Western Washington

857 
FXUS66 KSEW 171128
AFDSEW

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SEATTLE WA
330 AM PST THU DEC 17 2009

.SYNOPSIS...A LULL IN SHOWERS IS EXPECTED THIS MORNING BETWEEN 
WEATHER SYSTEMS. ANOTHER WEATHER SYSTEM WILL BRING A RENEWED THREAT 
OF RAIN TO MOST THE AREA LATER TODAY AND TONIGHT. SHOWERS WILL 
TAPPER OFF FRIDAY WITH RELATIVELY DRY WEATHER ON SATURDAY. SUNDAY 
INTO EARLY NEXT WEEK LOOK WET WITH SEVERAL WEATHER SYSTEMS MOVING 
THROUGH THE REGION. 

&&

.SHORT TERM...SHOWERS HAVE TAPERED OFF ACROSS THE AREA WITH JUST 
RESIDUAL LIGHT PRECIP IN THE CASCADES ACCORDING TO THE LATEST RADAR 
LOOP. A LULL OR BREAK IN PRECIP IS EXPECTED THIS MORNING BETWEEN 
WEATHER SYSTEMS. MODELS DEVELOP WEAK RIDGING OVER THE AREA TODAY 
WHICH WILL CAUSE THE NEXT INCOMING FRONTAL SYSTEM TO SLOW DOWN AND 
WEAKEN. MOST MODELS BRING LIGHT RAIN TO THE COAST DURING THE 
AFTERNOON...SLOWLY SPREADING INLAND LATE IN THE DAY AND THIS 
EVENING. THE GFS DEVELOPS A SECONDARY LOW ON THE FRONT TONIGHT WHICH 
MAY ENERGIZE THE SYSTEM AS THE MAIN PRECIP BAND PUSHES IN AFTER 
MIDNIGHT. EXPECT THE HEAVIEST RAINFALL TO OCCUR IN THE MOUNTAINS 
WITH STRONGER SLY FLOW ASSOCIATED WITH THE FRONT. THE MAIN SNOW 
LEVEL WILL RISE TO AROUND 5K FEET. HOWEVER...ELY FLOW ACROSS THE 
CASCADES MAY CONTINUE TO HOLD SOME OF THE HIGHER PASS TEMPS DOWN 
AROUND FREEZING. QPF AMOUNTS LOOK QUITE LIGHT IN THE CASCADES SO I 
WON'T ISSUE AN ADVISORY AT THIS TIME. SNOW/ICE ACCUMULATION WILL BE 
MINIMAL AT LEAST THROUGH TONIGHT. THERE COULD BE SOME SNOW 
ACCUMULATION IN THE HIGHER PASSES TOWARD FRIDAY MORNING ALONG AND 
BEHIND THE FRONT BUT SNOW AMOUNTS LOOK TO BE ONLY A FEW INCHES. 

SHOWERS GRADUALLY TAPPER OFF ON FRIDAY. DECIDED TO CUT BACK ON POPS 
BUT KEPT SOME CHANCE WITH WLY FLOW OVER THE AREA. HEIGHTS BUILD 
ON SATURDAY WITH ALL MODELS SHOWING DRY WEATHER. THE NEXT WARM FRONT 
SHOULD HOLD OFF UNTIL SATURDAY EVENING SO I DECIDED TO REMOVE POPS 
FOR MUCH OF THE AREA. I DID MAINTAIN SOME POPS ACROSS THE FAR S IN 
CASE THE WARM FRONT MOVES IN LITTLE QUICKER THAN MODELS SHOW WHICH 
IS OFTEN THE CASE IN PROGRESSIVE PATTERNS. 

.LONG TERM...A WARM FRONT SATURDAY NIGHT WILL BE FOLLOWED BY A 
TROUGH AND ASSOCIATED COLD FRONT ON SUNDAY. RAIN SHOULD INCREASE 
ACROSS THE ENTIRE AREA WITH SNOW LEVELS RISING ABOVE THE PASSES BUT 
THEN FALLING BACK TO THE HIGHER PASSES SUNDAY NIGHT. THE UPPER LOW 
SLOWS AND STALLS OVER WA EARLY NEXT WEEK WITH SHOWERS CONTINUING 
ACROSS THE AREA. THE GFS BRINGS ANOTHER WEAK SHORT WAVE THROUGH ON 
TUESDAY IN NW FLOW. SNOW LEVELS SHOULD COME WAY DOWN WITH COOLER AIR 
COMING IN FROM THE N. MODELS KEEP THE COLDEST AIR WELL E OF WA SO NO 
DRAMATIC COLD SNAP IS EXPECTED. MERCER

