Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 280051 AAB
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
651 PM MDT MON JUL 27 2015

.UPDATE...

WE REMOVED ANOTHER ROW OF COUNTIES FROM THE SEVERE THUNDERSTORM
WATCH...INCLUDING YELLOWSTONE...AS THE MAIN THREAT OF STRONG TO
SEVERE STORMS IS QUICKLY SHIFTING MORE DEEPLY INTO SOUTHEASTERN
MT. WE ALSO DECREASED POPS FOR THE REST OF THE EVENING IN SOUTH
CENTRAL MT BEHIND THE MAIN COMPLEX OF STORMS. SCHULTZ

PREVIOUS UPDATE...ISSUED AT 554 PM MDT MON JUL 27 2015...

WE CANCELLED THE SEVERE THUNDERSTORM WATCH EARLY FOR STILLWATER...
CARBON...AND GOLDEN VALLEY COUNTIES AS DEEP CONVECTION IS EAST OF
THERE AS OF 2345 UTC. WE WILL LIKELY BE ABLE TO CANCEL THE WATCH
FOR YELLOWSTONE AND MUSSELSHELL COUNTIES BY ABOUT 01 UTC /7 PM
MDT/...BUT NEED TO HANG ONTO IT FOR A BIT LONGER GIVEN STRONG
STORMS OBSERVED ON RADAR OVER FAR EASTERN PARTS OF THOSE COUNTIES
AT THIS TIME. THE THREAT FOR SEVERE WEATHER IS OVER WITH IN THE
BILLINGS METRO AREA THOUGH. SCHULTZ

&&

.SHORT TERM...VALID FOR TUE AND WED...

AT 19Z...COLD FRONT WAS FROM KLWT S TO NYE. FRONTOGENESIS WAS
ACCOMPANYING THE FRONT. VORTICITY WAS ROTATING NE INTO THE AREA
FROM ID PER WATER VAPOR IMAGERY...AND JET DIVERGENCE WAS OVER
WESTERN AREAS PER THE RAP. DESPITE TEMPERATURES IN THE 50S AND
60S...LITTLE CAPE AND WEAK LAPSE RATES...STORMS WERE STRENGTHENING
OVER THE WESTERN FORECAST AREA...WHICH SHOWED THE STRENGTH OF THE
DYNAMICS. HAVE RECEIVED SOME REPORTS OF HALF INCH HAIL. OTHER
CONVECTION WAS SLOW TO GET GOING IN THE INVERTED TROUGH OVER FAR
SE MT. RADAR SHOWED OTHER STORMS APPROACHING FROM WY. CONSENSUS OF
LATEST MODELS BROUGHT THE COLD FRONT TO KMLS BY 00Z TUE. MEANWHILE
CAPES OVER THE E HALF OF THE AREA RANGED FROM 1000 TO 2000
J/KG...AND SHEAR OVER CENTRAL PARTS OF THE AREA WAS 40-50 KT.

THE JET DIVERGENCE AND Q-VECTOR CONVERGENCE WILL LIFT N OF THE
AREA BEFORE 06Z...SO STRONG DYNAMICS WILL LAST INTO THE EARLY
EVENING HOURS. THE BEST CHANCE FOR SEVERE WEATHER WILL REMAIN OVER
THE E DUE TO THE HIGH CAPES...BUT A STRONG TO SEVERE STORM CANNOT
BE RULED OUT ANYWHERE OVER THE AREA. WILL ADJUST POPS TO GO WITH
HIGHEST VALUES CENTRAL AND E DUE TO A GENERALLY SLOWER SYSTEM
MOVEMENT. HAD CHANCE POPS OVER THE W AND KSHR AREA. PRECIPITATION
CHANCES WILL DECREASE FROM S TO N AFTER 06Z. STRONG PRESSURE RISES
WILL FOLLOW THE FRONT THIS EVENING ALLOWING FOR WINDY CONDITIONS.

WILL CONTINUE RED FLAG WARNING THROUGH 06Z. DOUBTFUL THAT
HUMIDITIES WILL BE VERY LOW DUE TO DEWPOINTS IN THE 50S TO AROUND
60...BUT DANGEROUS FIRE CONDITIONS WILL EXIST DUE TO WARM
TEMPERATURES...THE WIND SHIFT AND INCREASING WINDS WITH FRONTAL
PASSAGE AND INCREASING THUNDERSTORMS.

