Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 301449
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
849 AM MDT SAT AUG 30 2014

.UPDATE...
MINOR UPDATES TO THE FORECAST THIS MORNING...AS THE FORECAST
REASONING BELOW REMAINS ON TRACK. WILL BE WATCHING FOR THE LEADING
EDGE OF THE PRECIPITATION...FROM NEAR MILES CITY TO SHERIDAN...TO
DEVELOP INTO STRONGER THUNDERSTORMS NEAR BAKER AND EKALAKA BY
EARLY THIS AFTERNOON. THIS COULD BE OUR BEST CHANCE OF SEEING ANY
SEVERE THUNDERSTORMS IN THE EAST. ONCE THE FRONT PASSES THESE
LOCATIONS...THE SEVERE THREAT WILL BE ELIMINATED. EXPECT MORE
SHOWERS AND THUNDERSTORMS TO TRACK ACROSS THE AREA LATE THIS AFTERNOON
AS A SECONDARY SHORTWAVE...CURRENTLY ENTERING SOUTHWEST
IDAHO...TRACKS ACROSS THE FORECAST AREA BEHIND THE SURFACE FRONT.
DONT EXPECT THIS ACTIVE TO BE STRONG OR SEVERE...BUT COULD BE A
HEAVY RAIN PRODUCER.

CHURCH

&&

.SHORT TERM...VALID FOR TDY AND SUN...

ACTIVE WEATHER PATTERN FOR THE NEXT 36 HRS OR SO AS TWO SEPARATE
SHORT WAVES TRACK THROUGH A BROADER LONG WAVE TROUGH OVER THE
NORTHERN ROCKIES. INHERITED FORECAST LOOKED GOOD AND REQUIRED
LIMITED ADJUSTMENTS. WE CONTINUE TO FOCUS ON THE THREAT OF SEVERE
WEATHER THIS AFTERNOON IN THE FAR EASTERN COUNTIES...AND WET
BLUSTERY CONDITIONS THIS EVENING.

THE FIRST SHORT WAVE WILL ROUND THE TROUGH CURRENTLY OVER THE
PACIFIC NW AND RIDE THE SW FLOW ALOFT INTO OUR REGION THIS
MORNING. THIS WILL SPREAD SHOWERS AND SOME THUNDERSTORMS ACROSS
THE FORECAST AREA THROUGH THE DAY AS WE HAVE ANTICIPATED. IN
RESPONSE TO THE APPROACHING SYSTEM...THE MODELS ARE ALL PROGGING A
SURFACE LOW DEVELOPING SOMEWHERE FROM THE SE CORNER OF MONTANA TO
THE NE CORNER OF WYOMING. THIS WILL SET UP A GOOD SOUTHERLY FLOW
AND CONVERGENT AREA IN OUR FAR EASTERN ZONES...OUR TYPICAL SET UP
FOR SEVERE WEATHER. A NORTH TO SOUTH ORIENTED CORRIDOR OF
INSTABILITY AND HIGH CAPE ARE PROGGED JUST WEST OF THE
MONTANA/DAKOTA BORDER AS UPWARD FORCING MOVES THROUGH AT MID
AFTERNOON. SO A SHORT WINDOW OF FAVORABLE CONDITIONS WILL EXIST IN
THIS AREA LATER TODAY FOR SEVERE WEATHER. BUFKIT DATA INDICATES
THE CAP BREAKING BETWEEN 3PM AND 4PM IN THE BAKER AREA. WOULD NOT
BE SURPRISED TO SEE A WATCH BOX ISSUED FOR THESE AREAS LATER
TODAY. CIPS ANALOGS ALSO SHOW A HISTORY OF SEVERE WIND AND SOME
HAIL FOR THIS PATTERN WHICH PROVIDES US FURTHER CONFIDENCE OF THE
THREAT. THUS...WE WILL ADD SEVERE THUNDERSTORM WORDING TO ZONES
IN THE FAR EAST TODAY...AND FOCUS ON IT A LITTLE HARDER IN OUR WX
STORY ETC.

THE SECOND AND STRONGER SHORT WAVE ROUNDS THE BOTTOM OF THE LONG
WAVE TROUGH TONIGHT INTO EARLY SUNDAY. FAVORABLE JET DYNAMICS
WILL HELP ENHANCE FRONTOGENESIS ACROSS SOUTHERN MONTANA AND
NORTHERN WYOMING WHICH SHOULD LEAD TO WIDESPREAD PRECIPITATION
OVERNIGHT AND EARLY SUNDAY. I RAISED POPS SIGNIFICANTLY FOR EARLY
SUNDAY...MAINLY OVER SOUTHERN HALF OF THE FORECAST AREA. THE
ENERGY PUSHES OUT OF THE REGION BY SUNDAY EVENING LINGERING A FEW
SHOWERS BEHIND IT IN THE COLD AIR ALOFT ASSOCIATED WITH THE
TROUGH. BT


.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...

