Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 310329
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
929 PM MDT SAT AUG 30 2014

.UPDATE...
EVENING CONVECTION HAS WEAKENED WITH STRONGEST ACTIVITY HAVING
MOVED INTO THE DAKOTAS. REGIONAL RADAR SHOWING SOME ACTIVITY
MOVING INTO SOUTHWEST MONTANA SO DO EXPECT ANOTHER SHOT OF SHOWERS
LATER TONIGHT BUT CURRENT ACTIVITY IS VERY ISOLATED. DOES NOT LOOK
QUITE AS WET WITH THE NEXT ROUND AS PREVIOUSLY THOUGHT AS JET
ENERGY OVER OREGON IS TAKING A MORE SOUTHERN TRACK WHICH WILL PUT
BEST LIFT OVER SOUTHEAST IDAHO AND WESTERN WYOMING. UPDATED
FORECASTS. BORSUM

&&

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

SERIES OF SHORTWAVES IN THE CYCLONIC FLOW ALOFT ARE PROGRESSING
ACROSS THE FORECAST AREA THIS AFTERNOON. INITIAL SHORTWAVE IS
PUSHING ACROSS FAR EASTERN MONTANA AND WILL EXIT INTO THE DAKOTAS
LATER THIS AFTERNOON. A SECONDARY WAVE IS PUSHING INTO SOUTH
CENTRAL MONTANA OUT OF YELLOWSTONE PARK. LIGHTNING ACTIVITY HAS
BEEN MORE VIGOROUS WITH THIS WAVE ALL MORNING...EVEN BACK OVER
IDAHO EARLIER...INDICATING ENHANCED MID-LEVEL INSTABILITY. WOULD
STILL NOT RULE OUT A LINE OF THUNDERSTORMS DEVELOPING ACROSS
FALLON AND CARTER COUNTIES WITH THE INITIAL WAVE. IN
FACT...A THUNDERSTORM HAS STARTED TO DEVELOP NORTHEAST OF
GILLETTE WITH THIS LINE...AND IT REMAINS TO BE SEEN WHETHER A LINE
CAN UNZIP NORTHWARD DESPITE THE CIN THAT REMAINS IN PLACE. IF A
LINE CAN DEVELOP THERE...IT WILL PROVIDE THE BEST CHANCE AT AN
ISOLATED SEVERE REPORT BEFORE THE LINE EXITS INTO THE DAKOTAS.

THE SECONDARY WAVE IS STARTING TO DEVELOP A LINE FROM JUST SOUTH
OF RED LODGE DOWN TOWARD JACKSON WYOMING. TREND IN THE HRRR HAS
BEEN TO EVOLVE THIS LINE ACROSS BIG HORN COUNTY AND SOUTHEAST
MONTANA THROUGH THIS EVENING...WITH SOME STRONGER CELLS EMBEDDED.
MAIN THREATS WITH THIS LINE OF STORMS WILL LIKELY BE HEAVY
RAIN...FREQUENT LIGHTNING AND SMALL HAIL. WHILE WOULDNT RULE OUT
A SEVERE REPORT...ELEVATED NATURE OF THE CONVECTION BEHIND THE
SURFACE FRONT SHOULD HELP TO PRECLUDE ANY SEVERE ACTIVITY.

CYCLONIC FLOW WITH WEAK EMBEDDED SHORTWAVES WILL REMAIN IN PLACE
OVER THE FORECAST AREA THROUGH SUNDAY MORNING...THUS KEEPING AN
OVERALL WET FORECAST GOING THROUGH MID DAY SUNDAY. COULD SEE A
BREAK IN THE ACTIVITY BY SUNDAY AFTERNOON AND EVENING...BEFORE
MORE ISOLATED/SCATTERED SHOWERS DEVELOP ACROSS THE AREA MONDAY
AFTERNOON AS THE CYCLONIC FLOW REMAINS IN PLACE ALOFT.
TEMPERATURES THROUGH THIS PERIOD WILL REMAIN COOLER...WITH DAY
TIME HIGHS ONLY EXPECTED IN THE LOW 70S ON SUNDAY AND MONDAY.