&&

.HYDROLOGY...THE SKOKOMISH RIVER PEAKED NEAR 16.25 FT 
OVERNIGHT...BELOW THE 16.5 FT FLOOD STAGE. THE RIVER WILL CONTINUE 
TO RUN HIGH TODAY. WITH MORE RAIN ON THE WAY...POSSIBLY IN EXCESS OF 
2 INCHES OVER THE OLYMPICS TONIGHT AND FRIDAY MORNING...THERE IS A 
LOW THREAT OF FLOODING ON THE SKOKOMISH RIVER BY FRIDAY. CURRENT 
HYDRO RUNS KEEP THE RIVER WELL BELOW FLOOD STAGE SO I WILL NOT ISSUE 
A WATCH. BUT WITH THE RIVER ALREADY HIGH...THIS NEEDS TO BE WATCHED. 
QPF AMOUNTS DO NOT APPEAR HIGH ENOUGH FOR FLOODING CONCERNS ON OTHER 
RIVERS.

THE NEXT ROUND OF MODERATE RAIN IS NOT EXPECTED UNTIL SUNDAY WHEN 
THE NEXT COLD FRONT THROUGH WRN WA. AGAIN...THERE IS A LOW THREAT OF 
FLOODING ON THE SKOKOMISH RIVER WITH ANOTHER COUPLE INCHES OF RAIN 
POSSIBLE IN THE OLYMPICS. ELSEWHERE...FLOODING IS NOT EXPECTED. 

NO FLOODING IS EXPECTED ON THE GREEN RIVER. MERCER

&&

.AVIATION...WE HAVE WEST FLOW ALOFT OVER WESTERN WASHINGTON EARLY 
THIS MORNING AS A SMALL UPPER RIDGE PROGRESSES QUICKLY ACROSS 
WESTERN WASHINGTON. THE FLOW ALOFT WILL BACK TO SOUTHWEST AGAIN THIS 
AFTERNOON AS THE WARM FRONT OF THE NEXT PACIFIC FRONTAL SYSTEM 
REACHES THE AREA. THE COLD FRONT WILL MOVE ACROSS THE FORECAST AREA 
FROM THE WEST LATE TONIGHT AND FRIDAY MORNING. THE AIR MASS WILL 
REMAIN GENERALLY MOIST AND STABLE.

SCATTERED SHOWERS WILL CONTINUE OVER THE MOUNTAINS WITH JUST SPOTTY 
SHOWERS OVER THE WESTERN WASHINGTON LOWLANDS. WIDESPREAD STRATIFORM 
RAIN WITH THE INCOMING WARM FRONT WILL SPREAD ACROSS THE FORECAST 
AREA FROM THE SOUTHWEST LATER THIS AFTERNOON AND CONTINUE TONIGHT. 

ONCE AGAIN THERE IS QUITE A MIX OF CONDITIONS ACROSS WESTERN 
WASHINGTON EARLY THIS MORNING...RANGING FROM JUST SCATTERED CLOUDS 
IN A FEW SPOTS TO IFR CONDITIONS IN FOG OR STRATUS AT OTHERS. THE 
PREVAILING TREND THIS MORNING SHOULD BE FOR STRATUS TO BECOME MORE 
WIDESPREAD BUT NOT SOLID...GIVING PERIODS OF MVFR OR IFR CEILINGS TO 
MOST TERMINALS FOR SEVERAL HOURS AROUND DAYBREAK. WE SHOULD SEE 
IMPROVEMENT TO MAINLY VFR CONDITIONS LATER THIS MORNING...BUT THE 
WARM FRONT WILL BRING SOME DETERIORATING CONDITIONS AGAIN LATE THIS 
AFTERNOON THROUGH TONIGHT. 

KSEA...SOUTH WIND 6-10 KT...BECOMING SOUTHEAST 4-8 KT MIDDAY THROUGH 
TONIGHT. WHETHER OR NOT STRATUS WILL FILL IN AND FORM A CEILING AT 
KSEA AND KBFI THIS MORNING IS A VERY TOUGH CALL RIGHT NOW. IT MAY BE 
IN AND OUT FOR SEVERAL HOURS THIS MORNING AND BEST HANDLED WITH A 
TEMPO GROUP IN THE 12Z TAF. MCDONNAL

&&

.MARINE...A SURFACE RIDGE WILL BUILD ALONG THE NORTHERN ROCKIES 
TODAY...WITH A WARM FRONT OVER THE OFFSHORE WATERS MOVING INTO THE 
FORECAST AREA LATE TODAY. THE COLD FRONT WILL FOLLOW LATE TONIGHT 
AND FRIDAY MORNING...WEAKENING SOMEWHAT AS IT MOVES INLAND. 
SOUTHEAST WINDS WILL RISE AGAIN WITH THE ARRIVAL OF THIS FRONTAL 
SYSTEM...AND WE SHOULD SEE HIGH-END SMALL CRAFT ADVISORY WINDS OVER 
THE COASTAL WATERS...ENTRANCES TO THE STRAIT AND PERHAPS NORTHERN 
INLAND WATERS. THE GUIDANCE HAS BEEN CONSISTENT WITH THE IDEA THAT 
THIS SYSTEM WILL NOT PRODUCE GALES...AND IF ANY GALES WERE TO OCCUR 
THEY WOULD PROBABLY BE MARGINAL AND BRIEF AS THE WIND HITS ITS PEAK 
LATE THIS EVENING.

