Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 240931
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
331 AM MDT FRI APR 24 2015

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

SPRINGLIKE FORECAST ON TAP WITH MILD TEMPERATURES TODAY
ACCOMPANIED WITH SHOWERS AND THUNDERSTORMS ESPECIALLY OVERNIGHT.
UPPER LEVEL LOW PRESSURE ALONG BC COAST BEING UNDERCUT THIS
MORNING WITH A SURGE OF STRONGER FLOW OFF THE EASTERN PACIFIC.
FLOW IS ZONAL THIS MORNING OVER MONTANA AND WYOMING AND FAIRLY
WEAK BUT THIS ENERGY WILL CAUSE FLOW TO BECOME SOUTHWESTERLY THIS
AFTERNOON WITH A SHORTWAVE KICKING THROUGH SOUTHWEST MONTANA EARLY
THIS EVENING AND MOVING THROUGH SOUTH CENTRAL MONTANA OVERNIGHT.
PRESSURE FALLS AHEAD OF THIS WAVE WILL BRING LOW LEVEL EASTERLY
FLOW AND AIRMASS HAS BEEN SEEING INCREASING MOISTURE THE PAST FEW
DAYS SO DEWPOINTS WILL BE IN THE 40S WHICH IS ON THE HIGH SIDE FOR
APRIL. MODELS ARE PROJECTING CAPES 200-400 J/KG WITH NO CAP LATE
TODAY SO THINK SHOWER ACTIVITY WILL BE A BETTER SHOWER AND
THUNDERSTORM MIX. ACTIVITY WILL BE LARGELY TERRAIN DRIVEN THIS
AFTERNOON BUT BEGIN SPREADING EAST EARLY THIS EVENING AS A FRONT
BEGINS PROVIDING FORCING DURING THE LATER EVENING HOURS.

MOST IMPORTANT A NUMBER OF LOCATIONS IN SOUTH CENTRAL MONTANA ARE
GOING TO SEE A QUARTER INCH TO A HALF INCH OF MOISTURE. FOLKS WITH
OUTDOOR ACTIVITIES THIS EVENING WILL NEED TO BE AWARE OF THE
THUNDERSTORM THREAT DUE TO LIGHTNING...BUT IT REALLY SHOULD BE A
PERIOD OF WET WEATHER OVERNIGHT. THE ONLY AREAS UNDER A SNOWFALL
THREAT TONIGHT WILL BE LOCATIONS ABOVE 7000 FEET INCLUDING COOKE
CITY BUT THE FOOTHILLS LOOK LIKE RAIN.

PRECIP SHIFTS TO SOUTHEAST MONTANA SATURDAY MORNING AS THE FRONT
CONTINUES PROGRESSING EAST WITH A PERIOD OF DRYING FOR CENTRAL
AND WESTERN AREAS AS THE FLOW ALOFT TURNS SLIGHTLY ANTICYCLONIC.
WILL BE COOLER ON SATURDAY BEHIND THE FRONT WITH NORTHERLY WINDS
BUT WIND SPEEDS WILL BE DECREASING AS THE DAY PROGRESSES.

THE ENERGY WHICH HAD BEEN ALONG THE WEST COAST MOVES INLAND
SATURDAY AND BEGINS SPLITTING. THIS ALLOWS FOR A BETTER MOISTURE
TRANSPORT IN SOUTHERLY FLOW ALOFT INTO THE AREA AND BETTER CHANCES
FOR SHOWER ACTIVITY. GFS AND ECMWF AND NOT CONSISTENT IN HOW MUCH
PRECIP TO BRING INTO THE AREA WITH THE GFS NOW LOOKING TO HOLD
MORE PRECIP SOUTH OF THE AREA. ONLY HAVE SCATTERED SHOWER
ACTIVITY BUT COOLER TEMPERATURES WILL BRING LOWER SNOW LEVELS
ESPECIALLY FOR THE BIG HORN MOUNTAINS. HAVE LOW TEMPERATURES IN
THE MID 30S FOR THE FOOTHILLS SO WATCHING TO SEE IF AN INCH OR TWO
IS POSSIBLE IN RED LODGE. BORSUM
.LONG TERM...VALID FOR SUN...MON...TUE...WED...THU...

