Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 231458
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
858 AM MDT MON MAR 23 2015

.UPDATE...

ONLY UPDATE TO THE GOING FORECAST WAS TO TAPER DOWN CLOUD COVER
FOR THE NEXT SEVERAL HOURS TO MATCH CURRENT OBSERVATIONS. HIGH
TEMPERATURES TODAY WERE GOING TO BE TRICKY DUE TO CLOUD COVER AND
THE APPROACH OF AFTERNOON CONVECTION FROM THE WEST. SINGER

&&

.SHORT TERM...VALID FOR TDY AND TUE...

A RELATIVELY ACTIVE PERIOD WITH SHOWER CHANCES IS IN STORE DURING
THE NEXT TWO DAYS...WITH THE GREATEST CHANCE OF MOISTURE FOR MOST
AREAS COMING LATE THIS AFTERNOON THROUGH TONIGHT. AREA MOUNTAINS
WILL GET SEVERAL INCHES OF SNOW IN THIS PATTERN AS WELL.

FIRST OF ALL...WE HAVE PATCHY FOG IN THE FORECAST THROUGH THE MID
MORNING IN THE EKALAKA AND BAKER AREAS...WHERE VISIBILITY IS DOWN
TO 1/4SM AS OF 09 UTC. HRRR SIMULATIONS SUGGEST THE FOG SHOULD BE
DISSIPATING BY AROUND 15 UTC.

TODAY...A MILD DAY IS IN STORE WITH HIGHS MAINLY IN THE 60S F OUT
AHEAD OF THE APPROACHING 500-MB TROUGH. THE SPEED AT WHICH CLOUDS
THICKEN COULD PRODUCE SOME ERROR IN FORECAST HIGHS THOUGH. SHOWERS
WILL LIKELY BEGIN TO DEVELOP AND/OR MOVE INTO WESTERN PORTIONS OF
SOUTH CENTRAL MT THIS AFTERNOON AS HEIGHT FALLS COMMENCE AND LEAD
TO INCREASING QG-FORCING ALOFT. WE RELIED ON THE 00 UTC MODELS AND
MORE CONTEMPORARY HIGH-RESOLUTION AND CONVECTION-ALLOWING GUIDANCE
LIKE THE RAP AND HRRR TO HOLD OFF THE CHANCE OF SHOWERS WITHIN THE
FORECAST FOR BILLINGS EASTWARD ACROSS SOUTHEASTERN MT UNTIL 21 UTC
/3 PM MDT/. SPEAKING OF SOUTHEASTERN MT...POPS THIS AFTERNOON OVER
THAT PART OF THE STATE ARE CONDITIONAL ON WEAK INSTABILITY FORMING
AND CONTRIBUTING TO CONVECTIVE ELEMENTS DEEPENING ENOUGH TO YIELD
PRECIPITATION. THAT/S FAR FROM CLEAR...THOUGH THE FAVORED NON-NAM
SET OF 00 UTC GUIDANCE LIKE THE GFS DOES SUPPORT SOME 100-200 J/KG
OF MUCAPE THERE /AND BACK FURTHER WEST AROUND LIVINGSTON/ DUE TO A
PLUME OF STEEP MID-LEVEL LAPSE RATES EXCEEDING 8 C/KM...SO WE DID
LEAVE A SLIGHT CHANCE OF THUNDERSTORMS IN WITH THE SHOWERS IN BOTH
OF THOSE AREAS THIS AFTERNOON. WE LEFT THEM IN SOUTHEASTERN MT FOR
THE EARLY EVENING FOR SIMILAR REASONS.