A PERIOD OF RELATIVE LIGHT WINDS WILL FOLLOW THE COLD FRONT FRIDAY 
INTO SATURDAY...AS HIGH PRESSURE BUILDS OVER BRITISH COLUMBIA. 
ANOTHER WARM FRONT WILL LIFT NORTHEAST ACROSS THE FORECAST AREA FROM 
THE SOUTHWEST SATURDAY NIGHT AND SUNDAY.

WESTERLY SWELLS WILL GRADUALLY SUBSIDE OVER THE NEXT COUPLE DAYS BUT 
REMAIN ABOVE 10 FT. MCDONNAL

&&

.SEW WATCHES/WARNINGS/ADVISORIES...

WA...NONE.
PZ...SMALL CRAFT ADVISORY COASTAL WATERS...ENTRANCES TO THE STRAIT 
     OF JUAN DE FUCA...ADMIRALTY INLET...NORTHERN INLAND WATERS.
    .SMALL CRAFT ADVISORY FOR SEVERE BAR CONDITIONS GRAYS HARBOR.


$$

Southwestern Washington and Western Oregon

359 
FXUS66 KPQR 171029
AFDPQR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
226 AM PST THU DEC 17 2009
	
.SYNOPSIS...ANOTHER PACIFIC FRONTAL SYSTEM IS OFF THE COAST THIS
MORNING. THE WARM FRONT WILL BRING IN RAIN TODAY AND TONIGHT WITH THE
COLD FRONT MOVING ONSHORE LATE TONIGHT OR EARLY FRIDAY. AFTER A BRIEF
LULL THE NEXT WARM FRONT WILL MOVE THROUGH SATURDAY NIGHT FOLLOWED BY
THE COLD FRONT SUNDAY.

&&

.SHORT TERM...SATELLITE IMAGERY SHOWS THE NEXT SYSTEM JUST WEST OF
130 W EARLY THIS MORNING. WARM FRONTAL CLOUDINESS JUST OFF THE OREGON
COAST BUT WITH THE SURFACE LOW ABOUT 47 N 142 W THE WARM FRONT
APPEARS WEAK. MODELS HAVE THE COLD FRONT MOVING INLAND LATE TONIGHT
OR EARLY FRIDAY. BUILDING HEIGHTS FROM THE SOUTH AT 500 MB SUGGEST
THE FRONT WILL BE WEAKENING AND NOT HAVE A LOT OF PUNCH BEHIND IT.
THE SNOW LEVELS WILL REMAIN RELATIVE HIGH THROUGH THE WEEKEND WITH
TEMPERATURES NEAR TO ABOVE NORMA.. SS

.LONG TERM...NO CHANGES. PREVIOUS DISCUSSION FOLLOWS....MOST MODELS
IN GENERAL AGREEMENT BRINGING PAC SYSTEM THROUGH THE AREA TOWARDS THE
END OF THE WEEKEND FOR SOME MORE RAIN. ECMWF IS MOST AGGRESSIVE AT
BUILDING A STRONG PACIFIC RIDGE OVER THE PAC ON MONDAY AND DIGGING A
LOW DOWN THE WEST COAST WHICH HAS POTENTIAL FOR DECREASING
TEMPERATURES PARTICULARLY IF THE LOW REMAINS OFFSHORE. GFS ECHOES A
SIMILAR SITUATION THOUGH KEEPS LOW JUST TO THE EAST OF THE CASCADES.
BOTH SHOW A COOLER AND WETTER TREND...WILL HAVE TO WATCH FOR ANY SNOW
POTENTIAL GIVEN THE EUROS MORE WESTERLY LOW TRACK. SO DROPPED TEMPS
AND INCREASED POPS SUNDAY THROUGH TUESDAY.

