161
FXUS65 KBOI 241033 CCA
AFDBOI
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE BOISE ID
240 AM MST TUE NOV 24 2009
SHORT TERM...TODAY THROUGH WEDNESDAY
LIGHT NORTHWEST FLOW ALOFT
IS OVER OUR AREA TODAY AHEAD OF A BUILDING UPPER LEVEL RIDGE. WE ARE
SEEING THE START OF A TEMPERATURE INVERSION WHICH WILL INTENSIFY
TONIGHT AND WEDNESDAY. EARLY THIS MORNING MID LEVEL AND HIGH CLOUDS
ASSOCIATED WITH A WEAK SHORTWAVE ARE APPROACHING FROM WESTERN AND
CENTRAL OREGON. THESE CLOUDS WILL PARTIALLY DISSIPATE CROSSING THE
DEVELOPING RIDGE AXIS AND NO PRECIPITATION IS EXPECTED...BUT THERE
WILL BE ENOUGH SHADING...COMBINED WITH THE INVERSION AND LIGHT
SURFACE WINDS...TO HOLD TEMPERATURES BACK. SO HIGHS SHOULD BE A FEW
DEGREES BELOW YESTERDAY/S. THE RIDGE...ALONG WITH THE INVERSION...
WILL REACH MAXIMUM DEVELOPMENT WEDNESDAY AFTERNOON. THE COMBINATION
OF MORE SUN AND A BETTER DOWN VALLEY PRESSURE GRADIENT SHOULD
BALANCE THE DEEPER INVERSION...SO WE EXPECT HIGH TEMPERATURES
WEDNESDAY WILL BE CLOSE TO TODAY/S. WE ARE KEEPING PATCHY VALLEY
FOG AND STRATUS FOR LATE TONIGHT AND WEDNESDAY MORNING...BUT WITH
THE DRY AIRMASS CONFIDENCE IS RATHER LOW.
LONG TERM...WEDNESDAY NIGHT THROUGH TUESDAY
UPPER RIDGE BUILDS
OVER THE AREA WEDNESDAY NIGHT AND EARLY THURSDAY IN ADVANCE OF NEXT
PACIFIC SHORT WAVE. DURING THANKSGIVING DAY...RIDGE AXIS MOVES EAST
TO WYOMING AND MONTANA ALLOWING A SOUTHWEST FLOW OF WARMER AND DRY
AIR INTO THE REGION. EXTENDED MODELS IN GOOD AGREEMENT IN THIS TIME
RANGE BUT WILD CARD AT THIS TIME IS STRENGTH OF ASSOCIATED INVERSION
AND THE POSSIBILITY OF LOW CLOUDS AND FOG. FEELING IS THAT SINCE WE
HAVE BEEN QUITE DRY THIS MONTH AND ESPECIALLY RECENTLY..LOW CLOUD
INVERSION CONDITIONS MAY NOT SET UP YET. THIS MAY LEAD TO A QUITE
MILD...BREEZY AND DRY DAY FOR THANKSGIVING AND THIS IS WHAT WE HAVE
FORECAST. A PACIFIC SHORT WAVE MOVES ACROSS THE AREA FRIDAY AND
FRIDAY NIGHT FOR LIGHT AMOUNTS OF PRECIPITATION WITH SYSTEM ONCE
AGAIN EMBEDDED WITHIN A FAST PROGRESSIVE FLOW. BY SUNDAY...MODELS
AGREE WITH HIGH AMPLITUDE RIDGE REBUILDING OVER THE PACIFIC
NORTHWEST WHICH REMAINS THROUGH THE LAST DAY IN NOVEMBER.
TEMPERATURES AT SEASONAL VALUES THROUGH THE PERIOD BUT PRECIP LOOKS
TO BE BELOW NORMAL.
AVIATION
VFR CONDITIONS. LIGHT WINDS SURFACE AND ALOFT WITHIN
HIGH PRESSURE CENTER. LOW CLOUDS PRESENTLY IN THE UPPER SNAKE VALLEY
MAY DEVELOP WESTWARD THIS MORNING TOWARD THE KJER AND KTWF AS EAST
FLOW STRENGTHENS. ELSEWHERE...EXTENSIVE MID CLOUD SPREADING OVER THE
AREA FROM CENTRAL OREGON THIS MORNING...BUT DECREASING THIS
AFTERNOON AS WEAK WAVE MOVES EAST UNDER RIDGE. VISIBILITY
UNRESTRICTED BUT REDUCING TO 5-7SM IN HAZE AS HIGH PRESSURE
STAGNATES AND INVERSION INCREASES TONIGHT.
BOI WATCHES/WARNINGS/ADVISORIES
ID...NONE.
OR...NONE.
WEATHER.GOV/BOISE
SHORT TERM...JT
LONG TERM....GS
AVIATION.....GS
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