285  
FXUS65 KBOI 180336  
AFDBOI  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BOISE ID  
836 PM MST SUN FEB 17 2019  
   
DISCUSSION
 
NO UPDATES. THE DEEP UPPER LEVEL TROUGH CENTERED  
OVER THE GREAT BASIN WILL CONTINUE TO CIRCULATE MOIST AND  
UNSTABLE AIR NORTH AND WEST ALONG THE IDAHO-NEVADA BORDER, WITH  
MOST SNOW FALLING ON SOUTHERN TWIN FALLS AND EASTERN OWYHEE  
COUNTIES TONIGHT AND MONDAY MORNING. AS THE TROUGH EDGES EAST OVER  
THE ROCKIES, OUR AREA WILL SEE A DRYING AND COOLING TREND THROUGH  
TUESDAY UNDER NORTHERLY FLOW ALOFT ON THE WESTERN MARGIN OF THE  
TROUGH. THE NEXT PRECIPITATION EPISODE WILL BEGIN TUESDAY NIGHT  
AND CONTINUE THROUGH WEDNESDAY NIGHT AS ANOTHER UPPER LEVEL TROUGH  
DROPS SOUTH FROM CANADA. SNOWFALL AMOUNTS IN THE LOWER VALLEYS  
ARE EXPECTED TO RANGE FROM LESS THAN AN INCH TO AROUND 2 INCHES,  
WITH HEAVIER AMOUNTS IN THE MOUNTAINS. FOLLOWING A BRIEF BREAK  
THURSDAY AND FRIDAY, THE NEXT TROUGH WILL BRING MORE SNOW FOR THE  
WEEKEND, BUT TIMING IS STILL UNCERTAIN.  
 

 
   
AVIATION
 
MAINLY VFR CONDITIONS AS SHOWERS DIMINISH. EXCEPTION FOR MAGIC  
VALLEY AND ID/NV BORDER WHERE IFR/LIFR POSSIBLE DUE TO LINGERING  
SNOW SHOWERS AND MOUNTAIN OBSCURATIONS THROUGH MONDAY MORNING.  
PATCHY STRATUS AND FOG POSSIBLE OVERNIGHT. SURFACE WINDS: WEST TO  
NORTHWEST 5-15 KTS. WINDS ALOFT AT 10K FEET MSL: NORTHWEST 15-25 KTS.  
 

 
   
PREV DISCUSSION
 
 
SHORT TERM...TONIGHT AND MONDAY...SATELLITE IMAGERY AND MODELS  
SHOW A LARGE AND COMPLEX UPPER LOW OVER THE WESTERN US WITH  
SEVERAL EMBEDDED DISTURBANCES. THIS PATTERN GET INTERESTING FOR  
TONIGHT SHOWING AN UPPER DIFFLUENCE AREA LOCATED OVER SOUTHERN  
IDAHO. NAMNEST/ARW SHOWS THIS DEFORMATION ZONES SLOWLY PUSHING  
TOWARDS THE NV/ID/UT BORDER REGION AND WILL BE THE MAIN FOCUS OF  
SNOW AT LEAST THROUGH SUNRISE. AT THIS TIME, GENERALLY 1-2 INCHES  
OF SNOW ARE POSSIBLE ACROSS SOUTHERN TWIN FALLS COUNTY INCLUDING  
HIGHWAY 93...LESSER AMOUNTS ALONG STATE ROUTE 51. HIGHER  
ACCUMULATIONS POSSIBLE OVER THE HIGHER MOUNTAINS. OTHERWISE, THE  
BROAD UPPER LOW SAGS SOUTH AND EAST WITH TROUGHINESS LINGERING  
OVER THE SPINE OF THE ROCKY MOUNTAINS AS AN UPPER RIDGE EDGES INTO  
THE PACNW. LINGERING SNOW SHOWERS ARE POSSIBLE MONDAY OVER IDAHOS  
MOUNTAINS.  
 
LONG TERM...MONDAY NIGHT THROUGH SUNDAY...RELATIVELY DRY  
NORTHERLY FLOW ALOFT WILL LAST INTO EARLY TUESDAY AFTERNOON. A  
SIGNIFICANT SYSTEM WILL MOVE IN FROM THE NORTHWEST AT THAT TIME,  
BRINGING SNOW TO ALL ELEVATIONS. SNOW WILL MOVE INTO EASTERN  
OREGON TUE AFTERNOON, THEN OVERSPREAD THE REMAINDER OF THE AREA  
TUESDAY NIGHT. THE BEST CHANCE FOR SNOW WILL BE WEDNESDAY, AS AN  
UPPER LEVEL SHORTWAVE TROUGH MOVES THROUGH THE AREA. ADVISORIES  
AND/OR WARNINGS MAY BE NEEDED FOR THIS SYSTEM. IT IS LIKELY THAT  
ROADS WILL BE SNOW-COVERED THAT MORNING OVER MOST OF THE AREA. A  
REINFORCING COLD AIR MASS WILL FOLLOW THURSDAY, ALONG WITH  
SCATTERED SNOW SHOWERS. SHOWERS WILL DIMINISH THURSDAY NIGHT AS  
THE TROUGH MOVES AWAY, BUT ANOTHER WILL ARRIVE FRIDAY NIGHT AND  
BRING SNOW TO THE REGION THROUGH NEXT WEEKEND. TEMPS WILL REMAIN  
BELOW NORMAL THROUGH THE PERIOD.  
 

 
   
BOI WATCHES/WARNINGS/ADVISORIES
 
 
ID...WINTER WEATHER ADVISORY UNTIL 11 AM MST MONDAY IDZ015-030.  
OR...NONE.  
 

 
 

 
 
WWW.WEATHER.GOV/BOISE  
WWW.FACEBOOK.COM/NWSBOISE  
WWW.TWITTER.COM/NWSBOISE  
 
DISCUSSION...JT  
AVIATION.....SH  
PREV SHORT TERM...CR  
PREV LONG TERM....SP  
 
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