FXUS66 KOTX 301218
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
415 AM PST MON NOV 30 2009
.SYNOPSIS...
A WEAK PACIFIC FRONT WILL MOVE THROUGH THE AREA TONIGHT BRINGING
LIGHT PRECIPITATION TO THE CASCADES AND PANHANDLE MOUNTAINS. DRY
CONDITIONS WILL PREVAIL FOR THE REST OF THE WEEK UNTIL ANOTHER
POTENTIAL WEAK WEATHER SYSTEM MOVES INTO THE REGION BY THE END OF
THE WEEK.
&&
.DISCUSSION...
QUICK UPDATE TO THE FORECAST. DOT SENSORS AND WEBCAMS CONTINUE TO
SHOW DENSE FOG FORMING AT THE LOWER ELEVATIONS OF THE SPOKANE METRO
AREA. HAVE ISSUED A DENSE FOG ADVISORY FOR THIS MORNING FOR THE
SPOKANE ZONE ONLY. THERE IS LOCAL DENSE FOG IN THE MOSES LAKE AREA
BUT WILL OPT TO HANDLE THIS WITH NOWCASTS FOR NOW.
TODAY AND TONIGHT...SATELLITE IMAGERY TELLS THE STORY BEST FOR THE
NEXT 24 HOURS. THE FOG IMAGERY SHOWS AN EXTENSIVE AREA OF LOW
CLOUDS AND FOG EXTENDING FROM MOSES LAKE NORTHWARD TO THE OKANOGAN
VALLEY AND THEN EASTWARD ACROSS THE NORTHERN ZONES INTO NW
MONTANA. MOST OF THIS HAS BEEN THERE FOR THE PAST COUPLE OF DAYS.
AS SUCH THOSE AREAS SHOULDN'T SEE MUCH FOG...BUT SOME WA DOT
SENSORS NEAR LAURIER AND METALINE HAVE SHOWN SOME PERIODS OF LIGHT
FOG. THE BETTER CHANCE FOR DENSE FOG IS ALONG THE SOUTHERN FRINGE
OF THIS LOW CLOUD AREA WHERE THE FOG AND LOW CLOUDS ARE CURRENTLY
FORMING. MOSES LAKE VISIBILITY IS GOING UP AND DOWN AND SPOKANE
FELTS FIELD IS AT 1/4 MILE VISIBILITY. WEBCAMS AT SUNCREST AND 9
MILE FALLS SHOW FAIRLY THICK FOG AT THE MOMENT. HAVE TRIED TO
ADDRESS ALL OF THIS IN THE FORECAST GRIDS.
THE MODELS HAVE AND CONTINUE TO SHOW SOME LIGHT PRECIPITATION IN
THIS AREA. AND YET THE MODELS CORRECTLY ANALYZE THAT ALL OF THE
MOISTURE IS WELL BELOW 8000 FEET AND IS ALL WARMER THAN ABOUT -8C.
THIS WOULD INDICATE MORE DRIZZLE AND FLURRIES THAN ANY KIND OF
MEASURABLE RAIN OR SNOW. THE 850MB FORECASTS SHOW WEAK WARM
ADVECTION MAINLY OVER NE WASHINGTON AND THE NORTHERN
PANHANDLE...AND THIS IS OFTEN SUFFICIENT FOR DRIZZLE/FLURRIES. SO
HAVE ADDED THIS TO THE FORECAST GRIDS. COULD BE AN ICY DRIVE FOR
THE MORNING COMMUTERS...ALTHOUGH AT PRESENT THE DOT SENSORS SHOW
MOST MAJOR ROADS ARE SLIGHTLY ABOVE FREEZING AND MAY HAVE A TOUGH
TIME COOLING ANY FURTHER UNDER THE THICK LOW CLOUD DECK.
THE OTHER FEATURE ON SATELLITE IMAGERY IS THE STRETCHED OUT WEAK
FRONT THAT'S CURRENTLY DRAPED SOUTHWESTWARD FROM CENTRAL BC. WATER
VAPOR IMAGERY SHOW A SHORT WAVE BEHIND THIS FRONT THAT IS STARTING
TO PUSH IT SOUTHEASTWARD...AND THE IR IMAGERY IS STARTING TO SHOW
A CONCAVE SHAPE TO THE FRONT AT THIS POINT NEAR THE QUEEN
CHARLOTTE ISLANDS. THIS WEAK FRONT IS PROGGED TO MOVE
SOUTHEASTWARD OVER THE AREA LATE THIS AFTERNOON AND TONIGHT. ONLY
REAL CHANCE OF PRECIPITATION FROM THIS SYSTEM IS OVER THE CASCADE
CREST AND THE PANHANDLE MOUNTAINS. ANY PRECIPITATION THAT DOES
FALL WILL BE LIGHT.