TONIGHT...A RATHER STRONG...BUT QUICK-MOVING BATCH OF FORCING WILL
CROSS THE AREA AND LIKELY YIELD AN EASTWARD-MOVING ROUND OF SHOWER
ACTIVITY. WE HAVE THE HIGHEST /LIKELY-RANGE/ POPS IN PLACE ACROSS
SOUTHEASTERN MT WHERE THAT FORCING WITH THE 500-MB TROUGH LOOKS TO
INTERCEPT A NARROW RIBBON OF HIGHER MOISTURE THAT THE 00 UTC MODEL
GUIDANCE FORECASTS TO MOVE NORTHWARD ALONG THE HIGH PLAINS WITH AN
AXIS OF PRECIPITABLE WATER VALUES OF 0.50 INCHES MOVING OUT OF THE
SOUTHERN PLAINS AND INTO EASTERN MT OVERNIGHT. THE DODGE CITY...KS
OBSERVED SOUNDING FROM 00 UTC MARCH 23RD DID SAMPLE A PRECIPITABLE
WATER VALUE OF 0.42 INCHES...WHICH SUGGESTS THE GUIDANCE DOES HAVE
A HANDLE ON THIS SCENARIO. MOISTURE TOTALS WITH THE HIGHEST CHANCE
OF SOME QUARTER INCH RAIN TOTALS WILL THUS ALSO BE IN SOUTHEASTERN
MT. MEANWHILE...TIME-LAGGED AND ONE-RUN ENSEMBLE GUIDANCE BACK TO
THE WEST IN BILLINGS CONTINUES TO SUGGEST THE CITY WILL LIKELY GET
0.05 INCHES OR LESS OF MOISTURE OUT OF THIS SYSTEM.

TUESDAY INTO TUESDAY NIGHT...COOLER AND UNSETTLED WEATHER WILL BE
THE THEME BEHIND TONIGHT/S WAVE PASSAGE. NOTE THAT THE 00 UTC GEM
AND ECMWF ACTUALLY SUGGEST MORE BONAFIDE WRAP-AROUND MOISTURE AND
POSSIBLY EVEN SNOW IN BAKER EARLY TUESDAY MORNING AS THEY PLACE A
GREATER EMPHASIS ON THE NORTHERN PIECE OF THE TROUGH ALOFT. WE DO
NEED TO KEEP AN EYE ON THAT...BUT CONFIDENCE IN HOW THAT WILL END
UP PLAYING OUT IS LOW. OTHERWISE...THERE IS GREATER CONFIDENCE IN
ANOTHER WEAKER SHORTWAVE TROUGH DROPPING ACROSS SOUTH CENTRAL MT
TUESDAY AFTERNOON AND EVENING WITH CONVECTIVELY-AIDED SHOWERS OF
RAIN AND EVENTUALLY SNOW SHOWERS BY TUESDAY NIGHT. THIS SITUATION
IS ONE THAT CAN YIELD ACCUMULATING SNOW IN THE FOOTHILLS LIKE AT
RED LODGE...AND IF GUIDANCE REMAINS CONSISTENT IN ITS SIMULATION
OF THIS SCENARIO THEN WE MAY NEED TO INCREASE SNOW AMOUNTS WITH A
LATER FORECAST RELEASE IN THE FOOTHILLS. SCHULTZ

.LONG TERM...VALID FOR WED...THU...FRI...SAT...SUN...

COOLER AND UNSETTLED NORTHERLY FLOW WILL REMAIN OVER THE REGION
THROUGH THURSDAY. LAPSE RATES WILL BE STEEPEST ON WEDNESDAY WITH
SOME DIURNAL RAIN/SNOW SHOWERS ANTICIPATED...ESPECIALLY IN NW FLOW
FAVORED AREAS...BUT W/OUT MUCH SYNOPTIC FORCING. A SURGE OF
MOISTURE SPILLING OVER THE WESTERN CONUS RIDGE WILL KEEP THE
POTENTIAL FOR SHOWER ACTIVITY GOING WEDNESDAY NIGHT AND THURSDAY.
LATEST MODEL TRENDS SUGGEST BACKDOORING COOLING WHICH WILL
INCREASE THE LOW LEVEL BAROCLINICITY IN OUR CWA...THOUGH MODELS
ARE DIFFERENT IN WHERE THEY PAINT HIGHEST QPF. IF SFC TEMPS REMAIN
COOL ENOUGH WE COULD SEE SOME WET SNOWFALL IN A COMBINATION OF OUR
N-NW FLOW UPSLOPE AREAS AND ALONG SFC BOUNDARY. HAVE RAISED POPS
IN OUR SOUTH CENTRAL PARTS THURSDAY INTO THURSDAY NIGHT...AND HAVE
LOWERED TEMPS A BIT IN OUR CENTRAL AND EAST. OF COURSE THE NW FLOW
ALOFT WILL FAVOR THE BIGHORN MTNS FOR SNOWFALL THRU THE PERIOD.

