Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 041524
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
924 AM MDT FRI SEP 4 2015

.UPDATE...
LIGHT SHOWER ACTIVITY NEAR BAKER IS ABOUT TO EXIT OUR CWA AS
SHORTWAVE OVER THE NORTHERN PLAINS CONTINUES TO PUSH NORTHEAST.
AREAS OF RESIDUAL LOW CLOUD EXIST EAST OF HYSHAM AND ALSO IN
UPSLOPE AREAS OF OUR FAR WEST...AN INDICATION OF THE MOISTENING
OUR BOUNDARY LAYER HAS UNDERGONE OVER THE PAST 24 HOURS. OTHERWISE
QUIET WEATHER ACROSS THE AREA THIS MORNING. HAVE DROPPED EXPECTED
HIGH TEMPS TODAY JUST A BIT IN PLACES DUE TO CLOUD COVER. WARMEST
TEMPS /IN THE LOW TO MID 80S/ WILL BE IN OUR FAR EAST. WESTERN
FOOTHILLS WILL LIKELY STAY IN THE 60S TODAY.

MAIN BAROCLINIC ZONE ASSOCIATED WITH DEEP PACIFIC TROF WILL REMAIN
TO OUR WEST TODAY...SO PCPN CHANCES WILL BE TIED TO DIURNAL
DESTABILIZING AND WEAK SHORTWAVE EMBEDDED IN THE SW FLOW
ALOFT...WHICH WILL REACH OUR AREA BY LATE AFTERNOON AND EVENING.
HAVE PUSHED BACK POPS AT BILLINGS TIL AFTER 21Z...AND HAVE DRIED
OUT OUR EAST THIS AFTERNOON. BETTER CHANCE OF SHOWERS AND ISOLD
TSTMS ACROSS OUR CWA WILL BE AFTER 00Z. NO SEVERE WX ANTICIPATED
TODAY.

JKL

&&

.SHORT TERM...VALID FOR TDY AND SAT...

A DEEP UPPER TROUGH WAS POSITIONED OVER THE PACIFIC NORTHWEST
THIS MORNING. THIS TROUGH WILL BE THE WEATHER MAKER FOR THE
NORTHERN ROCKIES THE NEXT SEVERAL DAYS. SOUTHWEST FLOW ON THE
FRONT SIDE OF THE TROUGH HAS SENT SEVERAL DISTURBANCES INTO THE
FORECAST AREA OVERNIGHT FOR ROUNDS OF SHOWERS AND THUNDERSTORMS.
THE LAST OF THE STRONGER WAVES WAS MOVING THROUGH SOUTH CENTRAL
MONTANA THIS HOUR. WEAKER WAVES WERE PRESENT OVER NORTHERN
UTAH...BUT STRENGTH OF THIS WAVE DOES NOT APPEAR TO BE ENOUGH TO
OVERCOME CAPPING DUE TO LOW LEVEL NORTHEAST FLOW. THIS WILL LEAD
TO A DRY DAY FOR MOST OF THE DAY TODAY. A STRONGER WAVE DOES ROUND
THE TROUGH AND MOVE IN THIS EVENING AND THIS WILL GENERATE
SCATTERED SHOWERS AND THUNDERSTORMS.

THE UPPER TROUGH THEN KICKS NORTHEAST INTO NORTHERN MONTANA ON
SATURDAY. THIS WAS FARTHER NORTH THAN PREVIOUS RUNS AND THUS NOT
EXPECTING TREMENDOUSLY COOL WEATHER FOR SATURDAY. A POTENT
SHORTWAVE DOES RIP ACROSS THE FORECAST AREA SATURDAY AFTERNOON AND
EVENING FOR DYNAMIC ASCENT. CAP IN PLACE WITH COOL UPSLOPE LOW
LEVEL FLOW...BUT SHOULD SHOULD HAVE NO PROBLEM LIFTING THE
ATMOSPHERE ABOVE THE BOUNDARY LAYER AND TAPING INTO ELEVATED
INSTABILITY. MU CAPE GETS TO AROUND 1000J/KG FOR MOST OF THE
FORECAST AREA. EFFECTIVE BULK SHEAR WILL BE AROUND 45KTS...SO SOME
INGREDIENTS WILL BE IN PLACE FOR STRONG TO POSSIBLY SEVERE
THUNDERSTORMS. BOTH THE HI RES ARW AND NAM IGNITE STRONG STORMS
SOUTH TO SOUTHWEST OF BILLINGS LATE SATURDAY AFTERNOON. WILL KEEP
THE MENTION IN THE HWO. PRECIPITABLE WATERS OF AROUND 1 INCH WOULD
LEAD TO HEAVY RAIN. STORMS SHOULD BE MOVING AT A GOOD PACE WITH
500MB WINDS AT 50KTS...WHICH WOULD LIMIT THE FLASH FLOODING
THREAT. THAT BEING SAID...STORMS WILL PRODUCE VERY HEAVY RAIN AS
THEY MOVE THROUGH AND COULD PRODUCE WATER ISSUES FOR A BRIEF
PERIOD OF TIME.

