068
FXUS65 KBOI 071647
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
945 AM MST SAT NOV 7 2009
DISCUSSION
BAND OF LIGHT SHOWERS HAS BEEN WEAKENING AND MOVING
SLOWLY OFF TO THE SOUTH WITH LIGHT PRECIP OCCASIONALLY BEING
RECORDED AT TWIN FALLS ASOS AND JEROME ASOS. MODELS INDICATE FURTHER
WEAKENING OF THE BAND AFTER 18Z SO WILL FORECAST LOWER POPS THIS
AFTERNOON. ELSEWHERE...ISOLATED SHOWERS WERE OCCURRING IN THE
BOISE/WEST CENTRAL MOUNTAINS BUT ALL INDICATIONS WERE THAT THE
PRECIP IS VERY LIGHT. STEEP LAPSE RATES AND AFTERNOON HEATING WILL
SUPPORT LOW-END POPS IN THE MOUNTAINS THROUGH THIS AFTERNOON.
AVIATION
MOST OF SOUTHWESTERN IDAHO AND SOUTHEASTERN OREGON WILL
SEE VFR CONDITIONS SATURDAY THROUGH SUNDAY WITH LIGHT WINDS AT THE
SURFACE AND ALOFT. HOWEVER...LINGERING CUMULUS CLOUDS IN THE
CENTRAL IDAHO MOUNTAINS AND ALONG THE IDAHO-NEVADA BORDER WILL BE
ASSOCIATED WITH LOWER CEILINGS AND WILL OBSCURE MOUNTAIN TOPS AT
TIMES THROUGH SATURDAY AFTERNOON.
PREV DISCUSSION
SHORT TERM...AT 09Z KCBX RADAR SHOWED SHOWERS CONTINUING IN A BAND
EXTENDING FROM THE SW CORNER OF IDAHO NEWD TO SRN CAMAS
COUNTY...PARALLEL TO THE REMAINS OF FRIDAY/S COLD FRONT WHICH WAS
NEAR THE SRN IDAHO BORDER. STRONG WLY FLOW ALOFT CONTINUES TO ADVECT
COOL AND UNSTABLE AIR INTO OUR CWA BUT SO FAR OTHER SHOWERS HAVE
BEEN HARD TO FIND. SAPIX SHOWED NEXT SHORT WAVE TROUGH FROM THE
PACIFIC ALONG THE CASCADES AT 09Z AND MOVING RAPIDLY EAST...FOR A
CHANCE OF RAIN AND SNOW SHOWERS IN OUR ZONES LATER THIS
MORNING...BUT VERY LOW MOS POPS SUGGEST THEY WON/T HAPPEN. WE THINK
THEY WILL. MAX TEMPS WILL BE SLIGHTLY BELOW NORMAL TODAY AND
SUNDAY...WITH MIN TEMPS NEAR NORMAL DUE TO CONTINUING MIXING WINDS
AND CLOUD COVER.
LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...SHORTWAVE RIDGE WILL BUILD
OVER THE AREA SUNDAY NIGHT AND MONDAY WITH WARMER TEMPS ABOVE 4000 FT
MSL BUT LITTLE CHANGE BELOW 4000 FEET UNDER STABLE INVERSION. A COLD
FRONT WILL ADVANCE FROM THE WEST TUESDAY NIGHT IN CONJUNCTION WITH A
MOIST PACIFIC TROUGH FOR HIGHER POPS TUESDAY...AND SNOW LEVELS
FALLING TO AROUND 5K FEET MSL BEHIND THE FRONT WEDNESDAY.
CONSIDERABLE DISAGREEMENT REMAINS IN THE EXTENDED MODELS REGARDING
THE POSITION AND STRENGTH OF A LONGWAVE TROUGH BEYOND WEDNESDAY.
BASED ON THE 00Z RUNS THE GFS GIVES A FASTER AND MORE PROGRESSIVE
FLOW WHILE THE ECMWF FAVORS SLOWER TIMING BUT PAINTS A CLOSED LOW
OVER THE FORECAST AREA BY FRIDAY. WITH THIS MUCH UNCERTAINTY THE
NATIONAL GUIDANCE PREFERRED A COMPROMISE BETWEEN THE TWO. FOLLOWING
CLOSELY WITH THIS RESULTS IN ABOVE CLIMO POPS AND SLIGHTLY BELOW
NORMAL TEMPERATURES THROUGH THE PERIOD.
BOI WATCHES/WARNINGS/ADVISORIES
ID...NONE.
OR...NONE.
WEATHER.GOV/BOISE
DISCUSSION...BW
AVIATION.....JB
PREV SHORT TERM...LC
PREV LONG TERM....CD
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