CHURCH

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

EXTENDED FORECAST STARTS OFF QUIET FOR TUESDAY INTO WEDNESDAY AS MODELS
CONSISTENT WITH ZONAL DOWNSLOPE FLOW ACROSS THE AREA. CONDITIONS
BEGIN TO CHANGE LATE WEDNESDAY AS SYSTEM OVER WESTERN CANADA DROPS
SOUTH AND DEFLECTS THE FLOW OVER MONTANA TO THE SOUTHWEST
INCREASING THE CHANCES FOR AFTERNOON AND EVENING THUNDERSTORMS.
THE LATEST ECMWF AND CANADIAN SOLUTIONS DRAG THE BULK OF THE
PACIFIC SYSTEM THROUGH THE AREA ON THURSDAY WHILE THE GFS IS
SLOWER AND A BIT FURTHER NORTH WITH THIS FORCING AND THE BETTER
PRECIPITATION CHANCES. WEAK ENERGY AND GENERAL TROFINESS RESIDES
OVER THE AREA BEHIND THE SYSTEM INTO NEXT WEEKEND. SPLIT THE
DIFFERENCE BETWEEN THE MODELS ON THE TIMING OF STRONGEST FORCING
OVER THE AREA RESULTING IN THE HIGHEST PRECIPITATION CHANCES LATE
THURSDAY INTO FRIDAY...BUT IF ECMWF IS CORRECT THIS COULD BE A BIT
LATE. CONTINUED 20 TO 30 PERCENT PRECIPITATION CHANCES INTO THE
WEEKEND. TRENDED TEMPERATURES DOWN FROM WEDNESDAY INTO THE WEEKEND
WITH MID 70S WEDNESDAY DROPPING INTO THE UPPER 60S FOR THURSDAY
AND FRIDAY. CHAMBERS

&&

.AVIATION...

SCATTERED SHOWERS AND A FEW TSTMS WILL IMPACT THE AREA THROUGH THE
REMAINDER OF THE EVENING...WITH ANY CHANCE OF STRONGER STORMS
HAVING SHIFTED INTO THE DAKOTAS. ANOTHER DISTURBANCE FROM THE WEST
WILL BRING INCREASING SHOWERS ESPECIALLY WEST AND SOUTH OF KBIL
LATER TONIGHT...WITH ACTIVITY SPREADING EAST SUNDAY. AREAS OF MVFR
AND FREQUENT MOUNTAIN OBSCURATIONS CAN BE EXPECTED BETWEEN 06-18Z.
JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY SUN     MON     TUE     WED     THU     FRI
-------------------------------------------------------
BIL 071 054/068 051/069 050/078 054/077 050/069 049/069
    7/T 44/T    22/T    10/U    11/U    22/T    33/T
LVM 071 046/066 043/068 043/079 046/077 043/068 044/069
    7/T 43/T    22/T    10/U    12/T    23/T    33/T
HDN 074 054/069 051/071 051/080 053/081 051/072 051/073
    6/T 45/T    22/T    10/U    11/U    12/T    33/T
MLS 077 056/072 052/073 052/079 054/080 053/071 053/072
    4/T 34/T    12/T    10/U    01/U    12/T    22/T
4BQ 083 055/066 051/070 051/080 053/083 052/072 051/073
    5/T 35/T    23/T    10/U    01/U    22/T    33/T
BHK 079 054/071 049/070 049/077 051/080 050/073 049/070
    5/T 53/T    13/T    10/U    12/T    22/T    22/T
SHR 080 052/065 047/070 046/080 050/083 049/073 048/075
    6/T 35/T    22/T    10/U    11/U    12/T    33/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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