UPPER LOW/TROUGH WILL MOVE OUT OF E MT ON ON TUE. SHOWERS MAY
LINGER ACROSS THE N AND MOUNTAINS. THE STRONG PRESSURE GRADIENT
BEHIND THE DEPARTING LOW WILL CREATE WINDY CONDITIONS...ESPECIALLY
FROM ROSEBUD COUNTY E WITH MODELS SHOWING 850 MB WINDS FROM 45 TO
55 KT AND GOOD MIXING. WILL ISSUE A HIGH WIND WARNING FROM 12Z TO
03Z FOR THESE AREAS. GFS LOOKED WARMER AND DRIER THAN THE WRF...SO
WENT WITH A COMPROMISE FOR TEMPERATURES AND RELATIVE HUMIDITIES.
HUMIDITIES ENDED UP ABOVE 20 PERCENT SO WILL NOT ISSUE A RED FLAG
FOR TUE. FUTURE SHIFTS CAN WATCH PRECIPITATION TRENDS TO GET A
BETTER HANDLE ON HOW HUMIDITIES WILL BEHAVE ON TUE.

FLOW ALOFT BECOMES FLAT NW TUE NIGHT THROUGH WED NIGHT BRINGING
DRY AND WARMER WEATHER WITH LESS WIND. ARTHUR

.LONG TERM...VALID FOR THU...FRI...SAT...SUN...MON...

AFTER A GREAT RELIEF FROM THE SUMMERTIME HEAT IN THE SHORT
TERM...THINGS WILL BE WARMING UP AS WE ENTER MOSTLY ZONAL FLOW
ALOFT. TEMPERATURES WILL REMAIN JUST ABOVE NORMAL AS CHANCES FOR
RAIN WILL BE GREATLY REDUCED. LITTLE PIECES OF ENERGY COULD ROTATE
AROUND THE DESERT RIDGE ON FRIDAY AND SATURDAY AFTERNOONS WHICH
COULD HELP GENERATE ISOLATED THUNDERSTORMS...MAINLY OVER THE
MOUNTAINS. WEAK PIECE OF ENERGY ON SUNDAY IN THE NORTHERN STREAM
COULD PRODUCE A WEAK BACKDOOR COLD FRONT. THIS SHOULD PUSH
TEMPERATURES BACK TO NORMAL ON SUNDAY AND MONDAY.

DOBBS

&&

.AVIATION...

STRONG TO SEVERE STORMS WILL CONTINUE OVER SOUTHEASTERN MT AND
PARTS OF NORTH CENTRAL WY THROUGH MID-EVENING. A STRONG COLD FRONT
WILL CONTINUE PROGRESSING EASTWARD...BRINGING AN END TO THE STORMS
ALONG WITH AN INCREASE IN WEST-NORTHWEST WINDS. GUSTS TO 30 KT
WILL BE COMMON TONIGHT...AND GUSTS OF 40 KT WILL BE COMMON DURING
THE DAY TUESDAY. SCHULTZ

&&

.PRELIMINARY POINT TEMP/POPS...

    TUE     WED     THU     FRI     SAT     SUN     MON
-----------------------------------------------------------
BIL 050/075 053/085 057/092 060/094 061/091 061/090 060/088
    32/W    00/U    00/U    01/U    11/U    11/B    11/B
LVM 046/073 047/083 051/089 053/092 054/089 054/086 054/085
    32/W    00/U    00/U    01/U    11/U    12/T    21/B
HDN 049/076 051/087 054/094 058/096 060/092 061/091 060/090
    72/W    00/U    00/U    01/U    11/U    11/B    11/B
MLS 053/072 053/087 057/093 061/095 062/091 063/089 062/088
    83/T    10/U    00/U    01/U    11/U    11/U    11/U
4BQ 052/073 052/086 055/093 060/095 061/093 062/091 062/090
    51/N    00/U    00/U    01/U    11/U    11/B    11/B
BHK 053/070 052/084 055/090 057/092 060/088 060/085 059/085
    83/T    10/U    00/U    01/U    11/U    11/U    11/B
SHR 046/072 048/083 052/091 055/093 056/091 058/089 057/086
    51/N    00/U    00/U    00/U    01/U    12/T    21/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...RED FLAG WARNING IN EFFECT UNTIL MIDNIGHT MDT TONIGHT FOR
      ZONES 30>33-36>38-57-58.
     SEVERE THUNDERSTORM WATCH 456 IN EFFECT UNTIL 10 PM MDT THIS
      EVENING FOR ZONES 31>33-36-37-58.
     HIGH WIND WARNING IN EFFECT FROM 6 AM TO 9 PM MDT TUESDAY FOR
      ZONES 31>33-37.
WY...RED FLAG WARNING IN EFFECT UNTIL MIDNIGHT MDT TONIGHT FOR
      ZONES 98-99.
     SEVERE THUNDERSTORM WATCH 456 IN EFFECT UNTIL 10 PM MDT THIS
      EVENING FOR ZONES 98-99.

&&

$$
WEATHER.GOV/BILLINGS



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