624  
FXUS65 KBYZ 261532  
AFDBYZ  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE BILLINGS MT  
932 AM MDT WED JUN 26 2019  
   
UPDATE
 
 
MAY SEE SOME ISOLATED SHOWERS OVER THE MOUNTAINS AND NEARBY  
PLAINS THIS MORNING AS SATELLITE AND RADAR SHOWING SOME WEAK  
ECHOES TRACKING THROUGH. PROBABLY JUST SPRINKLES THOUGH. WE STILL  
ANTICIPATE A BUSY AFTERNOON AND EVENING OF THUNDERSTORMS. LARGE  
HAIL A DEFINITE THREAT ACROSS THE AREA. STRONGEST SIGNALS OF  
HELICITY TRACKS OVER CRAZIES TO ROUNDUP, AND SEVERAL FROM SOUTHERN  
BIG HORN INTO POWDER RIVER COUNTY AND SOUTHEAST CORNER OF MONTANA  
LATE TODAY. CANNOT RULE OUT A TORNADO THREAT EITHER...ESPECIALLY  
IN THE SOUTHEAST.  
 
FOLKS SHOULD KEEP A CLOSE EYE ON THE SKY, AND AN EAR TO LOCAL  
MEDIA FOR WATCHES AND WARNINGS. BE READY TO TAKE ACTION IF  
WARNINGS ARE ISSUED. BT  
 

 
   
SHORT TERM...VALID FOR TDY AND THU
 
 
TODAY IS DEFINITELY A DAY TO KEEP AN EYE TO THE SKY IF YOU HAVE  
OUTDOOR ACTIVITIES, AND HAVE A PLAN TO GET TO SAFE SHELTER WHEN  
STORMS APPROACH.  
 
EXPECT THUNDERSTORMS TO GET GOING EARLY AFTERNOON OVER THE  
SOUTHWEST MOUNTAINS AND PUSH NORTH AND EAST THROUGH THE AFTERNOON  
AND EVENING, MAKING THE DAKOTAS BY MIDNIGHT. AS WE HAVE BEEN  
DISCUSSING THE PAST FEW DAYS THE INGREDIENTS FOR SEVERE  
THUNDERSTORMS HAVE ARRIVED IN THE AREA, WITH EASTERLY LOW LEVEL  
WINDS BRINGING PLAINS MOISTURE AND ENHANCING SHEAR. CAPE VALUES  
WILL PUSH OVER 1500 J/KG THIS AFTERNOON OVER MOST OF THE FORECAST  
AREA, WHILE 6KM BULK SHEAR VALUES RANGE FROM 40 TO 60KTS, PLENTY  
OF ENERGY AND SHEAR TO SUPPORT SEVERE THUNDERSTORMS. SOUNDINGS FOR  
THIS AFTERNOON INDICATING HAIL AS THE MAIN THREAT WITH  
THUNDERSTORMS TODAY, WITH SARS HAIL SIZE ALGORITHM POINTING  
TOWARD 2 INCH DIAMETER HAIL BEING SUPPORTED BY THE STRONGEST  
STORMS TODAY. AS A RESULT SPC UPGRADED THE AREA TO A SLIGHT RISK  
FOR TODAY.  
 
TIMING OF STRONGEST STORMS TODAY: LIVINGSTON 1-5PM,  
BILLINGS/ROUNDUP 2-6PM, HARDIN 3-7PM, MILES CITY/BROADUS 6-10PM.  
 
THREAT OF STRONG TO SEVERE STORMS DEVELOPS AGAIN FOR THURSDAY  
AFTERNOON/EVENING. FOCUS OF STRONGEST STORMS IS FURTHER NORTH WITH  
A JET STREAK THAT PUSHES INTO NORTH CENTRAL MONTANA THURSDAY  
EVENING. THERE IS MORE OF A CAP IN PLACE TOMORROW ALONG WITH THE  
LACK OF A STRONG DISTURBANCE TO KICK START STORMS, SO CURRENT  
MODELS ARE KEYING IN ON AREAS ALONG AND NORTH OF A HARLOWTON TO  
MILES CITY LINE FOR SEVERE STORMS. HOWEVER, CAPE VALUES INCREASE  
FROM TODAY INTO TOMORROW WITH VALUES PUSHING ABOVE 2000 J/KG  
THURSDAY AFTERNOON, AND SHEAR VALUES IN THE 40-50KT RANGE  
PERSISTING. WHILE THERE IS A LACK OF A STRONG FORCING MECHANISM  
THERE IS A DRY LINE DEVELOPING ALONG THE MT/WY LINE ALONG WITH THE  
MOUNTAINS TO SEED CONVECTION. WHILE IT DOES'T LOOK LIKE THERE  
WILL BE A LOT OF STORMS ON THURSDAY, ANY STORMS THAT DO MANAGE TO  
GET GOING WILL HAVE PLENTY OF ENERGY AND SHEAR TO BECOME SEVERE.  
SO, WILL NEED TO KEEP A CLOSE EYE ON TOMORROWS FORECAST AND WILL  
SEE IF THE CAM MODELS KEY IN ON ANY OF THE WEAKER FORCING  
MECHANISMS AS THEY PUSH INTO THE THURSDAY AFTERNOON/EVENING TIME  
FRAME. CHAMBERS  
   
LONG TERM...VALID FOR FRI...SAT...SUN...MON...TUE
 
 
UNSETTLED WEATHER PATTERN LOOKS TO PERSIST THROUGH THE EXTENDED  
FORECAST PERIOD FROM FRIDAY THROUGH NEXT THURSDAY. EACH DAY WILL  
SEE A CHANCE FOR SHOWERS AND THUNDERSTORMS IN THE AFTERNOON AND  
EVENING. STRONG TO SEVERE STORMS ARE POSSIBLE AT LEAST FRIDAY,  
WITH FRONTAL PASSAGE.  
 