TRICKY FORECAST FOR TODAY'S HIGH TEMPERATURES. THE MODELS ALL SHOW
A FAIRLY GOOD PRE-FRONTAL SOUTHWESTERLY WIND THIS AFTERNOON. BUT
THIS IS A STABLE WARM ADVECTION WIND AND THESE TYPICALLY HAVE A
TOUGHER TIME MIXING DOWN TO THE SURFACE. HOWEVER...AS SHOWN BY
ELLENSBURG YESTERDAY /WHICH TOPPED OUT AT 58/ A LITTLE BIT OF
MIXING CAN REALLY CAUSE A JUMP IN TEMPERATURES. THE BEST CHANCE
FOR THIS TO HAPPEN TODAY WOULD BE SOUTH OF I-90...MAINLY OVER THE
PALOUSE. RJ
TUESDAY THROUGH WEDNESDAY NIGHT...DRY CONDITIONS WITH SEASONAL
TEMPERATURES WILL PREVAIL AS A MID LEVEL RIDGE BUILDS OVER THE
REGION. ON TUESDAY MORNING AN UPPER TROUGH EXITS TO THE EAST AND FLOW
ALOFT SHIFTS TO THE NORTH. THIS WILL DRAG A COLDER AND DRIER
AIR MASS INTO THE INLAND NORTHWEST...LESSENING THE THREAT OF FOG
AND LOW STRATUS. CLEARING SKIES AND LIGHT WINDS WILL ALLOW FOR
GOOD RADIATIONAL COOLING TUESDAY NIGHT...WITH TEMPERATURES
DROPPING INTO THE LOW 20S FOR MOST VALLEY LOCATIONS. SOME MID TO
HIGH CLOUDS WILL RIDE OVER THE RIDGE ON WEDNESDAY NIGHT...WITH A
MODERATING EFFECT ON OVERNIGHT LOWS.
THURSDAY THROUGH SUNDAY...MEDIUM RANGE MODELS ARE EXHIBITING DECENT
RUN TO RUN CONSISTENCY...BUT THIS MEANS THERE IS STILL QUITE A
SPREAD IN MODEL SOLUTIONS REGARDING THE TIMING OF AN UPPER TROUGH
PASSAGE TOWARD THE END OF THE WORKWEEK. THE ECMWF REMAINS THE SLOW
OUTLIER AND THE GFS CONTINUES ON THE FAST SIDE. SOME ENCOURAGING
NEWS IS THAT THE CANADIAN GEM HAS BECOME A BIT MORE CONSISTENT IN
SUPPORTING THE GFS TIMING. THE FORECAST CONTINUES TO LEAN TOWARD THE
GFS ENSEMBLE MEAN WITH A THURSDAY NIGHT TROUGH PASSAGE. THERE IS NOT
A LOT OF MOISTURE WITH THIS SYSTEM SO ANY SNOWFALL ACCUMULATIONS
SHOULD BE LIGHT.
THE BIG CHANGE IN THE FORECAST IS TO COOL TEMPERATURES FOR THE
WEEKEND AND THE START OF THE WORKWEEK. MODELS CONTINUE TO ADVERTISE
TEMPERATURES WELL BELOW SEASONAL NORMALS. BOTH THE GFS AND CANADIAN
MODELS BRING SOME VERY COLD AIR SOUTH INTO THE INLAND NORTHWEST. THE
SOURCE REGION FOR THIS AIRMASS IS WHERE LINES OF LONGITUDE MERGE TO
A POINT. THE EC IS NOT QUITE ON BOARD WITH THIS IDEA BUT STILL HAS
SOME PRETTY COLD TEMPERATURES IN THE DAY 7 FORECAST. 850MB TEMPS
PLUNGE TO THE -16 TO -22 RANGE...DEPENDING ON THE MODEL. WE COULD BE
LOOKING AT LOW TEMPERATURES MONDAY NIGHT IN THE TEENS WITH THE COLD
POCKETS IN THE NORTHEAST VALLEYS IN SINGLE DIGITS. /KELCH
&&
.AVIATION...
AREAS OF STRATUS AND FOG HAVE FORMED OVER THE NORTHERN AND WESTERN
VALLEYS THIS MORNING WITH BCFG IN THE WA PALOUSE AND CENTRAL
PANHANDLE VALLEYS. EXPECT VIS AND CIGS AT KSFF...KLWS...KMWH...AND
KEAT TO DEGRADE INTO LIFR AT TIMES THROUGH THE MORNING HOURS WITH
IMPROVING CONDITIONS INTO VFR IN THE AFTERNOON. A WEAK FRONT WILL
MOVE IN FROM THE NORTH TONIGHT. THIS WILL SHIFT THE FLOW REGIME INTO
A MORE DRIER NORTHERLY PATTERN. SOME INDICATION OF LOW STRATUS
DEVELOPING TOMORROW MORNING...BUT WILL BE HARDER TO DEVELOP WITH THE
DRIER AIR BEHIND THE FRONT. /SVH
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 41 28 36 23 36 26 / 0 10 0 0 0 0
COEUR D'ALENE 39 30 38 23 38 28 / 0 10 0 0 0 0
PULLMAN 46 32 38 26 38 27 / 0 10 10 0 0 0
LEWISTON 41 35 44 28 42 31 / 0 10 10 0 0 0
COLVILLE 39 29 37 23 36 29 / 10 20 0 0 0 0
SANDPOINT 36 30 34 21 33 25 / 10 20 10 0 0 0
KELLOGG 39 31 34 24 34 27 / 0 40 10 0 0 0
MOSES LAKE 45 30 42 23 39 25 / 0 0 0 0 0 0
WENATCHEE 45 32 42 27 40 29 / 0 0 0 0 0 0
OMAK 40 28 39 24 40 28 / 10 10 0 0 0 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...DENSE FOG ADVISORY UNTIL 10 AM PST THIS MORNING FOR SPOKANE
AREA.
&&
$$
