122  
FXUS65 KBYZ 182238  
AFDBYZ  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BILLINGS MT  
338 PM MST SUN FEB 18 2018  
   
SHORT TERM...VALID FOR MON AND TUE
 
 
COLD HIGH PRESSURE MOVING INTO THE AREA FROM THE NORTH WHILE UPPER  
LEVEL TROUGH OVER THE PACNW MOVING TOWARDS MONTANA FROM THE WEST.  
TROUGH IS FILLING AS IT APPROACHES THE AREA AND BECOMING LESS  
DYNAMIC WHICH IS COMBINING WITH DEEPENING COLD AIR TO REDUCE  
SNOWFALL RATES. HOWEVER SOUTHWEST FLOW ALOFT IS STILL PUSHING  
MOISTURE OVER THE COLD AIR AND ACCUMULATING SNOW IS EXPECTED TO  
CONTINUE TONIGHT INTO MONDAY. GREATEST SNOWFALL WILL BE OVER  
SOUTHERN AREAS ESPECIALLY SHERIDAN COUNTY TONIGHT AND THEN CARTER  
AND POWDER RIVER COUNTIES ON MONDAY. ELSEWHERE SNOW ACCUMULATIONS  
WILL BE CLOSER TO A HALF INCH IN 6 HOUR RATES. OTHER MAJOR CONCERN  
IS THE NEAR RECORD COLD WHICH WILL COMBINE WITH SOME WIND TO  
PRODUCE WELL BELOW ZERO WIND CHILLS.  
 
FOR TONIGHT A COUPLE OF SHORTWAVES PASSING THROUGH THE BASE OF THE  
TROUGH WILL BRING SLIGHT PERIODS OF HEAVIER SNOW AS IMBEDDED  
SHOWERS. FLOW BECOMES A BIT MORE CONFLUENT AT THE MID LEVELS  
DURING THE DAY ON MONDAY WHICH WILL BEGIN CAUSING THE SNOW TO WIND  
DOWN. HOWEVER ENERGY EJECTING FROM THE TROUGH WILL STILL STREAM  
OVER SOUTHEAST MONTANA AND SNOWFALL RATES WILL CONTINUE TO PRODUCE  
A COUPLE OF INCHES OF SNOW. LACK OF SUN AND THE COLD AIR IS LIKELY  
TO KEEP TEMPERATURES BELOW ZERO FOR MANY AREAS. PARTIALLY CLEARING  
SKIES MONDAY NIGHT AND FRESH SNOW COVER ARE GOING TO BRING NEAR  
RECORD LOW TEMPERATURES WITH SOME AREAS APPROACHING 20 BELOW ZERO.  
 
TUESDAY IS A DRIER DAY WITH SOME MODERATION IN TEMPERATURES BUT  
STILL WELL BELOW NORMAL. SHORTWAVE MOVES INTO NORTHERN MONTANA  
LATE TUESDAY NIGHT SUPPORTING A SWITCH TO MORE OF A WESTERLY WIND  
AND KEEPING TEMPERATURE FROM BEING QUITE AS COLD. BORSUM  
   
LONG TERM...VALID FOR WED...THU...FRI...SAT...SUN
 
 
A MOSTLY DRY FORECAST WAS IN STORE FOR THE EXTENDED PERIOD WITH  
LOW CHANCES OF SNOW OVER THE WESTERN MOUNTAINS FROM TIME TO TIME.  
THE WEEKEND LOOKED A BIT MORE UNCERTAIN DUE TO MODEL DIFFERENCES.  
A TROUGH OVER THE AREA ON WEDNESDAY WILL GIVE WAY TO BRIEF RIDGING  
ON THURSDAY. ANOTHER TROUGH WILL MOVE THROUGH THE AREA ON FRIDAY  
AND BECOME REINFORCED WITH UPSTREAM ENERGY ON SATURDAY. WEAK  
RIDGING RETURNS LATE ON SUNDAY. THE GFS MOVED MORE MOISTURE  
THROUGH THE AREA ON SATURDAY THAN THE ECMWF, SO MOVED A SLIGHT  
CHANCE OF SNOW THROUGH MUCH OF THE AREA SAT. THROUGH SAT. NIGHT.  
TEMPERATURES WILL MODERATE THROUGH THE PERIOD...REACHING THE 20S  
AND 30S ON FRIDAY. ARTHUR  
 

 
   
AVIATION
 
 
SNOW WILL GRADUALLY BECOME LIGHTER TONIGHT THROUGH MONDAY. MVFR TO  
LIFR CONDITIONS LATE THIS AFTERNOON WILL BECOME MVFR TO IFR THIS  
EVENING. CONDITIONS WILL IMPROVE FURTHER TO VFR AND MVFR MON.  
AFTERNOON. MOUNTAINS WILL BE MOSTLY OBSCURED INTO MONDAY, THEN  
OBSCURATIONS WILL DECREASE MON. AFTERNOON. THE GUSTY E SURFACE WINDS  
IN KLVM WILL DECREASE DURING MONDAY. ARTHUR  

 
   
PRELIMINARY POINT TEMP/POPS
 
 
MON TUE WED THU FRI SAT SUN  
-----------------------------------------------------------  
BIL 902/003 917/006 909/018 901/023 004/031 013/032 015/032  
96/J 21/B 11/B 10/B 11/B 12/J 31/B  
LVM 906/002 915/011 905/018 007/026 009/032 016/034 017/034  
94/J 21/B 11/B 10/B 22/J 12/J 32/J  
HDN 000/007 915/008 915/019 905/022 000/028 009/030 011/031  
96/J 21/B 11/B 00/U 01/U 11/B 21/B  
MLS 903/006 913/005 914/013 909/015 904/020 004/024 006/025  
76/J 31/B 01/U 10/U 01/B 11/B 11/B  
4BQ 000/004 914/005 915/016 906/020 901/026 007/029 010/030  
+8/J 31/B 00/U 00/U 01/B 11/B 12/J  
BHK 902/003 912/004 912/014 908/018 903/021 003/025 005/025  
66/J 31/E 01/U 10/U 01/B 11/B 11/B  
SHR 903/005 916/006 916/016 908/023 000/029 007/031 010/032  
+7/J 31/B 11/U 10/U 01/B 11/B 22/J  
 

 
   
BYZ WATCHES/WARNINGS/ADVISORIES
 
 
MT...WINTER WEATHER ADVISORY IN EFFECT UNTIL 5 PM MST MONDAY FOR  
ZONES 28-29-34-35-39>42-63>65.  
WINTER WEATHER ADVISORY IN EFFECT UNTIL 11 PM MST MONDAY FOR  
ZONES 30-31-36>38-57-58.  
WINTER STORM WARNING IN EFFECT UNTIL 5 PM MST MONDAY FOR  
ZONES 56-66>68.  
WY...WINTER WEATHER ADVISORY IN EFFECT UNTIL 11 PM MST MONDAY FOR  
ZONE 98.  
WINTER STORM WARNING IN EFFECT UNTIL 11 PM MST MONDAY FOR  
ZONE 99.  
 

 
 

 
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