STRONG RIDGE ALONG THE PAC COAST WILL BEGIN TO SHIFT EAST ON
FRIDAY BRINGING US RAPID DOWNSLOPE WARMING AS HEIGHTS SURGE INTO
THE 570S ACROSS WESTERN AND CENTRAL MT. SHOULD SEE HIGH TEMPS BACK
NEAR 70F IN OUR WEST BUT PROXIMITY TO SLOWER DEPARTING SFC HIGH IN
THE PLAINS SHOULD KEEP OUR EAST COOLER...ESPECIALLY AFTER A COLD
MORNING. HAVE ADJUSTED TEMPS IN OUR EAST DOWN SOME PER MODEL
CONSENSUS.

IT APPEARS SATURDAY WILL BE THE WARMEST DAY OF THE EXTENDED PERIOD
AS THE RIDGE AXIS SHIFTS FURTHER EAST AND BEGINS TO FLATTEN IN
RESPONSE TO NEXT SHORTWAVE OFF THE PACIFIC. MODELS HAVE TRENDED
SLOWER WITH A COLD FRONTAL PASSAGE...IT NOW LOOKS TO OCCUR
SATURDAY NIGHT...AND THIS WILL SET THE STAGE FOR A DRY/WINDY AND
VERY WARM SATURDAY. GIVEN SUCH ANOMALOUSLY HIGH HEIGHTS AND THE
STRONG DOWNSLOPE PREFRONTAL FLOW HAVE RAISED EXPECTED HIGHS
FURTHER INTO THE 70S.

MODEST COOL DOWN IN STORE FOR SUNDAY BEHIND THE CLIPPER SYSTEM...
WHICH MAY BRING A LITTLE SHOWER ACTIVITY SATURDAY NIGHT INTO
SUNDAY. IT IS LOOKING MORE AND MORE LIKE MARCH WILL END ON A WARM
NOTE WITH UPPER RIDGING EXPECTED TO PERSIST THRU EARLY NEXT WEEK.

JKL
&&

.AVIATION...

EXPECTING CLEAR SKIES THIS MORNING BEFORE THE CLOUDS START FILLING
IN AHEAD OF AN UPPER LEVEL DISTURBANCE. THE POTENTIAL FOR SOME
CONVECTION EXISTS MAINLY NEAR KLVM BY THIS AFTERNOON. RAIN SHOWERS
WILL FILL IN NEAR KBIL BY LATE THIS AFTERNOON...AND KMLS AND KBHK
BY THIS EVENING. THE SHOWER ACTIVITY WILL COINCIDE WITH A PACIFIC
COLD FRONT MOVING INTO THE AREA FROM THE WEST. MVFR CONDITIONS
WILL BE POSSIBLE WITH PRECIP ACTIVITY AND MOUNTAIN OBSCURATIONS
ARE POSSIBLE DUE TO SNOW SHOWER ACTIVITY AT HIGHER ELEVATIONS.
SINGER

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY TUE     WED     THU     FRI     SAT     SUN
-------------------------------------------------------
BIL 064 039/055 031/048 034/051 032/070 046/077 042/061
    2/W 54/W    43/W    32/W    10/B    01/N    22/W
LVM 058 031/048 028/048 034/055 035/070 047/072 041/061
    6/T 55/W    53/W    22/W    10/N    01/N    22/W
HDN 068 037/058 029/048 032/051 028/070 039/079 038/063
    2/W 53/W    33/W    32/W    10/B    01/N    22/W
MLS 068 039/055 027/045 026/048 026/066 039/076 036/060
    2/T 62/W    12/W    22/W    10/B    01/N    21/B
4BQ 070 037/056 027/045 026/047 026/064 038/078 037/060
    3/T 63/W    12/W    23/W    10/B    01/N    21/B
BHK 064 036/051 024/039 020/041 021/058 035/074 033/055
    1/B 74/W    12/J    22/J    10/B    01/N    21/B
SHR 066 035/053 027/045 028/048 026/065 038/078 039/060
    2/W 54/W    44/W    43/W    20/B    00/B    22/W

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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