085  
FXUS66 KOTX 181046  
AFDOTX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SPOKANE WA  
246 AM PST FRI JAN 18 2019  
   
SYNOPSIS
 
 
SNOW SHOWERS WILL LINGER OVER THE MOUNTAINS THIS MORNING, FOLLOWED  
BY A BRIEF BREAK THIS AFTERNOON. ANOTHER ROUND OF MOUNTAIN SNOW  
AND VALLEY RAIN WILL ARRIVE TONIGHT BRINGING MODERATE TO HEAVY  
ACCUMULATIONS TO THE CASCADES. THE ACTIVE WEATHER PATTERN WILL  
CONTINUE THROUGH THE MIDDLE OF NEXT WEEK WITH PERIODS OF SNOW IN  
THE MOUNTAINS AND MAINLY RAIN IN THE VALLEYS.  
 

 
   
DISCUSSION
 
 
TODAY: ONE WEATHER DISTURBANCE WILL EXIT THE IDAHO PANHANDLE THIS  
MORNING BEFORE THE NEXT ONE ARRIVES TONIGHT. LOOK FOR AN  
ADDITIONAL 1 TO 3 INCHES OF SNOW ACCUMULATION ABOVE 3000 FEET IN  
THE MOUNTAINS OF SHOSHONE COUNTY THIS MORNING WITH THE MOST  
SIGNIFICANT IMPACTS TO LOOKOUT PASS PRIOR TO SUNRISE. TEMPERATURES  
TODAY WILL BE ABOUT 5 DEGREES ABOVE AVERAGE WITH AFTERNOON  
TEMPERATURES IN THE UPPER 30S TO MID 40S ACROSS THE INLAND  
NORTHWEST. LOW CLOUDS AND FOG COULD LINGER INTO THE LATE MORNING  
OR EARLY AFTERNOON ACROSS THE WEST PLAINS TOWARD THE WATERVILLE  
PLATEAU WITH SOUTH WINDS PUSHING MOIST AIR (SURFACE DEWPOINTS IN  
THE MID 30S) UP THE RISING TERRAIN OVER THE CHILLY GROUND.  
 
TONIGHT: A DEEP AREA OF LOW PRESSURE IS FORECAST TO MAKE LANDFALL  
ON THE CENTRAL BC COAST PRIOR TO DAYBREAK ON SAT. THIS POWERFUL  
STORM WILL PRODUCE WIDESPREAD PRECIPITATION ACROSS THE INLAND  
NORTHWEST TONIGHT. SNOW LEVELS WILL LIKELY BE LOW ENOUGH FOR 1 TO  
4 INCHES OF SNOW ACCUMULATION IN THE METHOW VALLEY OVERNIGHT WITH  
SIMILAR AMOUNTS ABOVE 2000 FEET AROUND LEAVENWORTH. MOTORISTS WITH  
PLANS TO TRAVEL OVER STEVENS, BLEWETT, LOUP LOUP, OR SHERMAN PASS  
TONIGHT SHOULD BE PREPARED FOR WINTER DRIVING CONDITIONS. FOR THE  
VALLEYS OF NORTHEAST WASHINGTON INTO THE IDAHO PANHANDLE, A MIX  
OF RAIN AND WET SNOW IS EXPECTED. ELEVATIONS ABOVE 3000 FEET WILL  
HAVE THE BEST SHOT OF A COUPLE INCHES OF WET SNOW WHILE THE  
MAJORITY OF THE VALLEYS PROBABLY WON'T GET MUCH MORE THAN AN INCH.  
 
SATURDAY: FRIDAY NIGHT'S WET FRONTAL SYSTEM WILL PRODUCE VALLEY  
RAIN AND MOUNTAIN SNOW OVER THE IDAHO PANHANDLE SATURDAY MORNING  
BEFORE PRECIPITATION DECREASES TO SHOWERS IN THE AFTERNOON.  
REMNANTS OF THIS FRONT ARE FORECAST TO STALL OVER NORTHERN OREGON  
AND CENTRAL IDAHO SATURDAY AFTERNOON AND MAY LIFT NORTHWARD  
SATURDAY NIGHT INTO SUNDAY. AT THIS TIME, THERE IS SOME  
UNCERTAINTY ON HOW FAR NORTH THIS FRONT WILL LIFT SATURDAY NIGHT.  
A BLEND OF MODELS BRINGS A 20 TO 30 PERCENT CHANCE OF RAIN AND  
SNOW AS FAR NORTH AS THE CANADIAN BORDER BY SUNDAY MORNING, A LOW  
CONFIDENCE FORECAST. /GKOCH  
 
