274  
FXUS65 KBOI 230320  
AFDBOI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOISE ID  
820 PM MST TUE JAN 22 2019  
   
DISCUSSION
 
SNOWFALL CONTINUES TO MOVE INTO EASTERN OREGON THIS  
EVENING. THIS SNOWFALL WILL CONTINUE ITS EASTWARD PROGRESSION THIS  
EVENING, IMPACTING CENTRAL IDAHO AROUND MIDNIGHT. SNOWFALL,  
ESPECIALLY ACROSS IDAHO AND BAKER COUNTY OF OREGON, WILL CONTINUE  
INTO WEDNESDAY. SIGNIFICANT SNOWFALL IS EXPECTED ACROSS THE WEST  
CENTRAL MOUNTAINS OF IDAHO WHERE A WINTER WEATHER ADVISORY REMAINS  
IN EFFECT. ADDITIONAL LOCATIONS WILL SEE SNOWFALL, POTENTIALLY  
INCLUDING THE TREASURE VALLEY. SNOW ACROSS THE VALLEY IS POSSIBLE  
INTO THE EARLY MORNING HOURS, THOUGH ACCUMULATION ON ROADWAYS IS  
ANTICIPATED TO BE LIGHT AT GENERALLY LESS THAN AN INCH. HOWEVER,  
EVEN THESE LIGHT AMOUNTS COULD IMPACT THE MORNING COMMUTE.  
ACTIVITY IN THE VALLEY WILL CONVERT TO RAIN BY THE LATE MORNING  
HOURS, WITH MOUNTAIN SNOW AND VALLEY RAIN CONTINUING THROUGH THE  
EVENING HOURS BEFORE WEAKENING. THE ONLY UPDATE MADE WAS TO  
INCREASE PRECIPITATION PROBABILITIES THROUGH THE OVERNIGHT PERIOD  
ACROSS THE MOUNTAINS. ADDITIONAL UPDATES ARE NOT PLANNED UNLESS  
PRECIPITATION FORMS IN AN UNPLANNED LOCATION.  
 

 
   
AVIATION
 
MVFR/IFR SNOW SHOWERS THIS EVENING MAINLY IN THE HIGHER  
TERRAIN OF SOUTHEAST OREGON. SNOW WILL MOVE INTO HIGHER TERRAIN OF  
SOUTHWEST IDAHO LATER TONIGHT. KEUL AND KBOI COULD SEE BRIEF SNOW  
AROUND 06Z TONIGHT WITH ANOTHER CHANCE FOR RAIN AND SNOW AFTER 15Z  
WEDNESDAY MORNING. SURFACE WINDS: LIGHT AND VARIABLE, LESS THAN 10  
KTS. WINDS ALOFT AT 10K FEET MSL: WEST 20-30 KTS, INCREASING TO 40-  
60 KTS AFTER 23/15Z.  
 

 
   
