Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 292055
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
255 PM MDT WED APR 29 2015

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

UPPER TROUGH WORKING THROUGH IDAHO/WESTERN MONTANA TODAY WITH OUR
UPPER WINDS BACKING WITH ITS APPROACH. SOME DECENT DESTABILIZATIONAHEAD
OF THE ASSOCIATED COLD FRONT IS PROGGED TO OCCUR LATE TODAY IN OUR
FAR WESTERN ZONES. THE COLD FRONT IS EXPECTED INTO BILLINGS AROUND
10 PM THIS EVENING...WITH ISOLATED SHOWERS AND MAYBE THUNDER
MOVING IN SHORTLY BEHIND IT. THE CHANCE OF THUNDER OVERALL IS
SOMEWHAT QUESTIONABLE BEYOND ABOUT 7 PM AS MODELS ARE NOT IN
AGREEMENT AS TO THE AMOUNT OF CAPE...AND BEST FORCING GOES NORTH
OF OUR FORECAST AREA. HOWEVER...THERE IS SOME LINGERING WEAK SHEAR
AND INSTABILITY SO I WILL KEEP THE MENTION OF THUNDER THROUGH THE
ENTIRE EVENING....CHANGING TO JUST SHOWERS AFTER MIDNIGHT.

PROGGS ALSO DIFFER TO SOME DEGREE OVER HOW WIDESPREAD SHOWERS WILL
BE AFTER MIDNIGHT AND INTO THURSDAY MORNING. THE GFS AND WRF
CERTAINLY BREAK UP THE SHOWERS ACROSS OUR CENTRAL ZONES AS THE
ACTIVITY MOVES EAST OVERNIGHT...BUT THE ECWMF STILL PAINTS QPF
OVER MOST ZONES. ECMWF SEEMS OVERDONE GIVEN THE BEST FORCING
DRIVES NORTHEAST OF US. I DONT ANTICIPATE ANYONE GETTING A GREAT
DEAL OF PRECIPITATION EITHER WAY...SO HAVE CONTINUED TO BLEND
MODELS FOR POPS THROUGH THURSDAY..BASICALLY DRYING THINGS OUT
AFTER NOON TOMORROW.

MODELS AGREE ON A ZONAL FLOW FOR THE THURSDAY NIGHT/FRIDAY TIME
FRAME. THIS SHOULD MEAN A DRY FRIDAY WITH A GOOD REBOUND IN
AFTERNOON HIGHS AFTER A COOLER THURSDAY. BT

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

ZONAL FLOW WILL USHER IN THE EXTENDED FORECAST THIS WEEKEND. DRY
AND FAIRLY WARM TEMPS WILL ENVELOPE THE REGION ON SATURDAY BEFORE
A COLD FRONT MOVES THROUGH BY SATURDAY EVENING. SUNDAY TEMPS WILL
BE QUITE A BIT LOWER DUE TO MUCH COOLER 850MB AIR ALOFT.

BY MONDAY...A STRONG UPPER LEVEL LOW OFF THE BRITISH COLUMBIA
COAST WILL START MAKING ITS WAY INLAND. THE LATEST SOLUTION FROM

THE EUROPEAN MODEL TRACKS THIS LOW A LITTLE FURTHER NORTH THAN
PREVIOUS RUNS. THE MOISTURE FETCH FROM THE GULF OF MEXICO STILL
MAINTAINS A CONNECTION WITH THIS SYSTEM SETTING UP A NICE TROWAL
LIKE FEATURE OVER SOUTHER ALBERTA ON THE BACK EDGE OF THE UPPER
SYSTEM BY WEDNESDAY NIGHT.

THE GFS SOLUTION TRACKS THE LOW ON A MORE SOUTHERLY
EXTENT...TAPPING INTO THE GULF MOISTURE AND BRINGING MORE
WIDESPREAD PRECIPITATION OVER THE ENTIRE AREA. LOOKING AT THE CIPS
TIME LAGGED ENSEMBLE GUIDANCE...THE LAST SEVERAL RUNS OF THE GFS
BRING AT LEAST A TENTH OF AN INCH OF PRECIP OVER MUCH OF SOUTHEAST
MONTANA.

AT THIS POINT IN TIME...DECIDED TO GO WITH THE GFS SOLUTION AND
UP POPS EVER SO SLIGHTLY FOR NEXT WEDS AND THURSDAY.
FURTHER...DECIDED TO KEEP MENTION OF THUNDER IN THE FORECAST AS
THIS SOUTHWESTERLY FLOW PATTERN IS ONE THAT COULD WARRANT SOME
STRONGER CONVECTION.

LOOKING EVEN FURTHER OUT INTO THE FUTURE...IT LOOKS LIKE IT COULD
BE FAIRLY WET...KEEPING IN TUNE WITH OUR CLIMATE NORMALS WITH MAY
BEING ONE OF OUR WETTER MONTHS. SINGER


&&

.AVIATION...

THE CHANCE INCREASES FOR SOME PREFRONTAL CONVECTION...ISOLATED IN
NATURE...BY THIS EVENING. A COLD FRONT WILL MOVE THROUGH THE
REGION AT THAT TIME...BRINGING WITH IT GUSTIER WINDS OUT OF THE
NORTHWEST. THE BEST CHANCE FOR AN ISOLATED THUNDERSTORM WILL BE
NEAR KLVM...BUT KBIL COULD SEE SOME SHOWER ACTIVITY AS WELL. WIND
GUSTS COULD APPROACH 40 MPH AT TIMES WITH FRONTAL PASSAGE. BOTTOM
LINE...EXPECT ERRATIC CROSSWINDS WITH MVFR CONDITIONS WITH ANY
PRECIPITATION ACTIVITY. SINGER &&

.PRELIMINARY POINT TEMP/POPS...

    THU     FRI     SAT     SUN     MON     TUE     WED
-----------------------------------------------------------
BIL 049/066 041/078 046/078 044/064 043/065 040/074 046/068
    32/W    00/U    00/B    23/T    32/T    22/T    24/T
LVM 041/063 034/073 039/073 038/065 036/067 036/079 039/068
    42/W    00/U    01/B    23/T    32/T    23/T    34/T
HDN 046/067 037/078 042/080 043/068 040/068 042/075 045/075
    22/W    00/U    00/B    22/T    32/T    22/T    24/T
MLS 049/066 039/076 044/075 045/064 039/063 040/070 044/072
    22/W    00/U    00/B    22/T    33/T    11/B    23/T
4BQ 045/065 036/075 042/080 043/069 043/061 042/069 043/069
    02/W    00/U    00/U    12/T    33/T    22/T    24/T
BHK 044/066 035/075 041/076 041/063 040/060 037/066 043/067
    23/W    00/U    00/B    22/T    33/T    11/B    24/T
SHR 044/060 035/073 038/074 040/065 039/061 040/067 040/065
    02/W    00/U    00/U    13/T    33/T    23/T    34/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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