550  
FXUS66 KOTX 242345  
AFDOTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SPOKANE WA  
345 PM PST FRI NOV 24 2017  
   
SYNOPSIS
 
 
ISOLATED SHOWERS WILL LINGER IN THE MOUNTAINS TONIGHT, OTHERWISE  
THERE WILL BE A BRIEF BREAK IN THE WEATHER. MORE WET AND UNSETTLED  
WEATHER WILL MOVE BACK INTO THE REGION LATE SATURDAY INTO SUNDAY  
WITH ANOTHER WEATHER DISTURBANCE MOVING IN EARLY NEXT WEEK.  
 

 
   
DISCUSSION
 
 
TONIGHT: VERY BROAD FLAT RIDGE WILL PERSIST OVER THE REGION THIS  
EVENING INTO SATURDAY. THIS WILL KEEP CONDITIONS MOSTLY DRY EXCEPT  
FOR SOME VERY ISOLATED SHOWERS ALONG THE CASCADE CREST AND  
MOUNTAINS OF N ID. CLOUDS WILL THIN AND PARTIALLY DISSIPATE THIS  
EVENING AS DRIER AIR FROM THE SOUTH BEGINS TO MOVE IN. FORECAST  
CHALLENGE FOR TONIGHT WILL BE THE EXTENT OF STRATUS AND/OR FOG.  
MODELS ARE SHOWING SOME BOUNDARY LAYER MOISTURE ACROSS THE NORTH  
AS WELL AS DOWN INTO THE COLUMBIA BASIN BY ABOUT MIDNIGHT, THEN  
TOWARDS MORNING THAT MOISTURE GETS PUSHED INTO THE CASCADES. HAVE  
ADJUSTED OUR FOG FORECAST TO SHOW THE PROGRESSION OF THE GROWING  
PATCHY FOG TOWARDS MORNING.  
 
SATURDAY AND SATURDAY NIGHT: A TROUGH WILL MOVE SOUTH OUT OF THE  
GULF OF ALASKA SATURDAY MORNING AND APPROACH THE WEST COAST. BY  
AFTERNOON THE NEXT WARM FRONT WILL BEGIN TO PUSH IN FROM THE  
SOUTH. THE MAIN IMPACT WILL BE AN INCREASE IN CLOUDS. BY LATE  
AFTERNOON PRECIPITATION WILL MOVE IN FROM THE SOUTH, AND DURING  
THE EVENING MOST LOCATIONS WILL SEE RAIN OR HIGH MOUNTAIN SNOW.  
THE FRONT IS FAST MOVING AND HAVE DECREASED OUR CHANCE OF PRECIP  
ACROSS THE SOUTH OVERNIGHT WHILE KEEPING CHANCE OF PRECIP HIGH  
ACROSS NORTHERN WA AND ID. SNOW LEVELS WILL RISE THROUGH THE NIGHT  
WITH SNOW LEVELS IN THE NORTH RANGING FROM 4000-5000+ FT. SNOW  
AMOUNTS WILL BE QUITE LIGHT ACROSS NE WA AND N ID WITH AN INCH OR  
TWO POSSIBLE. THE CASCADES WILL SEE MORE SNOW AS THEY WILL HAVE  
GOOD UPSLOPE FLOW INTO THE EAST SLOPES. GENERALLY 1-3 INCHES OF  
SNOW WITH LOCALLY UP TO 5 OR 7 INCHES WILL BE POSSIBLE ALONG THE  
HIGHER PEAKS AND CREST. TEMPERATURES WILL BE ABOUT 4-10 DEGREES  
ABOVE AVERAGE FOR THIS TIME OF THE YEAR. /NISBET  
 
SUNDAY THROUGH FRIDAY...GENERAL AGREEMENT EXISTS BETWEEN THE  
LATEST GFS...ECMWF AND CANADIAN MODELS REGARDING THE OVERALL  
FIELD OF MOTION THROUGH MOST OF THE UPCOMING WEEK. A SERIES OF  
TROUGHS WILL BRING PERIODS OF ENHANCED PRECIPITATION CHANCES WITH  
WEAK SHORT WAVE RIDGE PATTERNS BRINGING QUIET INTERREGNUMS WITH  
SCATTERED MOUNTAIN SNOW SHOWERS.  
 
