Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 131504
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
904 AM MDT SUN JUL 13 2014

.UPDATE...
MINOR TWEAK TO CURRENT FORECAST THIS MORNING. PUSHED BACK
ISOLATED POPS OVER THE SOUTHWEST MOUNTAINS UNTIL LATE MORNING. A
WEAK DISTURBANCE WILL MOVE THROUGH AN AMPLIFIED RIDGE OF HIGH
PRESSURE OVER WESTERN MONTANA. THIS WAVE ALONG WITH OROGRAPHIC
LIFT WILL BRING A FEW ISOLATED STORMS TO THE SOUTHWEST MOUNTAINS
LATE MORNING THROUGH EARLY THIS EVENING. THE PLAINS WILL REMAIN
DRY WITH STRONG SUBSIDENCE OVER THE REGION. TEMPERATURE FORECAST
FOR TODAY ON TRACK BASED ON CURRENT 12Z GUIDANCE AND NO CHANGES
MADE. RICHMOND

&&

.SHORT TERM...VALID FOR TDY AND MON...

THE WEATHER WILL REMAIN QUIET FOR AT LEAST THE NEXT 36 HOURS WITH
ISOLATED SHOWERS AND STORMS CONFINED TO THE MOUNTAINS TODAY...AND
THE NEXT CHANCE OF MOISTURE FOR THE LOWER ELEVATIONS ACROSS SOUTH
CENTRAL MT NOT ARRIVING UNTIL MON EVENING. LARGE-SCALE FLOW ALOFT
WILL BE VERY AMPLIFIED OVER THE LOWER 48 THE NEXT FEW DAYS WITH A
UNSEASONABLY DEEP 500-MB LOW DROPPING INTO THE MIDWEST AND A MORE
SUMMER-LIKE SUBTROPICAL RIDGE CENTERED OVER THE GREAT BASIN. THIS
ALLOWS SOME COLD AIR ADVECTION TO TAKE PLACE ALOFT OVER SOUTHEAST
MT TODAY...WITH MIXING TO 700 MB PER FORECAST SOUNDINGS PROVIDING
FOR HIGHS ONLY IN THE UPPER 70S F IN PLACES LIKE BAKER WHILE MOST
OF THE REST OF THE AREA REACHES WELL INTO THE 80S F AGAIN. MIXING
WILL BE SIGNIFICANTLY LESS BY MON WHEN LOW-LEVEL EASTERLY FLOW IS
WELL-ESTABLISHED...MAKING FOR A COOLER DAY EVERYWHERE.

THE 00 UTC CONVECTION-ALLOWING MODEL GUIDANCE SUGGESTS ANY SHOWER
AND STORM ACTIVITY TODAY WILL BE LIMITED TO THE MOUNTAINS AND DIE
OFF QUICKLY EARLY THIS EVENING. FORECAST SOUNDINGS ARE SUPPORTIVE
OF THAT IDEA WITH NON-EXISTENT INSTABILITY OVER THE PLAINS TODAY.
THAT IS TIED TO A SUBSIDENCE INVERSION ABOVE 700 MB. CAPPING WILL
BE EVEN MORE PREVALENT MON...AND THE NON-NAM 00 UTC MODELS DO NOT
SUPPORT THE APPROACH OF A SHORTWAVE TROUGH UNTIL MON EVENING...SO
WE CHOSE TO PUSH BACK THE ARRIVAL OF CONVECTIVE CHANCES OVER PART
OF SOUTH CENTRAL MT LIKE AT BILLINGS UNTIL AFTER MIDNIGHT. MODELS
ARE CONSISTENT IN ADVERTISING PRECIPITABLE WATER VALUES RISING TO
AROUND AN INCH MON NIGHT OVER SOUTH CENTRAL MT WHEN THE WAVE DOES
APPROACH...SO SOME CONVECTIN IS CERTAINLY POSSIBLE THEN. NOTE THE
00 UTC NAM TIMING WAS SET ASIDE BECAUSE IT IS AN OUTLIER AND FAST
TIMING OF WAVES IS A TYPICAL BIAS OF THAT MODEL. SCHULTZ

