Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 231402
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
802 AM MDT THU APR 23 2015

.UPDATE...
MADE A QUICK UPDATE TO STRETCH POPS FARTHER EAST THIS MORNING.
WEAK BAND OF SHOWERS FROM LIVINGSTON TO JUST NORTH OF COLUMBUS
HOLDING ON. THOUGH HRRR DOES WEAKEN THEM IN TIME...THEY HAVE BEEN
HOLDING ON TO THEIR STRENGTH THE LAST COUPLE OF HOURS. TWH

&&

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

EARLY MORNING AREA OF SHOWERS MOVING THROUGH NORTHERN PORTIONS OF
SOUTHEAST MONTANA PRODUCING ONLY LIGHT RAIN BUT EXPECT ACTIVITY TO
PERSIST FOR A WHILE AFTER 12Z. FLATTER FLOW BEHIND THIS WAVE IS
CLEARING OUT SOUTH CENTRAL MONTANA BUT WATER VAPOR IMAGERY SHOWS A
DECENT AMOUNT OF MOISTURE IS LINGERING IN PLACE BEHIND THE SYSTEM.
NOT MUCH IN THE WAY OF FORCING TODAY BUT PRECIPITABLE WATERS .50
TO .75 WILL COMBINE WITH DIURNAL WARMING TO ALLOW FOR SOME SHOWER
ACTIVITY WITH THE MOUNTAINS BEING FAVORED. A THUNDERSTORM OR TWO
CANNOT BE RULED OUT BUT ANY CELL MOVEMENT SHOULD BE PRETTY SLOW SO
EXPECT MOST CELLS TO REMAIN AS RAIN SHOWERS. TEMPERATURES WILL BE
COOLER TODAY WITH THE FLATTER FLOW ALOFT.

BROADER HEIGHT FALLS UPSTREAM OVERNIGHT OVER WASHINGTON AND BC
TURN THE FLOW ALOFT SOUTHWESTERLY. THE INITIAL HEIGHT RISES OVER
THE AREA ASSOCIATED WITH THIS PROCESS WILL STABILIZE THE AIRMASS
AFTER MIDNIGHT WHICH WILL BRING CLEARING AND ALLOW FOR A BIT
COOLER TEMPERATURES OVERNIGHT.

FRIDAY THE FLOW ALOFT BECOMES SLIGHTLY DIFFLUENT OVER THE AREA
WHICH ALLOWS A SURFACE TROUGH TO DEVELOP ALONG THE FOOTHILLS. THIS
ALLOWS MOISTURE TO DEEPEN AND SET UP A BETTER CHANCE FOR SHOWERS
OVER THE MOUNTAINS. BY AFTERNOON AND EVENING A DISTURBANCE ROTATES
THROUGH SOUTHWEST MONTANA AND THIS BRINGS A MUCH BETTER CHANCE FOR
SHOWER ACTIVITY WITH INCREASING MID LEVEL WINDS. THIS WILL SPEED
UP STORM MOVEMENT AND ALLOW SHOWERS TO BEGIN SPREADING INTO THE
PLAINS. AT THE SAME TIME A COOL FRONT BEGINS MOVING ACROSS THE
AREA FRIDAY NIGHT WHICH PROVIDES A BETTER TRIGGER FOR SHOWERS AND
ISOLATED THUNDERSTORMS. HAVE INCREASED POPS ESPECIALLY FOR FRIDAY
NIGHT AFTER MIDNIGHT AS MODELS ARE PRETTY CONSISTENT  WITH THIS
EVOLUTION AND SREF PLUMES ARE ADVERTISING .30 INCHES OF PRECIP FOR
BILLINGS AREA. BORSUM

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

SATURDAY WILL BEGIN WITH A WEAK SHORTWAVE IN OUR CENTRAL PARTS
MOVING TOWARD THE EAST IN SW FLOW ALOFT. GOOD CHANCE OF SHOWERS
ALONG INVERTED TROF ACROSS OUR EAST AND HAVE RAISED POPS.
SUBSIDENCE ALONG WITH LOW LEVEL DRYING WILL LIMIT PCPN CHANCES
BEHIND THIS WAVE...UNTIL UPPER DIVERGENCE BEGINS TO INCREASE AGAIN
IN OUR FAR WEST PER APPROACHING DEEPER LOW. HAVE REDUCED POPS AND
TAKEN OUT THUNDER ACROSS OUR CENTRAL PARTS ON SATURDAY. THIS
INCLUDES BILLINGS WHICH SHOULD ONLY SEE A CHANCE OF SHOWERS EARLY
IN THE DAY. TEMPS WILL BE SEASONAL WITH HIGHS IN THE UPPER 50S TO
MID 60S.

