501  
FXUS65 KMSO 202149  
AFDMSO  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE MISSOULA MT  
249 PM MST TUE FEB 20 2018  
   
DISCUSSION
 
THANKS TO RELATIVELY WEAK WINDS, MODERATELY STRONG  
HIGH PRESSURE AND FRESH SNOW-COVER, LOW TEMPERATURES DROPPED WELL  
BELOW ZERO ACROSS MUCH OF WESTERN MONTANA AND PORTIONS OF CENTRAL  
IDAHO. THE COLDEST SPOT THAT WE COULD FIND WAS POLEBRIDGE WHICH  
BOTTOMED OUT AT 41 DEGREES BELOW ZERO. KALISPELL, BUTTE AND HUNGRY  
HORSE ALL SAW DAILY RECORD LOW TEMPERATURES BROKEN WHILE THE 9  
DEGREES AT PIERCE, IDAHO RANKED 6TH COLDEST.  
 
THANKS TO THE ARCTIC AIRMASS IN PLACE AND ABOVE FREEZING WATER  
TEMPERATURES, A LAKE EFFECT SNOW BAND DEVELOPED AROUND DAYBREAK  
AND DIDN'T DISSIPATE UNTIL THE EARLY AFTERNOON NEAR YELLOW BAY,  
FLATHEAD LAKE. A NWS EMPLOYEE REPORTED 3 INCHES OF SNOW JUST  
NORTH OF YELLOW BAY THAT COVERED HIGHWAY 35.  
 
A WEAK UPPER LEVEL WAVE WILL TRAVERSE ACROSS THE AREA THIS  
AFTERNOON INTO TONIGHT. WHILE IT DOES THIS, WE WILL SEE PERIODS OF  
LIGHT SNOW. ALREADY LOOKOUT PASS HAS BEEN SNOWING OFF AND ON SINCE  
NOON. EXPECT MAYBE AN INCH OR LESS OF ACCUMULATION ACROSS  
NORTHWEST AND WEST-CENTRAL MONTANA. THERE IS A LITTLE BETTER LIFT  
AND MOISTURE OVER CENTRAL IDAHO, SO SOME PLACES INCLUDING ELK  
CITY, LOWELL, DIXIE, WILLIAMS CREEK SUMMIT MAY END UP WITH A  
COUPLE OF INCHES THROUGH EARLY WEDNESDAY MORNING. IT IS THE  
INCREASE IN MID-LEVEL CLOUDS, THAT WILL HELP TEMPER THE LOW  
TEMPERATURES TONIGHT. SOME LOCATIONS ACROSS NORTHWEST MONTANA  
MIGHT BE ABLE TO CLEAR OUT FASTER AND THEREFORE COOL FASTER THAN  
FORECAST.  
 
THERE IS SOME INDICATION THAT ANOTHER LAKE EFFECT BAND MAY SET UP  
OVER SOUTHEASTERN FLATHEAD LAKE THIS EVENING OR TONIGHT.  
CONFIDENCE IS LOW ON THE EXACT LOCATION IT WILL SETUP, BUT SOME  
HIGH RESOLUTION GUIDANCE SUGGESTS THAT FINLEY POINT AND PORTIONS  
OF HIGHWAY 35 NEAR THERE TO BLUE BAY COULD GET SOME SNOW.  
 
THE REST OF THIS WEEK WILL BE COLD WITH INTERMITTENT LIGHT SNOW  
SHOWERS. THE JET STREAM IS SOUTH OF THE AREA AND HOLDING THE COLD  
AIR IN PLACE, HOWEVER, IT IS ALSO DIRECTING MOST OF THE MOISTURE  
FARTHER SOUTH TOO, SO ANY SNOW SHOWERS WE HAVE WILL BE LIGHT WITH  
LOW DENSITY SNOW.  
 
A SERIES OF WEATHER DISTURBANCES WILL BEGIN TO IMPACT THE NORTHERN  
ROCKIES FRIDAY NIGHT, AND LIKELY REMAINING ACTIVE INTO NEXT WEEK.  
LITTLE HAS CHANGED IN THE FORECAST REGARDING THE NORTH PACIFIC  
WEATHER SYSTEM FOR THIS WEEKEND. BELOW NORMAL TEMPERATURES LEADING  
UP TO THIS WEEKEND, WILL SUPPORT PRECIPITATION BEING ALL SNOW FOR  
MOST LOCATIONS ACROSS THE REGION. IT'S STILL TOO EARLY TO TELL  
WHERE THE HEAVIEST PRECIPITATION WILL FALL, HOWEVER WIDESPREAD  
ACCUMULATING SNOW IN THE MOUNTAINS AND VALLEYS SHOULD BE EXPECTED  
FOR THOSE TRAVELING THIS WEEKEND. STAY TUNED TO THE FORECAST, AS  
WE IRON OUT THE DETAILS IN THE NEXT DAY OR SO.  
 
ANOTHER NORTH PACIFIC LOW PRESSURE SYSTEM WILL MOVE THROUGH THE  
NORTHERN ROCKIES FOR THE START OF NEXT WEEK, THAT HAS THE  
POTENTIAL TO IMPACT THE MONDAY MORNING COMMUTE, IF CURRENT  
FORECASTS HOLD TRUE.  
 

 
   
AVIATION
 
A WEAK DISTURBANCE LATER THIS AFTERNOON AND EVENING  
WILL BRING PERIODS OF LIGHT SNOW TO THE NORTHERN ROCKIES. EXPECT  
LOWER CEILINGS AND VISIBILITY ESPECIALLY AT KGPI AFTER 21/0000Z  
AND ACROSS CENTRAL IDAHO INCLUDING GRANGEVILLE AFTER 21/0400Z.  
CONFIDENCE IS LOW, BUT THERE COULD BE SOME FREEZING FOG THAT  
DEVELOPS NEAR KBTM BY 21/1200Z. A LAKE EFFECT SNOW BAND WITH  
MODERATE TO HEAVY SNOW INTENSITIES MAY SETUP OVER THE SOUTHEASTERN  
PART OF FLATHEAD LAKE BETWEEN 21/0300Z AND 22/1600Z.  
 

 
   
MSO WATCHES/WARNINGS/ADVISORIES
 
 
MT...NONE.  
ID...NONE.  

 
 

 
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab MT Page
The Nexlab ID Page Main Text Page