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

MODELS HAVE COME INTO BETTER AGREEMENT THROUGH THE UPCOMING WEEK
BUT BIG DIFFERENCES REMAIN FOR THE END OF THE WEEK AND INTO THE
WEEKEND. THE ECMWF WAS THE MODEL THAT HAS DIVERGED THE MOST FROM
ITS PREVIOUS SOLUTION...ESPECIALLY FOR THE WEEKEND AND INTO EARLY
NEXT WEEK...SO WILL CONTINUE TO LEAN ON THE GFS FOR THE FORECAST
DETAILS.

TUESDAY WILL BE THE COOLEST DAY WITH HIGHS BEING HELD IN THE
UPPER 70S TO LOWER 80S WITH PERSISTENT EAST TO NORTHEAST LOW LEVEL
WINDS KEEPING 850MB TEMPERATURES DOWN. CLOUD COVER WILL SERVE TO
SUPPRESS SUNSHINE WITH SHORTWAVE ENERGY CRUISING THROUGH THE
FORECAST AREA. PRECIPITABLE WATER FORECAST VALUES HAVE BEEN
CONSISTENTLY RISING FOR TUESDAY AND NOW WERE UPWARDS OF AN
INCH...SO DO EXPECT SHOWERS AND THUNDERSTORMS...WITH LOCALLY HEAVY
RAIN A STRONG POSSIBILITY.

DRIED OUT WEDNESDAY AS THE SHORTWAVE ENERGY WAS PROGGED TO
PROGRESS QUICKLY TO THE SOUTH. THIS IS THE SOLUTION FROM ALL
MODELS...SO FELT COMFORTABLE DROPPING POPS. THURSDAY AND FRIDAY
WILL BE WARMER WITH MID LEVEL DOWNSLOPE FLOW INCREASING WITH A
BRITISH COLUMBIA UPPER TROUGH DROPPING INTO NORTHERN IDAHO.
LOWERING HEIGHTS WILL ALLOW FOR INCREASING THUNDERSTORM CHANCES
AND DID RAISE POPS FOR THIS. THE TROUGH IS PROGGED TO SLICE
THROUGH THE AREA BY SATURDAY AND WOULD EXPECT COOLER AND DRIER AIR
TO START THE WEEKEND. TWH
&&

.AVIATION...

ISOLATED THUNDERSTORMS ARE POSSIBLE OVER THE MOUNTAINS AGAIN THIS
AFTERNOON AND EVENING. OTHERWISE...DRY WEATHER IS EXPECTED WITH
VFR FLYING CONDITIONS ACROSS THE REGION. TWH

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY MON     TUE     WED     THU     FRI     SAT
-------------------------------------------------------
BIL 088 058/081 056/079 056/087 058/093 060/090 059/084
    0/U 00/B    22/T    22/T    12/T    23/T    32/T
LVM 089 052/083 052/078 050/084 053/089 054/086 052/081
    0/U 02/T    33/T    33/T    13/T    33/T    32/T
HDN 089 055/082 054/082 056/087 059/094 061/092 061/086
    0/U 00/U    22/T    22/T    12/T    23/T    32/T
MLS 085 053/077 054/081 056/086 060/093 063/093 063/087
    0/U 00/U    01/U    11/U    12/T    22/T    22/T
4BQ 085 053/077 053/078 055/084 059/091 062/093 062/085
    0/U 00/U    02/T    22/T    11/U    12/T    23/T
BHK 079 047/071 047/076 052/081 057/088 060/090 061/083
    0/U 00/U    01/U    11/U    11/U    12/T    23/T
SHR 085 052/080 052/075 051/080 054/088 057/089 057/082
    0/U 00/U    23/T    32/T    12/T    22/T    22/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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