FXUS65 KBOI 231043
AFDBOI

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
343 AM MST WED DEC 23 2009

.SHORT TERM...TODAY THROUGH THURSDAY...SURFACE HIGH PRESSURE RIDGE
AXIS FROM BRITISH COLUMBA THROUGH OREGON EARLY THIS WEDNESADY
MORNING WILL BE OVER IDAHO TONIGHT. STRONGER/COLDER HIGH SHIFTS
SOUTH ALONG THE DIVIDE AND EAST. WHILE MAIN SURGE OF COLDEST AIR
BUILDS SOUTH...EAST OF THE CONTINENTAL DIVIDE...A BUBBLE 1042MB
CENTER IN B.C. DOES DRIFT ACROSS OUR NORTHERN ZONES WHICH BRINGS
THE MOST COOLING ACROSS THE NORTHERN TIER TODAY. THERMAL PROFILES
CHANGE LITTLE THIS MORNING VS THURSDAY MORNING THEN WARM ALOFT
THURSDAY AFTERNOON. WINDS WILL BE LIGHT 5-10 MPH TONIGHT/THURSDAY
VERSUS 10 TO LOCALLY NEARLY 25 MPH AT 3 AM. ALSO FOR EXTRA SURFACE
COOLING...THE LOW CLOUDS IN THE MAGIC VALLEY ARE EXPECTED TO BE
SHIFTED INTO SE IDAHO UNTIL POSSIBLY THURSDAY AFTERNOON WHEN WEAK
SURFACE LOW SHIFTS BACK EAST OVER TWF-MUO. COUNTING ON SNOW
COVER... WHICH IS PATCHY BELOW ABOUT 3K FT...TO COMBINE WITH
CLEAR SKIES AND LIGHT WINDS FOR COLDER TEMPS EARLY THURSDAY BUT
DID WARM THEM SOME BELOW 3K FT PER LATE AFTERNOON SNOWCOVER
ESTIMATE AND CURRENT OBS IN THE ARCTIC AIR OVER B.C. FINALLY SW
IDAHO LOOKS TO BE IN A SQUEEZE FROM MODIFIED ARTIC AIR SEEPING IN
FROM NE/N-CENTRAL OREGON AND SE IDAHO SO A CONVERGENCGE ZONE MAY
SET UP AS DEPICTED IN NAM12 BOUNDARY LAYER WINDS THURSDAY IN SW
IDAHO. LOW LEVEL MOISTURE AND MET GUIDANCE GENERALLY PREFERRED
OVER MAV/MEX/MEN THE NEXT THREE PERIODS.

.LONG TERM...THURSDAY NIGHT THROUGH TUESDAY...UPPER LEVEL RIDGE 
ALONG THE WEST COAST WILL BUILD INLAND ON FRIDAY...FORCING NORTHERLY 
FLOW EAST OF THE FORECAST AREA. WARMING ALOFT WILL ALLOW HIGHER 
ELEVATION SITES TO GRADUALLY WARM FRIDAY THROUGH SUNDAY...BUT 
VALLEYS LIKELY TO REMAIN INVERTED FOR HIGH TEMPERATURES AT OR BELOW 
FREEZING. CONFIDENCE WANES BY EARLY NEXT WEEK AS MODELS STRUGGLE 
WITH THE BREAKDOWN OF THE UPPER RIDGE AND SUBSEQUENT PLACEMENT OF 
THE NEXT PACIFIC SYSTEM. GFS DIGS THE UPPER LOW WELL SOUTH OF THE 
FORECAST AREA /ALONG THE CALIFORNIA COAST/ FOR DRY CONDITIONS ACROSS 
ORE/ID. THE ECMWF PREFERS A MORE EASTERLY PROGRESSION OVER THE GREAT 
BASIN. FOR NOW...HAVE KEPT POPS NEAR CLIMATOLOGY AND MONDAY - 
WEDNESDAY TEMPERATURES AT OR BELOW NORMAL.

&&

.AVIATION...PREDOMINANTLY VFR UNDER MOSTLY CLEAR SKIES - EXCEPT EAST OF 
KMUO WHERE IFR STRATUS /CIGS 1K TO 3K FT AGL/ WILL CONTINUE THROUGH 
16Z...AND THROUGHOUT ID MTN VALLEYS WHERE IFR FOG IS EXPECTED TO 
DEVELOP BY 12Z. LIGHT TO MODERATE SURFACE WINDS...WITH GUSTS TO 25 
KTS ACROSS THE MAGIC VALLEY. 

&&

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

$$

WEATHER.GOV/BOISE

SHORT TERM...VM
LONG TERM....MT/JDS
AVIATION.....MT