FXUS66 KOTX 291155
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
355 AM PST SUN NOV 29 2009
.SYNOPSIS...
HIGH PRESSURE WILL BE THE MAIN WEATHER FEATURE OVER THE PACIFIC
NORTHWEST FOR THE FIRST HALF OF THE WEEK. LOOK FOR MAINLY DRY
CONDITIONS...CHILLY TEMPERATURES...AND AREAS OF LOW CLOUDS AND
FOG IN THE VALLEYS.
&&
.DISCUSSION...
TODAY AND TONIGHT...RELATIVELY QUIET WEATHER IN THE SHORT TERM.
EARLY MORNING WATER VAPOR IMAGERY SHOWS A FLAT UPPER LEVEL RIDGE
OVER THE PACIFIC NORTHWEST...AND THE NORTHERN BRANCH OF THE POLAR
JET DIRECTED INTO BRITISH COLUMBIA. THERE IS AN ABUNDANCE OF MID
AND HIGH LEVEL MOISTURE MOVING INTO BRITISH COLUMBIA THIS
MORNING...ASSOCIATED WITH A WEAKENING JET MAX TRACKING WELL NORTH
OF THE SPOKANE FORECAST AREA. THE FLOW PERPENDICULAR TO THE
CASCADES HAS CAUSED A MID LEVEL STANDING WAVE CLOUD OVER THE EAST
SLOPES AND OKANOGAN VALLEY. THIS FEATURE HAS BEEN DETECTED BY THE
SPOKANE RADAR ALL NIGHT WITH WEAK RETURNS BETWEEN 6000-8000 FEET
AGL. NO SIGNIFICANT PRECIPITATION IS OCCURRING WITH THIS NEARLY
STATIONARY CLOUD FEATURE...AND THESE MID LEVEL CLOUDS WILL LIKELY
DISSIPATE BY LATE MORNING AS DRYING BETWEEN 700-500MB INVADES
EASTERN WASHINGTON.
THE 10Z SATELLITE FOG CHANNEL SHOWS AN ABUNDANCE OF STRATUS NORTH
OF HIGHWAY 2...ENVELOPING THE OKANOGAN VALLEY...THE COLUMBIA
RIVER VALLEY...AND THE SANDPOINT/BONNERS FERRY AREAS. THE GFS HAS
INITIALIZED THIS LOW LEVEL MOISTURE BETTER THAN THE NAM. WITH VERY
LITTLE MIXING EXPECTED TODAY...CLOUDS WILL LIKELY REMAIN TRAPPED
IN THESE VALLEY FOR MOST OF THE DAY. FOG AND STRATUS DEVELOPMENT
IS LIKELY TONIGHT ESPECIALLY OVER THE WATERVILLE PLATEAU AND ALONG
THE EAST SLOPES OF THE CASCADES. BOTH THE NAM AND GFS FORECAST
LIGHT SOUTHEASTERLY FLOW IN THE BOUNDARY LAYER WHICH FAVORS FOG
AND STRATUS DEVELOPMENT FOR THESE AREAS. /GKOCH
MONDAY THROUGH TUESDAY NIGHT...MODELS START OUT IN GOOD AGREEMENT ON
BRINGING A SHORTWAVE TROUGH ACROSS BRITISH COLUMBIA MONDAY AND INTO
WESTERN MONTANA MONDAY NIGHT. THIS WILL BRUSH THE NORTHERN TIER WITH
SOME LIGHT PRECIPITATION MONDAY THAT WILL SHIFT TO THE EASTERN ZONES
MONDAY NIGHT. THIS SYSTEM QUICKLY LOSES ITS MOISTURE TAP SO MOUNTAIN
SNOWFALL ACCUMULATIONS WILL BE LIGHT. AS THE RIDGE REBOUNDS TUESDAY
NIGHT...NORTHERLY FLOW WILL DRAG A COLDER AND DRIER AIR MASS INTO THE
INLAND NORTHWEST...LESSENING THE THREAT OF FOG IN THE NORTHEAST
VALLEYS AND ACROSS THE COLUMBIA BASIN. TEMPERATURES WILL BE ON A
COOLING TREND THAT WILL CONTINUE THROUGH THE WEEK.
