FXUS66 KOTX 092354
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
354 PM PST WED DEC 9 2009
.SYNOPSIS...
MAINLY DRY AND COLD CONDITIONS WILL CONTINUE THROUGH THE REST OF
THE WORK WEEK...WITH A SLOW WARMING TREND BACK TO NEAR NORMAL
TEMPERATURES BY FRIDAY. THE REGION WILL BE BRUSHED BY A PACIFIC
STORM SYSTEM SATURDAY THROUGH SUNDAY...WITH THE MAIN THREAT OF
SNOW FROM THIS STORM SOUTH OF INTERSTATE 90. A MORE ACTIVE AND
UNSETTLED WINTER PATTERN IS EXPECTED NEXT WEEK.
&&
.DISCUSSION...
TONIGHT AND THURSDAY...SATELLITE INDICATES THE FORECAST AREA IS
LOCKED UNDER A COLD NORTHERLY FLOW...WITH WEAK EMBEDDED WAVES
PERIODICALLY SWIPING THE EASTERN REACHES OF THE FORECAST AREA WITH
MAINLY CLOUDS AND A STRAY MOUNTAIN SNOW SHOWER. LATEST MODELS ARE
IN GOOD AGREEMENT IN DEPICTING THIS RELATIVELY STATIC AND SIMPLE
FLOW REGIME THROUGH THE NEXT 24 TO 36 HOURS. COLD TEMPERATURES
WILL CONTINUE TONIGHT...BUT PROBABLY A COUPLE DEGREES WARMER THAN
LAST NIGHT ESPECIALLY OVER THE EASTERN HALF OF THE FORECAST AREA
WHERE SHIELDS OF MID AND HIGH CLOUDS WILL PASS THROUGH THE REGION
PERIODICALLY. THERE IS ALSO A CHANCE OF FLURRIES AND MOUNTAIN SNOW
SHOWERS IN THIS FLOW WITH WEAK EMBEDDED WAVES AND DISTURBANCES...BUT
NO APPRECIABLE ACCUMULATION IS EXPECTED WITH A DEARTH OF DYNAMIC
FORCING AND WELL DEFINED FRONTAL FOCUS. ON THURSDAY SOME WEAK WARM
ADVECTION WILL FINALLY BEGIN TO PUSH INTO THE REGION FROM THE WEST
AND ALLOW THURSDAY'S HIGH TEMPS TO PEAK A FEW DEGREES ABOVE
TODAY'S...BUT STILL WELL BELOW NORMAL. /FUGAZZI
THURSDAY NIGHT THROUGH SATURDAY...MODELS IN GOOD AGREEMENT THROUGH
FRIDAY WITH A DRY NORTHWEST FLOW OVER THE AREA. DESPITE SOME
MODERATION IN 850MB TEMPS...POOR MIXING POTENTIAL WITH LIGHT WINDS
SHOULD RESULT IN CONTINUED COLD TEMPERATURES WITH ONLY SLIGHT
MODERATION EXPECTED. UNCERTAINTY THEN INCREASES WITH TWO POTENTIAL
SYSTEMS TO IMPACT THE AREA LATE FRIDAY NIGHT AND SATURDAY.
AS A PACIFIC SYSTEM OFF THE CALIFORNIA COAST NEAR 140W UNDERCUTS
THE BLOCKING RIDGE IN THE EASTERN PACIFIC AND MOVES INTO
OREGON...ANOTHER ARCTIC COLD FRONT WILL BEGIN TO SAG SOUTH FROM
CANADA TOWARDS THE NORTHWEST US. THE GFS HAS BEEN CONSISTENT IN
SHOWING PACIFIC MOISTURE WORKING ITS WAY NORTHEAST INTO
OREGON...SE WA...AND THE LEWISTON AREA. GFS SHOWS A SFC BOUNDARY
STALLING IN THIS AREA WITH A NARROW BAND OF ACCUMULATING SNOWFALL.
