FXUS65 KBOI 160338
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
838 PM MST TUE DEC 15 2009

.DISCUSSION...HEAVY SNOW CONTINUES TO POUND THE WEST CENTRAL AND
BOISE MOUNTAINS. RADAR AND SATELLITE TRENDS INDICATE HEAVY SNOW
WILL CONTINUE IN THESE AREAS UNTIL AT LEAST 7 AM WEDNESDAY
MORNING AND PROBABLY BEYOND. IN FACT...A DARKENING IN THE GOES WATER
VAPOR IMAGERY SUGGESTS THAT AN UPPER LEVEL SHORTWAVE TROUGH APPROACHING
THE OREGON COAST IS AMPLIFYING AND ENHANCING THE PRECIPITATION OUT
IN FRONT OF THE WAVE. THIS WAVE WILL MOVE SLOWLY EASTWARD KEEPING
THE FORECAST AREA AT THE FOCUS OF THE DEEP MOISTURE PLUME WITH
ORIGINS IN THE TROPICAL PACIFIC OCEAN. FOR NOW...WE HAVE EXTENDED
THE WINTER STORM WARNING UNTIL 7 AM WEDNESDAY MORNING FOR THE
MOUNTAINS WHERE IMPRESSIVE SNOW AMOUNTS CONTINUE TO PILE UP.
NATIONAL WEATHER SERVICE CO-OP OBSERVERS AND STORM SPOTTERS
INDICATE THAT 7 TO 12 INCHES OF SNOW HAS ALREADY ACCUMULATED IN
MOST OF THE WINTER STORM WARNING AREA...WITH 19 INCHES OF SNOW
REPORTED NEAR HALFWAY OREGON IN BAKER COUNTY. SEE THE LATEST LSR
REPORT FOR A COMPLETE LIST OF OBSERVED ACCUMULATIONS. SNOW LEVELS
ARE AROUND 4500 FEET WITH MODERATE RAIN NOW FALLING IN MOST VALLEY
LOCATIONS. SNOW LEVELS WILL RISE TO AROUND 5000 FEET ON WEDNESDAY.

&&

.HYDROLOGY...MODERATE RAIN IN PORTIONS OF THE UPPER AND LOWER TREASURE
VALLEY COMBINED WITH SNOW MELT IS CAUSING SIGNIFICANT RUNOFF AND
PONDING OF WATER. WITH FROZEN SOIL...THIS WATER WILL BE SLOW TO
SEEP INTO THE GROUND. THERE ARE NO REPORTS OF FLOODING AT THIS
TIME...BUT PEOPLE SHOULD BE CAREFUL AROUND DRAINAGE DITCHES AND
OTHER LOW AREAS WHICH MAY BE FULL OF WATER.

&&

.AVIATION...WIDESPREAD IFR IN THE MOUNTAINS OF SW IDAHO AND SE
OREGON THROUGH WEDNESDAY MORNING. LOW-VFR AND MVFR CONDITIONS OVER
LOWER VALLEYS INCLUDING THE TREASURE AND WESTERN MAGIC. BEST
CHANCE FOR VFR CONDITIONS IN THE MTNS IS WEDNESDAY AFTERNOON
THOUGH AREAS THAT DO BREAK OUT WILL BE BACK TO IFR BY WEDNESDAY
NIGHT. LOWER VALLEYS VFR ON WEDNESDAY WITH CEILINGS OF 7K TO 10K
FEET MSL. LITTLE CHANGE IN WINDS SURFACE AND ALOFT THROUGH
WEDNESDAY.

&&

.BOI WATCHES/WARNINGS/ADVISORIES...
ID...WINTER STORM WARNING UNTIL 7 AM MST WEDNESDAY FOR IDZ011-IDZ013-
     IDZ033.
     WINTER WEATHER ADVISORY UNTIL 11 PM MST THIS EVENING FOR IDZ016-
     IDZ028.
OR...WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR ORZ062.
&&

$$

WEATHER.GOV/BOISE

DISCUSSION...JB
HYDROLOGY...JB
AVIATION.....DG