SUNDAY AND SUNDAY NIGHT: A TROUGH OF LOW PRESSURE WILL MOVE IN OFF  
OF THE EASTERN PACIFIC. THERE WILL BE PORTION OF THE ENERGY  
ASSOCIATED WITH THIS TROUGH THAT TRAVERSES RIGHT UP ACROSS THE  
SOUTHEAST PORTION OF THE FORECAST AREA. THE STRONGER DYNAMICS  
ALOFT WILL ACTUALLY MISS THE INLAND NORTHWEST AND DIVE DOWN ACROSS  
SOUTHERN OR AND INTO CA. HOWEVER, THE ENERGY THAT DOES IMPACT THE  
INLAND NORTHWEST IS POTENT ENOUGH TO SPIN UP A SURFACE LOW OVER  
NORTHEAST OR SUNDAY MORNING THAT MOVES INTO THE SOUTHERN ID  
PANHANDLE BY SUNDAY AFTERNOON. THE 00Z GFS HAS THE STRONGEST  
SURFACE REFLECTION AND IS FURTHER NORTH WITH BEST POTENTIAL FOR  
WINTER IMPACTS ACROSS EASTERN WA AND INTO THE CENTRAL TO NORTHERN  
IDAHO PANHANDLE. THE 00Z ECMWF, CANADIAN AND NAM SOLUTIONS ARE A  
BIT WEAKER AND FURTHER SOUTH WITH PRECIP PRIMARILY FALLING  
SOUTHEAST OF A LINE FROM ELLENSBURG TO SANDPOINT. I TREATED THE  
GFS SOLUTION AS AN OUTLIER HOLDING ON TO THE HIGHEST PRECIP  
CHANCES ACROSS THE SOUTHEAST PORTION OF THE REGION AND DECREASED  
PRECIP CHANCES ACROSS THE NORTHWEST PORTION OF THE REGION. SNOW  
LEVELS WILL BE BETWEEN 3000 AND 4000 FEET DURING THE DAY ON SUNDAY  
AND THEN DROP SUNDAY NIGHT AS THIS SYSTEM EXITS WITH MINOR VALLEY  
ACCUMULATIONS POSSIBLE AT THAT POINT. MAIN IMPACTS LOOK TO BE OVER  
THE PASSES, INCLUDING LOOKOUT PASS AND OVER THE CAMAS PRAIRIE,  
ESPECIALLY AS TEMPERATURES COOL BY SUNDAY EVENING.  
 
MONDAY THROUGH FRIDAY: COLDER AND DRIER AIR WILL PUSH IN ACROSS  
THE REGION OUT OF CANADA BEHIND THE EXITING WEATHER SYSTEM SUNDAY  
NIGHT. THIS WILL SET UP A POTENTIALLY MORE SIGNIFICANTLY IMPACTFUL  
WINTER STORM SYSTEM ON TUESDAY. SNOW LEVELS WILL BE DOWN TO VALLEY  
FLOORS WITH HEAVIEST PRECIPITATION LOOKING TO MOVE IN DURING THE  
NIGHTTIME HOURS. THE SHORTWAVE DISTURBANCE WILL PUSH IN OUT OF A  
NORTHWEST FLOW PATTERN. THIS KIND OF FLOW PATTERN TYPICALLY FAVORS  
THE IDAHO PANHANDLE. HOWEVER, MODELS INDICATE FRONTOGENESIS STRONG  
ENOUGH TO SPREAD PRECIP ACROSS THE BASIN AND INTO THE  
SPOKANE/COEUR D'ALENE CORRIDOR AND ON THE PALOUSE. THE TUESDAY  
EVENING AND/OR WEDNESDAY COMMUTES COULD BE MESSY WITH WINTER  
DRIVING CONDITIONS POSSIBLE, MAINLY ALONG AND NORTH OF THE HIGHWAY  
2 CORRIDOR. THERE IS HIGH CONFIDENCE FOR DRIER CONDITIONS  
THURSDAY AND FRIDAY. /SVH  
 

 
   
AVIATION
 
 
06Z TAFS: SMALL SCALE DISTURBANCES MOVING THROUGH THE COLD AND  
CONDITIONALLY UNSTABLE AIRMASS OVER THE AVIATION AREA ARE  
PRODUCING RAIN AND SNOW SHOWERS TONIGHT. IN ADDITION TO THE  
SHOWERS THE BOUNDARY LAYER REMAINS VERY SATURATED FROM ALL THE  
RECENT PRECIPITATION, HENCE IFR/MVFR CEILINGS AND VISIBILITIES DUE  
TO STRATUS AND/OR FOG OR PRODUCED BY THE SHOWERS THAT ARE MOVING  
THROUGH ARE A POSSIBILITY TONIGHT INTO EARLY TOMORROW. IN ADDITION  
ANOTHER SYNOPTIC SCALE LOW PRESSURE SYSTEM WILL BRING STABLE RAIN  
WITH HIGH MOUNTAIN SNOW INTO THE REGION AND SPREAD IT TO THE NORTH  
AND EAST STARTING AS EARLY AS 2Z SATURDAY NEAR KEAT AND KMWH AND  
NEAR 6Z SATURDAY AND BEYOND FOR REMAINING TAF SITES TO THE EAST  
WHICH WOULD INCLUDE KGEG,KSFF,KCOE,KPUW, AND KLWS. /PELATTI  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
SPOKANE 39 33 42 32 37 25 / 10 100 70 30 50 30  
COEUR D'ALENE 39 34 41 32 37 28 / 30 90 90 30 50 40  
PULLMAN 42 35 43 35 39 30 / 10 100 70 40 80 60  
LEWISTON 48 39 49 38 46 35 / 10 90 60 50 80 60  
COLVILLE 38 32 42 29 40 21 / 20 90 70 20 20 20  
SANDPOINT 37 33 37 32 37 27 / 50 90 100 30 40 40  
KELLOGG 38 33 41 33 38 30 / 60 90 90 50 70 60  
MOSES LAKE 44 36 47 33 40 28 / 0 80 10 20 40 10  
WENATCHEE 40 33 43 31 37 28 / 10 100 10 20 30 10  
OMAK 39 33 41 28 37 24 / 10 90 30 10 10 10  
 

 
   
OTX WATCHES/WARNINGS/ADVISORIES
 
 
ID...WINTER WEATHER ADVISORY UNTIL 7 AM PST THIS MORNING FOR CENTRAL  
PANHANDLE MOUNTAINS.  
 
WA...NONE.  
 

 
 

 
 
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