420  
FXUS65 KBYZ 161545  
AFDBYZ  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE BILLINGS MT  
945 AM MDT THU AUG 16 2018  
   
UPDATE
 
 
UPPER RIDGE BUILDING INTO THE AREA TODAY. SMOKE WILL CONTINUE TO  
PROVIDE A THIN LAYER OF CLOUDS AND HAZE. THE GFS WAS REALLY THE  
ONLY MODEL PROVIDING ASCENT FOR POTENTIAL CONVECTION OVER THE  
WESTERN ZONES THIS AFTERNOON AND EVENING. WATER VAPOR IMAGERY DOES  
SHOW SOME MONSOON MOISTURE ROTATING UP THE BACK SIDE OF THE RIDGE  
FOR LATE THIS AFTERNOON, WITH WEAK ENERGY. CAN'T DISCOUNT THE  
CHANCE OF DRY CONVECTION OVER THE WEST, BUT LOOKS TO BE MAINLY TO  
THE WEST OF THE AREA. WILL LEAVE THE FORECAST AS IS. TWH  
 

 
   
SHORT TERM...VALID FOR TDY AND FRI
 
 
UPPER RIDGE WILL BRING SUNNY AND DRY CONDITIONS TO THE AREA TODAY.  
EXPECT TEMPERATURES TO BUMP UP INTO THE LOWER 90S ACROSS THE LOWER  
ELEVATIONS. SMOKE DENSITY LOOKS TO INCREASE TODAY UNDER THE UPPER  
RIDGE AS SUBSIDENCE MOVES IT DOWN FROM THE MID LEVELS. WESTERN  
AREAS WILL SEE A PUSH OF MONSOONAL MOISTURE LATE IN THE DAY INTO  
THIS EVENING THAT MAY BE ENOUGH TO TRIGGER ISOLATED DRY  
THUNDERSTORMS OVER THE HIGHER TERRAIN AND FOOTHILLS. WIND GUSTS  
OVER 40 MPH AND LIGHTNING WILL BE THE MAIN THREATS WITH THIS  
ACTIVITY.  
 
FRIDAY IS A PRE-FRONTAL DAY ACROSS THE AREA AS A PACIFIC SYSTEM  
APPROACHES FROM THE WEST DURING THE DAY. EXPECT SOUTHWEST WINDS TO  
INCREASE A BIT AHEAD OF THIS SYSTEM ENHANCING DOWNSLOPE WARMING  
AND PUSHING HIGHS INTO THE MID-UPPER 90S FOR THE WARMEST DAY OF  
THE NEXT WEEK. ATMOSPHERIC MOISTURE CONTINUES TO INCREASE FROM THE  
WEST AS THE SYSTEM MOVES CLOSER AND WILL SEE AN CORRESPONDING  
INCREASE IN SHOWER AND THUNDERSTORM CHANCES FROM THE AFTERNOON  
THROUGH FRIDAY NIGHT. BY LATE FRIDAY NIGHT WILL SEE LIKELY  
PRECIPITATION CHANCES SPREADING FROM WESTERN INTO CENTRAL ZONES.  
 
PRE-FRONTAL DAYS THIS TIME OF YEAR ARE ASSOCIATED WITH ENHANCED  
FIRE WEATHER CONCERNS. WILL CONTINUE THE FIRE WEATHER WATCH FOR  
WESTERN ZONES. WINDS ARE BORDERLINE AT THIS TIME, BUT ENHANCED  
CONVECTION, HOT TEMPERATURES AND LOW RH VALUES ALL CHECK THE BOX  
FOR AN UPGRADE IF THE FORECAST REMAINS CONSISTENT. CHAMBERS  
   
LONG TERM...VALID FOR SAT...SUN...MON...TUE...WED
 
 
UNSETTLED AND COOLER PERIOD WAS STILL IN STORE FOR THE EXTENDED.  
HOWEVER, THE GEFS SHOWED WIDE SPREADS WITH VARIOUS PARAMETERS  
THROUGH THE PERIOD AND THE ECMWF ENSEMBLES SHOWED UNCERTAINTY WITH  
THE PATTERN BEGINNING ON MONDAY. THAT BEING SAID, THERE WAS ENOUGH  
CONFIDENCE TO RAISE POPS FOR MUCH OF THE WEEKEND.  
 
