FXUS66 KOTX 261138
AFDOTX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SPOKANE WA
333 AM PST SAT DEC 26 2009
.SYNOPSIS...
STRONG HIGH PRESSURE WILL PROMOTE CONTINUED DRY AND COOL CONDITIONS
OVER THE INLAND NORTHWEST THROUGH THE WEEKEND. A SERIES OF WEAK
WEATHER SYSTEMS NEXT WEEK WILL BRING SMALL TO MODERATE CHANCES OF
LIGHT SNOW TO THE REGION...BUT NO SIGNIFICANT STORMS ARE EXPECTED.
&&
.DISCUSSION...
SATELLITE INDICATES A HIGHLY ELONGATED DRY RIDGE OVER THE
FORECAST AREA. THE OFFSHORE UPSTREAM TROUGH IS TRYING TO BREAK THE
RIDGE DOWN...WITH AN UNDERCUTTING SYSTEM ENCROACHING ON NORTHERN
CALIFORNIA. LATEST MODELS ARE IN GOOD AGREEMENT AND PLAUSIBLE
AGAINST SATELLITE EXTRAPOLATION. THE NORCAL SYSTEM WILL SIMPLY
PINCH THE RIDGE INTO A CLOSED UPPER HIGH OVER SOUTHERN CANADA.
THIS HIGH WILL EFFECTIVELY PREVENT ANY NORTHWARD MOVEMENT OF THE
INCOMING CALIFORNIA SYSTEM AND KEEP THE FORECAST AREA HIGH AND DRY
ON THE NORTHERN FRINGE OF THE MID AND UPPER LEVEL CLOUD SHIELD BY
SUNDAY AFTERNOON. THUS LARGELY A PERSISTENCE FORECAST WITH THE
WEATHER CONDITIONS OF THE LAST FEW DAYS CONTINUING THROUGH TODAY
AND SUNDAY...THUS A DRY FORECAST WITH AREAS OF LOW CLOUDS AND
PATCHY FOG WILL CONTINUE FOR THE NEXT 36 HOURS AT LEAST.
TEMPERATURES WILL REMAIN BELOW CLIMATOLOGY. /FUGAZZI
SUNDAY NIGHT THROUGH MONDAY NIGHT...MODELS ARE IN GENERAL
AGREEMENT OF A WEAKENING AND SPLITTING SHORT WAVE TROUGH PASSING
THROUGH THE INLAND NW ON MONDAY AND MONDAY NIGHT. OVERALL MOISTURE
IS SHALLOW WITH THIS FEATURE SO POPS REMAIN LOW THROUGH MONDAY
NIGHT. CONCERNING FOG/STRATUS POTENTIAL...THE BOUNDARY LAYER WILL
RAPIDLY SATURATE OVER THE VALLEYS SUNDAY NIGHT INTO MONDAY MORNING
AS THE EASTERLY GRADIENT SUBSIDES AND 925-850MB WINDS COME AROUND
TO THE SOUTH AND ADVECT IN INCREASED LOW LEVEL MOISTURE. THUS A
QUICK EXPANSION IN STRATUS AND FOG IS EXPECTED DURING THIS TIME
FRAME. THEN WITH THE MON/MON NGT SYSTEM BEING VERY WEAK...FCST
SOUNDINGS SHOW VERY LITTLE MIXING POTENTIAL SO STRATUS AND FOG
WILL PERSIST INTO MONDAY NIGHT. WHAT THIS WEAK SYSTEM MAY DO IS
INCREASE THE POTENTIAL FOR FLURRIES OR FREEZING DRIZZLE SO THIS
WILL HAVE TO BE EVALUATED BY FUTURE SHIFTS.
