Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 262121
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
321 PM MDT WED AUG 26 2015

.SHORT TERM...VALID FOR THU AND FRI...

THROUGH THE REMAINDER OF THIS AFTERNOON SHOWERS AND THUNDERSTORMS
WILL BEGIN TO FORM MOSTLY SOUTH OF A LINE FROM BROADUS TO BILLINGS
TO LIVINGSTON. THIS DEVELOPMENT IS ASSOCIATED  WITH MONSOONAL
MOISTURE AND AN UPPER LEVEL DISTURBANCE ROUNDING THE RIDGE AXIS
CURRENTLY OVER US. SOME STRONG STORMS ARE POSSIBLE THIS
EVENING...BUT THIS WILL BE CONFINED TO EXTREME SOUTHEAST MONTANA.
SO FAR THIS AFTERNOON CLOUDS HAVE KEPT HIGH TEMPERATURES LOWER
AND HELPED KEEP SOUTHERN LOCATIONS FROM BECOMING MORE UNSTABLE. IN
ADDITION...MID-LEVEL TEMPERATURES ARE NOT VERY FRIENDLY FOR
CONVECTION AT THIS TIME. WATER VAPOR LOOPS SHOW MORE MOISTURE
MOVING IN FROM THE SOUTHWEST SO HAVE NOT LOWERED POPS AS MOST OF
THE GUIDANCE STILL DEVELOPS SHOWERS AND THUNDERSTORMS FAIRLY LATE
THIS EVENING...AFTER 6PM. THIS ACTIVITY SHOULD MOVE EAST OVER
NIGHT AS THE ENERGY ALOFT ROTATES AROUND THE RIDGE AXIS.

FOR TOMORROW AFTERNOON THE BROAD LONGWAVE TROUGH OVER THE
NORTHEASTERN PACIFIC OCEAN WILL SLOWLY SHIFT EAST AND HELP LOWER
HEIGHTS OVER THE AREA TOMORROW. THIS WILL ALLOW SOME BETTER LAPSE
RATES AND COOLER 700MB TEMPERATURES TO MOVE IN GIVING MOST OF THE
AREA A BETTER CHANCE FOR SHOWERS AND THUNDERSTORMS. PWATS SHOULD
ALSO INCREASE COMPARED TO WEDNESDAYS VALUES PROVIDING US WITH
BETTER INSTABILITY. SREF GUIDANCE SUGGESTS GOOD PROBABILITIES OF
SURFACE CAPES IN THE VICINITY OF 1000 J/KG FOR MOST LOCATIONS SO
STORMS ARE POSSIBLE. A FEW COULD BE STRONG. HOWEVER...SHEAR
REMAINS WEAK AND ONLY AROUND 10 OR 15 KNOTS SO SEVERE STORMS ARE
NOT ANTICIPATED. THROUGH THE LATE AFTERNOON BETTER CHANCES FOR
THUNDERSTORMS MOVE EAST AS THE ENERGY ALOFT MOVES EAST.

FOR FRIDAY AFTERNOON SHORTWAVE RIDGING IN ADVANCE OF SATURDAYS
COLD FRONT...AND THE ABSENCE OF MONSOONAL MOISTURE...SHOULD ALLOW
TEMPERATURES TO WARM AND CUT OFF THE CHANCES FOR RAIN UNTIL
WEEKEND. SOME PERIODS OF WESTERLY WINDS COULD ALLOW AREAS OF SMOKE
TO RETURN TO THE FORECAST BUT WILL WAIT UNTIL WE GET CLOSER TO ADD
SMOKE TO THE GRIDS. DOBBS/SINGER

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

THE GFS AND ECMWF SHOWED GOOD AGREEMENT THROUGH SUN
MORNING...LENDING HIGHER CONFIDENCE TO THE FORECAST...REINFORCED BY
THE LOW SPREAD IN GFS AND ECMWF ENSEMBLES UNTIL SUNDAY AFTERNOON.