THERE HAS BEEN A SIGNIFICANT CHANGE FROM PREVIOUS MODEL RUNS THAT  
WERE FAIRLY CONSISTENT OVER THE LAST FEW DAYS. UPPER LEVEL PACIFIC  
LOW IS NO LONGER PROGGED TO LIFT DIRECTLY NORTHWEST INTO CANADA.  
THE MODELS NOW STALL THE PACIFIC LOW OVER OREGON AND WASHINGTON  
THROUGH MONDAY FOR THE GFS, WHILE THE ECMWF DOES NOT EVEN MOVE THE  
LOW ONTO THE COAST UNTIL TUESDAY. EITHER WAY THIS POINTS TO  
PERSISTENT SOUTHWEST FLOW ALOFT OVER THE REGION FROM FRIDAY  
THROUGH TUESDAY. UNSETTLED SOUTHWEST FLOW PERSISTS THROUGH THE  
REMAINDER OF THE PERIOD. THE GFS INDICATES CLOSED PACIFIC LOW  
SHIFTING INTO WESTERN MONTANA TUESDAY, BEFORE OPENING UP AND  
STALLING ONCE AGAIN. MEANWHILE, THE ECMWF KEEPS THE CLOSED LOW  
TOGETHER AND GENERALLY STALLED ON THE PACIFIC COAST. EITHER WAY,  
THIS POINTS CONTINUED UNSETTLED WEATHER.  
 
THIS PATTERN WILL KEEP INSTABILITY, MOISTURE, AND JET FORCING  
PRESENT TO GIVE CHANCES FOR STORMS THROUGHOUT THE EXTENDED  
FORECAST PERIOD. TEMPERATURES LOOK TO STAY IN THE 80S INTO NEXT  
WEEK, WITH A FEW 90S POSSIBLE.  
 
MODELS ARE IN POOR AGREEMENT AS THEY TRANSITION TO A NEW  
SIGNATURE, BUT THE PATH OF THE PACIFIC LOW INDICATED IN THE GFS IS  
QUITE SIMILAR TO THE ONE ADVERTISED 6 OR 7 DAYS AGO, BEFORE  
SHIFTING TO THE PERSISTENT NORTHWESTERLY TRACK THAT HAS BEEN  
ADVERTISED OVER THE PAST FEW DAYS. LIKEWISE, ENSEMBLES SEEM TO LAG  
WHEN THESE MODEL CHANGES OCCUR. SO FAR, AT THIS TIME, SEVERE  
POTENTIAL APPEARS TO MUCH LOWER FOLLOWING FRIDAY FROPA, WITH  
REDUCED SHEAR AND CAPE, BUT MODELS ARE IN FLUX AT THIS POINT. SO,  
UNCERTAINTY IS A BIT HIGHER LATER IN THE PERIOD.  
 
GILSTAD  
 

 
   
AVIATION
 
 
EXPECT VFR THROUGH THIS MORNING. SCATTERED THUNDERSTORMS WILL  
DEVELOP THIS AFTERNOON, AND THESE STORMS WILL BE CAPABLE OF  
PRODUCING HAIL AND STRONG WINDS, ALONG WITH LOCALIZED MVFR/IFR  
FLIGHT CONDITIONS. GILSTAD/JKL  
 

 
   
PRELIMINARY POINT TEMP/POPS
 
 
TDY THU FRI SAT SUN MON TUE  
-------------------------------------------------------  
BIL 079 055/087 058/084 056/080 055/081 057/081 057/083  
4/T 52/T 22/T 22/T 23/T 33/T 32/T  
LVM 075 050/081 052/079 048/076 048/078 051/078 050/079  
5/T 63/T 23/T 22/T 22/T 33/T 32/T  
HDN 083 055/088 058/086 056/080 056/082 057/081 057/082  
5/T 62/T 22/T 22/T 33/T 33/T 32/T  
MLS 083 058/086 060/088 058/080 056/081 057/080 057/081  
1/B 42/T 32/T 31/B 43/T 44/T 43/T  
4BQ 084 057/088 060/091 058/083 057/081 057/080 057/081  
2/T 61/U 21/U 21/B 33/T 54/T 43/T  
BHK 081 057/082 060/088 058/080 055/079 056/078 055/079  
2/W 62/T 22/T 21/B 33/T 44/T 43/T  
SHR 083 052/089 055/090 053/082 053/082 054/081 054/081  
2/T 31/B 11/U 22/T 43/T 44/T 44/T  
 

 
   
BYZ WATCHES/WARNINGS/ADVISORIES
 
 
MT...NONE.  
WY...NONE.  
 

 
 

 
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