GOING INTO MIDWEEK...IF RIDGE TRANSLATES EAST TEMPS SHOULD WARM AND 
PRECIP CHANCES SHOULD DROP...IF IT STAYS OFFSHORE WE MAY CONTINUE TO 
BE COOL AND WET. FOR NOW TRENDED TOWARDS WARMER AND DRIER. WOLFE

&&

.AVIATION...SOME IFR TO LOW MVFR CONDITIONS HAVE DEVELOPED AS THE 
AIR MASS HAS STABILIZED OVERNIGHT...MOST PREVALENT ALONG THE COAST 
AND IN THE N WILLAMETTE VALLEY. AS WARM AIR ADVECTION CLOUDS SPREAD 
IN...EXPECT VISIBILITIES IN FOG TO IMPROVE EARLY THIS MORNING...BUT 
LOW CIGS TO PERSIST. LIGHT RAIN DEVELOPING TODAY EXPECTED AT TIMES 
TO BRING VISIBILITIES DOWN INTO MVFR RANGE. CIGS MAY IMPROVE LATE 
TODAY AND OVERNIGHT AS WARM FRONT LIFTS N.

KPDX AND APPROACHES...PATCHY IFR FOG NEAR THE AIRPORT WILL PERSIST 
THROUGH THE EARLY MORNING HOURS. CIGS EXPECTED TO SETTLE INTO MVFR 
CATEGORY AFTER 12Z...WITH LIGHT RAIN DEVELOPING LATER IN THE MORNING 
OR AFTERNOON. EXPECT CIGS TO SLOWLY RISE LATER IN THE DAY...AND 
SHOULD BE BACK TO LOW END VFR BY EVENING.
&&

.MARINE...SW SWELL NOT PANNING OUT AS HIGH EARLIER EXPECTED...SO 
WILL NEED TO DROP THE HIGH SURF ADVISORY. OTHERWISE WITH THE ACTIVE 
PATTERN WILL SEE SEAS REMAINING LARGELY IN THE 10 TO 15 FT RANGE 
THROUGH THE WEEKEND BEFORE RIDGING ALLOWS SEAS TO SUBSIDE. SOUTHERLY 
WINDS DEVELOPING AHEAD OF A WARM FRONT WILL INCREASE INTO SMALL 
CRAFT CATEGORY TODAY...WITH GUSTS APPROACHING GALE FORCE IN THE 
NORTHERN OUTER WATERS. WINDS EXPECTED TO DROP OFF LATE TONIGHT AS 
COLD FRONT PUSHES THROUGH THE WATERS. AFTER A BREAK BETWEEN 
SYSTEMS...WINDS NOT EXPECTED TO RETURN TO SMALL CRAFT CRITERIA UNTIL 
SAT NIGHT OR SUN WHEN THE NEXT STORM SYSTEM APPROACHES. AT HIS TIME 
EXPECT THIS SYSTEM TO BRING SMALL CRAFT WINDS...BUT GALE FORCE WINDS 
ARE NOT OUT OF THE QUESTION.
&&

.PQR WATCHES/WARNINGS/ADVISORIES...
OR/WA...SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS CAPE SHOALWATER
	 TO FLORENCE THROUGH FRI.
	SMALL CRAFT ADVISORY FOR WIND CAPE SHOALWATER TO FLORENCE
	 10-60 NM THROUGH TONIGHT.
	SMALL CRAFT ADVISORY FOR WIND CAPE SHOALWATER TO FLORENCE
	 0-10 NM THROUGH 1 AM TONIGHT.
	SMALL CRAFT ADVISORY FOR ROUGH COLUMBIA RIVER BAR THROUGH
	 TONIGHT.
&&

$$

MORE WEATHER INFORMATION ONLINE AT...
HTTP://WEATHER.GOV/PORTLAND

THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM
THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY
REFERRED TO AS THE FORECAST AREA.

Southeastern Washington and Northeastern Oregon

020 
FXUS66 KPDT 171158 AAA
AFDPDT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
358 AM PST THU DEC 17 2009

UPDATED AVIATION DISCUSSION

.SHORT TERM...TODAY THROUGH FRIDAY NIGHT...THE ACTIVE AND 
PROGRESSIVE WEATHER PATTERN WILL CONTINUE THROUGH THE SHORT TERM 
PERIOD...I.E. THROUGH THE REMAINDER OF THE WEEK. ANOTHER WEATHER 
SYSTEM WILL MOVE INTO THE REGION LATER TODAY WHICH WILL BE FOLLOWED 
BY BRIEF HIGH PRESSURE AND A DRIER PERIOD FRIDAY AND THEN ANOTHER 
SYSTEM WILL ARRIVE LATE FRIDAY NIGHT OR EARLY SATURDAY. SNOW LEVELS 
WILL REMAIN FAIRLY HIGH SO ANY SNOW FROM THESE SYSTEMS WILL REMAIN 
IN THE HIGHER ELEVATIONS...BUT MAY IMPACT THE HIGHWAY PASSES OVER 
THE MOUNTAINS. ANOTHER CONCERN IS THAT WITH ANY CLEARING THAT MAY 
TAKE PLACE BETWEEN SYSTEMS IT WILL NOT TAKE MUCH FOR DENSE FOG TO 
FORM. THIS IS ESPECIALLY TRUE IN THE LOWER COLUMBIA BASIN AND 
ADJACENT VALLEYS WHERE THE AIR IS COOLER AND CLOSER TO THE DEW POINT 
TEMPERATURES...WITH ABUNDANT MOISTURE FROM THE RECENT RAIN...ICE AND 
SNOW EVENTS STILL TRAPPED THERE. THE UNSETTLED WEATHER PATTERN 
WILL CONTINUE INTO THE EXTENDED PERIOD. THERE ARE STILL SOME LIGHT 
SNOW SHOWERS SPILLING OVER THE CASCADES THIS MORNING...BUT WILL END 
THE WINTER WEATHER ADVISORY THERE AT ITS SCHEDULED EXPIRATION TIME 
OF 4 AM AS SIGNIFICANT SNOW ACCUMULATIONS ARE NO LONGER EXPECTED 
THERE. 88