THE 12Z ECMWF HAS NOW TRENDED TOWARDS THE GFS WHILE THE NAM STILL
KEEPS EVERYTHING TO THE SOUTH. GIVEN BETTER CONSISTENCY IN THE GFS
FCST LEANS THIS WAY WITH THE BEST SNOW CHANCES SOUTH AND EAST OF
SPOKANE. MEANWHILE...THE CANADIAN...SREF...AND NAM SHOW INCREASED
FORCING AND LIFT OVER NORTHERN WA/IDAHO SATURDAY AFTERNOON AS AN
ARCTIC FRONT BEGINS TO WORK SOUTH IN CANADA WHILE THE GFS/ECMWF
KEEP THIS ACTIVITY NORTH OF THE CANADIAN BORDER. FCST LEANS
TOWARDS THE GFS/ECMWF WITH THIS FEATURE AS WELL. GIVEN COMPLEX
PATTERN WITH THESE TWO FEATURES OF INTEREST OVERALL FCST
CONFIDENCE IN THE DETAILS IS LOW. JW
SATURDAY NIGHT THROUGH WEDNESDAY...THE OVERALL CONFIDENCE ON THE
PATTERN THROUGH THE BULK OF THE EXTENDED IS FAIRLY LOW AFTER THE
FIRST 12 TO 24 HOURS. IN THAT FIRST PERIOD...THE CONTINUITY OF THE
GFS AND SUPPORT COMING IN LINE FROM THE 12Z ECMWF AND CANADIAN IN
TRACKING A SYSTEM ACROSS THE SOUTHERN AND EASTERN PORTIONS OF THE
FORECAST IS A BIT HIGHER. AFTER THAT TIME...DUE TO DIFFERENCES IN
THE WAY THE MODELS ARE HANDLING BRUTALLY COLD AIR OVER CANADA AND
THE EVOLUTION AND PROGRESSION OF A LARGE DEEP POLAR VORTEX OVER
CENTRAL CANADA...CONFIDENCE IN THE FORECAST EVOLUTION FALLS OFF
CONSIDERABLY.
THE GFS...ECMWF...AND CANADIAN ALL TRACK A WAVE THAT SPLITS OFF
FROM THE MAIN POLAR JET FLOW OVER THE PACIFIC WEST OF NORTHERN
CALIFORNIA OR OREGON AND THEN ATTEMPT TO REPHASE THIS WAVE WITH
THE POLAR STREAM SOMEWHERE NEAR THE SOUTHEASTERN PORTION OF THE
FORECAST AREA ON SATURDAY NIGHT. THE CANADIAN SOLUTION IS THE MOST
PHASED WITH THE GFS AND ECMWF EACH BECOMING PROGRESSIVELY LESS
PHASED BY SATURDAY NIGHT AND SUNDAY. THE AMOUNT OF PHASING OF THE
STREAMS THAT OCCURS WILL BE DIRECTLY PROPORTIONAL TO THE STRENGTH
OF WHATEVER SYSTEM MAY TRACK DOWN THIS BOUNDARY. ALSO...ANOTHER
COMPLICATING FACTOR IS A SECONDARY SURGE OF COLDER ARCTIC AIR FROM
THE NORTH THAT COMES INTO PLAY DOWN THE BRITISH COLUMBIA COAST AND
AFFECTS THE POLAR JET DEVELOPMENT OVER THE AREA AS IT DIGS DOWN
THE COAST. THE CANADIAN AND GFS BOTH KEEP THE TWO FEATURES VERY
DISTINCT...WHILE THE ECMWF DOES NOT. THIS ALLOWS THE ECMWF TO
QUICKLY PINCH OFF THE SYSTEM ALONG THE COAST BETWEEN OFF SHORE
RIDGING AND THE SYSTEM NEAR THE SOUTHEASTERN PORTION OF OUR CWA BY
MONDAY. THE RESULT IS A MUCH WEAKER ARCTIC PUSH FROM THE NORTH
ACROSS THE AREA WITH A MEAGER PUSH OF FRONTAL SNOWFALL ACROSS THE
AREA SUNDAY NIGHT INTO MONDAY. THE GFS AND CANADIAN BOTH KEEP THE
PIECE OF ENERGY THAT SLIDES DOWN THE COAST MORE DISTINCT. THIS
SYSTEM HAS ITS ORIGINS OVER WESTERN PORTIONS OF NUNAVUT AT THE
MOMENT AS A DEEP CLOSED UPPER LOW. THE MODELS AND CURRENT
SATELLITE TRENDS SUPPORT STRETCHING THIS SYSTEM...AND GRADUALLY
BREAKING IT INTO TWO DISTINCT VORTEXES BY MONDAY...WITH THE
WESTERN ONE TRACKING DOWN THE WEST COAST OF NORTH AMERICA OR DOWN
THE SPINE OF THE ROCKIES. HOWEVER...THE ECMWF'S QUICK REPHASING OF
THE SYSTEM WITH THE MAIN FLOW AND ITS BROTHER VORTEX FAILS TO
ALLOW A SIGNIFICANT ENOUGH LOW LEVEL SYSTEM TO SPIN UP TO ALLOW
SIGNIFICANT COLD AIR PENETRATION INTO THE INLAND NORTHWEST.
