Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 211441
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
841 AM MDT THU MAY 21 2015

.UPDATE...
JUST A FEW MINOR TWEAKS TO THE FORECAST FOR THE MORNING UPDATE.
REMOVED POPS FROM THE BIG HORNS FOR THE MORNING AND REDUCED THEM A
BIT ON THE EAST SECTIONS OF THE BEARTOOTHS. REST OF FORECAST IN
GOOD SHAPE. BT

&&

.SHORT TERM...VALID FOR TDY AND FRI...

WEAK FLOW ALOFT WITH DRIER AIR HAVING BEEN PUSHED INTO THE EASTERN
HALF OF THE AREA BY A CUTOFF RIDGE OVER SOUTHERN CANADA. LOW ALONG
THE CALIFORNIA COAST IS GOING TO DIG A BIT MORE THAN PREVIOUSLY
EXPECTED TODAY AND THIS MEANS THE REGION WILL SEE ONLY AN
INCREMENTAL CHANGE IN THE WEATHER. MOST OF THE REGION WILL BE DRY
BUT ENOUGH MOISTURE WILL BE PUSHED INTO THE SOUTHWEST MOUNTAINS
FOR LOW CHANCE OF SHOWERS. DID LOWER POPS FOR THE FOOTHILLS LATE
TODAY AND OVERNIGHT AS GFS AND ECMWF INDICATE THE MOISTURE WILL
UNLIKELY TRAVEL OFF OF THE HIGHER TERRAIN. OVER THE PLAINS LOW
LEVEL FLOW REMAINS EASTERLY BUT DOES TREND A BIT TOWARDS
SOUTHEASTERLY WHICH WILL WEAKEN THE UPSLOPE COMPONENT A BIT AND
SUPPORT WARMER TEMPERATURES.

FRIDAY THE UPPER LOW MOVES ACROSS CALIFORNIA TOWARDS THE SOUTHERN
GREAT BASIN AND STRONGER MID LEVEL WINDS TRANSLATING DOWNSTREAM
CAUSE FALLING SURFACE PRESSURES ALONG THE COLORADO FRONT RANGE.
WHILE FLOW ALOFT OVER MONTANA AND NORTHERN WYOMING REMAIN WEAK
MOISTURE IS MOVING NORTHWARD ESPECIALLY AS THE CANADIAN RIDGE
LOSES THE ABILITY TO PUSH DRIER AIR OUT INTO THE AREA.
PRECIPITABLE WATERS INCREASING WILL SUPPORT BETTER MOISTURE FOR
DEEP CONVECTION WITH THE TEMPERATURES WARMING UP INTO THE 70S.
EXPECT SHOWERS AND THUNDERSTORMS TO MOVE OFF OF THE HIGHER
TERRAIN...ESPECIALLY AS A WEAK LOBE OF ENERGY MOVES THROUGH THE
AREA FRIDAY NIGHT. DID RAISE POPS OVER SOUTHEAST MONTANA TO
INDICATE BETTER CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORMS.
BORSUM

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

KEPT THE EXISTING LONG TERM FORECAST IN TACT AND JUST MADE SOME
SMALL ADJUSTMENTS HERE AND THERE TO POPS. THE MAIN FOCUS WAS TO
BUMP POPS UP OVER THE EAST FOR SATURDAY NIGHT THROUGH THE DAY
SUNDAY. MODELS WERE CONSISTENTLY BRINGING THE NORTHERN PART OF A
STRETCHED OUT UPPER LOW INTO NORTHEAST WYOMING SATURDAY NIGHT AND
SLOWLY TRACKING INTO NORTHEAST INTO NORTH DAKOTA ON SUNDAY.
PERSISTENT EAST TO SOUTHEAST SURFACE WINDS WILL ALLOW PRECIPITABLE
WATER AMOUNTS OF AROUND AN INCH TO MOVE INTO SOUTHEAST MONTANA.
ATMOSHPERE NOT EXPECTED TO BE TERRIBLY UNSTABLE...BUT WITH DEEP
MOISTURE AND WEAK STEERING WINDS...COULD HAVE SHOWERS WITH HEAVY
RAIN.

THE NEXT SYSTEM TO IMPACT THE AREA WILL BE ON TUESDAY. AN UPPER
LOW OVER WESTERN BRITISH COLUMBIA DROPS SOUTHEAST INTO WASHINGTON
ON MONDAY. ENERGY OUT AHEAD OF THIS LOW WILL KICK ACROSS WESTERN
AND CENTRAL ZONES ON TUESDAY. BOTH ECMWF AND THE GFS WERE SHOWING
THIS. THIS WILL LIKELY BE THE BEST CHANCE OF GETTING SHOWERS INTO
THE BILLINGS AREA. SHOWERS OVER THE WEEKEND WILL LIKELY BE TIED TO
THE TERRAIN AND WEAK STEERING WINDS WILL CAUSE TROUBLE FOR THE
SHOWERS IN THEIR ATTEMPT TO MOVE OFF THE FOOTHILLS. TEMPERATURES
WILL BE SEASONAL WITH LOW LEVEL EAST WINDS. TWH
&&

.AVIATION...

CLOUDS WILL INCREASE OVER THE SOUTHWEST MOUNTAINS TODAY WITH A
WEAK SYSTEM IN SOUTHERN IDAHO SLOWLY APPROACHING WESTERN MONTANA.
A FEW SHOWERS WILL DEVELOP OVER THE BEARTOOTH/ABSAROKA MOUNTAINS
BY EARLY AFTERNOON. CONDITIONS WILL REAMIN VFR...BUT LOCAL MVFR
CONDITIONS ARE POSSIBLE IN HEAVIER SHOWERS FROM KLVM SOUTHWARD.
MOUNTAINS WILL BE PARTIALLY OBSCURED...ESPECIALLY THIS AFTERNOON
IN SHOWERS. TWH/AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY FRI     SAT     SUN     MON     TUE     WED
-------------------------------------------------------
BIL 067 044/071 046/064 045/062 045/070 048/069 048/070
    0/B 02/T    43/T    33/T    32/T    23/T    33/T
LVM 064 040/067 043/062 042/062 039/067 043/065 042/069
    2/T 24/T    44/T    43/T    33/T    34/T    44/T
HDN 070 044/073 045/066 045/063 045/071 048/071 047/073
    0/U 02/T    33/T    33/T    32/T    23/T    33/T
MLS 070 045/072 046/065 047/063 047/069 048/071 049/072
    0/U 02/T    23/T    44/T    43/T    22/T    23/T
4BQ 067 043/068 044/061 047/059 044/067 046/069 047/069
    0/U 02/T    24/T    56/T    43/T    23/T    33/T
BHK 068 041/068 042/060 045/060 044/065 044/069 045/067
    0/U 01/N    24/T    56/T    55/T    32/T    33/T
SHR 064 041/065 041/060 043/058 040/067 043/066 043/068
    0/B 13/T    34/T    44/T    32/T    24/T    43/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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