Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 022105
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
305 PM MDT SUN AUG 2 2015

.SHORT TERM...VALID FOR MON AND TUE...

WARM AND DRY WEATHER WILL CONTINUE THROUGH MONDAY...AND THEN THE
CHANCE OF SHOWERS AND STORMS WILL INCREASE SIGNIFICANTLY TUESDAY.

TONIGHT...EASTERLY FLOW WILL BE IN PLACE UNDER RIDGING ALOFT AND
THAT WILL MAKE FOR A DRY AND QUIET NIGHT WITH LOWS OF 55 TO 65 F.

MONDAY...WINDS WILL REMAIN EASTERLY AND THAT WILL LIMIT MIXING TO
AN EXTENT. EVEN SO...HIGHS ARE STILL FORECAST TO BE IN THE UPPER
80S TO LOWER 90S F PER THE 12 UTC MULTI-MODEL CONSENSUS WHICH WAS
USED TO BUILD THE FORECAST. FORECAST SOUNDINGS SUGGEST A STRONGLY
CAPPED AIR MASS OVER THE LOWER ELEVATIONS AND SO ANY CONVECTION
DURING THE AFTERNOON WILL BE RELEGATED TO THE HIGHER TERRAIN. WE
DID LEAVE LOW-END POPS IN THE FOOTHILLS FROM LIVINGSTON SOUTHEAST
TO RED LODGE AFTER 18 UTC TOO...BUT CONFIDENCE IN ANYTHING COMING
OFF OF THE MOUNTAINS BEFORE EVENING IS LOW.

MONDAY NIGHT...LOW POPS ARE IN PLAY ACROSS MOST OF THE AREA AS A
SHORTWAVE TROUGH APPROACHES THE AREA FROM THE SOUTHWEST. THERE/S
NOT MUCH...IF ANY...QPF SIGNAL IN THE 12 UTC MODEL GUIDANCE OVER
THE PLAINS. HOWEVER...WE FELT THAT AT LEAST A LOW PROBABILITY OF
SHOWERS AND STORMS WAS NECESSARY IN MOST PLACES OVERNIGHT AS A 30
TO 40 KT SOUTHEASTERLY LOW-LEVEL JET DEVELOPS ACROSS THE AREA IN
TANDEM WITH MODEST ELEVATED CAPE PER MODEL-FORECAST SOUNDINGS.

TUESDAY...WE HAVE HIGH-END /50 TO 70 PERCENT/ POPS MOVING WEST TO
EAST ACROSS THE AREA TUESDAY AND TUESDAY EVENING...FOLLOWING A
SHORTWAVE TROUGH AND MONSOONAL MOISTURE PLUME. PRECIPITABLE WATER
VALUES ARE FORECAST TO RISE ABOVE AN INCH AND IF THE 12 UTC NAM
IS RIGHT THEY WILL BE CLOSE TO 1.50 INCHES IN SOUTHEASTERN MT BY
TUESDAY AFTERNOON...SO ANY CONVECTION WILL BE EFFICIENT AT MAKING
WETTING AND LOCALLY HEAVY RAINFALL. THE TIMING AND TRACK OF THE
SHORTWAVE IS STILL SOMEWHAT UNCERTAIN GIVEN RATHER WEAK KINEMATICS
OWING TO ITS RIDGE-UNDERCUTTING NATURE...SO FORECAST DETAILS COULD
CHANGE BY TUESDAY. HOWEVER...RIGHT NOW IT APPEARS CONVECTION WILL
BE MOST VIGOROUS OVER SOUTHEASTERN MT WHERE EARLY-DAY HEATING IS
MOST LIKELY TO CONTRIBUTE TO MLCAPE OVER 1000 J/KG. THE DEEP-LAYER
SHEAR IS FORECAST TO GENERALLY BE UNDER 25 KT THOUGH...SO THERE/S
LITTLE APPARENT RISK OF BONAFIDE SEVERE STORMS AT THIS JUNCTURE.
CLOUDS AND SHOWERS WILL KEEP SOUTH CENTRAL MT MUCH COOLER TUESDAY
AS WELL...BUT HIGHS WELL INTO THE 80S F ARE POSSIBLE FURTHER EAST
IF THE SHORTWAVE ARRIVES THERE LATE ENOUGH IN THE DAY. SCHULTZ