WEDNESDAY THROUGH SATURDAY...MEDIUM RANGE MODELS CONTINUE WITH QUITE
A SPREAD OF SOLUTIONS. THEY ALL ADVERTISE A TROUGH PASSAGE BUT
DIFFER SIGNIFICANTLY ON THE TIMING. THE 00Z ECMWF CAME IN EVEN SLOWER
THAN ITS PREV RUN WHICH WAS THE SLOWEST OF THE 12Z GUIDANCE. THE
GFS IS THE FAST OUTLIER AND THE CANADIAN GEM HAS BEEN FLITTING IN
BETWEEN THE OTHERS. THE LATEST GEM NOW LEANS TOWARD THE EC TIMING.
SINCE MOST OF THE GEFS ENSEMBLE MEMBERS SUPPORT THE SLOWER
TIMING...THE FORECAST WILL TREND TOWARD THE THURSDAY NIGHT TIMING
OF THE GEFS ENSEMBLE MEAN. POPS HAVE BEEN RAISED ACCORDINGLY.
THERE IS ALSO THE POTENTIAL FOR SOME VERY COLD AIR TO MOVE INTO THE
NORTHEAST PORTION OF THE FORECAST AREA FOR THE WEEKEND. THE GEM IS
THE COLDEST WITH A 1000-500 MB HEIGHT CONTOUR OF 516 DAM ACROSS THE
NORTHERN PANHANDLE SUNDAY MORNING. OTHER MODELS ARE NOT QUITE SO
COLD...KEEPING THE LOWEST HEIGHTS NORTH AND EAST OF THE FORECAST
AREA. TEMPERATURES COULD DIP WELL BELOW SEASONAL NORMALS IN THE
NORTHEAST VALLEYS DEPENDING ON HOW FAR SOUTH THE ARCTIC AIR
INFILTRATES. /KELCH
&&
.AVIATION...
HIGH PRESSURE WILL BE BUILDING INTO THE REGION TODAY. LOW STRATUS
AND FOG WILL BE THE MAIN CONCERN THIS MORNING. KGEG...KSFF...KCOE
HAVE BEEN MOISTENING THROUGH THE EARLY MORNING HOURS. LOW STRATUS
BETWEEN 2-3 KFT AGL HAVE ALREADY BEGAN DEVELOPING IN KSFF AND
KCOE...EXPECT REDUCING CIGS TO 1-2 KFT AGL INTO KGEG BETWEEN 13Z AND
14Z LASTING THROUGH 18Z. KMWH SHOULD SEE FOG DEVELOPING AROUND 14Z
WITH LIFR CIGS AND VIS POSSIBLE. FOG AND LOW STRATUS SHOULD LIFT AND
BREAK AROUND 17-18Z THIS MORNING WITH VFR CONDITIONS THROUGH THE
AFTERNOON AND EVENING HOURS. /SVH
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 40 29 41 29 39 25 / 0 0 0 0 0 0
COEUR D'ALENE 39 32 41 30 39 26 / 0 0 0 10 0 0
PULLMAN 43 30 42 33 40 27 / 0 0 0 10 0 0
LEWISTON 44 32 46 36 45 31 / 0 0 0 10 0 0
COLVILLE 37 36 41 29 39 26 / 10 0 10 20 0 0
SANDPOINT 37 33 37 28 35 24 / 10 10 10 20 0 0
KELLOGG 38 29 39 30 36 28 / 10 0 10 20 10 0
MOSES LAKE 43 28 43 30 42 27 / 0 0 0 0 0 0
WENATCHEE 43 32 44 33 43 31 / 0 0 0 0 0 0
OMAK 40 32 43 29 42 28 / 0 0 0 10 0 0
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...NONE.
WA...NONE.
&&
$$
