Expires:No;;911632 FXUS66 KOTX 102351 AFDOTX AREA FORECAST DISCUSSION...UPDATED AVIATION DISCUSSION NATIONAL WEATHER SERVICE SPOKANE WA 351 PM PST TUE FEB 10 2009 .SYNOPSIS... A MORE ACTIVE WEATHER PATTERN WILL RESULT IN A SERIES OF PACIFIC STORMS PASSING MOSTLY SOUTH OF THE REGION THROUGH THE WEEK. THE INLAND NORTHWEST OF WASHINGTON AND IDAHO WILL LIKELY RECEIVE MINOR SNOW ACCUMULATIONS FROM THE FRINGES OF THESE STORMS. && .DISCUSSION... TONIGHT...LIGHT PRECIPITATION WILL SPREAD ACROSS THE INLAND NORTHWEST TONIGHT AS A WARM FRONT ADVANCES ACROSS THE REGION. THE 20Z SATELLITE WATER VAPOR IMAGERY SHOWS THE MOISTURE ASSOCIATED WITH THE WARM FRONT BEING PUSHED AHEAD OF THE UPPER LOW SPINNING OFF THE WASHINGTON COAST. MODELS ARE IN VERY GOOD AGREEMENT ON TRACKING THE SURFACE LOW SOUTH ALONG THE COAST BUT HAVE SLOWED THE EASTWARD PROGRESSION OF THE PRECIPITATION FIELD SOMEWHAT. WEBCAMS INDICATE THAT SNOW HAS BEEN FALLING THIS AFTERNOON AT THE CASCADE PASSES BUT IS ONLY SLOWLY ADVANCING PAST THE CREST. POPS HAVE BEEN TRIMMED BACK FOR THE AFTERNOON HOURS TO ACCOUNT FOR THIS. THERE IS AGREEMENT ON THE FORMATION OF A DEFORMATION BAND ACROSS THE SOUTHEAST PORTION OF THE FORECAST AREA AS A BOUNDARY SETS UP OVER THE AREA OVERNIGHT. THE EXACT LOCATION OF THIS BOUNDARY WILL DETERMINE WHICH AREA RECEIVES ANY SIGNIFICANT SNOWFALL. LATEST GUIDANCE PLACES IT IN THE GENERAL AREA OF THE PALOUSE SO HIGHEST POPS HAVE BEEN PAINTED ACROSS THIS AREA TONIGHT. POPS HAVE BEEN TRIMMED ACROSS THE NORTHEAST ZONES AS WE EXPECT THE BOUNDARY WILL HAVE A DIFFICULT TIME MAKING IT THAT FAR NORTH AS THE PARENT LOW CONTINUES TO SINK SOUTH. SNOW LEVELS WILL CONTINUE AT VALLEY FLOORS WITH AN INCH OR LESS OF SNOWFALL EXPECTED FOR MOST OF THE FORECAST AREA. THE EXCEPTION WILL BE ALONG THE EAST SLOPES AND UNDER THE DEFORMATION BAND WHERE GENERALLY 1 TO 2 INCHES CAN BE EXPECTED WITH LOCAL AMOUNTS UP TO 3 INCHES POSSIBLE DEPENDING ON THE STRENGTH AND DURATION OF ANY SNOWBANDS. LOCAL SNOWFALL AMOUNTS WILL BE BORDERLINE ADVISORY BUT I DO NOT HAVE THE CONFIDENCE LEVEL REQUIRED TO ISSUE WINTER WEATHER HIGHLIGHTS AT THIS TIME. /KELCH WEDNESDAY THROUGH FRIDAY NIGHT...MODELS ARE IN GOOD AGREEMENT DURING THIS PERIOD. VERTICALLY STACKED LOW OFF THE CENTRAL OREGON COAST WED AM WILL DROP SOUTH TOWARDS NORTHERN CALIFORNIA WED AFTERNOON. AS THIS OCCURS WHAT IS LEFT OF A DEFORMATION ZONE OVER SE WASHINGTON INTO THE CENTRAL PANHANDLE WILL RAPIDLY WEAKEN. THUS LIGHT SNOW ACCUMULATIONS WILL CONTINUE ON WEDNESDAY OVER THESE AREAS BEFORE ENDING. THE SPOKANE/COEUR D'ALENE AREAS LOOK TO BE ON THE EDGE OF THIS DEFORMATION ZONE WEDNESDAY RESULTING IN A CHANCE FOR LIGHT SNOW...WITH PRECIP CHANCES QUICKLY DECREASING NORTH AND WEST OF THE SPOKANE AREA. FOR WED NGT A SHORT WAVE RIDGE BUILDS IN BRINGING LIGHT WINDS...WHICH IN COMBINATION WITH A MOIST BOUNDARY LAYER WILL LEAD TO AREAS OF FREEZING FOG ESPECIALLY AREAS THAT HAVE FRESH SNOW COVER FROM TONIGHT AND WEDNESDAY SNOWFALL. THE PATTERN FOR WEDNESDAY NIGHT THROUGH FRIDAY FOR CENTRAL AND