PREV DISCUSSION
 
 
SHORT TERM...TONIGHT THROUGH THURSDAY...AMPLE MOISTURE STREAMING  
UP AND OVER A RIDGE OFF THE COAST OF CALIFORNIA WILL BEGIN  
IMPACTING THE AREA (MAINLY THE IDAHO CENTRAL MOUNTAINS) TONIGHT  
THROUGH TOMORROW. A WARM FRONT MOVING THROUGH EARLY TOMORROW WILL  
INCREASE SNOW LEVELS, BUT NOT BEFORE MOST AREAS WILL SEE SNOWFALL.  
THE FORECAST CHALLENGE IS EXACTLY HOW FAR SOUTH THAT MOISTURE  
WILL GO, AND IF IT DOES, HOW EARLY IT DOES SO. THIS WILL DETERMINE  
HOW MUCH, IF ANY, SNOW OCCURS IN THE TREASURE AND MAGIC VALLEYS  
AND AREAS SOUTH. HOWEVER, CONFIDENCE IS HIGH THAT POPULATED AREAS  
IN THE IDAHO CENTRAL MOUNTAINS WILL RECEIVE 2-5 INCHES OF SNOW  
THIS EVENING THROUGH TOMORROW AFTERNOON. HIGHER SNOW AMOUNTS WILL  
FALL IN THE HIGHEST ELEVATIONS. THE SNOW WILL LIKELY START AS A  
LIGHTER FLUFFIER SNOW WITH RATIOS AROUND 14:1, THEN DECREASE TO  
AROUND 10:1 PRODUCING A WETTER AND HEAVIER SNOW. A WINTER WEATHER  
ADVISORY HAS BEEN ISSUED FOR THE IDAHO CENTRAL MOUNTAINS FOR THE  
SNOWFALL AND ITS IMPACT TO TRAVEL AND DRIVING CONDITIONS. HOWEVER,  
AS MENTIONED BEFORE, A BIT OF SNOWFALL IS POSSIBLE EARLY TOMORROW  
MORNING IN THE TREASURE VALLEY, SO EVEN IF A COUPLE TENTHS OF AN  
INCH FALL, IT COULD STILL CREATE IMPACTS TO THE MORNING COMMUTE.  
SNOW LEVELS RISE THROUGH THE DAY ON WEDNESDAY, SO MOST VALLEY  
LOCATIONS (EXCEPT THE LONG VALLEY) WILL CHANGE OVER TO RAIN  
SOMETIME BETWEEN 8 AM AND 11 AM MST. CONDITIONS DRY OUT FOR  
THURSDAY UNDER A NORTHWEST FLOW WITH THE RIDGE TO THE WEST  
CONTINUING TO BUILD.  
 
LONG TERM...THURSDAY NIGHT THROUGH SUNDAY...DRY NORTHWEST FLOW  
CONTINUES AS AN UPPER LEVEL RIDGE BUILDS OFF THE WEST COAST. AS FLOW  
SHIFTS NORTHERLY FRIDAY NIGHT, A WEAK SHORTWAVE PASSES ALONG THE  
CONTINENTAL DIVIDE, THOUGH ANY THREAT OF SNOW SHOWERS WILL BE  
CONFINED TO HIGHER ELEVATIONS IN VALLEY COUNTY. NORTHWEST FLOW  
PERSISTS THROUGH SUNDAY, AS CONDITIONS REMAIN DRY AND TEMPERATURES  
STAY SEVERAL DEGREES ABOVE NORMAL.  
 
SUNDAY NIGHT THROUGH TUESDAY NIGHT...CLEAR TO PARTLY CLOUDY SKIES  
WITH BREEZY WINDS ARE ANTICIPATED ACROSS MOST OF REGION AS DRY,  
STABLE RIDGING IS EXPECTED TO DOMINATE. HOWEVER, THE NORTHEAST  
QUADRANT IS EXPECTED TO SEE SNOW SHOWERS AS A MOIST TROUGH DROPS IN  
FROM THE NORTH AT THE START OF THE PERIOD. THIS TROUGH IS EXPECTED  
TO COMPLETELY EXIT THE CWA BY MONDAY EVENING, WHERE CONDITIONS IN  
THE NORTHEAST SHOULD IMPROVE AS RIDGING TAKES FULL CONTROL. WINDS  
SHOULD ALSO LIGHTEN SOME BY MONDAY EVENING AS THE GRADIENT LOOSENS.  
HIGH AND LOW TEMPERATURES WILL MEASURE IN A FEW DEGREES ABOVE NORMAL.  
 

 
   
BOI WATCHES/WARNINGS/ADVISORIES
 
 
ID...WINTER WEATHER ADVISORY UNTIL 5 PM MST WEDNESDAY IDZ011-033.  
OR...NONE.  
 

 
 

 
 
WWW.WEATHER.GOV/BOISE  
WWW.FACEBOOK.COM/NWSBOISE  
WWW.TWITTER.COM/NWSBOISE  
 
DISCUSSION...KB  
AVIATION.....JS  
PREV SHORT TERM...EP  
PREV LONG TERM....AL/WH  
 
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