132  
FXUS66 KOTX 221140  
AFDOTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SPOKANE WA  
340 AM PST MON JAN 22 2018  
   
SYNOPSIS
 
 
AN ACTIVE WEATHER PATTERN IS EXPECTED THROUGH THE WEEK. A WET AND  
MILD WEATHER SYSTEM WILL BRING SIGNIFICANT PRECIPITATION TUESDAY  
NIGHT INTO WEDNESDAY AND AGAIN NEXT WEEKEND WITH A MIX OF RAIN AND  
SNOW ACROSS THE LOWER ELEVATIONS AND SNOW IN THE MOUNTAINS.  
TRAVEL IMPACTS ARE EXPECTED AT TIMES, ESPECIALLY OVER THE MOUNTAIN  
PASSES.  
 

 
   
DISCUSSION
 
 
TODAY AND TONIGHT...ANOTHER SHORT WAVE DISTURBANCE VISIBLE ON  
SATELLITE AS AN AREA OF INCREASING ENHANCEMENT ON THE INFRARED  
SATELLITE LOOP MOVING INTO THE OLYMPICS AND VANCOUVER ISLE EARLY  
THIS MORNING WILL TRANSIT THE FORECAST AREA TODAY BRINGING ANOTHER  
1 TO 3 HOUR ROUND OF SNOW SHOWERS AND AFTERNOON VALLEY RAIN  
SHOWERS TO MAINLY THE EASTERN REACHES OF THE FORECAST AREA WHILE  
LARGELY SKIPPING OVER THE DEEP BASIN IN THE LEE OF THE CASCADES.  
SNOW AMOUNTS WILL BE LIGHT AND SPOTTY IN THE VALLEYS AND BASIN  
THIS MORNING...BUT WITH THE POTENTIAL FOR A FEW INCHES IN THE  
PANHANDLE MOUNTAINS WITH SOME SLIPPERY TRAVEL POSSIBLE ACROSS  
LOOKOUT PASS THIS AFTERNOON. OTHERWISE GENERALLY CLOUDY CONDITIONS  
ACROSS THE EASTERN PORTION OF THE FORECAST WITH AT LEAST PARTIALLY  
SUNNY SKIES IN THE DOWNSLOPED DEEP BASIN AND HIGH TEMPERATURES  
CONTINUING TO RUN ABOVE NORMAL FOR THIS TIME OF YEAR ARE  
EXPECTED. TONIGHT WILL BE A QUIET AND COOL BREAK PERIOD BEFORE THE  
NEXT SIGNIFICANT STORM SYSTEM ENVELOPS THE REGION. /FUGAZZI  
   
..HEAVY SNOW TUESDAY INTO WEDNESDAY ACROSS THE NORTHERN MOUNTAINS
 
 
TUESDAY THROUGH WEDNESDAY NIGHT: A WET AND MILD STORM SYSTEM WILL  
IMPACT THE NORTHWESTERN US BRINGING THE POTENTIAL FOR HEAVY  
SNOWS, MIX OF LOWLAND SNOW AND RAIN, AND BREEZY WIND AT TIMES. A  
WARM FRONT WILL USHER IN A RICH FETCH OF SUBTROPICAL MOISTURE  
STARTING TUESDAY MORNING ACROSS THE CASCADES AND EXPANDING ACROSS  
MUCH OF EASTERN WA AND NORTH IDAHO BY THE AFTERNOON HOURS.  
PRECIPITATION WITHIN THE WARM SECTOR WILL PERSIST WELL INTO  
WEDNESDAY THEN END OR TRANSITION TOWARD SHOWERS WEDNESDAY NIGHT  
WITH THE PASSAGE OF A COLD FRONT. BETWEEN HALF AND ONE INCH OF QPF  
WILL FALL BY WEDNESDAY MORNING ALONG AND NORTH OF HIGHWAY 2 FROM  
STEVENS PASS TO SANDPOINT THEN AN ADDITIONAL QUARTER TO INCH WILL  
BE POSSIBLE FOR THE NEXT 24 HOURS. SNOW LEVELS WILL START OFF LOW  
AND WILL NO DOUBT RISE FROM SOUTH TO NORTH WITH THE INLAND NW  
REMAINING IN THE WARM SECTOR FOR 24-36 HOURS UNDER 25-40KTS OF  
SOUTHERLY FLOW AROUND 4000 FEET AGL.  
 
