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AREA FORECAST DISCUSSION

 
 FXUS66 KOTX 241145
 AFDOTX
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE SPOKANE WA
 340 AM PST TUE NOV 24 2009
 
 .SYNOPSIS...
 A WEAK FRONTAL SYSTEM WILL BRING SOME VERY LIGHT RAIN TO THE
 REGION THIS MORNING...FOLLOWED BY A DRY BUT MOSTLY CLOUDY
 AFTERNOON...WITH A RETURN OF THE SAME FRONT WITH A CHANCE OF LIGHT
 PRECIPITATION TONIGHT. THE THANKSGIVING HOLIDAY WILL BE MAINLY DRY
 BUT CLOUDY. ON FRIDAY A COLD FRONT WILL PASS THROUGH WITH ANOTHER
 REASONABLE CHANCE OF MOUNTAIN SNOW AND VALLEY RAIN OR SNOW.
 CONDITIONS WILL REMAIN CLOUDY AND UNSETTLED INTO NEXT WEEKEND.
 
 &&
 
 .DISCUSSION...
 SATELLITE REVEALS A WEAK SHORT WAVE TROUGH IS BRUSHING THE
 FORECAST AREA THIS MORNING AS IT SWALES BY TO THE NORTH IN
 BRITISH COLUMBIA. THIS WAVE IS DIRECTING A DEEP AND WELL ORIENTED
 FETCH OF PRECIPITABLE WATER INTO THE REGION THIS MORNING...WHICH
 IS ENHANCING INTO A BAND OF LIGHT PRECIPITATION ALONG A WEAK COLD
 FRONT DRAPED ACROSS THE FORECAST AREA FROM SANDPOINT TO WENATCHEE.
 THIS FRONT...GENERATED BY THE WAVE PASSAGE TO THE NORTH...WILL
 SLUMP DOWN FROM NORTH TO SOUTH THROUGH THE REGION THIS MORNING.
 BRINGING SOME LIGHT MOUNTAIN SNOW AND A MIX OF RAIN OR WET NON-
 ACCUMULATING SNOW TO THE VALLEYS...EXCEPT FORT HE CASCADES LEE
 ZONES WHERE A RAIN SHADOW WILL KEEP PRECIPITATION VERY ISOLATED. BY
 THIS AFTERNOON MOST OF THE FORECAST AREA WILL BE BEHIND THE FRONT
 WITH DRY BUT CONTINUED MOSTLY CLOUDY SKIES AND ROUGHLY NORMAL HIGH
 TEMPERATURES.
 
 FOR TONIGHT...LATEST MODELS ARE IN GOOD AGREEMENT IN BUILDING A
 SHORT WAVE RIDGE OVER THE REGION. THIS BUILDING RIDGE WILL
 STIMULATE THIS MORNING`S FRONT TO BEGIN TO MIGRATE BACK NORTH THIS
 TIME AS A WARM FRONT...MOVING FROM SOUTH TO NORTH ACROSS THE
 FORECAST AREA. THE DIFFERENCE IS THAT BY THIS TIME THE DEEP
 PRECIPITABLE WATER FETCH WILL BE GONE...BUT THERE WILL BE ENOUGH
 RESIDUAL AMBIENT PWAT TO ALLOW WEAK ISENTROPIC ENHANCEMENT AT
 LEAST INTO HEAVY CLOUDS AND PROBABLY SOME VERY LIGHT PRECIPITATION
 OVER THE FORECAST AREA NORTH OF INTERSTATE 90. POPS REFLECTED IN
 THE FORECAST WILL BE FOR MEASURABLE PRECIPITATION...WITH A HIGHER
 LIKELIHOOD THAT MANY LOCATIONS NORTH OF I-90 WILL PROBABLY TRACE
 WITH SPRINKLES THIS EVENING. 
 
 FOR WEDNESDAY THE WARM FRONT WILL KICK NORTH INTO CANADA ENDING
 ANY PRECIPITATION THREAT OVER THE EAST ZONES...WHILE A NEW AND
 DEEP PACIFIC MOISTURE FEED WILL BEGIN TO IMPINGE ON THE CASCADES
 WITH ANOTHER THREAT OF PRECIPITATION NEAR THE CREST. FREEZING
 LEVELS WILL INCREASE DRAMATICALLY ON WEDNESDAY KEEPING SNOW ONLY
 ON THE HIGHER CASCADE PEAKS WITH MAINLY VARIABLY THICK MID AND
 HIGH LEVEL CLOUD DECKS ELSEWHERE. HIGH TEMPERATURES WEDNESDAY WILL
 CLIMB ABOVE NORMAL IN THE WARM SECTOR AHEAD OF THE NEXT
 STRONG PACIFIC TROUGH. /FUGAZZI
 