.LONG TERM...SATURDAY THROUGH MONDAY...CONSENSUS AMONG EXTENDED 
MODELS SHOWS A DEEP MID/UPPER LEVEL PACIFIC TROUGH OFF THE COAST 
BETWEEN 130-140W WITH A MID/UPPER LEVEL RIDGE OF HIGH PRESSURE OVER 
THE PACIFIC NORTHWEST. THIS PATTERN ALLOWS WARM AIR ADVECTION 
ASSOCIATED WITH A WARM FRONT TO BRING A CHANCE OF RAIN EAST OF THE 
CASCADE CRESTS AND INTO THE FORECAST AREA ON SATURDAY WITH SNOW 
LEVELS AT OR ABOVE 6000 FT ON SATURDAY RISING ABOVE 7000 FEET ON 
SUNDAY. SATURDAY NIGHT POPS INCREASE TO LIKELY CATEGORY ACROSS FAR 
NORTH CENTRAL AND NORTHEAST OREGON AND ALL OF EASTERN WASHINGTON. ON 
SUNDAY THE WARM FRONT LIFTS NORTHWARD INTO NORTHEAST WASHINGTON 
FOLLOWED BY A COLD FRONT MOVING INTO THE FORECAST AREA SUNDAY 
AFTERNOON AND EVENING WITH SNOW LEVELS LOWERING TO AROUND 5000 FEET 
LATE MONDAY.  POLAN

MONDAY NIGHT THROUGH WEDNESDAY...MODELS HAVE VERY DIFFERENT 
SOLUTIONS FOR THIS TIME PERIOD. THE ECMWF SHOWS AN UPPER LEVEL LOW 
OFF THE COAST MOVING INLAND OVER THE PACIFIC NORTHWEST MONDAY 
NIGHT...FOLLOWED BY ANOTHER LOW DROPPING OUT OF CANADA TUESDAY AND 
WEDNESDAY. THE GFS HAS THE UPPER LEVEL LOW MOVING INLAND OVER 
CENTRAL OREGON TO NEVADA MONDAY NIGHT FOLLOWED BY A FEW DISTURBANCES 
IN NORTHERLY FLOW. THE ENSEMBLE SPREAD IS HIGH AND MODEL TIMING HAS 
BEEN INCONSISTENT. THIS GIVES A LOW CONFIDENCE IN TIMING AND 
STRENGTH...SO KEPT A BROAD BRUSH CHANCE OF PRECIPITATION IN THE 
MOUNTAINS AND A SLIGHT CHANCE IN THE VALLEYS THROUGH THE PERIOD. 

&&

.AVIATION...12Z TAFS...VFR CIGS AND VFR/MVFR VIS ARE EXPECTED AT ALL 
TAF SITES...EXCEPT AT KDLS WHERE VIS WILL BE RANGE FROM IFR TO VLIFR 
UNTIL AROUND 17/16 UTC THIS MORNING AND AT KYKM UNTIL AROUND 17/15 
UTC. THERE IS THE POSSIBILITY THAT SOME LIGHT MIST MAY DRIFT TO NEAR 
KALW MID MORNING TODAY IF WINDS SHIFT TO THE SOUTHWEST. KRDM 
SHOULD BE VFR THROUGH THE PERIOD WITH A VICINITY SHOWER POSSIBLE MID 
DAY THURSDAY.  POLAN

&&

.PRELIMINARY POINT TEMPS/POPS...
PDT  41  31  42  34 /  20  30  30  20 
ALW  42  33  41  36 /  20  30  30  20 
PSC  40  31  41  33 /  20  30  30  20 
YKM  37  28  39  30 /  20  30  30  20 
HRI  41  31  40  33 /  20  30  30  20 
ELN  37  27  38  32 /  30  40  40  30 
RDM  45  28  45  30 /  30  30  30  20 
LGD  40  28  39  30 /  30  30  30  20 
GCD  42  27  41  31 /  20  30  30  20 
DLS  42  34  41  34 /  40  50  50  30 

&&

.PDT WATCHES/WARNINGS/ADVISORIES...
OR...NONE.
WA...NONE.