LOW OVER THE PAC NW SATURDAY WILL DRIVE TOWARD THE CENTRAL AND
SOUTHERN ROCKIES SUNDAY. MODELS IN SOME DISAGREEMENT IN PATH OF
MID LEVEL LOW AND PCPN CHANCES IN OUR CWA...WITH THE GFS SHOWING A
FAIRLY WET UPSLOPE EVENT TRANSITIONING TO OUR SOUTHEAST SATURDAY
NIGHT THROUGH SUNDAY. THE ECMWF SUGGESTS WE WILL BE MORE DOMINATED
BY THE NORTHERN WEAKER SPLIT WITH LESS LOW LEVEL MOISTURE
ADVECTION...AND IS THUS DRIER. WILL LEAN TOWARD THE CONSENSUS/
SREF AND KEEP HIGH POPS ESPECIALLY FOR OUR SOUTHERN TIER THESE
PERIODS. PCPN AMOUNTS ON THE ORDER OF A HALF INCH POSSIBLE IN
THESE AREAS AND COULD SEE SOME WET SNOWFALL FOR THE FOOTHILLS
INCLUDING LIVINGSTON...RED LODGE AND STORY AS 850MB TEMPS MAY
APPROACH +1C WITH DYNAMIC COOLING...WARMER IF THE EC VERIFIES OF
COURSE. DO NOT SEE A HIGH IMPACT THREAT HERE JUST SOME MUCH-NEEDED
PCPN AND SOME SNOW OVER THE NORTH ASPECTS OF THE MOUNTAINS. SYSTEM
WILL CONTINUE TO DRIVE SOUTHWARD AND OUR PCPN POTENTIAL WILL
DIMINISH SUNDAY NIGHT AS DRIER NW FLOW TAKES OVER. TEMPS ON SUNDAY
LOOK TO BE THE COOLEST OF THE EXTENDED PERIOD WITH UPPER 40S AND
50S FOR HIGHS.

UPPER RIDGE WITH ABOVE NORMAL HEIGHTS WILL BRING US DRY AND WARMER
WEATHER MONDAY THROUGH WEDNESDAY...THOUGH MODELS DIVERGE HORRIBLY
WITH RESPECT THE OVERALL AMPLITUDE OF THE FLOW ACROSS THE EASTERN
PACIFIC AND CONUS. CONFIDENCE IS HIGH THAT OUR WX WILL BE DRY.
BIGGER QUESTION IS HOW WARM IT WILL GET AND HOW FAST. GFS SUGGESTS
A COUPLE DAYS OF EAST WINDS WHEREAS THE FLATTER ECMWF CREATES
STRONGER DOWNSLOPE WARMING. EITHER WAY WE SHOULD SEE TEMPS GET
BACK INTO THE 70S BY THE MIDDLE OF NEXT WEEK...WITH 80S ALSO
POSSIBLE.

JKL

&&

.AVIATION...

ISOLATED TO SCATTERED SHOWERS WILL AFFECT THE REGION TODAY AND
TONIGHT WITH LOCAL MVFR AND SOME MOUNTAIN OBSCURATIONS POSSIBLE.
VFR FLIGHT CONDITIONS WILL PREVAIL OTHERWISE. THERE IS POTENTIAL
FOR A FEW TSTMS THIS AFTERNOON AND EVENING. JKL

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY FRI     SAT     SUN     MON     TUE     WED
-------------------------------------------------------
BIL 065 044/069 043/063 039/055 038/068 042/072 044/076
    2/T 22/T    63/W    66/W    31/B    00/B    00/U
LVM 065 038/064 037/059 035/053 031/067 037/073 039/075
    4/T 34/T    64/T    76/W    31/B    00/B    00/B
HDN 068 040/072 040/065 039/054 038/067 037/073 040/076
    2/T 21/B    54/W    56/W    41/B    00/B    00/U
MLS 067 038/071 041/062 040/056 039/066 037/070 041/073
    2/T 11/B    37/W    46/W    51/B    10/B    00/U
4BQ 069 040/070 041/062 040/055 039/063 037/069 039/072
    2/T 21/B    25/T    47/W    61/B    10/B    00/U
BHK 065 035/067 039/059 040/055 038/062 037/065 037/069
    2/T 11/B    17/W    46/W    52/W    10/B    00/B
SHR 065 039/067 039/061 037/050 036/064 036/069 038/072
    2/T 23/T    42/W    47/W    51/B    00/B    00/U

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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