Area Forecast Discussion
Issued by NWS Boise, ID

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000
FXUS65 KBOI 101658
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
958 AM MST WED FEB 10 2016

.DISCUSSION...LOW CLOUDS AND FOG ARE PRESENT AGAIN THIS MORNING IN
THE INVERTED VALLEYS. DENSE FOG IS LOCATED IN MAINLY ADA...MALHEUR
...AND HARNEY COUNTIES...ALONG WITH AROUND MCCALL. A DENSE FOG
ADVISORY IS IN EFFECT UNTIL 1 PM MST / NOON PST / IN THOSE AREAS.
AN UPDATE WILL BE ISSUED SHORTLY TO FURTHER TWEAK THE SKY AND
WEATHER GRIDS TO BETTER DEFINE THE LOCATIONS OF LOW CLOUDS AND FOG
THROUGH THE REMAINDER OF TODAY.

&&

.AVIATION...MVFR-LIFR STRATUS AND FOG SHOULD PERSIST IN MOST VALLEY
LOCATIONS THROUGH WED/21Z. ANTICIPATING FOG TO PERSIST AT KBNO AND
SURROUNDING AREAS IN SE OREGON THROUGH THE AFTERNOON. ABOVE THE
INVERSION...WILL SEE AN INCREASE IN HIGH CIRRUS TODAY. STRATUS AND
FOG SHOULD RETURN TO ALL VALLEY TAF SITES AFTER SUNSET TONIGHT.
SURFACE WINDS...VARIABLE MAINLY LESS THAN 10 KTS. STRONGER WINDS AT
KJER WILL DECREASE BY WED/19Z. WINDS ALOFT THROUGH 10K FT
MSL...SOUTHWEST TO WEST 10-20 KTS.

&&

.AIR STAGNATION...STRONG SURFACE-BASED INVERSION WILL REMAIN THROUGH
AT LEAST THURSDAY WHEN UPPER LEVEL RIDGE BEGINS TO WEAKEN AND SHIFT
SOUTHWARD. TOP OF THE INVERSION WAS NEAR 8000FT MSL ON LAST
EVENING/S SOUNDING AND SHOULD BE AGAIN TODAY.

&&

.PREV DISCUSSION...
SHORT TERM...SURFACE-BASED INVERSION IS NOW FULLY ESTABLISHED UNDER
HIGH PRESSURE ALOFT AND THE FORECAST THROUGH THURSDAY WILL BE BASED
ON PERSISTENCE.  DENSE FOG HAS FORMED IN MANY VALLEYS OF EASTERN
OREGON AND SWRN IDAHO AND A DENSE FOG ADVISORY IS IN EFFECT IN THESE
AREAS UNTIL 20Z.  AFTER SOME IMPROVEMENT THIS AFTERNOON AND EVENING
FOG AND STRATUS WILL EXPAND AGAIN TONIGHT BUT WE WILL NOT ATTEMPT TO
PINPOINT DENSE FOG IN THIS FORECAST.  TEMPS AND DEW POINTS ARE BASED
MAINLY ON OBSERVED VALUES FROM YESTERDAY...WHICH IN MANY CASES ARE
MUCH DIFFERENT FROM MODEL FORECASTS.  FOGGY AREAS WILL STAY IN THE
30S TO LOWER 40S...WHILE AREAS WITH NO FOG OR SNOW COVER WILL REACH
50. LIGHT WINDS THROUGH THURSDAY.

LONG TERM...THURSDAY NIGHT THROUGH WEDNESDAY...UPPER LEVEL RIDGE
CONTINUES TO WEAKEN THURSDAY NIGHT THROUGH FRIDAY WITH PASSAGE OF A
WEAK SHORT WAVE TROUGH. THE INVERSION WILL REMAIN BUT THINK STRATUS
AND FOG WILL BE LIMITED BY INCREASING SOUTHEASTERLY FLOW. MODELS IN
GOOD AGREEMENT BRINGING LIGHT SHOWERS TO THE MOUNTAINS OF SOUTHEAST
OREGON AND WEST CENTRAL IDAHO ON FRIDAY AND THUS ADDED SOME LOW POPS.
UPPER LEVEL TROUGH WILL MOVE ACROSS THE REGION LATE FRIDAY INTO
EARLY SATURDAY FOLLOWED BY A MOIST NORTHWESTERLY FLOW ALOFT THROUGH
SUNDAY. MOST OF THE REGION WILL SEE LIGHT PRECIPITATION OVER THE
WEEKEND. TEMPERATURES WILL INCREASE IN THE VALLEYS AS THE INVERSION
BREAKS...INTO THE LOWER 50S FRIDAY THROUGH SUNDAY. THE UPPER LEVEL
RIDGE REBUILDS BEGINNING MONDAY...PUSHING THE MOISTURE PLUME TO THE
NORTH AND ALLOWING TEMPERATURES TO RISE INTO THE MID TO UPPER 50S.
THE REGION SHOULD REMAIN DRY UNTIL WEDNESDAY WHEN THE NEXT UPPER
LEVEL TROUGH MOVES INLAND.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...DENSE FOG ADVISORY UNTIL 1 PM MST THIS AFTERNOON IDZ011-014.
OR...DENSE FOG ADVISORY UNTIL 1 PM MST /NOON PST/ THIS AFTERNOON
     ORZ061-063.

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...SP
AVIATION.....AB
AIR STAGNATION...LC
PREV SHORT TERM...LC
PREV LONG TERM....JDS


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