EASTERN WA...AS WELL AS NORTH IDAHO WILL BE FOR GENERALLY DRY CONDITIONS AS ANOTHER LOW DROPS SOUTH TOWARDS CALIFORNIA THU NGT/FRIDAY. JUST A SLIGHT CHANCE FOR SNOW SHOWERS IS FORECAST FOR THE EAST SLOPES OF THE NORTH WA CASCADES GIVEN CLOSEST PROXIMITY TO THIS FEATURE ALONG WITH A LOW AND MID LEVEL UPSLOPE FLOW COMPONENT. THERE WILL ALSO BE A SLIGHT CHANCE FOR MOUNTAIN SNOW SHOWERS OVER NORTH IDAHO AS VERY WEAK IMPULSES TRACK SE FROM BRITISH COLUMBIA INTO MONTANA. TEMPERATURES WILL REMAIN BELOW NORMAL FOR THIS TIME OF YEAR WITH THE TROUGH PATTERN PERSISTING ALONG THE WESTERN US. JW SATURDAY THROUGH TUESDAY...THE PRIMARY STORM TRACK WILL LIKELY CONTINUE TO REMAIN FOCUSED INTO CALIFORNIA THIS WEEKEND INTO EARLY NEXT WEEK. THERE IS SOME INDICATION THAT THE WEATHER PATTERN MAY SHIFT A BIT BY THE MIDDLE OF NEXT WEEK...BUT THE MEDIUM RANGE MODELS CONTINUE TO FOCUS THE POLAR JET INTO CALIFORNIA THROUGH AT LEAST NEXT WEDNESDAY. THE GFS ENSEMBLES AS WELL AS THE OPERATIONAL ECMWF AGREE THAT THE RIDGE CURRENTLY ANCHORED ALONG 150W WILL SLOWLY RETROGRADE TO ABOUT 170W BY EARLY NEXT WEEK. SO BY THE SECOND HALF OF NEXT WEEK...WE MAY EXPERIENCE A PATTERN SHIFT THAT WILL BE MORE FAVORABLE FOR MORE PRECIPITATION. UNTIL THEN...THE MAIN JET DYNAMICS AND DEEP MOISTURE PLUME WILL BE WELL SOUTH OF THE SPOKANE FORECAST AREA. PRECIPITATION CHANCES WERE HELD BELOW CLIMATOLOGY ON SATURDAY WITH THE PRESENCE OF A WEAK SHORTWAVE RIDGE. THE MODELS BEGIN TO DIVERGE ON SUNDAY...WITH THE 06Z AND 12Z RUNS OF THE GFS FORECASTING A WEAK UPPER TROUGH TRANSLATING ACROSS WASHINGTON SUNDAY INTO MONDAY. THE ECMWF CARRIES ALMOST NO UPPER TROUGH. GIVEN THE MODEL UNCERTAINTY...THE FORECAST HAS BEEN TRENDED TOWARD CLIMATOLOGY SUNDAY...MONDAY...AND TUESDAY. EVEN IF THE GFS VERIFIES...I WOULDN'T EXPECT ANY BIG SNOW ACCUMULATIONS. AS FOR TEMPERATURES...GFS GUIDANCE LOOKS TOO WARM GIVEN THE LIGHT PRESSURE GRADIENT AND COOL 850MB TEMPERATURES. HIGHS HAVE BEEN KEPT AT OR BELOW AVERAGE...WHICH IS CLOSER TO THE GFS ENSEMBLE NUMBERS. /GKOCH && .AVIATION... A BAND OF -SN THAT STRETCHED FROM KYKM TO KEAT AS OF 2330Z WILL MOVE EAST THIS EVENING LEADING TO LOWERING CIGS AND VSBYS AT ALL TAF SITES. MVFR AND IFR CIGS/VSBYS WILL BE COMMON ONCE -SN DEVELOPS. LIGHT SNOW ACCUMULATIONS ARE EXPECTED WITH THE HIGHEST ACCUMULATIONS AT KPUW. SOME IMPROVEMENT IS FORECAST ON WEDNESDAY...BUT VERY MOIST CONDITIONS IN THE LOW LEVELS WILL LIKELY LEAD TO MVFR/IFR STRATUS AFTER SNOW STOPS. JW && .PRELIMINARY POINT TEMPS/POPS... SPOKANE 24 32 21 32 23 35 / 60 50 10 10 10 0 COEUR D'ALENE 23 33 21 33 21 37 / 70 50 10 10 10 10 PULLMAN 28 32 21 35 19 36 / 80 70 10 10 10 0 LEWISTON 31 39 27 41 26 42 / 60 50 10 10 10 0 COLVILLE 20 35 18 35 19 39 / 50 20 10 20 10 10 SANDPOINT 21 33 20 33 21 35 / 50 30 20 20 10 10 KELLOGG 24 33 24 36 21 39 / 70 60 30 30 20 10 MOSES LAKE 25 36 21 35 22 39 / 90 20 0 0 0 0 WENATCHEE 25 34 23 33 24 38 / 90 10 0 0 0 0 OMAK 21 34 17 33 18 36 / 80 0 10 10 0 0 && .OTX WATCHES/WARNINGS/ADVISORIES... ID...NONE. WA...NONE. && $$