 WEDNESDAY NIGHT THROUGH MONDAY...GUIDANCE INDICATES AN ACTIVE AND
 AMPLIFIED FLOW OVER THE PACIFIC BASIN. A TROUGH POSITIONS ITSELF
 NEAR 140W BY WEDNESDAY NIGHT AND PLACES OUR AREA IN A SWLY FLOW.
 THIS HOLDS A PLUME OF MOISTURE AND ITS ASSOCIATED PRECIPITATION 
 TO THE COAST AND AROUND THE CASCADES THROUGH THURSDAY...WITH
 CHANCES SKIMMING THE CANADIAN BORDER. AN OCCLUDING SYSTEM SWINGS
 IN THURSDAY NIGHT AND FRIDAY...SPREADING PRECIPITATION FROM THE
 CASCADES EAST TO IDAHO IN THE SAME TIME FRAME. A DEVELOPING NW
 FLOW AND WRAP-AROUND MOISTURE WITH THE PASSING TROWAL WILL KEEP
 PRECIPITATION CHANCES HIGH OVER AT LEAST THE EASTERN THIRD OF THE
 CWA DURING THE DAY FRIDAY. MODELS SUGGEST RAIN THURSDAY NIGHT
 TRANSITIONING TO A RAIN/SNOW MIX OR ALL SNOW AS FRIDAY PROGRESSES
 INTO FRIDAY EVENING. SOME MODERATE MOUNTAIN SNOWS WILL BE POSSIBLE
 OVER IDAHO...THOUGH RIGHT SNOW AMOUNTS REMAIN UNDER HIGHLIGHT
 CRITERIA. CONFIDENCE IN THE DETAILS OF PRECISE PRECIPITATION ONSET
 AND RETURN OF COLDER AIR IS NOT AS FIRM AS I WOULD LIKE...AS
 GUIDANCE CONTINUES TO WAVER IN THIS REGARD. THE FORECAST IS A
 BLEND OF THE GFS/NAM/ECMWF.
 
 FRIDAY NIGHT INTO SATURDAY MORNING...A CLIPPER-LIKE DISTURBANCE
 SLIDES SOMEWHERE ACROSS THE NW STATES TO KEEP THE RISK FOR
 PRECIPITATION ALIVE. ACCUMULATING VALLEY SNOWS ARE NOT OUT OF THE
 QUESTION. HOWEVER WITH MODELS DEPICTING VARYING SOLUTIONS THAT
 COULD ALLOW THE SYSTEM TO MISS THE REGION...IT IS IMPRACTICAL TO
 SPEAK SPECIFICS. FROM SATURDAY AFTERNOON ON MODELS GENERALLY
 INDICATE HIGH PRESSURE BUILDING IN. THE 00Z/24 GFS DID DEPICT A
 SYSTEM ON MONDAY. YET THIS DIVERGES FROM ITS PREVIOUS RUNS AND
 OTHER GUIDANCE WHICH HOLDS IT BACK UNTIL MONDAY NIGHT OR TUESDAY.
 SO IT WILL BE DISCOUNTED FOR NOW. THIS LEAVES MAINLY OROGRAPHIC
 SHOWER CHANCES FOR THE MOUNTAINS AND RENEWS THE RISK FOR VALLEY
 STRATUS/PATCHY FOG. TEMPERATURES ARE EXPECTED TO BE AROUND NORMAL.
 /JCOTE
 
 &&
 
 .AVIATION...
 A MOIST MID LEVEL FRONT RUNNING FROM KYKM TO KCOE AT 12Z WILL MOVE 
 SOUTH TO KDLS TO KLWS BY 18Z. WHILE A RAIN SHADOW OFF THE CASCADES 
 WILL ALLOW VFR CONDITIONS AT KMWH AND KEAT...THIS FRONT WILL PROMOTE 
 LOW VFR OR MVFR CEILINGS AT KGEG/KSFF/KCOE AND KPUW THIS MORNING IN 
 MIXED PRECIPITATION AS THE FRONT PASSES. VFR CONDITIONS ARE THEN 
 EXPECTED AT THESE TAF SITES WITH THICK MID LEVEL CLOUDS. THE FRONT 
 WILL MOVE BACK NORTH TONIGHT AS A WARM FRONT WITH LOWERING CIGS AT 
 ALL TAF SITES...AND VERY LIGHT RAIN NORTH OF INTERSTATE 90 BGINNING 
 AROUND 03 TO 06Z. CONDITIONS WILL PROBABLY REMAIN VFR AT ALL TAF 
 SITES...WITH BRIEF MVFR CEILINGS POSSIBLE AT THE KGEG VCNTY SITES. 
 MOUNTAINS NORTH AND EAST OF THE BASIN WILL EXPERIENCE ARAES OF 
 OBSCURATIONS THROUGH 12Z WEDNESDAY.   
 
 
 &&
 
 .PRELIMINARY POINT TEMPS/POPS...
 SPOKANE        39  33  43  33  41  34 /  60  20   0   0  10  30 
 COEUR D`ALENE  39  32  44  32  41  34 /  60  20  10   0   0  30 
 PULLMAN        40  31  45  33  45  35 /  60  10   0   0   0  30 
 LEWISTON       45  35  47  35  48  39 /  30  10   0   0   0  20 
 COLVILLE       40  31  43  33  42  34 /  10  30  20  20  20  40 
 SANDPOINT      38  29  43  31  39  33 /  50  20  10  10  10  20 
 KELLOGG        35  31  43  30  41  33 /  60  30  10   0   0  20 
 MOSES LAKE     45  32  44  33  42  34 /  20  10   0  10  10  40 
 WENATCHEE      43  34  45  33  41  36 /  10  10   0  10  20  30 
 OMAK           43  31  42  32  41  35 /  10  20  10  20  30  40 
 
 &&
 
 .OTX WATCHES/WARNINGS/ADVISORIES...
 ID...NONE.
 WA...NONE.
 &&
 
 

 
 
 
 
 
 
 
 

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