MINIMAL CHANGES ONCE AGAIN TO THE EXTENDED FORECAST THIS
MORNING...AS MODELS REMAIN IN GOOD AGREEMENT AS TO THE OVERALL
PATTERN. MODELS ARE HOWEVER TAKING TAKING DIFFERENT TACK ON HOW
THE SYSTEM IS MOVING ACROSS THE REGION FOR THE END OF THE WORK
WEEK AND EARLY WEEKEND.

ZONAL FLOW ALOFT TAKES HOLD ACROSS THE REGION ON TUESDAY...WHICH
HOLDS THROUGH WEDNESDAY AHEAD OF THE NEXT PACIFIC TROF. THERE IS
ALSO SOME INDICATION OF SHALLOW RIDGING...WHICH WILL SUPPORT DRY
AND WARM CONDITIONS THROUGH THE PERIOD. TEMPS WILL BE AROUND
SEASONAL AVERAGE...CLIMBING ONLY TO AROUND 80 DEGREES. AN UPPER
TROF WILL IMPACT THE REGION THROUGH THE REMAINDER OF THE
PERIOD...BUT MODELS VARY A BIT ON TIMING OF WAVES THROUGH THE
REGION AS WELL AS WHETHER TROF AXIS CROSS THE REGION LATE IN THE
PERIOD OR NOT. THE GFS SEEMS TO FAVOR KEEPING THE TROF ANCHORED
OVER THE NORTHERN CALIFORNIA COAST...AND ANGLING INTO WESTERN
MONTANA. MEANWHILE THE ECMWF SPLITS THE TROF...AND KEEPS THE BEST
ENERGY NORTH AND SOUTH OF THE REGION. HAVE OPTED TO CONTINUE WITH
POPS THROUGH THE LATTER PORTIONS OF THE EXTENDED PERIOD...AS THE
GFS SEEMS MOST SIMILAR TO PREVIOUS RUNS...WHILE ECMWF IS A
SIGNIFICANT DEPARTURE FROM 24HRS AGO. THEREFORE...WILL ALSO
CONTINUE WITH COOLER TEMPS AT THIS TIME...WITH HIGHS OF 10 TO 15
DEGREES BELOW AVERAGE FOR THURSDAY THROUGH SATURDAY. AAG
&&

.AVIATION...

SHOWER AND THUNDERSTORM ACTIVITY WILL BECOME WIDESPREAD ACROSS THE
AREA THIS AFTERNOON THROUGH THIS EVENING. ISOLATED STRONG TO
SEVERE STORMS ARE POSSIBLE EAST OF A MILES CITY TO BROADUS LINE
THIS AFTERNOON. LOCAL MVFR CONDITIONS IN MODERATE TO HEAVY RAIN
CAN BE EXPECTED WITH SHOWER AND THUNDERSTORM ACTIVITY. MOUNTAIN
OBSCURATION WILL BECOME PERSISTENT THIS AFTERNOON THROUGH LATE
TONIGHT. CHAMBERS

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY SUN     MON     TUE     WED     THU     FRI
-------------------------------------------------------
BIL 071 054/069 051/070 050/078 052/077 051/072 047/068
    7/T 64/T    22/T    11/U    01/U    22/T    33/T
LVM 071 046/067 044/068 044/078 045/077 046/072 046/067
    7/T 63/T    22/T    21/U    02/T    22/T    33/T
HDN 074 054/072 051/071 051/080 052/080 053/075 051/072
    6/T 55/T    22/T    11/U    01/U    22/T    33/T
MLS 077 056/073 053/072 052/080 054/080 053/075 050/071
    4/T 44/T    12/T    11/U    01/U    22/T    33/T
4BQ 083 055/070 051/071 051/080 053/082 054/076 053/074
    5/T 65/T    12/T    11/U    01/U    23/T    33/T
BHK 079 054/071 049/071 049/078 051/078 052/074 053/070
    5/T 63/T    13/T    11/U    01/U    23/T    33/T
SHR 080 052/068 047/070 045/080 048/080 050/075 049/072
    6/T 55/T    22/T    21/U    01/U    22/T    33/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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