Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 310430
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
930 PM MST FRI JAN 30 2015

.UPDATE...
QUIET WEATHER THIS EVENING WITH CLEAR SKIES IN OUR NORTH AND HIGH
CLOUDS IN THE SOUTH...THE LATTER DUE TO HIGH LEVEL MOISTURE ON
NORTHERN FRINGES OF BROAD LOW OVER THE GREAT BASIN. IMMEDIATE
SHORT TERM CONCERN IS POTENTIAL FOR FOG AND STRATUS IN OUR EAST.
LARGE AREA OF STRATUS IS PUSHING SLOWLY TO THE SOUTHWEST...WITH
ITS LEADING EDGE IN NORTHEAST MT BUT NOT YET TO KOLF AND KSDY.
GIVEN THE SLOWER EVOLUTION OF THIS STRATUS THAN MODELS SUGGESTED
EARLIER...HAVE SCALED BACK -ZL CHANCES PRIOR TO 12Z BUT WILL KEEP
PATCHY FOG FROM HYSHAM EASTWARD BEGINNING 09Z. LOW LEVEL MOISTURE
SHOULD DEEPEN EARLY TOMORROW SO IT STILL APPEARS THERE IS A WINDOW
OF A FEW HOURS WHERE LIGHT FREEZING DRIZZLE IS A POSSIBILITY
ACROSS OUR NORTHEAST PARTS PRIOR TO THE ARRIVAL OF SHORTWAVE FROM
THE NW AND SEEDING. MID SHIFT WILL NEED TO KEEP AN EYE ON THIS.
BILLINGS SHOULD SEE A WESTERLY COMPONENT OF WIND THROUGH THE
NIGHT...SHIFTING TO THE NORTH WITH THE FROPA AROUND 18Z...SO DO
NOT SEE A FOG OR DRIZZLE THREAT AS FAR WEST AS BILLINGS. OVERALL
FORECAST IS IN GOOD SHAPE AND HAVE MADE ONLY FEW TWEAKS TO
TEMPS...SKY AND WX. JKL

&&

.SHORT TERM...VALID FOR SAT AND SUN...

SHORT TERM PROGS ARE IN GOOD AGREEMENT OF MOVING THE COLDER AIR
IN SOONER THAN WE SAW ON YESTERDAYS CYCLES...AND IN RETURN ALSO
MOVING IT OUT QUICKER. WE HAVE ADJUSTED POPS FOR THIS AND ALSO
ADDED SOME OTHER DETAILS AS OUTLINED BELOW.

FIRST OFF...IT APPEARS WE WILL HAVE SOME LOW CLOUDS AND FOG MOVE
INTO OUR NE ZONES /FORSYTH TO BAKER/ LATER TONIGHT. THERE IS A
CHANCE OF SEEING SOME PATCHY LIGHT FREEZING DRIZZLE DEVELOP
OVERNIGHT IN THESE AREAS AS WELL...AND SOUNDINGS SUGGEST THIS
POTENTIAL THROUGH AT LEAST MID MORNING. SO THIS HAS BEEN ADDED TO
THE FORECASTS.

SHORT WAVE TRACKING ACROSS CENTRAL ALBERTA WILL DROP ACROSS
EASTERN MONTANA TOMORROW MORNING...OPENING THE DOOR TO A POOL OF
COLDER AIR AND LOW LEVEL MOISTURE. MODELS HAVE KEPT THE ASSOCIATED
JET STREAM OVER THE FRONT RANGE AND OUR WESTERN ZONES WHICH WILL
MAKE IT TOUGH TO DEEPEN THE COLD AIR INTO THE FOOTHILLS AND THUS
THIS SHOULD LIMIT UPSLOPE ON THE NORTH FACING SLOPES OF THE
BEARTOOTHS. CROSS SECTIONS INDICATE A NARROW AREA/BAND OF STRONGER
FORCING DEVELOPING ANYWHERE FROM BIG TIMBER TO BILLINGS ENHANCED
BY THE JET. SO THERE COULD BE A LOCAL BAND THAT DROPS A COUPLE OF
INCHES. OTHERWISE MOST AREAS WILL SEE AROUND AN INCH OR LESS OF
ACCUMULATION THROUGH SATURDAY NIGHT.

THE THREAT OF ICY ROADS IS REALLY THE MAIN IMPACT HERE SINCE THE
PRECIPITATION IS EXPECTED EARLIER. WE ANTICIPATE A STRETCH OF
ROADS THAT MAY BE WET INITIALLY AS LIGHT RAIN/SNOW SHOWERS MOVE IN
AND QUICKLY TURN TO ALL SNOW. MODELS SUGGEST ROAD TEMPS WILL DROP
TO BELOW FREEZING THEN BETWEEN 4 PM AND 6 PM IN MANY AREAS LEADING
TO ICY CONDITIONS. WE STARTED PLAYING THIS SCENARIO UP YESTERDAY
AND WILL CONTINUE TO FOCUS ON THIS FOR OUR SOCIAL MEDIA AND
HAZARDOUS WEATHER OUTLOOK. SINCE SNOWFALL ACCUMULATIONS ARE
LIMITED AND ITS TOUGH TO SAY EXACTLY WHERE THE BIGGEST THREAT
OF ICY ROADS WILL BE AT THIS TIME...WE DO NOT PLAN TO ISSUE ANY
HIGHLIGHTS WITH THIS PACKAGE.

