Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 271506
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
906 AM MDT WED MAY 27 2015

.UPDATE...
SLOW MOVING UPPER LOW REMAINS OVER NORTHERN ID. WEAK SHORTWAVE
MOVING INTO EASTERN MT IN SW FLOW ALOFT IS PRODUCING AN AREA OF
SHOWERS WITH A FEW EMBEDDED LIGHTNING STRIKES EAST OF BILLINGS...
GETTING INTO MILES CITY AS OF 9 AM. MID LEVEL FLOW IS VEERING
WESTERLY WITH SUBSIDENCE SPREADING OFF OUR FOOTHILLS IN THE WAKE
OF THIS ENERGY...SO SHOWERS ARE UNDERGOING A DIMINISHING TREND
ACROSS OUR WEST. HAVE ADJUSTED POPS THROUGH THE REMAINDER OF THE
MORNING PER THESE TRENDS. LIKELY POPS ACROSS OUR EAST THIS AFTN
LOOK GOOD. FOR OUR FAR WEST...WE WILL SEE A BREAK INTO THE EARLY
AFTN BUT WOULD EXPECT DIURNAL DEVELOPMENT WITH CONVECTIVE TEMPS IN
THE UPPER 60S TO AROUND 70...UNDER PERSISTENT DIFFLUENT FLOW ALOFT
ASSOCIATED WITH LOW TO OUR WEST. WILL KEEP LIKELY POPS ALSO IN OUR
FAR WEST THIS AFTN. AS FOR BILLINGS...AFTER THE FEW MORNING
SHOWERS MOVE OUT OVER THE NEXT 1-2 HOURS...WE COULD SEE A BREAK
UNTIL 02-03Z GIVEN PERIOD OF SUBSIDENCE...BUT PER THE CYCLONIC
FLOW ALOFT AND ACHIEVABLE CONVECTIVE TEMPS CANNOT RULE OUT AT
LEAST ISOLD SHOWERS AND TSTMS AFTER 21Z OR SO. ANY CONVECTION
TODAY SHOULD STAY NON-SEVERE PER THE WEAK SHEAR AND MODEST CAPE
VALUES. RISKS WILL BE LOCALLY HEAVY RAIN AND SMALL HAIL.

&&

.SHORT TERM...VALID FOR TDY AND THU...

A SLOW MOVING UPPER LOW WAS POSITIONED OVER NORTHERN IDAHO THIS
MORNING. MODELS DROP THIS SYSTEM INTO NORTHEAST IDAHO BY THIS
EVENING. THIS PROCESS WILL PROVIDE UPPER DIFFLUENT FLOW OVER THE
FORECAST AREA TODAY WITH WEAK WAVES KICKING OUT FROM THE LOW.
MODELS WERE IN GOOD AGREEMENT ON GENERAL POSITION OF THE LOW TODAY
AND TONIGHT BUT DIFFER SOME ON PLACEMENT OF WAVES KICKING OFF THE
LOW. THE ECMWF PUSHES A WAVE OUT THIS AFTERNOON WITH SUBSIDENCE
THIS EVENING OVER THE CENTRAL ZONES. THE GFS WAS EARLIER WITH THE
INITIAL WAVE AND BRINGS ANOTHER WEAK WAVE BACK IN THIS EVENING FOR
MORE SHOWER DEVELOPMENT. HAVE SIDED WITH THE GFS BASED ON ACTIVITY
ALREADY MOVING INTO SOUTHWEST MONTANA AS OF THIS WRITING.
CAPE...LIKE YESTERDAY...WAS DEEP BUT THIN ON BUFKIT SOUNDINGS.
THIS WILL LEAD TO SIMILAR CONVECTION TO YESTERDAY WITH SLOW MOVING
CELLS WITH SOMEWHAT LOW FREEZING LEVELS. EXPECT PULSING CELLS WITH
POSSIBLY SMALL HAIL. LOCALLY HEAVY RAIN AGAIN EXPECTED WITH WEAK
STEERING WINDS.