SW FLOW WILL GRADUALLY OVERTAKE THE REGION ON SAT AS UPPER RIDGING
SHIFTS OFF TO THE EAST. THE COLD FRONT SHOULD PUSH EAST A BIT
LATER INTO THE AREA THEN PREVIOUSLY FORECAST...PASSING THROUGH NO
LATER THAN 12Z SUNDAY MORNING WITH LOW CHANCES FOR SHOWERS AND
THUNDERSTORMS IN CENTRAL AND WEST PORTIONS. IT WILL BE HOT AND
DRY AHEAD OF THE FRONT ON SAT...BUT WINDS WILL NOT BE OVERLY
STRONG SO NOT TOO CONCERNED ABOUT FIRE WEATHER AT THIS TIME...WITH
ONLY LOW POPS LIMITED TO MOUNTAINS AND NEARBY FOOTHILLS.

ON SUN AFTERNOON THROUGH WED...THE GFS AND EURO MAINTAIN SW FLOW
OVER THE AREA...WITH VERY WEAK SHORTWAVE IMPULSES AVAILABLE TO
SUPPORT LIMITED INSTABILITY MONDAY AND TUESDAY AFTERNOONS NEAR
BEARTOOTHS AND FOOTHILLS.

SAT WILL BE THE HOTTEST DAY OF THE PERIOD AHEAD OF THE COLD
FRONT..WITH TEMPS IN THE UPPER 90S OUT IN EASTERN PORTIONS. HIGHS
WILL BE IN THE MID TO LOW 80S THE REST OF THE PERIOD.
MROWELL/SINGER

&&

.AVIATION...

VFR CONDITIONS SHOULD DOMINATE MOST TERMINALS BUT THERE WILL BE A
SLIGHT CHANCE OF THUNDERSTORMS IN FAR SOUTHEAST MT INTO THE
EVENING... WITH INCREASED PRECIPITATION COVERAGE BY 02Z
TONIGHT...INCLUDING AROUND KSHR. LOCALIZED MVFR CONDITIONS ARE
POSSIBLE WITH THE THUNDERSTORMS...WITH AREAS OF MOUNTAIN
OBSCURATION. THE SLIGHT CHANCE OF THUNDERSTORMS WILL SPREAD TOWARD
THE NORTHEAST THIS EVENING TO INCLUDE AREAS NEAR OR SOUTH OF
KMLS. MVFR TO IFR CONDITIONS ARE POSSIBLE IN THE AREAS OF
INCREASED PRECIPITATION OVERNIGHT NEAR KSHR WHICH SHOULD CLEAR BY
LATE MORNING. MROWELL/SINGER

&&

.PRELIMINARY POINT TEMP/POPS...

    THU     FRI     SAT     SUN     MON     TUE     WED
-----------------------------------------------------------
BIL 064/090 060/089 062/095 063/083 057/083 053/082 053/082
    23/T    31/B    11/B    12/T    21/B    11/U    11/B
LVM 056/085 053/084 056/089 054/080 050/080 045/079 047/080
    34/T    31/B    11/B    12/T    22/T    11/B    11/B
HDN 063/093 058/091 060/097 062/088 056/085 052/084 052/085
    23/T    31/B    01/B    12/T    22/T    11/U    10/B
MLS 066/092 062/092 064/098 065/088 060/086 055/085 054/084
    12/T    21/B    00/B    01/B    11/B    11/U    11/U
4BQ 063/087 058/091 061/097 062/087 058/086 055/084 055/085
    33/T    21/B    00/U    01/B    11/B    11/U    11/B
BHK 061/086 058/092 061/095 062/088 057/086 054/083 053/085
    22/T    11/B    00/U    01/B    11/B    11/B    11/U
SHR 059/085 054/084 055/093 057/087 053/085 050/083 049/083
    33/T    31/B    10/U    21/B    11/B    11/U    11/U

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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