832  
FXUS65 KBYZ 172121  
AFDBYZ  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE BILLINGS MT  
321 PM MDT SUN JUN 17 2018  
   
SHORT TERM...VALID FOR MON AND TUE
 
 
WATER VAPOR IMAGERY SHOWED AN UPPER LOW OVER W NV AND A MOISTURE  
TAP FLOWING INTO THE FORECAST AREA FROM THE REMNANTS OF TROPICAL  
STORM BUD. CONVECTION WAS DEVELOPING OVER SE ID AND S WY WHERE  
MUCAPES WERE 500-1000 J/KG AND BULK EFFECTIVE SHEAR WAS IN THE  
35-50 KT RANGE. EXPECT SOME OF THESE THUNDERSTORMS TO MOVE NE  
INTO THE SW ZONES THIS EVENING, SO HAVE INCREASED THUNDER CHANCES  
THERE. MODELS CONTINUED TO SHOW THE HEAVIEST RAINFALL W OF KBIL  
TONIGHT SO HAD HIGHEST POPS THERE AND MENTION OF HEAVY RAIN. JET  
DIVERGENCE OVER THE AREA, DIFLUENCE AND EASTERLY UPSLOPE FLOW WILL  
ALL CONTRIBUTE TO THE HEAVY RAINFALL. WILL CONTINUE A SLIGHT  
CHANCE OF THUNDER ACROSS THE AREA OVERNIGHT DUE TO THE TROPICAL  
MOISTURE IN THE REGION. WILL KEEP THE ADVISORY GOING FOR THE  
BEARTOOTH PASS, WITH SEVERAL INCHES OF SNOW EXPECTED AT THE  
HIGHEST ELEVATIONS. PRECIPITABLE WATERS WILL REMAIN AT AN INCH OR  
HIGHER THROUGH THE PERIOD.  
 
JET DIVERGENCE, DIFLUENCE AND EAST FLOW CONTINUE INTO MONDAY AS  
THE UPPER LOW MOVES OVER ID. THE TROPICAL MOISTURE WILL WORK IT'S  
WAY E OUT OF THE AREA. HAD CATEGORICAL POPS FROM KBIL W IN THE  
MORNING WITH A CONTINUED MENTION OF HEAVY RAIN. CHANCES FOR HEAVY  
RAIN SPREAD A BIT FURTHER E IN THE AFTERNOON. WILL CONTINUE A  
SLIGHT CHANCE OF THUNDER MON. AFTERNOON AND EVENING. POPS DECREASE  
A BIT OVER THE BEARTOOTH HIGHWAY IN THE AFTERNOON AND 700 MB  
TEMPERATURES WILL BE AROUND +3 DEGREES C, SO HAD LESS SNOW IN THE  
HIGH ELEVATIONS. UPPER LOW REMAINS STATIONARY MON. NIGHT THEN  
WEAKENS AND MOVES INTO SW MT ON TUESDAY. QPF IS PROGGED TO LIFT N  
DURING MON. NIGHT SO HAD DECREASING POPS THROUGH THE NIGHT FROM S  
TO N. WITH SOME MORE SNOW POSSIBLE OVER THE BEARTOOTH HIGHWAY MON.  
NIGHT, LEFT THE ADVISORY IN PLACE. HIGHEST POPS WILL BE OVER THE W  
FOR TUE. WITH CONTINUED SLIGHT CHANCES FOR DIURNAL THUNDER. HAD  
CHANCES FOR SHOWERS TUE. NIGHT AS THE REMNANT LOW REMAINED OVER  
THE AREA.  
 
QPF TOTALS THROUGH MON. NIGHT WILL BE /1.50-2.00/ INCHES W OF  
KBIL. WITH ALL THE RAIN COMING IN, WE HAVE ISSUED A FLOOD WARNING  
FOR THE CLARKS FORK AND AN ESF FOR MUCH OF THE REMAINDER OF THE  
AREA. THE GOING AREAL FLOOD WATCH FROM TONIGHT THROUGH MON. NIGHT  
FOR THE WESTERN CWA WAS IN GOOD SHAPE. ARTHUR  
   
