Area Forecast Discussion
Issued by NWS Billings, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KBYZ 240049
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
649 PM MDT SAT AUG 23 2014

.UPDATE...
UPPER LOW CONTINUES TO MOVE SLOWLY EAST WHILE PRODUCING WIDESPREAD
PCPN WITH THE EXCEPTION OF PARTS OF OUR SOUTHEAST WHERE SOME MID
LEVEL DRY SLOTTING EXISTS. PUSH OF NORTHERLY ISENTROPIC ASCENT
ALONG WITH VEERED LOW-MID LEVEL WINDS HAS ALLOWED FOR PCPN TO PICK
UP IN OUR WEST TO CENTRAL PARTS INCLUDING BILLINGS. LATEST RAP
SHOWS THIS CONTINUING FOR SEVERAL HOURS BEFORE ASCENT SHIFTS
N-NE...SO HAVE MAXED OUT POPS IN THIS AREA THIS EVENING. OTHER
THAN THE POP ADJUSTMENTS THE FORECAST REMAINS ON TRACK. BIGGEST
IMPACT IS THE HEAVY PCPN AND ITS IMPACT ON RIVERS AND STREAMS SO
WILL CONTINUE TO MONITOR THESE. GIVEN WE ARE GETTING ON THE TROWAL
SIDE OF THIS SYSTEM WE ARE PAST THE HEAVIEST RAINFALL RATES NOW.
JKL

&&

.SHORT TERM...VALID FOR SUN AND MON...

NEGATIVE TILT TROUGH TRACKING RIGHT ACROSS OUR REGION TONIGHT.
STRONG ISENTROPIC LIFT UNDER DIFFLUENT FLOW ALOFT AHEAD OF LOW
PRESSURE SYSTEM HAS PRODUCED CONSIDERABLE RAINFALL OVER THE
REGION. WE HAVE HAD 1-3 INCHES COMMON OVER MUCH OF THE FORECAST
AREA...ALONG WITH REPORTS OF OVER 4 INCHES IN MUSSELSHELL...NEAR
BIG TIMBER AND OUT SOUTH OF BAKER. DUE TO THE POTENTIAL OF AN
ADDITIONAL 1 OR 2 INCHES WE HAVE UPGRADED WATCHES TO WARNINGS
ACROSS OUR NW ZONES...AND A SMALL STREAM FLOOD ADVISORY IN THE
BAKER VICINITY.

MODELS BEGIN TO SWING THE FLOW AROUND THE LOW PRESSURE SYSTEM
TO THE N/NW IN OUR WESTERN ZONES LATER THIS EVENING AS SYSTEM
LIFTS E/NE ACROSS SOUTHERN MONTANA. THIS SETS UP A TROWAL FEATURE
HEADING INTO SUNDAY WITH PRECIP WRAPPING AROUND INTO OUR NORTHERN
AND CENTRAL ZONES FROM THE NORTH...INCLUDING NORTHERN
ROSEBUD/TREASURE/NORTHERN CUSTER AND MAYBE NE YELLOWSTONE
COUNTIES. THIS AREA WILL SEE THE HIGHEST POPS AND QPF FOR THE
REST OF THIS EVENT. THE PRECIP FINALLY DIMINISHES BY SUNDAY
EVENING AS THE UPPER LOW RACES ACROSS EASTERN NORTH DAKOTA.

WE GET A BREAK IN THE WEATHER MONDAY BEHIND THE EXITING UPPER
LOW...BUT THE SOUTHERN BRANCH OF SPLIT JET DROPS ENERGY INTO THE
DESERT SW WHICH WILL BRING A TROUGH AXIS THROUGH SOUTHERN MONTANA
BY MONDAY EVENING. I PULLED BACK THE POPS A BIT WEST FOR THIS AS
FORCING IS WEAK AND LIMITED TO MAINLY SW MONTANA AND OUR
BEARTOOTH/ABSAROKA RANGES. BT

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

MODELS CONTINUE TO BE IN GOOD AGREEMENT...PROMPTING A FEW CHANGES
TO THE EXTENDED FORECAST PERIOD. CHANGES CENTERED AROUND GENERALLY
COOLING TEMPS SLIGHTLY THROUGHOUT THE PERIOD...RESULTING IN A
SLIGHTLY MORE GRADUAL WARM UP. OTHER CHANGES WERE TO ADD SOME
SLIGHT POPS ACROSS THE REGION FOR THE LATTER PORTION OF THE
PERIOD.

