Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 260321
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
921 PM MDT MON AUG 25 2014

.UPDATE...
WEAK ENERGY FROM THE SW PRODUCING A COUPLE ECHOES NEAR LIVINGSTON
AND THE PARADISE VALLEY AND WILL SUSTAIN ISOLD POPS FOR OUR SW
THRU THE REMAINDER OF THE EVENING. BETTER CHANCE OF PCPN SHOULD
EMERGE LATER TONIGHT INTO TUESDAY MORNING IN OUR FAR EAST. 850MB
WINDS WILL TURN TO THE SE AND LOW LEVEL JET WILL ADVECT SOME
DEGREE OF HIGH PLAINS MOISTURE INTO OUR SE LATER TONIGHT...SUCH
THAT WE WILL SEE A COUPLE HUNDRED J/KG OF ELEVATED CAPE. SHEARED
SHORTWAVE WILL EVENTUALLY SLIDE ACROSS FROM THE WEST...AND THE
COMBINATION SHOULD BE ENOUGH FOR ISOLD TO SCT SHOWERS AND MAYBE A
FEW TSTMS IN FAR SE MT LATE TONIGHT AND TUESDAY. HAVE ADJUSTED
POPS DOWN AND REMOVED MENTION OF TS IN OUR WEST THIS EVENING.
TEMPS SHOULD DROP TO THE 40S MOST PLACES TONIGHT...A LITTLE WARMER
THAN LAST NIGHT BUT STILL CHILLY FOR LATE AUGUST. WARMING TREND
WILL CONTINUE TOMORROW WITH HIGHS INTO THE 70S. JKL

&&

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

A RELATIVELY QUITE WEATHER PATTERN IS IN STORE FOR THE NEXT
SEVERAL DAYS. THE CHANCE OF PRECIPITATION WILL BE MAINLY CONFINED
TO THE MOUNTAINS AND SOUTHERN LOCATIONS. TEMPERATURES WILL
MODERATE BACK TO ABOVE SEASONAL CONDITIONS BY WEDNESDAY.

ON UPPER TROUGH WAS CURRENTLY SINKING INTO NORTHERN NEVADA THIS
AFTERNOON. MODELS CONTINUE TO DROP THE SYSTEM SOUTHEAST INTO
CENTRAL UTAH BY TUESDAY AFTERNOON. JET ENERGY OUT AHEAD OF THE
SYSTEM WILL STREAM INTO SOUTHERN ZONES TONIGHT ALONG WITH A WEAK
SHORTWAVE. THE WAVE WEAKENS OVER TIME AS IT ENCOUNTERS
ANTICYCLONIC FLOW OVER WYOMING. WILL KEEP POPS IN THE MOUNTAINS
THIS EVENING AND INTO THE SOUTHEAST OVERNIGHT.

A NORTHERN STREAM WAVE WILL SLIDE SOUTHEAST TOWARD SOUTHEAST
MONTANA LATE TONIGHT AND EARLY TUESDAY. THIS WILL KEEP THE CHANCE
OF POPS GOING THROUGH THE DAY TUESDAY IN THE SOUTHEAST. ZONAL FLOW
WILL TAKE OVER FOR TUESDAY NIGHT AND WEDNESDAY FOR A DRY PERIOD OF
WEATHER. TEMPERATURES WILL GRADUALLY WARM INTO THE 70S TUESDAY AND
THE LOWER TO MID 80S ON WEDNESDAY. TWH

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

NOTED THE ECMWF ENSEMBLE FORECASTS SHOWED HIGHER CONFIDENCE THAN
THEY SHOWED YESTERDAY FOR MUCH OF THE PERIOD. THE GFS ENSEMBLES
WERE SHOWING HIGH CONFIDENCE AS WELL. HOWEVER...THE APPROACH OF A
PACIFIC TROUGH FOR SUN AND MON HAD SOME TIMING AND STRENGTH
DIFFERENCES AMONG THE MODELS.

THE PATTERN WILL CONTINUE TO FEATURE ZONAL FLOW/WEAK RIDGING FOR
THU AND FRI. THE FLOW WILL THEN TURN SW AHEAD OF THE PACIFIC
TROUGH ON SAT. CONTINUED THE DRY FORECAST INTO FRI MORNING...AND
DID NOT CHANGE THE MOUNTAIN POPS FRI AFTERNOON AND EVENING AS THE
MODELS CONTINUED TO SHOW SOME QPF OVER THESE AREAS...WITH THE
ECMWF GOING HIGHER WITH AMOUNTS THAN THE GFS. MODELS HAD A COLD
FRONT MOVING INTO THE AREA FROM THE W ON SAT AND CROSSING THE
REGION SAT NIGHT. THERE WERE MODEL DIFFERENCES IN QPF PLACEMENT SO
KEPT THE LOW POPS ACROSS THE ENTIRE AREA.

ON SUN...THE ECMWF HAD THE TROUGH AXIS CROSSING THE AREA WITH A
SLIGHT NEGATIVE TILT...WHILE THE GFS KEPT THE AXIS TO THE W.
INCREASED POPS TO CHANCE W OF KBIL...OTHERWISE CONTINUED THE
WIDESPREAD LOW POPS. THE ECMWF WAS FASTER THAN THE GFS IN MOVING
THE TROUGH OUT OF THE AREA ON MON. SAW NO REASON TO CHANGE THE
WIDESPREAD SLIGHT CHANCE POPS. WILL NEED TO WAIT FOR MODELS TO
COME INTO BETTER AGREEMENT WITH THE DETAILS OF THE TROUGH TIMING
AND STRENGTH BEFORE MAKING CHANGES TO THE LATER FORECAST PERIODS.

TEMPERATURES WILL CONTINUE TO BE IN THE 80S THROUGH SAT...THEN A
COOLDOWN WILL OCCUR SUN THROUGH MON. ARTHUR
&&

.AVIATION...

MAINLY VFR FLIGHT CONDITIONS WILL PREVAIL ACROSS THE REGION
OVERNIGHT AND THROUGH THE DAY TUESDAY. ISOLD SHOWERS AND
THUNDERSTORMS ARE POSSIBLE IN THE HIGH TERRAIN AND EXTREME
SOUTHEAST MONTANA OVERNIGHT AND THROUGH MUCH OF THE DAY TUESDAY.
LOCALIZED MVFR CONDITIONS ARE EXPECTED WITH HEAVIER PRECIP. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    TUE     WED     THU     FRI     SAT     SUN     MON
-----------------------------------------------------------
BIL 048/076 053/082 057/087 059/086 059/085 061/074 053/069
    11/B    00/U    00/U    01/U    12/T    22/T    22/T
LVM 045/076 047/081 051/086 051/086 052/083 052/071 047/068
    21/B    10/U    10/U    01/U    13/T    33/T    32/T
HDN 049/077 052/084 057/088 057/089 058/087 060/078 054/073
    11/B    01/U    10/U    01/U    12/T    22/T    22/T
MLS 048/076 054/083 059/087 060/089 061/088 061/080 056/073
    11/B    01/U    11/U    11/U    12/T    22/T    22/T
4BQ 049/076 053/082 057/087 058/089 060/089 060/082 055/075
    22/T    12/T    11/U    01/U    11/U    22/T    22/T
BHK 045/073 049/079 056/083 056/086 057/085 059/079 053/071
    12/T    11/U    11/U    11/U    12/T    22/T    22/T
SHR 048/075 049/080 053/087 053/089 055/087 056/080 051/073
    22/T    21/B    10/U    01/U    12/T    22/T    22/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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