&&

THREAT INDEX
TODAY : GREEN
FRIDAY : GREEN
SATURDAY : GREEN

GREEN: NONE OR LIMITED NEED FOR WATCHES, WARNINGS, OR ADVISORIES.
YELLOW: A FEW WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.
RED: NUMEROUS WATCHES, WARNINGS, OR ADVISORIES POSSIBLE OR IN EFFECT.

FOR ADDITIONAL WEATHER INFORMATION, CHECK OUR WEB SITE AT...
WWW.WEATHER.GOV/PENDLETON

$$

88/99/99

Northeastern Washington and Northern Idaho

824 
FXUS66 KOTX 171354
AFDOTX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
554 AM PST THU DEC 17 2009

.SYNOPSIS...
THE INLAND NORTHWEST WILL EXPERIENCE A BREAK IN THE ACTIVE WEATHER
PATTERN TODAY. MOST OF THE REGION WILL BE CLOUDY...BUT
PRECIPITATION CHANCES WILL BE LOW THROUGH THIS EVENING. THE NEXT
FRONTAL SYSTEM WILL ARRIVE ON FRIDAY. AREAS OF FREEZING RAIN WILL
BE POSSIBLE FRIDAY MORNING ALONG THE EAST SLOPES OF THE
CASCADES...BUT THE MAJORITY OF EASTERN WASHINGTON WILL BE WARM
ENOUGH THAT PRECIPITATION WILL FALL IN THE FORM OF RAIN. ANOTHER
STORM SYSTEM WILL BRING RAIN AND MOUNTAIN SNOW TO THE REGION ON
SUNDAY. 


&&

.DISCUSSION...

TODAY...THE INLAND NORTHWEST WILL BE IN BETWEEN SYSTEMS TODAY. A 
WEAK SHORTWAVE RIDGE WILL BUILD OVER THE REGION PROVIDING A 
RELATIVELY DRY PERIOD IN THE ACTIVE PATTERN THIS WEEK. LOW CLOUDS 
AND FOG WILL REMAIN LOCKED IN THE LOW ELEVATIONS OF CENTRAL AND 
NORTHEAST WASHINGTON TODAY AND TONIGHT. MOSES LAKE...WENATCHEE... 
OMAK...AND COLVILLE HAVE LITTLE CHANCE OF BREAKING OUT OF THE 
STRATUS WITH WEAK EAST OR SOUTHEAST FLOW IN THE BOUNDARY LAYER. THE 
MID 30S DEWPOINTS IN THE LOWER COLUMBIA BASIN WILL BE DRAWN INTO 
THESE AREAS...WHICH WILL ONLY REINFORCE THE LOW CLOUDS AND FOG. 
SPOKANE COULD CONCEIVABLY EXPERIENCE SOME BREAKS IN THE LOW CLOUDS 
THIS AFTERNOON...BUT THAT COULD BE A STRETCH. THERE IS SO MUCH 
GROUND MOISTURE AFTER THE RECENT RAIN AND SNOW...STRATUS WILL BE 
VERY STUBBORN.

TONIGHT...THE NEXT LOW PRESSURE SYSTEM WILL APPROACH THE COAST 
TONIGHT. THE CENTER OF THE SURFACE LOW WILL TRACK INTO NORTHERN 
BRITISH COLUMBIA BY 12Z...AND THE TRAILING COLD FRONT WILL BARELY 
REACH THE CASCADE CREST BY SUNRISE. NEITHER THE NAM OR GFS FORECASTS 
MUCH DEEP LAYER MOISTURE ADVECTION AHEAD OF THE COLD FRONT. I 
SUSPECT THAT THE SUBTROPICAL MOISTURE PLUME ASSOCIATED WITH THIS 
STORM WILL BE STRETCHED SIGNIFICANTLY BY THE TIME IT REACHES 
WASHINGTON SINCE THE SURFACE LOW WILL TRACK WELL NORTH OF OUR 
REGION. MODEL SOUNDINGS FAIL TO SATURATE THE COLUMN UNTIL THE COLD 
FRONT PASSES FRIDAY MORNING. SO UNTIL THE FRONT ARRIVES...PLACES 
LIKE WENATCHEE...OMAK...AND MOSES LAKE WILL ONLY RECEIVE VERY LIGHT 
PRECIPITATION AMOUNTS. MODEL SOUNDINGS LOOK FAVORABLE FOR DRIZZLE 
WITH SATURATION FROM THE BOUNDARY LAYER UP TO 4000 FEET AGL. AND 
WITH BOUNDARY LAYER FLOW OUT OF THE SOUTHEAST...LIGHT UPSLOPE INTO 
THE EAST SLOPES SUGGESTS AT LEAST THE POTENTIAL FOR FREEZING DRIZZLE 
OVERNIGHT FOR THE WATERVILLE PLATEAU...PORTIONS OF THE EAST 
SLOPES...AND WENATCHEE. OMAK AND MOSES LAKE ALSO SHARE SIMILAR 
MOISTURE PROFILES...BUT WITHOUT THE CONTRIBUTION OF TERRAIN UPSLOPE 
FREEZING DRIZZLE MAY BE A LITTLE TOUGHER TO REALIZE. /GKOCH