UPPER LOW/STRONG SHORTWAVE WILL MOVE SE THROUGH THE AREA ON  
SATURDAY AND EXIT THE AREA LATE SAT. NIGHT. PRECIPITABLE WATERS  
WILL BE AROUND AN INCH. THE COMBINATION OF THE LOW AND MOISTURE  
WILL BRING THE LIKELIHOOD OF SHOWERS AND SOME THUNDERSTORMS TO THE  
AREA ON SATURDAY. THE HIGHER POPS WILL SHIFT E DURING SAT. NIGHT.  
BLENDS SHOWED TEMPERATURES REACHING THE UPPER 70S W TO THE UPPER  
80S E ON SATURDAY. WEAK UPPER RIDGING WILL BE OVER THE AREA ON  
SUNDAY WHILE A WEAK BACKDOOR FRONT SINKS INTO THE AREA THROUGH  
SUN. NIGHT, BRINGING UPSLOPE FLOW TO THE AREA. PRECIPITABLE WATERS  
REMAIN AROUND AN INCH, SO KEPT SCATTERED POPS IN THROUGH SUN.  
NIGHT. HIGHS WILL BE MAINLY IN THE 70S ON SUNDAY BASED ON BLENDED  
GUIDANCE. MODELS DIFFERED ON MONDAY WITH THE GFS BRINGING IN  
DIFFLUENCE AHEAD OF THE NEXT PACIFIC LOW, WHILE THE ECMWF MOVES  
AN UPPER TROUGH S INTO THE REGION. PRECIPITABLE WATERS REMAIN  
AROUND AN INCH, SUPPORTING HIGH SCATTERED POPS GIVEN EITHER MODEL  
SOLUTION. HIGHS AGAIN LOOKED TO BE IN THE 70S. UPPER RIDGING AND  
DRIER AIR MOVE IN FOR TUESDAY WITH SLIGHTLY WARMER CONDITIONS. GFS  
MAINTAINS THE RIDGE FOR WEDNESDAY, WHILE THE ECMWF MOVES A  
SHORTWAVE E THROUGH THE AREA. KEPT FORECAST DRY AND WARMER. ZONAL  
CONDITIONS WERE IN STORE FOR THURSDAY FOR A CONTINUED DRY AND  
WARMER TREND. ARTHUR  
 

 
   
AVIATION
 
 
VFR WILL PREVAIL TODAY AND TONIGHT. HOWEVER, SLANTWISE VERTICAL  
VISIBILITY WILL BE REDUCED IN SMOKE FROM AREA WILDFIRES, AND SOME  
SURFACE SMOKE MAY REACH THE TERMINALS BY 12Z FRIDAY, REDUCING  
SURFACE VISIBILITIES. A FEW DRY THUNDERSTORMS ARE POSSIBLE LATE  
THIS AFTERNOON INTO THIS EVENING OVER AND NEAR THE WESTERN  
MOUNTAINS. ARTHUR  
 

 
   
PRELIMINARY POINT TEMP/POPS
 
 
TDY FRI SAT SUN MON TUE WED  
-------------------------------------------------------  
BIL 093 061/094 064/081 058/078 056/076 054/082 057/088  
0/K 00/U 56/T 52/T 44/T 21/U 11/U  
LVM 092 052/092 055/079 049/078 049/077 047/083 049/089  
1/T 13/T 67/T 43/T 44/T 22/T 21/U  
HDN 094 059/096 063/081 056/080 055/078 052/084 055/090  
0/K 00/U 46/T 53/T 44/T 21/U 11/U  
MLS 091 062/097 065/086 058/080 056/078 053/083 056/090  
0/K 00/U 15/T 52/T 34/T 21/U 11/U  
4BQ 091 060/095 064/085 056/079 053/079 052/084 055/090  
0/K 00/U 26/T 63/T 34/T 31/U 11/U  
BHK 090 059/094 062/088 056/078 050/076 049/082 052/088  
0/K 00/U 15/T 52/T 23/T 21/U 00/U  
SHR 091 056/094 059/081 053/078 052/078 051/082 053/088  
0/K 01/U 47/T 64/T 44/T 31/B 11/B  
 

 
   
BYZ WATCHES/WARNINGS/ADVISORIES
 
 
MT...FIRE WEATHER WATCH IN EFFECT FROM FRIDAY AFTERNOON THROUGH  
FRIDAY EVENING FOR ZONES 117-123-124.  
WY...NONE.  
 

 
 

 
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