FXUS66 KOTX 022226
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
226 PM PST WED DEC 2 2009
.SYNOPSIS...
DRY...COOL AND QUIET WEATHER CONDITIONS WILL CONTINUE OVER THE
REGION UNTIL LATE FRIDAY AND INTO SATURDAY...WHEN A RELATIVELY
WEAK STORM SYSTEM WILL BRING A CHANCE OF LIGHT SNOW. IN THE WAKE
OF THIS STORM...MUCH COLDER TEMPERATURES WITH GENERALLY DRY
CONDITIONS ARE EXPECTED THROUGH THE MIDDLE OF NEXT WEEK.
&&
.DISCUSSION...
TONIGHT AND THURSDAY...SATELLITE LOOP THIS AFTERNOON INDICATES
FORECAST AREA IS UNDER A CLEAR AND DRY RIDGE ALOFT. AT THE SURFACE
A HIGH PRESSURE CENTERED OVER SOUTHERN BRITISH COLUMBIA CONTINUES
TO PROMOTE LIGHT NORTHERLY WINDS ADVECTING DRY AND COOL CANADIAN
CONTINENTAL AIR INTO THE REGION. SIMILAR TO LAST NIGHT...WITH NO
SIGNIFICANT AIR MASS CHANGES OVER LAST NIGHT...ANOTHER COLD FROSTY
MORNING ON THURSDAY IS EXPECTED AFTER A LONG NIGHT OF RADIATIONAL
COOLING. ONCE AGAIN A FEW AREAS OF FOG WILL DEVELOP NEAR RIVERS
AND IN PROTECTED VALLEYS...BUT QUICKLY ERODE AFTER SUNRISE. ON
THURSDAY LITTLE CHANGE TO THE OVERALL PATTERN IS EXPECTED WITH
MODELS IN GOOD AGREEMENT IN MAINTAINING DRY NORTHERLY FLOW OVER
THE REGION...DESPITE A FLATTENING OF THE STRONG RIDGE AS A RESULT
OF THE NEXT INCOMING PACIFIC WAVE. NO SIGNIFICANT WEATHER IS
FORECAST FOR THE NEXT 24 HOURS WITH DRY COOL AND STABLE
CONDITIONS. /FUGAZZI
THURSDAY NIGHT TO SATURDAY NIGHT...THE WEST UNDERGOES A PATTERN
CHANGE AS A COUPLE SYSTEMS COME IN...AND HELP REPLACE THE RIDGE
WITH A TROUGH. THE 1ST SYSTEM WAS CROSSING 150W AT 22Z/02. IT
APPROACHES THURSDAY NIGHT WITH INCREASING HIGHER CLOUDS. A COLD
FRONT SLIDES BY FRIDAY WITH A RISK FOR MAINLY MOUNTAIN SNOW. THE
FRONT LACKS A REAL MOISTURE TAP...SO ANY SNOW LOOKS LIGHT. THE
ASSOCIATED MID-LEVEL TROUGH COMES IN FRIDAY NIGHT AND THE 2ND
SYSTEM (WHICH NEARED SW ALASKA AT 22Z/02) COMES ON ITS HEELS. THIS
2ND SYSTEM DIVES TOWARD SW B.C. SATURDAY...AND DEEPENS A LOW NEAR
THE WA COAST SUNDAY MORNING. THESE FEATURES DRAW ON MOISTURE
NOSING OVER NW B.C. AND THE YUKON...AND SO EXPANDS THE RISK FOR
SNOW ACROSS THE REGION FRIDAY NIGHT TO SATURDAY. YET GUIDANCE
STILL GENERATES ONLY LIGHT PRECIPITATION. USING RATIOS OF 15:1 TO
20:1...AVERAGE 24-HR SNOW AMOUNTS ARE LESS THE HALF INCH (LOCALLY
UP TO 2 OR 3 IN THE PANHANDLE MOUNTAINS). BY SATURDAY NIGHT
PRECIPITATION CHANCES WANE FROM THE NORTHEAST WITH INCREASING
WINDS AND DRIER AIR FROM THAT DIRECTION. TEMPERATURES DIP FURTHER
BELOW NORMAL INTO SATURDAY...WITH COLDER AIR STILL TO COME. /JCOTE
SUNDAY THROUGH WEDNESDAY...MUCH COLDER AND WINDY CONDITIONS ARE
EXPECTED THROUGH MUCH OF THIS PERIOD. MANY OF THE GFS ENSEMBLE
MEMBERS AND THE ECMWF AGREE ON THE LARGE SCALE UPPER LEVEL
PATTERN WITH THE LOW PRESSURE TROUGH OVER THE REGION FROM SATURDAY
CONTINUING TO DIG SOUTH AND WEST INTO OREGON WHICH IS NOT ALL THAT
COMMON BUT NOT IMPOSSIBLE TO BELIEVE. THE ALMOST NORTHERLY...CANADIAN
ORIGIN OF LOW WILL NOT ATTRACT A GREAT DEAL OF MOISTURE AROUND THE
BACK OR NORTH SIDE OF THE LOW SUNDAY SO PROBABILITIES OF
PRECIPITATION IN THE FORM OF SNOW WILL BE LOW.
