FXUS65 KBOI 281557
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
857 AM MST SAT NOV 28 2009

.DISCUSSION...MODERATE WEST-NORTHWESTERLY WINDS THIS MORNING MIXED
AND DRIED THE LOW-LEVEL AIR MASS AND DISSIPATED LAST NIGHT/S FOG,  
TODAY WILL BE A BRISK COOL DAY AS SURFACE HIGH PRESSURE FINISHES 
BUILDING IN FROM THE NORTHWEST.  THE SURFACE HIGH WILL SETTLE OVER 
CENTRAL IDAHO TONIGHT AND WINDS WILL DIE DOWN AND RADIATIONAL 
COOLING WILL OCCUR.  AS NOTED IN EARLIER DISCUSSION ENOUGH LOW
LEVEL MOISTURE WILL REMAIN FOR PATCHY FOG LATE TONIGHT IN OUR COLDER 
EASTERN VALLEYS.  SURFACE INVERSION WILL GRADUALLY INTENSIFY SUNDAY 
AND MONDAY DUE TO WARMING ALOFT AS HIGH PRESSURE BUILDS IN FROM
THE WEST.  BUT IT WILL TAKE A COUPLE OF DAYS FOR AIR QUALITY TO 
DETERIORATE NOTICEABLY IN THE VALLEYS.  NO REALISTIC CHANCE OF
MORE RAIN OR SNOW UNTIL NEXT WEEKEND.  NO UPDATES.

&&  

.AVIATION...IFR-MVFR CEILINGS IN STRATUS IN THE SNAKE RIVER VALLEY 
EAST OF KMUO INTO THE WESTERN MAGIC VALLEY THIS MORNING.  CONDITIONS 
WILL SLOWLY IMPROVE TO VFR BY 19Z.  OTHERWISE VFR CONDITIONS TODAY 
UNDER MOSTLY CLEAR SKIES.  SURFACE WINDS TODAY WILL BE LIGHT OUT OF 
THE WEST WITH MODERATE NORTH WINDS ALOFT.  

TONIGHT VFR CONDITIONS WILL LAST UNTIL AT LEAST 03Z WITH IFR 
CONDITIONS IN VALLEY FOG AND STRATUS DEVELOPING AFTER 03Z.  WITH 
LIGHT WEST WINDS IN THE TREASURE VALLEY FROM KONO TO KBOI EXPECT 
SOURCE OF THE IFR TO BE FOG AND NOT STRATUS WHICH COULD BRING 
LIFR-VLIFR CONDITIONS TO KBOI AND OTHER AIRPORTS IN THE TREASURE 
VALLEY SUNDAY MORNING.

&&

.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH SUNDAY...PATCHY DENSE FOG IN SOUTH 
CENTRAL IDAHO WITH TEMPERATURES CLOSE TO OR BELOW FREEZING IS 
EXPECTED TO LIFT EARLY THIS MORNING. WEST WINDS AROUND 13 MPH 
ACCOMPANIED THIS FOG. THAT FOG WAS LIKELY THE RESULT OF 
COOLING/CONDENSATION WITH THE FRONT AS IT WAS ACCOMPANIED BY WSW 
WINDS AROUND 13 MPH. WINDS AROUND 15 MPH...GUSTS AROUND 30 MPH IN 
ONTARIO OREGON...INHIBITED RADIATION FOG MOST OTHER PLACES IN SPITE 
OF RAIN AND SNOW FRIDAY. TONIGHT WILL BE A DIFFERENT STORY. BUT 
FIRST TODAY...SURFACE HIGH CENTER BUILDING INTO OREGON/CENTRAL IDAHO 
WILL KEEP NW-SE SFC PRESSURE GRADIENT AND SOME WIND ACROSS THE 
REGION WITH MOSTLY SUNNY SKIES. THIS RESULTS IN TEMPERATURES CLOSE 
TO MOS. ALOFT A FOLD-OVER RIDGE WITH A DEVELOPING SUBSIDENCE 
INVERSION TODAY NARROWS ACROSS THE AREA TONIGHT ALLOWING SOME HIGH 
CLOUDS FAR NORTH. THE SURFACE HIGH CENTER EXPANDS THROUGH THE REGION 
FOR LIGHT WINDS AND COLD TEMPS. ENOUGH MOISTURE IS EXPECTED TO BE 
AVAILABLE FOR AREAS OF FOG /AND STRATUS MAINLY KJER-FAFI1/ TO 
DEVELOP LATE TONIGHT AND PERSIST INTO SUNDAY MORNING. EXPANSIVE HIGH 
REMAINS OVER THE AREA SUNDAY ...THO CENTERED IN CENTRAL IDAHO 
MOUNTAINS...FOR VALLEY TEMPERATURES BELOW MOS. A COUPLE OF DAYS OF 
STAGNANT CONDITIONS ARE LIKELY STARTING SUNDAY.

LONG TERM...SUNDAY NIGHT THROUGH FRIDAY...INVERSION IN PLACE MONDAY 
WITH MORE FOG/STRATUS IN VALLEYS MONDAY MORNING. MODELS ARE HINTING 
TOWARD A MORE NEWD TRACK FOR THE TROUGH ON TUESDAY. EFFECT WOULD BE 
LOWER POPS AND TEMPS OVER WEST CENTRAL AND BOISE MTNS AND GREATER 
CHANCE THAT INVERSION IN THE LOWER VALLEYS REMAINS INTACT. STILL 
ENOUGH UNCERTAINTY TO KEEP FOG AND STRATUS OUT OF FORECAST FOR 
TUESDAY AT THIS POINT. RIDGE AXIS RESETS ALONG THE PAC NW COAST FOR 
WED-FRI KEEPING FORECAST AREA IN A DRY NW FLOW ALOFT. WEAK INVERSION 
REMAINS IN PLACE KEEPING VALLEY TEMPS NEAR NORMAL. NEXT CHANCE FOR 
PRECIP WOULD BE FRI/SAT...THOUGH WITH N-NW SOURCE NO SIGNS OF 
TAPPING INTO ANY DEEP MOISTURE WHICH WILL LIMIT PRECIP AMOUNTS.

&&

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

&&

$$

WEATHER.GOV/BOISE

DISCUSSION...LC
AVIATION.....JA
PREV SHORT TERM...VM
PREV LONG TERM....DG