTERN OREGON...SLIGHTLY LOWER THAN
YESTERDAY IN THE UPPER TREASURE VALLEY...AND ABOUT THE SAME AS
YESTERDAY ELSEWHERE.  WARMEST AREAS WILL BE ABOVE THE VALLEYS
IN OREGON WHERE TEMPERATURES WILL RISE WELL INTO THE 50S.
LITTLE CHANGE TONIGHT AND WEDNESDAY.  INTERESTING TO NOTE THAT
THE 500 MB RIDGE IS THE STRONGEST ON RECORD BY HEIGHT AND TEMPERATURE
FOR THE MONTHS OF FEBRUARY MARCH AND APRIL AS FAR BACK AS 1948.
LOW SUN ANGLE...SNOW COVER...AND LIGHT WINDS ARE KEEPING THE SURFACE
RELATIVELY COLD AND MAINTAINING THE INVERSION.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY...UPPER LEVEL RIDGE
BEGINS TO WEAKEN FRIDAY WITH APPROACHING UPPER LEVEL TROUGH FROM THE
WEST. VALLEY INVERSIONS WILL REMAIN IN PLACE THURSDAY NIGHT AND
FRIDAY...BUT VALLEY FOG AND STRATUS MAY BE LIMITED DUE TO AN
INCREASING EAST OR SOUTHEAST FLOW OVER THE REGION. TEMPERATURES IN
THE VALLEY WILL BE DEPENDENT ON STRATUS COVERAGE WHICH FAVORS THE
LOWER TREASURE VALLEY AND WESTERN MAGIC VALLEY. UPPER LEVEL TROUGH
MOVES THROUGH THE REGION SATURDAY FOR LIGHT PRECIPITATION ACROSS
MUCH OF THE AREA. THE UPPER RIDGE REBUILDS SUNDAY THROUGH TUESDAY
BRINGING DRY CONDITIONS AND ABOVE NORMAL TEMPERATURES AGAIN.

&&

.AVIATION...EXPECT PATCHY VALLEY FOG AND LOW STRATUS...WITH
CONDITIONS RANGING FROM MVFR TO LIFR...IMPROVING LATE AFTERNOON
THROUGH EARLY EVENING. KONO...KJER...AND KTWF MAY STAY IN THE
STRATUS ALL DAY BUT KBOI AND KMUO WILL LIKELY CLEAR OUT BY EARLY
AFTERNOON.  SURFACE WINDS...VARIABLE BUT MAINLY EAST 10 KTS OR LESS.
WINDS ALOFT...NORTHWEST 5-15 KTS BECOMING SOUTHWEST 10-20 KTS AFTER
18Z THROUGH 10K FT MSL.

&&

.AIR STAGNATION...00Z/TUE SOUNDING AT BOISE REVEALED A STRONG
TEMPERATURE INVERSION BETWEEN 5100 AND 8500 FEET MSL.  INVERSION
WILL CONTINUE THROUGH FRIDAY AS AN UNSEASONABLY STRONG RIDGE
ALOFT CONTINUES OVER THE REGION. THE RIDGE AXIS WILL SLOWLY
TRANSITION EWD ACROSS THE REGION THROUGH TUESDAY AFTERNOON WITH
LIGHT WINDS ALOFT. COOL/MOIST AIR IN THE VALLEYS WILL HELP FORM
LOW CLOUDS AND FOG BELOW 5000 FT MSL.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.

&&

$$

WEATHER.GOV/BOISE

SHORT TERM...LC
LONG TERM....JDS
AVIATION.....JDS
AIR STAGNATION...LC



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