FRIDAY THROUGH SUNDAY NIGHT...THE MESOSCALE AND GLOBAL MODEL
SOLUTIONS GENERALLY FAVOR A SHORT WAVE PASSAGE ALONG THE CANADIAN
BORDER ON FRIDAY...WITH WEAK SHORT WAVE RIDGING PREVAILING
SATURDAY...AND A MUCH STRONGER AND DEEPER SYSTEM APPROACHING THE
COAST BY SUNDAY. THE MODEL SPREAD THROUGHOUT THE PERIOD STARTS OUT
VERY SMALL FRIDAY...BEFORE GRADUALLY INCREASING THROUGH SUNDAY
NIGHT. THE SPREAD IS SUCH THAT THE GFS AND ITS ENSEMBLES ARE THE
FASTEST SOLUTIONS...AND THE ECMWF IS THE SLOWEST. THE NAM AND
CANADIAN ARE ONLY SLIGHTLY SLOWER THAN THE GFS...SO THE FORECAST
GENERALLY FEATURES A COMPROMISE OF THE GFS AND NAM...GIVEN THEIR
RELATIVE AGREEMENT RELATIVE TO THE SLOW OUTLYING ECMWF.

WARM ADVECTION ALOFT ADVANCES ACROSS THE CWA FROM SOUTHWEST TO
NORTHEAST AND WEAKENS OVER TIME ON FRIDAY. LIFT IN THE 290-300K
LAYER BASICALLY MAXIMIZES NORTHWEST OF A LINE FROM MOSES LAKE TO
BONNERS FERRY THROUGH THE DAY...WITH A HIGHLY SHEARED VORT MAX AND
UNFAVORABLY CURVED UPPER JET MAXIMA THE CULPRIT FOR SYNOPTIC SCALE
ASCENT. WITH WARM ADVECTION ALOFT AND ISENTROPIC ASCENT BEING
AIDED BY EFFECTIVE ASCENT FROM THE COLD DOME OF AIR STILL EVIDENT
EAST OF THE CASCADES ON THE GFS/NAM...AND A LACK OF DOWNSLOPE
POTENTIAL DUE TO THE ABSOLUTE STABILITY OF THE BOUNDARY
LAYER...CATEGORICAL POPS WERE CARRIED ACROSS THE WESTERN CWA ON
FRIDAY MORNING...TRANSITIONING TO LIKELY POPS FARTHER NORTHEAST
THROUGH THE DAY. UNDER THE LIFT THAT TRANSITIONS...THE
THERMODYNAMIC PROFILES VARY RADICALLY ACROSS THE AREA. WEAK
EASTERLY FLOW WILL HOLD THE COLD AIR IN AROUND
WENATCHEE...OMAK...THE EAST SLOPE VALLEYS...AND THE WATERVILLE
PLATEAU. AS TEMPERATURES GENERALLY ABOVE 3000 FEET SURGE ABOVE
FREEZING OVER ABOUT A 2000 FOOT LAYER PER THE NAM BUFKIT TIME
HEIGHT SECTIONS GENERALLY ACROSS THE WENATCHEE AREA AND WATERVILLE
PLATEAU WITH THE SURFACE LAYER SOLIDLY BELOW
FREEZING...SIGNIFICANT CONCERN EXISTS FOR FREEZING RAIN AND ICE
ACCUMULATIONS IN THESE AREAS FRIDAY MORNING. WINTER WEATHER
HEADLINES MAY BE REQUIRED FOR THIS ON FUTURE SHIFTS. ELSEWHERE...A
DEEPER COLD ATMOSPHERE AND A NEGLIGIBLE WARM TONGUE ARE LIKELY TO
ALLOW THE BULK OF THE OKANOGAN VALLEY TO REMAIN ALL SNOW ON
FRIDAY. FARTHER EAST...COLD AIR HAS ALREADY BEEN SCOURED OUT
GENERALLY FROM MOSES LAKE THROUGH THE NORTHEASTERN PORTION OF
WASHINGTON IN THE VALLEYS. THIS WILL ALLOW MOST PRECIPITATION THAT
FALLS IN THE VALLEYS TO FALL AS RAIN...WITH SNOW LEVELS VARYING
FROM ABOUT 6000 FEET ACROSS THE SOUTH TO 2500 FEET ALONG THE
CANADIAN BORDER.