THE MILLION DOLLAR QUESTION IS WHAT WILL SNOW LEVELS START AT AND HOW  
FAST WILL THEY RISE? MODELS CONTINUE TO FORECAST A COOL AIR MASS  
SETTLING IN TONIGHT AND MONDAY CHARACTERIZED BY 850MB TEMPERATURES  
OF -3 TO -7C. THIS LEADS TO HIGH CONFIDENCE FOR SNOW IN THE  
NORTHERN MOUNTAINS THROUGH WEDNESDAY MORNING THEN RISING SOME  
WEDNESDAY AFTERNOON. IN MOST WINTERS, TEMPERATURES OF THIS NATURE  
WERE A SURE BET FOR SNOW IN THE VALLEYS WHEN THE CALENDAR READ  
JANUARY BUT AS WE HAVE SEEN IN THE LAST FEW SYSTEMS, WE ARE  
EXPERIENCING RATHER MILD LOWLAND CONDITIONS RESULTING IN LESS SNOW  
THAN MODELS ARE SUGGESTING. TEMPERATURES WILL WARM INTO THE MID  
TO UPPER 30S MONDAY AFTERNOON. THERE LOOKS TO BE SOME CLEARING  
TOMORROW NIGHT BEFORE THE CLOUD SHIELD BEGINS TO THICKEN. MODELS  
INDICATE TEMPERATURES DIP INTO THE MID TO LOW 20S BUT I AM NOT  
BUYING THIS. FIRST OF ALL, THE 00Z GUIDANCE IS ALREADY OFF BY AS  
MUCH AS 8F FOR LOCATIONS LIKE OMAK AND WINTHROP. INITIALIZATION IS  
NOT AS BAD IN BASIN AND IDAHO PANHANDLE. NONETHELESS, I FEEL THE  
NORTHERN VALLEYS WILL DIP BELOW FREEZING BUT STICKING WITH UPPER  
20S TO LOWER 30S VS GUIDANCE NUMBERS. THIS SHOULD ALLOW  
PRECIPTIATION TO START AS SNOW NORTH OF I-90 BUT QUICKLY  
TRANSITION TO RAIN OR NON-ACCUMULATING SNOW FOR FOR MOST LOCATIONS  
SOUTH OF HIGHWAY 2. VALLEYS NORTH OF THE THE HIGHWAY WILL STAND A  
BETTER SHOT OF LIGHT TO MODERATE SNOW ACCUMULATIONS BEFORE  
SWITCHING OVER TO RAIN LATER TUESDAY. IF THE PRECIPTIATION  
INTENSITY IS TO DRIVE DOWN TEMPERATURES AND HOLD THEM STEADY,  
MODERATE TO HEAVY SNOW AMOUNTS WILL BE POSSIBLE FOR THESE LOWLANDS  
SPANNING FROM SANDPOINT TO CHEWELAH TO OMAK AND INTO THE METHOW  
VALLEY. FORECAST WILL NEED TO BE FINE TUNED AS WE SEE THERMAL  
PROFILES MONDAY NIGHT.  
 
THE LOWER COLUMBIA BASIN AND PALOUSE WILL LARGELY BE BREEZY WITH  
RAIN AND LIGHTER AMOUNTS THAN EXPECTED ACROSS THE NORTH. SNOW  
WILL FALL OVER THE CENTRAL PANHANDLE MOUNTAINS AND POSSIBLY THE  
HIGHER TERRAIN AROUND THE CAMAS PRAIRIE AND BLUES TUESDAY  
AFTERNOON BUT A TRANSITION TO RAIN WITH SNOW LEVELS AROUND 4000  
FEET SHOULD LEAD MINIMAL TRAVEL IMPACTS. THAT IS UNTIL WEDNESDAY  
NIGHT WHEN THE COLD FRONT DRIVES DOWN SNOW LEVELS AND FAVORABLE  
WINDS LEAD TO RENEWED SNOW CHANCES INTO THURSDAY MORNING. THE  
STRONGEST WINDS WILL OCCUR IN THE FOOTHILLS OF THE BLUE MOUNTAINS  
AND AROUND THE SNAKE RIVER VALLEY. GUSTS AROUND 40 MPH ARE  
POSSIBLE. /SB  
 