FOR SUNDAY...THE COLDER AIR MASS THAT INFILTRATES SATURDAY GETS
QUICKLY PUSHED ASIDE AS ANOTHER SYSTEM TO THE WEST PUSHES TOWARD
US AND A WEAK WARM FRONT SPREADS ACROSS OUR FORECAST AREA LATER
IN THE DAY. LOOK FOR SNOW SHOWERS TO INCREASE OVER THE MOUNTAINS
BY SUNDAY EVENING AND SPREAD TO THE PLAINS. NO SIGNIFICANT
ACCUMULATIONS ARE EXPECTED FROM THIS SYSTEM THROUGH SUNDAY NIGHT.
BT

.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...

THE MESSAGE IN THE LONG TERM IS TWO-FOLD...1/ A PERIOD OF SNOW
AND COLDER TEMPERATURES IS POSSIBLE IF NOT LIKELY SOMETIME FROM
MONDAY NIGHT THROUGH WEDNESDAY...AND 2/ WE HAVE HIGH CONFIDENCE
THAT WARM WEATHER WILL RETURN BY LATE NEXT WEEK AND BEYOND.

THE LAST SEVERAL MODEL CYCLES HAVE OFFERED UP SUBTLE...BUT DRASTIC
DIFFERENCES IN THE TIMING OF ANOTHER ARCTIC COLD FRONTAL INTRUSION
IN THE EARLY TO MIDDLE PART OF NEXT WEEK. A MULTI-MODEL AND MULTI-
RUN MEAN APPROACH SUGGESTS THE HIGHEST PROBABILITY OF SNOW WILL BE
TUESDAY AFTERNOON INTO TUESDAY EVENING...AND THE 12 UTC ECMWF DID
SPEED UP ITS DEPICTION OF THE ARCTIC FRONT AND POST-FRONTAL SNOW
AND THUS MATCHED THAT IDEA BETTER THAN ITS 00 UTC RUN. CONFIDENCE
REMAINS MODEST AT BEST THOUGH. ONE TREND THAT IS APPARENT IN THE
LAST FEW RUNS OF BOTH THE GFS AND ECMWF IS FOR LOWER QPF /LIQUID-
EQUIVALENT MOISTURE/...SO WHILE ACCUMULATING SNOW IS VERY
POSSIBLE...THE RISK OF OUTRIGHT HEAVY SNOW IS QUESTIONABLE.

THE 12 UTC GFS...ECMWF AND RELATED ENSEMBLE DATA INCLUDING NAEFS
OUTPUT STRONGLY AGREES THAT UPPER-LEVEL RIDGING WILL NUDGE EAST
AGAIN BY LATE NEXT WEEK. AN ANOMALOUSLY WARM AIR MASS WILL AGAIN
FOLLOW WITH HIGHS ABOVE 50 F LIKELY AGAIN STARTING NEXT FRIDAY.
SCHULTZ

&&

.AVIATION...

VFR CONDITIONS WILL CONTINUE THROUGH THIS EVENING...BUT THERE IS
A HIGH PROBABILITY OF IFR CEILINGS AND VISIBILITIES WITH LOW
CLOUDS AND PATCHY FOG DEVELOPING IN SOUTHEAST MT BETWEEN 06 AND 12
UTC. LIGHT FREEZING DRIZZLE IS EVEN POSSIBLE IN SOUTHEAST MT AT
KMLS AND KBHK LATE TONIGHT AND SATURDAY MORNING UNTIL THE CLOUD
LAYER DEEPENS ENOUGH FOR LIGHT SNOW TO BEGIN BY SATURDAY
AFTERNOON. THE CEILINGS WILL ALSO LOWER TO SUB-VR LEVELS ELSEWHERE
ACROSS THE AREA BY SATURDAY AFTERNOON AS THAT LIGHT SNOW DEVELOPS.
SCHULTZ

&&

.PRELIMINARY POINT TEMP/POPS...

    SAT     SUN     MON     TUE     WED     THU     FRI
-----------------------------------------------------------
BIL 029/038 015/031 028/045 028/028 012/028 021/043 033/053
    06/S    71/E    43/O    45/S    42/J    11/B    11/N
LVM 024/041 016/037 031/047 034/040 020/035 026/046 034/055
    02/O    51/E    43/R    46/R    42/J    21/B    11/N
HDN 024/036 011/030 022/043 024/028 006/026 015/041 026/051
    06/S    61/E    33/O    35/S    41/B    21/B    11/B
MLS 022/030 007/024 018/035 018/019 000/019 009/035 023/047
    07/S    61/E    33/O    54/S    21/B    11/B    11/B
4BQ 025/041 011/027 021/043 025/029 007/023 016/042 027/055
    03/O    71/E    23/O    24/S    41/B    11/B    11/B
BHK 021/026 003/019 012/033 016/018 901/014 005/034 022/046
    18/S    81/E    23/S    44/S    21/B    11/B    11/B
SHR 020/040 011/029 021/044 025/036 009/030 015/042 026/053
    01/B    31/B    22/O    25/O    52/J    11/B    11/B

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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