SHOWER ACTIVITY WILL CONTINUE TONIGHT WITH PERSISTENT DIFFLUENT
FLOW. INSTABILITY WILL WANE SOME WITH NIGHT TIME COOLING...BUT
ENOUGH ASCENT TO KEEP SCATTERED SHOWERS IN PLACE. THE UPPER LOW
MOVES INTO NORTHWEST WYOMING ON THURSDAY. THIS POSITION WILL ALLOW
FOR DEEPER UPSLOPE FLOW TO DEVELOP AND THUS WILL GIVE THE AREA THE
BEST CHANCE OF PRECIPITATION. THIS WILL BE THE TIME THAT SHOWERS
WILL ALIGN OVER THE EAST SLOPES...INCLUDING THE BIGHORNS INTO
SHERIDAN COUNTY. A HALF INCH TO THREE QUARTERS OF AN INCH OF
ADDITIONAL RAINFALL IS POSSIBLE ON THURSDAY...WITH LOCALLY HIGHER
AMOUNTS NOT OUT OF THE QUESTION. THIS ADDITIONAL RAIN WILL
CERTAINLY SLOW RECEDING WATER LEVELS ON AREA RIVERS...IF NOT
CONTINUE ONGOING FLOODING IN SHERIDAN COUNTY. TWH

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

FRIDAY INTO SATURDAY WILL BE DOMINATED BY A FLAT RIDGE. THIS
WESTERLY FLOW WILL GENERALLY HELP TO REDUCE THE RAIN CHANCES
ACROSS MUCH OF THE AREA OUTSIDE OF THE MOUNTAINS. OFFSETTING THIS
WILL BE SOME INSTABILITY PRODUCED AS A LOW OVER ALBERTA SLOWLY
MOVES EAST. TEMPERATURES WILL BE COOLER FOR FRIDAY AS SOME
CANADIAN AIR WORKS ITS WAY INTO THE AREA AS A QUICK CLIPPER MOVES
ACROSS THE NORTHERN PLAINS.

THROUGH THE WEEKEND...TEMPERATURES WILL BE WARMING WITH HIGH
TEMPERATURES SUNDAY AND MONDAY REACHING NEAR 80 DEGREES. THIS
WARMING TREND WILL BE AIDED BY COMPRESSIONAL WARMING AHEAD OF THE
APPROACHING LOW OVER THE PACIFIC NORTHWEST. BY SUNDAY FLOW WILL
START TO BECOME SOUTHWESTERLY AS THE LOW MOVES EAST...AND WILL
MORE SOUTHWESTERLY FOR THE START TO THE WORK WEEK. SURFACE WINDS
WILL BECOME MORE EASTERLY HELPING TO BRING IN MORE MOISTURE. THE
AREA WILL SEE CAPE VALUES AND DEEP SHEAR INCREASING EARLY NEXT
WEEK...GIVING BETTER CHANCES FOR STRONGER CONVECTION. REIMER
&&

.AVIATION...

SHOWERS AND THUNDERSTORMS WILL INCREASE INTO THIS AFTERNOON AND
EVENING. THE MOST WIDESPREAD ACTIVITY IS EXPECTED TO BE NORTH AND
EAST OF KBIL..INCLUDING KMLS. VFR CONDITIONS WILL PREVAIL...WITH
LOCALIZED MVFR CONDITIONS DEVELOPING WITH HEAVIER RAIN SHOWERS
THIS AFTERNOON AND EVENING. ANTICIPATE FREQUENT MOUNTAIN
OBSCURATIONS. FRIEDERS

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY THU     FRI     SAT     SUN     MON     TUE
-------------------------------------------------------
BIL 071 050/070 048/064 047/077 053/081 054/080 053/076
    3/T 46/T    64/T    22/W    22/T    23/T    33/T
LVM 067 044/066 045/064 045/072 049/077 050/075 047/071
    6/T 56/T    64/T    23/W    33/T    33/T    33/T
HDN 073 049/073 048/067 047/078 052/083 055/083 053/078
    4/T 35/T    64/W    22/W    22/T    23/T    33/T
MLS 070 052/075 048/066 046/074 053/081 056/081 056/076
    7/T 44/T    43/W    12/W    22/T    23/T    33/T
4BQ 071 050/073 049/064 046/072 053/079 055/080 055/076
    6/T 34/T    54/W    12/W    22/T    22/T    44/T
BHK 071 049/073 045/063 040/066 047/076 052/078 052/074
    7/T 53/T    33/W    12/W    22/T    23/T    33/T
SHR 069 046/068 046/060 043/071 049/077 051/078 050/075
    3/T 36/T    66/T    22/W    22/T    23/T    33/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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