UPPER LOW OVER THE PAC NW SAT WILL DRIVE TOWARD THE CENTRAL AND
SOUTHERN ROCKIES SUN BEFORE SLIDING INTO THE SOUTHERN PLAINS BY
MON. TRACK OF THIS SYSTEM IS LESS THAN IDEAL FOR A SIGNIFICANT
UPSLOPE EVENT IN OUR CWA...AND THIS THINKING IS CONSISTENT WITH
WHAT IS SHOWN ON THE LATEST 72HR CIPS ANALOGS WHICH SUGGEST MUCH
GREATER POTENTIAL TO OUR SOUTH. THAT BEING SAID THERE WILL BE A
PERIOD OF MODEST UPPER LEVEL ASCENT WITH DECENT MOISTURE ADVECTION
IN THE SOUTHERLY FLOW. BELIEVE THERE WILL BE A PERIOD OF UPSLOPE
PCPN ON THE NORTH SLOPES OF THE BEARTOOTH ABSAROKAS BUT OVER TIME
THE GREATER PCPN POTENTIAL SHOULD SHIFT TO OUR SOUTHEAST WHERE
ASCENT WILL BE OF LONGER DURATION ALONG A LOW LEVEL INVERTED TROF.
AM EXPECTING PCPN IN THE FORM OF RAIN TO ACCUMULATE TO A HALF INCH
OR MORE IN PARTS OF OUR EAST SUNDAY INTO EARLY MONDAY. MODELS HAVE
TRENDED WARMER AT LOWER ELEVATIONS AND THIS IS CONSISTENT WITH
EXPECTATION OF WEAKER DYNAMIC COOLING...SO NO REAL THREAT OF
LOWER ELEVATION SNOWFALL...THOUGH A MIX WITH WET SNOW IS POSSIBLE
AT PLACES SUCH AS RED LODGE AND STORY. COULD SEE SEVERAL INCHES
OF SNOW OVER THE HIGHER ELEVATIONS ESPECIALLY THE BIGHORNS WHERE
PCPN SHOULD BE HEAVIEST PER THE DEEP EASTERLY FLOW. PCPN SHOULD
LINGER IN OUR EAST INTO EARLY MON...AFTER WHICH SUBSIDENCE BEHIND
NORTHERN BRANCH SHORTWAVE WILL BRING DRIER AIR FROM THE WEST.

FOR BILLINGS...THOUGH WE SHOULD CATCH SOME SHOWER ACTIVITY ON
SUNDAY THE ASCENT IS NOT STRONG AND INSTABILITY IS LACKING SO
BELIEVE PCPN AMOUNTS WILL BE FAIRLY LIGHT AT A TENTH OF AN INCH OR
LESS. HAVE ACTUALLY REDUCED POPS A BIT TO SHOW SCATTERED COVERAGE
SUNDAY INTO SUNDAY EVENING.

A TRANSITION TO STRONG UPPER LEVEL RIDGING AND MUCH ABOVE NORMAL
TEMPERATURES IS IN STORE FOR MON-THU. AFTER A RELATIVELY COOL
SUN...WARMING TREND WILL BEGIN MON. LOOK FOR HIGHS IN THE 60S MON
THEN 70S TUE...WARMEST IN OUR WEST CLOSER TO UPPER RIDGE AXIS. WED
AND THU SHOULD BE VERY WARM DAYS WITH HIGHS TO 80 DEGREES IF NOT
WARMER. SOME MODEL DIFFERENCES HERE REGARDING WEAK PACIFIC ENERGY
AND POTENTIAL FOR SOME ENHANCED DOWNSLOPE WINDS...BUT GENERAL
THEME IS QUITE WARM FOR THE MIDDLE TO LATTER PART OF NEXT WEEK.
ANY CHANCE OF SHOWERS SHOULD HOLD OFF TO WED NITE OR THU DEPENDING
ON SHORTWAVE ENERGY. WILL KEEP DAY 7 POPS AT SLIGHT CHANCE TO
COVER THIS.

JKL
&&

.AVIATION...

ISOLATED SHOWERS THIS MORNING WILL BECOME MORE NUMEROUS THIS
AFTERNOON AND TONIGHT AS A DISTURBANCE FROM THE WEST MOVES THROUGH
THE REGION. GREATEST COVERAGE OF SHOWERS WILL BE FROM KBIL WEST
AND NORTH...WITH LOCAL MVFR CONDITIONS EXPECTED AT LOWER
ELEVATIONS ALONG WITH FREQUENT MOUNTAIN OBSCURATIONS. SOME TSTM
ACTIVITY IS ALSO ANTICIPATED LATE THIS AFTERNOON AND EVENING. JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY SAT     SUN     MON     TUE     WED     THU
-------------------------------------------------------
BIL 069 043/059 041/056 038/067 042/074 046/080 048/080
    3/T 73/W    45/W    31/B    00/U    00/U    11/B
LVM 063 037/056 036/052 031/068 037/075 041/079 046/076
    6/T 74/T    56/W    30/B    00/U    00/U    12/W
HDN 073 042/062 039/056 038/067 036/075 040/080 044/080
    2/T 54/W    35/W    41/B    00/U    00/U    11/B
MLS 073 042/057 038/059 039/066 037/072 041/079 044/078
    2/T 47/W    25/W    51/B    00/U    00/U    11/U
4BQ 071 041/056 038/056 039/063 036/070 040/076 044/077
    2/T 37/T    37/W    72/W    00/U    00/U    11/U
BHK 070 038/058 037/056 038/061 035/067 037/075 042/076
    1/B 27/W    47/W    73/W    00/U    00/U    11/U
SHR 068 040/057 038/050 036/064 035/071 038/076 044/076
    3/T 43/W    47/W    61/B    00/U    00/U    11/B

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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