SUNDAY WILL BE A WET PERIOD WITH ANOTHER SUBTROPICAL ORIGIN  
MOISTURE FEED ENHANCING ALONG A TRANSITING COLD FRONT. SNOW LEVELS  
WILL REMAIN HIGH AND ONLY BEGIN DROPPING AFTER THE FROPA...WHICH  
WILL ALSO FEATURE BREEZY AND GUSTY WINDS BUT NOT AS BAD AS  
YESTERDAYS FRONTAL PASSAGE.  
 
MONDAY AND MONDAY NIGHT WILL BE A DRY BREAK PERIOD FOLLOWED BY  
DETERIORATING CONDITIONS ON TUESDAY AS THE NEXT TROUGH ENTERS THE  
REGION. THIS WAVE WILL ARRIVE ON A MORE NORTHWESTERLY TRAJECTORY  
AND SNOW LEVELS WILL BE NOTICEABLY LOWER...AROUND 3000 FEET DURING  
THE DAY BUT MAY DROP TO VALLEY FLOORS AND THE HIGHER BASIN FLOOR  
TUESDAY NIGHT. THE FOCUS OF PRECIPITATION WILL BE MAINLY OVER THE  
IDAHO PANHANDLE BUT SNOW SHOWERS MAY BACKFILL INTO THE EASTERN  
BASIN AS THE AXIS PASSES THROUGH.  
 
WEDNESDAY WILL BE ANOTHER BREAK DAY...WITH A DRY CANADIAN POLAR  
AIR MASS INFILTRATING THE REGION PROMOTING A COOLING TREND BACK  
TOWARD NORMAL FOR THE REST OF THE UPCOMING WEEK.  
 
FOR THURSDAY AND FRIDAY MODEL AGREEMENT BEGINS TO  
DETERIORATE...ESPECIALLY FOR TIMING THE NEXT WAVE OF MOISTURE  
AS EARLY AS THURSDAY FOR THE ECMWF AND AS LATE AS FRIDAY FOR THE  
GFS.  
 
IT DOES APPEAR THAT THE TUESDAY NIGHT SYSTEM MAY HERALD A PATTERN  
SHIFT FOR THE REGION FROM A MILD AND MOIST MARITIME REGIME TO  
MORE OF A NORMAL CONTINENTAL POLAR REGIME WITH LOWER SNOW LEVELS  
DURING PASSING DISTURBANCES AND COOLER TEMPERATURES MORE  
SEASONABLY CHARACTERISTIC FOR LATE NOVEMBER. /FUGAZZI  
 

 
   
AVIATION
 
 
00Z TAFS: WESTERLY FLOW WILL BE OVER THE REGION TONIGHT WITH  
TRANSIENT MID LEVEL CLOUDS AND HIGH CIRRUS. SOME VALLEY FG AND  
IFR CEILING STRATUS ARE POSSIBLE BETWEEN 11Z AND 17Z MAINLY AT  
THE KMWH AND KEAT TAF SITES WHERE A WEAK LOW LEVEL EASTERLY  
GRADIENT WILL BANK DEEPER MOIST BOUNDARY LAYER AIR AGAINST THE  
CASCADES. AFTER ANY MORNING FG OR STRATUS BREAKS UP...VFR  
CONDITIONS EXPECTED AT ALL TAF SITES...BUT WITH LOWERING CEILINGS  
AS A MOIST STORM SYSTEM APPROACHES THE REGION FROM THE SOUTHWEST.  
ANY PRECIPITATION AND MVFR CONDITIONS SHOULD HOLD OFF UNTIL AFTER  
00Z SUNDAY. /MJF  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
SPOKANE 32 44 39 52 34 41 / 0 0 80 70 60 10  
COEUR D'ALENE 32 45 37 51 34 41 / 0 0 80 50 90 20  
PULLMAN 34 47 42 54 35 43 / 0 0 60 50 90 10  
LEWISTON 35 51 42 57 38 48 / 0 10 30 30 70 10  
COLVILLE 33 42 35 46 32 42 / 10 0 80 80 70 10  
SANDPOINT 32 41 35 46 34 40 / 10 0 80 60 100 20  
KELLOGG 31 43 36 49 33 38 / 10 0 70 60 90 40  
MOSES LAKE 31 45 35 50 31 46 / 0 20 60 50 40 10  
WENATCHEE 32 41 35 46 32 43 / 0 30 80 60 20 10  
OMAK 33 42 36 45 32 42 / 10 10 70 80 50 0  
 

 
   
OTX WATCHES/WARNINGS/ADVISORIES
 
 
ID...NONE.  
WA...NONE.  
 

 
 

 
 
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