HOWEVER...THE GFS AND CANADIAN BOTH SPIN UP VERY STRONG LOW LEVEL
SYSTEMS...WITH THE GFS INDICATING VERY IMPRESSIVE FRONTOGENETICAL
OMEGAS AS THE -37C ISOTHERM AT 850 MB MOVES INTO SOUTHERN B.C.
BEHIND THE FRONT. THE FORECAST HAS BEEN ADJUSTED TO ACCOUNT FOR A
BALANCE OF THE TWO OPPOSING GFS/CANADIAN AND ECMWF
SCENARIOS...WITH A SLIGHT LEAN TOWARD THE COLDER GFS/CANADIAN
GIVEN THE CANADIAN'S CONSISTENCY IN TRACKING A CLOSED SYSTEM OVER
THE INLAND NORTHWEST ON MONDAY AND A TREND BY THE GFS AND ECMWF TO
DO AS WELL ALSO.
AFTER THE SYSTEM FOR MONDAY PASSES EASTWARD...THE GFS AND THE
CANADIAN ENTRENCH COLD AIR OVER THE INLAND NORTHWEST THROUGH ABOUT
MID-WEEK BEFORE ERODING IT GRADUALLY AS FIRST A SHORT WAVE RIDGE
THEN ON SHORE FLOW COMMENCE. THE ECMWF IS MUCH QUICKER TO ERODE
THE COLD AIR...WITH THE PATTERN QUICKLY SHIFTING TO A BROAD
SOUTHWEST FLOW ALOFT. HERE AGAIN...THE FORECAST ATTEMPTS TO WALK
DOWN THE MIDDLE WITH SNOW LEVELS REMAINING LOW...BUT FORECAST
TEMPERATURES STILL SIGNIFICANT HIGHER THAN WOULD BE INDICATED BY
THE CANADIAN OR GFS. /FRIES
&&
.AVIATION...
VFR CONDITIONS SHOULD PREVAIL THROUGH 11/00Z. CIGS NEAR 5 KFT NEAR
AND EAST OF KGEG WILL GRADUALLY SCATTER OUT LATE THIS AFTERNOON.
ANOTHER AREA OF MID CLOUDS WILL APPROACH FROM THE NORTH OVERNIGHT.
THIS WILL YIELD A BROKEN TO OVERCAST DECK BETWEEN 6 AND 10 KFT FOR
THE EASTERN SITES AGAIN OVERNIGHT. PRECIPITATION WILL BE LIMITED TO
-SHSN IN THE MTNS OVER THE IDAHO PANHANDLE AWAY FROM ALL SITES.
/FRIES
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 6 18 9 20 12 23 / 0 0 0 0 10 30
COEUR D'ALENE 7 18 10 23 15 26 / 10 10 0 0 10 40
PULLMAN 1 22 9 24 15 27 / 0 0 0 0 10 50
LEWISTON 4 25 10 29 19 31 / 0 0 0 0 10 50
COLVILLE 7 16 10 20 13 25 / 0 0 0 10 20 20
SANDPOINT 6 16 6 19 12 21 / 20 20 0 10 20 30
KELLOGG 3 17 8 22 13 25 / 10 10 10 0 20 50
MOSES LAKE -1 18 4 21 10 25 / 0 0 0 0 10 20
WENATCHEE 7 22 7 21 12 26 / 0 0 0 0 10 20
OMAK 6 19 4 19 9 25 / 0 0 0 0 20 20
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