TUESDAY THROUGH NEW YEARS DAY...VERY FEW FORECAST CHANGES MADE
DURING THIS TIME FRAME. A SLIGHTLY STRONGER SYSTEM IS EXPECTED TUE
NGT/WED BUT THIS SYSTEM WILL ALSO BE ENCOUNTERING A SPLIT FLOW AND
WEAKENING AS IT CROSSES THE AREA. AS A RESULT POPS REMAIN IN THE
SLIGHT CHANCE AND CHANCE RANGE. FCST SOUNDINGS FROM THE GFS SHOW
SLIGHTLY BETTER MIXING BEHIND THIS SYSTEM BUT LIKELY NOT STRONG
ENOUGH TO COMPLETELY SCOUR OUT THE LOW CLOUDS WHICH MAY PERSIST
INTO THURSDAY AS A SHORT WAVE RIDGE MOVES OVER THE AREA. A WARM
FRONT TRACKS THROUGH THE AREA ON NEW YEARS DAY FOR A BETTER SHOT
OF PRECIPITATION WITH SNOW LEVELS POSSIBLY RISING ESPECIALLY OVER
SOUTHERN WASHINGTON AND THE LEWISTON AREA AS SOUTHERLY FLOW AT
850MB USHERS IN WARMER AIR. JW
&&
.AVIATION...
STRONG HIGH PRESSURE ALOFT IS PROMOTING A STRONG INVERSION
OVER THE COLUMBIA BASIN AND VALLEYS NORTH AND WEST OF THE BASIN.
SURFACE HIGH PRESSURE TO THE EAST OF THE AREA IS ALLOWING AREAS OF
LOW MVFR AND IFR AND LOCAL LIFR CEILINGS IN STRATUS WITH TOPS AROUND
3.5 KFT MSL TO DEVELOP OVER THE LOWER ELEVATIONS OF THE COLUMBIA
BASIN. THESE LOW CEILINGS WILL PERSIST MAINLY AT KLWS AND KEAT
THROUGH 18Z WITH SOME BREAK UP DURING THE AFTERNOON. VFR CONDITIONS
ARE EXPECTED TODAY AT ALL OTHER TAF SITES. TONIGHT THE AREA OF LOW
STRATUS MAY BROADEN OUT TO ENCOMPASS THE KMWH TAF SITE IN ADDITION
TO KLWS AND KEAT...WITH A SMALL POSSIBILITY OF IFR CONDITIONS IN THE
SPOKANE AREA TAF SITES BY 12Z SUNDAY.
&&
.PRELIMINARY POINT TEMPS/POPS...
SPOKANE 28 17 28 17 26 19 / 0 0 0 0 10 10
COEUR D'ALENE 29 19 28 18 28 19 / 0 0 0 0 10 10
PULLMAN 31 20 30 20 27 21 / 0 0 0 0 10 10
LEWISTON 28 22 31 22 30 22 / 0 0 0 0 0 10
COLVILLE 28 15 30 14 27 16 / 0 0 0 0 10 10
SANDPOINT 27 18 27 15 28 16 / 0 0 0 0 10 10
KELLOGG 27 14 32 17 29 18 / 0 0 0 0 10 10
MOSES LAKE 32 18 28 15 28 17 / 0 0 0 0 10 10
WENATCHEE 28 21 26 17 26 20 / 0 0 0 0 10 10
OMAK 27 13 27 13 23 14 / 0 0 0 0 10 10
&&
.OTX WATCHES/WARNINGS/ADVISORIES...
ID...AIR STAGNATION ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR
CENTRAL PANHANDLE MOUNTAINS...COEUR D'ALENE AREA...IDAHO
PALOUSE...LEWIS AND SOUTHERN NEZ PERCE COUNTIES...LEWISTON
AREA...NORTHERN PANHANDLE.
WA...AIR STAGNATION ADVISORY UNTIL 4 PM PST THIS AFTERNOON FOR EAST
SLOPES NORTHERN CASCADES...LOWER GARFIELD AND ASOTIN
COUNTIES...MOSES LAKE AREA...NORTHEAST MOUNTAINS...OKANOGAN
HIGHLANDS...OKANOGAN VALLEY...SPOKANE AREA...UPPER COLUMBIA
BASIN...WASHINGTON PALOUSE...WATERVILLE PLATEAU...WENATCHEE
AREA.
&&
$$