OF MORE INTEREST IS THE COLD...CONTINENTAL AIR MASS TO SWIFTLY
FOLLOW THE LOW QUICKLY COOLING THE BOUNDARY LAYER AND PRODUCING
STRONG NORTHEAST WINDS EARLY SUNDAY INTO MONDAY. 850 TEMP CHANGES
FROM SATURDAY TO SUNDAY WILL BE FROM ABOUT -8 C TO -15 C ON
AVERAGE. STRONG NORTHEAST SURFACE PRESSURE GRADIENTS WILL FUNNEL
WINDS DOWN THE NORTHERN VALLEYS OF EAST WASHINGTON AND THE IDAHO
PANHANDLE INTO THE PANHANDLE AND BASIN AT 15 TO 25 MPH WITH GUSTS
NEARING 35 MPH POSSIBLE SUNDAY. ALONG WITH THE WINDS WILL BE WIND
CHILLS MAKING TEMPERATURES FEEL MUCH COLDER AT NIGHT AND DURING
THE DAY THROUGH MONDAY.
BY MONDAY AFTERNOON THE COLD AIR MASS WILL BE WELL ENTRENCHED INTO
THE REGION BUT WINDS WILL SLACKEN. WITH SOME CLEARING EXPECT LOW
TEMPERATURES TUESDAY MORNING INTO THE SINGLE DIGITS TO MID TEENS
IN THE VALLEYS. DURING THE DAY TUESDAY CLOUDS WILL INCREASE AHEAD
OF THE NEXT WAVE IN NORTHWEST TO NORTH FLOW ALOFT. AGAIN MOISTURE
WILL BE LIMITED SO SOME FLURRIES MAY BE POSSIBLE IN THE NORTH
MOUNTAINS MAINLY. LATEST MODEL DATA HINTS AT A PATTERN TRANSITION
TUESDAY NIGHT INTO WEDNESDAY WITH A STALLING...DRY CANADIAN FRONT
AND A SYSTEM PUSHING IN FROM THE PACIFIC THROUGH OREGON AND
WESTERN WASHINGTON. PRECIPITATION TIMING RIGHT NOW IS LATE
WEDNESDAY BUT THIS IS A DAY 7 FORECAST SO THE TIMING WILL LIKELY
CHANGE. RIGHT NOW SOME INCREASE IN POPS AND CLOUDS IS WARRANTED.
THIS PATTERN TRANSITION COULD SIGNAL THE START OF A SERIES OF
PACIFIC DISTURBANCES TAKING THE REGION OUT THE MAINLY COLD AND DRY
PATTERN. TC
&&
.AVIATION...
A RIDGE OF HIGH PRESSURE ALONG THE WEST COAST WILL KEEP THE INLAND
PACIFIC NORTHWEST IN A DRY NORTHERLY FLOW FOR THE NEXT 24 HOURS. AS
A RESULT...EXPECT LIGHT AND VARIABLE WINDS AND VFR CONDITIONS AT
MOST TAF SITES THROUGH 18Z THURSDAY. THERE IS A SMALL CHANCE OF
SHALLOW FOG OVERNIGHT TONIGHT NEAR RIVERS...POSSIBLY IMPACTING
THE KLWS AND KSFF TAF SITES.
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 16 32 17 32 20 29 / 0 0 0 10 20 30
COEUR D'ALENE 17 34 18 34 20 29 / 0 0 0 10 20 30
PULLMAN 19 32 19 34 20 29 / 0 0 0 10 30 40
LEWISTON 22 39 20 40 25 34 / 0 0 0 10 20 20
COLVILLE 19 34 19 34 24 33 / 0 0 0 10 20 30
SANDPOINT 13 27 14 31 22 29 / 0 0 0 20 30 40
KELLOGG 18 29 18 32 19 27 / 0 0 0 10 40 40
MOSES LAKE 17 36 16 34 23 33 / 0 0 0 10 20 20
WENATCHEE 20 36 20 37 25 33 / 0 0 0 10 20 20
OMAK 19 36 19 34 24 33 / 0 0 0 10 20 20
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