UPSLOPE SHOWERS PER THE GFS/CANADIAN/NAM CONTINUE IN THE IDAHO
PANHANDLE INTO SATURDAY AND SATURDAY NIGHT EVEN AS THE FRIDAY
SYSTEM SHEARS OUT EASTWARD. MEANWHILE...SHORT WAVE RIDGING AND A
WEAK NORTHERLY INTRUSION OF SOME DRIER AND COOLER AIR INTO THE
WESTERN CWA AND BASIN WILL TEMPORARILY END PRECIPITATION IN THESE
AREAS. HOWEVER...THE RIDGE AXIS SLIPS EAST OF THE CWA BY SUNDAY.
AS A RESULT...ON SHORE FLOW STARTS TO BRING PACIFIC MOISTURE BACK
TOWARD THE AREA. A WARM FRONT LOOKS TO LIFT ACROSS THE AREA ON
SUNDAY. POST FRONTAL MIXING MAY FINALLY BE ENOUGH TO DISLODGE THE
COLD AIR FROM THE EAST SLOPES OF THE CASCADES...WITH SNOW LEVELS
RISING TREMENDOUSLY BEHIND THE FRONT...MOST ALL LOCATIONS SHOULD
GENERALLY TURN TO RAIN BY SUNDAY NIGHT.

BEYOND SUNDAY NIGHT...MODEL AGREEMENT BREAKS DOWN QUICKLY IN THE
EXTENDED PORTION OF THE FORECAST. THE GFS AND CANADIAN QUICKLY
BRING RIDGING TOWARD THE WEST COAST OF THE UNITED STATES BY THE
EARLY HALF OF NEXT WEEK. HOWEVER...THE ECMWF PHASES A DEEP PACIFIC
LOW WITH A SOUTHERLY DROPPING CANADIAN WAVE RIGHT OVER THE
OLYMPICS AND DROPS THE PHASED LOW OVER CENTRAL WASHINGTON. THIS
PLACES OUR CWA DIRECTLY INTO THE DEFORMATION/TROWAL BAND OF
PRECIPITATION WITH THIS SYSTEM. THE THERMAL PROFILES SUGGESTED BY
THE ECMWF WOULD SUPPORT A RAIN CHANGING TO SNOW SCENARIO WITH
IMPRESSIVE QPF BEING GENERATED BY THE MODEL IN THIS SCENARIO. IT
SEEMS LIKE A VERY LONG SHOT TO VERIFY...AND THE CURRENT FORECAST
THINKING DOES NOT FAVOR THE SOLUTION OF THE ECMWF...HOWEVER RUN-
TO-RUN CONSISTENCY OF ALL THE MODELS IN THE EXTENDED IS POOR. AS A
RESULT...THE FORECAST TRENDS TOWARD CLIMATOLOGY AND VERY FEW
CHANGES WERE MADE. /FRIES

&&

.AVIATION...
LOW CLOUDS AND FOG WILL IMPACT THE WENATCHEE...MOSES LAKE...AND 
SPOKANE AREAS TODAY. SOME IMPROVEMENT IS EXPECTED THIS AFTERNOON IN 
THE SPOKANE AREA...BUT THE IMPROVEMENT WILL BE SLOW. IF THE STRATUS 
BREAKS THIS AFTERNOON AT KGEG...THERE IS A GOOD CHANCE THAT IT WILL 
REDEVELOP IN THE EVENING. THICK FOG AND LOW CLOUDS WILL LIKELY 
PLAGUE THE MOSES LAKE AND WENTCHEE AIRPORTS TODAY AND INTO TONIGHT. 
SOME LIGHT FREEZING DRIZZLE OR LIGHT SNOW MAY OCCUR TONIGHT. /GKOCH



&&

.PRELIMINARY POINT TEMPS/POPS...
SPOKANE        39  31  38  32  37  32 /  10  10  50  30  20  50 
COEUR D'ALENE  40  31  38  33  38  33 /  20  10  60  40  20  30 
PULLMAN        40  32  41  34  40  34 /  20  10  30  20  20  60 
LEWISTON       47  34  43  34  43  36 /  10  10  10  10  10  20 
COLVILLE       38  31  35  32  37  31 /  10  30  70  20  10  40 
SANDPOINT      39  31  34  31  36  29 /  30  20  60  40  20  20 
KELLOGG        39  26  36  33  36  33 /  50  10  40  40  40  50 
MOSES LAKE     34  30  37  30  35  31 /  20  30  70  10  10  70 
WENATCHEE      31  28  32  27  32  28 /  20  30  80   0   0  70 
OMAK           35  29  33  28  32  29 /  20  30  80  10   0  40 

&&

.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&

$$