FXUS65 KBOI 231614
AFDBOI
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOISE ID
914 AM MST WED DEC 23 2009
.DISCUSSION...CURRENT FORECAST LOOKS GOOD WITH DRY WX EXPECTED
THROUGH THE CHRISTMAS WEEKEND EXCEPT FOR PATCHY VALLEY FOG NIGHTS
AND MORNINGS. WE MAY UPDATE WINDS IN THE SNAKE BASIN FROM MUO
THROUGH TWF WHERE SPEEDS THIS MORNING HAVE BEEN 15-25 KTS...ABOUT
5 KTS STRONGER THAN FORECAST. AS DESCRIBED IN PREVIOUS SHORT
TERM...TONIGHT WILL BE COLDER THAN LAST NIGHT AS WINDS DIE DOWN
AND SKIES BECOME CLEAR.
&&
.AVIATION...MODERATE WESTERLY SURFACE WINDS IN THE WESTERN MAGIC
VALLEY AT KJER/KTWF UNTIL 21Z. LIGHT NORTHWEST WINDS ELSEWHERE.
MODERATE TO STRONG NORTH TO NORTHWEST WINDS ALOFT. MOUNTAIN VALLEYS
LOCAL LIFR IN FOG UNTIL 18Z. OTHERWISE VFR UNTIL AFTER 03Z WITH
AREAS OF FOG DEVELOPING AND CONTINUING UNTIL AT LEAST 15Z THURSDAY.
&&
.PREV DISCUSSION...
SHORT TERM...TODAY THROUGH THURSDAY...SURFACE HIGH PRESSURE RIDGE
AXIS FROM BRITISH COLUMBIA 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.
&&
.BOI WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
OR...NONE.
&&
$$
WEATHER.GOV/BOISE
DISCUSSION...LC
AVIATION.....CD
PREV SHORT TERM...VM
PREV LONG TERM....MT/JDS