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

FAIRLY ACTIVE WEATHER LOOKS TO CONTINUE THROUGH THE EXTENDED
PERIOD. TUESDAY SHORTWAVE WILL DEPART TO THE DAKOTAS BY EARLY
WEDNESDAY...BUT MORE ENERGY COMING OUT OF THE NORTHERN GREAT BASIN
WILL LIFT INTO OUR REGION BY LATE AFTERNOON AND WEDNESDAY NIGHT.
PWATS WILL REMAIN SEASONABLY HIGH AND WOULD EXPECT ANOTHER ROUND
OF SHOWERS AND TSTMS. 0-6KM BULK SHEAR VALUES NEAR 30 KTS COULD
SUPPORT SOME STRONGER STORMS IN OUR EAST. WE WILL BEGIN TO PULL
DRIER AIR IN FROM THE WEST IN THE WAKE OF THIS SHORTWAVE ON
THURSDAY...SO WILL KEEP HIGHEST POPS IN OUR EAST NEAR CONVERGENT
SFC TROF. IT SHOULD BE NOTED THAT THE ECMWF/UKMET HAVE TRENDED
FURTHER SOUTH WITH SW CANADA LOW AND SHOW LOWER HEIGHTS THAN THE
GFS INTO FRIDAY. THIS WOULD PROBABLY TRANSLATE TO INCREASED WIND
POTENTIAL FOR OUR CWA...BUT HAVE ALSO KEPT WITH SOME SLIGHT POPS
LATE THURSDAY AND AGAIN IN SOME AREAS FRIDAY. GENERALLY SPEAKING
THIS SHOULD BE THE DRIEST PART OF THE EXTENDED PERIOD. BY SATURDAY
WE BEGIN TO SEE THE IMPACTS FROM NEXT TROF LIFTING OUT OF THE
GREAT BASIN WITH GOOD AGREEMENT BETWEEN THE GFS AND ECMWF. WITH
CONFIDENCE HAVE RAISED POPS FOR NEXT WEEKEND.

TEMPERATURES FROM WEDNESDAY THROUGH NEXT SUNDAY SHOULD REMAIN NEAR
OR SLIGHTLY BELOW NORMAL...WITH HIGHS MOSTLY IN THE 80S...AND
POTENTIAL FOR 70S NEXT WEEKEND DEPENDING ON FATE OF DAYS 6-7 TROF.

JKL

&&

.AVIATION...

VFR CONDITIONS WILL PREVAIL TONIGHT AND MONDAY AS THE REGION
REMAINS UNDER THE INFLUENCE OF STRONG HIGH PRESSURE ALOFT. EXPECT
EASTERLY SFC WINDS OF LESS THAN 20 KTS. THE POTENTIAL FOR TSTMS
WILL INCREASE OVER THE MOUNTAINS AND FOOTHILLS BY LATE TOMORROW
AFTERNOON. JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    MON     TUE     WED     THU     FRI     SAT     SUN
-----------------------------------------------------------
BIL 060/093 063/079 057/085 058/086 058/086 059/085 059/084
    01/U    25/T    43/T    42/T    21/B    13/T    33/T
LVM 054/090 058/077 052/083 052/084 051/085 053/083 052/081
    02/T    35/T    34/T    42/T    21/B    13/T    33/T
HDN 058/095 062/082 055/086 055/086 056/087 056/088 056/086
    01/U    26/T    43/T    42/T    21/B    12/T    33/T
MLS 060/094 065/087 060/084 057/084 058/086 059/088 060/086
    00/U    26/T    72/T    44/T    22/T    22/T    33/T
4BQ 058/092 062/084 058/081 057/081 058/087 058/086 059/085
    00/U    26/T    62/T    44/T    32/T    12/T    33/T
BHK 056/088 060/085 058/079 055/078 056/084 056/085 058/084
    00/U    14/T    73/T    44/T    32/T    22/T    34/T
SHR 055/091 058/074 053/083 053/083 053/086 054/085 053/084
    01/B    36/T    43/T    32/T    21/B    12/T    33/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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