LONG TERM...VALID FOR WED...THU...FRI...SAT...SUN
 
 
REMNANTS OF THE UPPER LOW THAT HAS BEEN OVER THE AREA DURING THE  
SHORT-TERM WILL REMAIN OVER THE AREA ON WEDNESDAY, THEN SHIFT SE  
INTO THE CENTRAL PLAINS ON THURSDAY. WEAK RIDGING WILL BE OVER THE  
AREA ON FRIDAY, BUT ENERGY WILL CONTINUE MOVING THROUGH THE FLOW.  
MODELS SHOWED ANOTHER WAVE OF LOW PRESSURE APPROACHING THE REGION  
FROM THE W FRI. NIGHT, AND CROSSING THE AREA IN THE SATURDAY/SAT.  
NIGHT TIME FRAME WITH SOME TIMING DIFFERENCES. ON SUNDAY, MODELS  
DEPICTED A WEAK HIGH OVER LOW PATTERN.  
 
MOISTURE CONTINUED OVER THE AREA FOR WED., WITH MODELS TAPPING  
GULF OF MEXICO MOISTURE. THURSDAY AND FRIDAY LOOKED LIKE  
RELATIVELY DRIER PERIODS, THEN MODEL AGREEMENT WAS NOT GREAT FOR  
THE WEEKEND IN TERMS OF MOISTURE. THUS, KEPT THE HIGH CHANCE TO  
LIKELY POPS FOR WEDNESDAY, THEN HAD LOW POPS THROUGH FRIDAY.  
BLENDED THE MODELS AND HAD ISOLATED TO SCATTERED POPS FOR THE  
WEEKEND. WILL KEEP A SLIGHT CHANCE OF THUNDER IN FOR EACH  
AFTERNOON AND EVENING. PRECIPITABLE WATERS WILL REMAIN CLOSE TO AN  
INCH THROUGH THE PERIOD. COOLER WEATHER CONTINUES FOR WED., THEN  
HIGHS WILL REACH THE 70S WITH SOME LOWER 80S FOR THE REST OF THE  
PERIOD. ARTHUR  
 

 
   
AVIATION
 
 
RAIN WILL DEVELOP THIS EVENING ALONG AND WEST OF A ROUNDUP- KBIL-  
KSHR LINE AND CONTINUE THROUGH MONDAY. THE RAIN MAY BE HEAVY AT  
TIMES. MVFR CONDITIONS WILL PREVAIL WITH AREAS OF IFR AND LIFR  
CONDITIONS IN HEAVIER ACTIVITY. ELSEWHERE, SCATTERED SHOWERS AND  
ISOLATED THUNDERSTORMS CAN BE EXPECTED WITH VFR CONDITIONS  
PREVAILING WITH OCCASIONAL MVFR CONDITIONS. THE MOUNTAINS WILL BE  
OBSCURED THROUGH MONDAY. HOOLEY  
 

 
   
PRELIMINARY POINT TEMP/POPS
 
 
MON TUE WED THU FRI SAT SUN  
-----------------------------------------------------------  
BIL 054/063 051/067 053/067 052/075 056/079 056/075 056/077  
88/T 85/T 55/T 22/T 32/T 22/T 32/T  
LVM 048/059 046/063 047/065 047/074 048/077 048/072 047/075  
79/T 67/T 64/T 23/T 23/T 33/T 32/W  
HDN 053/068 050/071 053/069 052/077 055/082 055/077 055/078  
47/T 83/T 55/T 32/T 22/T 42/T 43/T  
MLS 054/069 054/072 057/069 055/076 057/080 058/078 058/079  
23/T 23/T 55/T 32/T 21/B 23/T 43/T  
4BQ 053/065 052/070 055/068 053/074 054/081 056/078 056/078  
34/T 43/T 66/T 22/T 22/W 32/T 44/T  
BHK 050/068 050/070 054/070 052/073 053/077 054/079 055/078  
12/T 22/T 44/T 32/T 33/W 12/T 33/T  
SHR 051/067 047/068 050/067 048/073 051/078 052/075 051/075  
55/T 65/T 66/T 22/T 23/T 34/T 43/T  
 

 
   
BYZ WATCHES/WARNINGS/ADVISORIES
 
 
MT...FLOOD WATCH IN EFFECT THROUGH LATE MONDAY NIGHT FOR ZONES  
28-34-39>42-56-63>68.  
WINTER WEATHER ADVISORY IN EFFECT UNTIL MIDNIGHT MDT MONDAY  
NIGHT FOR THE BEARTOOTH HIGHWAY FOR ZONE 67.  
WY...NONE.  
 

 
 

 
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