THURSDAY THROUGH SUNDAY...AN ACTIVE AND WET PATTERN WILL CONTINUE  
THROUGH THE END OF THE EXTENDED PERIOD. THURSDAY LOOKS LIKE AN  
UNSETTLED SHOWERY DAY WITH MODELS IN DECENT AGREEMENT IN EJECTING  
WHAT IS LEFT OF THE OFFSHORE TROUGH THROUGH THE REGION WITH  
PROBABLY SOME SHALLOW INSTABILITY AND COOLER TEMPERATURES  
PROMOTING SCATTERED SNOW SHOWERS WITH LOCAL MINOR ACCUMULATIONS  
ESPECIALLY IN THE MOUNTAINS. INCREASINGLY MOIST WESTERLY ZONAL  
FLOW ON FRIDAY WILL CONTINUE A THREAT OF MAINLY MOUNTAIN SNOW  
SHOWERS. SATURDAY THE GFS AND EC MODELS ARE IN DECENT AGREEMENT  
FEATURING A WARM FRONT PASSAGE FOR A THREAT OF WIDESPREAD  
PRECIPITATION. THE MODELS DEVELOP THIS FRONT DURING THE MORNING  
HOURS LEADING TO REASONABLE CONFIDENCE THAT MOST LOCATIONS WILL  
SEE LIGHT SNOW AT LEAST INITIALLY...BEFORE THE VALLEYS AND BASIN  
CHANGE OVER TO RAIN OR A WET MIX DURING THE AFTERNOON.  
HOWEVER...THIS STORM APPEARS TO BE AN OPENING ACT FOR A  
POTENTIALLY MUCH WETTER DIRECT HOSING FROM A SUB-TROPICAL PACIFIC  
MOISTURE FEED ON SUNDAY...AND THIS POTENTIAL BRINGS THE  
POSSIBILITY OF HEAVIER MOUNTAIN SNOW AND VALLEY WINTRY MIX  
TRANSITIONING TO SOIL SATURATING RAIN DURING THE DAY...WITH  
ATTENDANT SMALL STREAM RISES AND MUD SLIDE CONCERNS BY THE  
BEGINNING OF NEXT WEEK. /FUGAZZI  
 

 
   
AVIATION
 
 
12Z TAFS: SATELLITE IMAGERY SHOWS A FIELD OF LOW STRATUS OVER THE  
KGEG AREA TO KCOE WITH MVFR CEILINGS AT KSFF AND KCOE...WITH KGEG  
ON THE VERY EDGE OF IFR CEILING STRATUS. THIS STRATUS MAY BE IN-  
AND-OUT AT KGEG UNTIL 15Z-16Z WHEN AN APPROACHING DISTURBANCE  
WILL HELP MIX THE BOUNDARY LAYER AND IMPROVE TO VFR. THIS WEAK  
COLD FRONT WILL SWEEP THROUGH THE EASTERN TAF SITES BETWEEN 18Z  
AND 21Z WITH SCATTERED -SHRA/-SHRASN WITH MVFR CEILINGS WHICH  
WILL BE HANDLED WITH TEMPO GROUPS. KEAT AND KMWH WILL BE LARGELY  
SKIPPED BY THIS WAVE DUE TO DOWNSLOPE FROM THE CASCADES WITH  
ISOLATED -SHSN IN THE VICINITY OF THE TAF SITES EARLIER IN THE DAY  
BEFORE CLEARING OUT BEHIND THE FRONT. OVERNIGHT TONIGHT STRATUS  
LAYERS WILL LIKELY RETURN TO THE KGEG AREA TAF SITES BETWEEN 06Z  
AND 12Z. /MJF  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
SPOKANE 37 29 36 35 40 30 / 70 10 50 100 80 70  
COEUR D'ALENE 37 29 35 34 39 30 / 70 20 40 100 90 80  
PULLMAN 39 30 37 36 42 32 / 50 20 20 80 80 70  
LEWISTON 45 33 42 41 47 35 / 20 10 20 60 70 60  
COLVILLE 37 27 34 33 38 29 / 40 10 70 100 90 90  
SANDPOINT 36 27 34 33 37 29 / 60 40 50 100 90 90  
KELLOGG 36 28 35 34 37 29 / 80 40 20 90 80 80  
MOSES LAKE 43 29 39 37 44 31 / 20 0 70 90 60 20  
WENATCHEE 41 28 35 33 38 28 / 10 0 90 90 70 30  
OMAK 37 28 34 33 36 28 / 30 0 100 100 90 50  
 

 
   
OTX WATCHES/WARNINGS/ADVISORIES
 
 
ID...WINTER STORM WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY  
MORNING FOR NORTHERN PANHANDLE.  
 
WA...WINTER STORM WATCH FROM TUESDAY MORNING THROUGH WEDNESDAY  
MORNING FOR EAST SLOPES NORTHERN CASCADES-NORTHEAST  
MOUNTAINS-OKANOGAN HIGHLANDS.  
 

 
 

 
 
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