THE SYSTEM KICKS NORTHEAST QUICKLY AND ENDS UP IN NORTH CENTRAL
MONTANA BY 12Z SUNDAY. THIS DRIES THE AREA IN SHORT ORDER...SO
LOWERED POPS OVERNIGHT SATURDAY NIGHT. WINDS WILL INCREASE AND
BECOME QUITE GUSTY SATURDAY NIGHT AS THE LOW DEEPENS OVER SOUTHERN
CANADA. 850-700MB WINDS WERE NOT AS STRONG THIS MODEL RUN WITH THE
SYSTEM MOVING FARTHER NORTH. 700MB TEMPERATURES WERE NOT AS COLD
THIS MODEL RUNS...SINCE THE UPPER TROUGH WAS FARTHER NORTH...BUT
STILL COLD ENOUGH FOR SNOW POTENTIAL OVER THE HIGHER PEAKS. THIS
SNOW CHANCE LOOKS LIMITED THOUGH AS THE LOW KICKS NORTHEAST SO
QUICKLY AND DRIES THE AREA OUT. TWH

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

THE LABOR DAY WEEKEND WILL END ON A COOLER...BUT LIKELY DRY TUNE.
THE 00 UTC GFS...ECMWF...AND GEM ALL AGREED ON A STRONG WESTERLY
/DOWNSLOPE/ FLOW DEVELOPING SUNDAY ON THE SOUTHERN FLANK OF THE
DEEP UPPER-LEVEL LOW THAT WILL BE SITUATED ACROSS SOUTHERN CANADA
BY THAT TIME. WE THEREFORE REDUCED POPS SIGNIFICANTLY SUNDAY AND
WENT WITH A DRY FORECAST IN MOST PLACES BY AFTERNOON. SUNDAY WILL
BE WINDY WITH SUSTAINED SPEEDS NEAR 30 MPH AND GUSTS AROUND 40 MPH
LIKELY BASED ON MEAN BOUNDARY LAYER WINDS OF 30 KT IN THE 00 UTC
MODEL GUIDANCE. THE WINDS WILL SETTLE DOWN CONSIDERABLY FOR LABOR
DAY AS THE GRADIENT RELAXES...BUT HIGHS ON BOTH SUNDAY AND MONDAY
WILL ONLY BE IN THE 60S F IN MOST LOWER-ELEVATION LOCATIONS.

HEADING INTO NEXT WEEK...IT APPEARS THAT WEAK 500-MB TROUGHING IS
GOING TO PREVAIL TUESDAY AND WEDNESDAY BEFORE HEIGHTS ALOFT BEGIN
TO MORE STEADILY REBOUND THURSDAY AND FRIDAY. THE RESULT WILL BE A
DISTINCT WARMING TREND WITH HIGHS INCREASING FROM AROUND 70 F ON
TUESDAY TO NEAR 80 F BY THURSDAY. THAT SCENARIO WAS WELL-CAPTURED
BY THE 00 UTC MULTI-MODEL CONSENSUS THAT WE USED TO BUILD THE
LONG TERM FORECAST. THAT GUIDANCE LED US TO A DRY FORECAST FOR
MOST PLACES AND DAYS NEXT WEEK AS WELL...THOUGH IF WEAK SHORTWAVE
IMPULSES ARRIVE IN THE MEAN TROUGH TUESDAY OR WEDNESDAY THERE MAY
BE SOME ISOLATED SHOWER ACTIVITY IN SPOTS THOSE DAYS. SCHULTZ

&&

.AVIATION...

MVFR CIGS PERSIST OVER EASTERN ROUTES THIS MORNING...INCLUDING
KBHK AND KMLS...BUT SHOULD BEGIN TO CLEAR BY LATE MORNING.
OTHERWISE...VFR CONDITIONS WILL PREVAIL TODAY WITH ONLY ISOLATED
SHOWERS AND THUNDERSTORMS THIS AFTERNOON AND EVENING. SHOWERS AND
THUNDERSTORM CHANCES...WITH LOCAL MVFR CONDITIONS...WILL INCREASE
SOMEWHAT AFTER 00 UTC. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY SAT     SUN     MON     TUE     WED     THU
-------------------------------------------------------
BIL 072 053/070 050/067 043/068 042/071 045/077 049/079
    2/T 34/T    72/T    01/B    11/B    11/B    11/U
LVM 069 046/071 043/064 036/067 036/071 040/076 044/080
    3/T 56/T    82/T    11/B    11/B    11/B    11/U
HDN 077 053/076 049/070 043/070 041/073 043/078 048/081
    1/B 33/T    62/T    01/B    11/U    11/B    11/U
MLS 079 059/079 053/068 044/069 042/072 045/077 049/080
    1/B 44/T    52/T    11/U    11/U    11/U    11/U
4BQ 082 060/083 054/069 046/069 045/071 047/076 050/079
    1/B 32/T    41/N    01/U    11/B    11/U    11/U
BHK 084 060/081 054/069 044/068 041/070 043/075 047/077
    2/W 44/T    52/T    01/U    11/U    11/U    11/U
SHR 081 052/080 047/070 040/070 038/072 039/077 043/080
    1/B 32/T    41/N    01/U    11/B    11/U    11/U

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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