A SECOND UPPER LOW EMBEDDED WITHIN THE BROAD TROF CONTINUES
PASSAGE THROUGH THE REGION TUESDAY. THIS KEEPS SHOWER AND
THUNDERSTORM POTENTIAL INTACT ACROSS THE ENTIRE FORECAST AREA
THROUGH TUESDAY. THEREFORE TEMPS WILL REMAIN WELL BELOW NORMAL
TUESDAY...WITH READINGS ONLY IN THE 60S TO LOWER 70S. THE UPPER
LEVEL LOW IS PROGGED TO SHIFT EAST WITH RIDGING BUILDING IN ON
WEDNESDAY...WITH RIDGING CONTINUING INTO FRIDAY. A WARMING TREND
WILL BEGIN AT THIS POINT...WITH HIGHS STILL BELOW SEASONAL AVERAGE
AT MID 70S TO AROUND 80 WEDNESDAY. HAVE ADDED SOME SLIGHT EVENING
POPS IN THE EAST WEDNESDAY...AS A WEAK WAVE PUSHES THROUGH THE
AREA TO INTERACT WITH PEAK DIURNAL HEATING...AND SIGNIFICANT SFC
WATER. DRYING CONDITIONS ARE EXPECTED...BUT THE AMOUNT OF
MOISTURE AVAILABLE ON THE GROUND CAUSES SOME CONCERN. HAVE OPTED
TO KEEP THURSDAY DRY WITH RIDGING IN CONTROL OVER THE REGION...BUT
WEAK WAVES CONTINUE THROUGH THE FLOW...AND RIDGE IS NOT VERY
STRONG. BRING SLIGHT MOUNTAIN POPS BACK THURSDAY NIGHT THROUGH
FRIDAY...AS RIDGE FLATTENS. ZONAL FLOW TAKES OVER LATE
FRIDAY...AND THERE WILL AGAIN BE SOME POTENTIAL FOR ISOLATED
SHOWERS AND THUNDERSTORMS THROUGH THE REMAINDER OF THE
PERIOD. TEMPS RETURN TO ABOUT SEASONAL AVERAGE ON THURSDAY...AND
CLIMBING SLIGHTLY ABOVE NORMAL FOR FRIDAY AND SATURDAY. DID PAIR
TEMPS BACK SLIGHTLY THROUGHOUT THE PERIOD...BUT STILL A GRADUAL
WARMUP. AAG
&&

.AVIATION...

WIDESPREAD RAINFALL...HEAVY AT TIME...IS EXPECTED TO CONTINUE
ACROSS THE REGION THROUGH THE NIGHT. ISOLATED THUNDERSTORMS ARE
OCCURRING IN SOUTHEASTERN MONTANA AS WELL. MVFR TO IFR CIGS WILL
CONTINUE TO BE COMMON...WITH LIFR TO VLIFR CONDITIONS IN HEAVIER
PRECIP...LOWERING CIGS AND FOG. GUSTY WINDS HAVE DEVELOPED THIS
AFTERNOON...WITH GUSTS TO 30KTS. WINDS ARE FROM THE WEST AND NORTHWEST
IN THE WESTERN ZONES...AND FROM THE EAST AND NORTHEAST IN THE EASTERN
ZONES. AREA MOUNTAINS WILL BE OBSCURED THROUGHOUT THE DAY. AAG


&&

.PRELIMINARY POINT TEMP/POPS...

    SUN     MON     TUE     WED     THU     FRI     SAT
-----------------------------------------------------------
BIL 047/062 047/066 050/071 050/080 057/085 061/087 061/085
    +6/W    11/E    22/T    11/U    01/U    11/U    22/T
LVM 046/063 042/066 045/071 045/081 051/084 051/086 053/085
    74/W    23/T    32/T    11/U    10/U    12/T    22/T
HDN 049/063 045/070 050/073 048/081 055/086 059/090 059/087
    +7/W    11/E    22/T    11/U    01/U    11/U    12/T
MLS 051/059 047/068 051/070 050/080 057/085 062/092 062/091
    +7/W    31/E    22/T    11/U    11/U    12/T    22/T
4BQ 050/061 046/068 052/069 048/079 056/085 060/091 062/091
    64/W    21/B    43/T    22/T    21/U    12/T    22/T
BHK 050/059 045/064 046/067 045/076 053/081 059/088 058/087
    66/W    31/E    34/T    22/T    21/U    12/T    22/T
SHR 046/063 044/068 048/070 045/079 051/085 055/091 056/088
    73/W    11/B    34/T    21/U    00/U    11/U    12/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...FLOOD WATCH IN EFFECT THROUGH SUNDAY AFTERNOON FOR ZONES
      30>33-35>37-58.
WY...NONE.

&&

$$
WEATHER.GOV/BILLINGS


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.