FXUS65 KBOI 252126
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
226 PM MST WED NOV 25 2009

.SHORT TERM...PERSISTENT WX WITH LOW-LEVEL INVERSION AND HAZE IN THE 
VALLEYS WILL CONTINUE THROUGH THURSDAY NIGHT...AFTER WHICH PACIFIC 
COLD FRONT...CURRENTLY OFF NW COAST...WILL COME IN.  GFS BRINGS THE 
FRONT IN FASTEST...NAM SLOWEST...ECM IN BETWEEN.  LARGE AMPLITUDE OF 
THE UPPER TROUGH SUPPORTS THE SPEED OF THE SLOWER NAM.  LIGHT TO 
MODERATE PCPN WILL COME THROUGH OUR OREGON ZONES FRIDAY...AND IDAHO 
ZONES FRIDAY AFTERNOON AND EVENING.  PRE-FRONTAL WINDS AND CLOUD 
COVER WILL AFFECT TEMPS FRIDAY...WINDS WILL MIX OUT COLD AIR IN THE 
VALLEYS...AND CLOUDS WILL LIMIT DAYTIME WARMING.  PCPN WILL BE IN 
THE FORM OF RAIN BELOW 4000-4500 FEET...AND SNOW ABOVE WITH 2 TO 4 
INCHES EXPECTED...NOT A BIG EVENT.  LIGHT TO MODERATE EAST-SOUTHEAST 
WINDS THROUGH FRIDAY MORNING WILL SHIFT TO LIGHT NORTHWESTERLY 
BEHIND THE FRONT AS NEW CLEANER AIR MASS COMES IN.

.LONG TERM...FRIDAY NIGHT THROUGH WEDNESDAY...UPPER RIDGE REBUILDS 
SATURDAY BEHIND THE PACIFIC SHORT WAVE. LATEST MODEL RUNS SHOWING
A SURGE OF MOISTURE MOVE OVER THE TOP OF THE RIDGE AND INTO THE 
NORTHERN MOUNTAIN ZONES SATURDAY AFTERNOON...WHICH IS FURTHER NORTH 
THAN THE PREVIOUS MODEL RUNS. MODELS SHOWING THE RIDGE BREAKING DOWN 
EARLY NEXT WEEK AS A STRONG PACIFIC SHORT WAVE MOVES ACROSS THE 
NORTHWEST. TIMING BETWEEN THE ECMWF AND GFS VARIES QUITE A BIT WITH 
THE GFS MUCH FASTER. THINK THE SLOWER ECMWF SOLUTION HAS THE BETTER 
TIMING SO HAVE TRENDED FORECAST TOWARDS THE SLOWER TIMING. STRONG 
UPPER RIDGE REDEVELOPS OVER THE WESTERN U.S./EASTERN PACIFIC AND 
DEPENDING ON THE RIDGE AXIS LOCATION COULD BRING ARCTIC AIR FROM 
CANADA/ALASKA. ALSO...DEPENDING ON HOW MUCH RAIN OR SNOW FALLS OVER 
THE WEEKEND...THIS MAY HAVE IMPLICATIONS FOR INVERSION DEVELOPMENT 
ALONG WITH LOW CLOUDS AND FOG IN A STRONGER RIDGE PATTERN SETTING UP 
EARLY NEXT WEEK.     

&&

.AVIATION...VFR TONIGHT AND THURSDAY...EXCEPT FOR VALLEY STRATUS AND 
FOG. EXPECT STRATUS AND FOG TO REDEVELOP IN MCCALL TONIGHT AND 
POSSIBLE JEROME AND TWIN FALLS. STRATUS FROM EASTERN IDAHO COULD 
MOVE INTO THE WESTERN MAGIC VALLEY BY 12Z THURSDAY MORNING. 
INVERSION REMAINING OVER THE AREA FOR WIDESPREAD HAZE IN THE LOWER 
VALLEYS TOMORROW. VSBY MAY REDUCE TO 5 TO 7SM IN HAZE BEFORE LOW 
LEVEL EAST FLOW PICKS UP AHEAD OF APPROACHING PACIFIC SHORT WAVE ON 
FRIDAY. SURFACE WINDS LIGHT TONIGHT THROUGH THURSDAY WITH LIGHT 
WINDS ALOFT. 

&&

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

&&

$$

WEATHER.GOV/BOISE

SHORT TERM...LC
LONG TERM....JS/BB
AVIATION.....JS