Area Forecast Discussion
Issued by NWS Billings, MT

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS65 KBYZ 242233
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
333 PM MST MON NOV 24 2014

.SHORT TERM...VALID FOR TUE AND WED...

WINTER WEATHER AND RELATED TRAVEL IMPACTS COMING FROM SNOW-COVERED
AND SLIPPERY ROADS WITH REDUCED VISIBILITIES IS OUR MAIN FOCUS FOR
THE NEXT FEW DAYS.

STRONG WINDS GUSTING TO 70 MPH ARE STILL EXPECTED TONIGHT AND INTO
TUESDAY MORNING IN THE LIVINGSTON AND NYE AREAS...UNTIL THE STABLE
LAYER AT MOUNTAIN-TOP LEVEL IS DISRUPTED BY 18 UTC TUESDAY.

IN SOUTHEASTERN MT LATE TONIGHT AND ESPECIALLY ON TUESDAY...WE ARE
EXPECTING 1 TO 2 INCHES OF SNOWFALL AND NORTHWEST WINDS GUSTING TO
30 MPH. THAT/S NOT ENOUGH FOR AN ADVISORY AS VISIBILITY REDUCTIONS
WILL BE TIED TO FALLING SNOW AND THUS THEY COULD BE QUITE VARIABLE
IN TIME AND SPACE AS SNOW SHOWERS WILL BE CONVECTIVELY-ENHANCED AS
MID-LEVEL LAPSE RATES STEEPEN. THE RAPID APPROACH OF THE LEFT EXIT
REGION OF A 150 KT 300-MB JET AND ASSOCIATED RAMP-UP IN QG FORCING
WILL DRIVE THIS QUICK-HITTING EVENT AND FOR THAT REASON WE DO HAVE
LIKELY POPS IN THE FORECAST BY TUESDAY MORNING IN SOUTHEASTERN MT.

WE THEN EXPECT A 2 TO 5 INCH SNOWFALL OVER THE LOWER ELEVATIONS OF
SOUTH CENTRAL MT AND NORTH CENTRAL WY TUESDAY NIGHT AND WEDNESDAY.
THAT SNOW WILL BE DRIVEN BY LOW- AND MID-LEVEL FRONTOGENESIS ALONG
WITH MOISTURE ADVECTION ALOFT OVER THE TOP OF THE FRONTAL ZONE. WE
CONTINUED TO UTILIZE THE LOWER-END OF MOST MODEL LIQUID-EQUIVALENT
MOISTURE TOTALS WITH THIS EVENT BECAUSE QG-FORCING ABOVE THE FRONT
IS LACKING WITH THE MAIN 300-MB JET AXIS DISPLACED NORTHEAST A BIT
TOO FAR FOR MORE THAN A BROAD RESPONSE IN VERTICAL MOTION. WE ALSO
EXPECT SNOW-TO-LIQUID RATIOS TO BE HELD IN THE 10 OR 12 TO 1 RANGE
SINCE THERMAL PROFILES WILL ACTUALLY WARM DURING THE EVENT AND ARE
NOT EXPECTED TO SUPPORT MUCH DENDRITIC GROWTH TO BEGIN WITH. WE DO
NEED TO NOTE ONE SUBTLE TREND IN THE 12 UTC GFS AND 09 UTC SREF IS
TO DELAY THE START AND END OF THE SNOW...ESPECIALLY NEAR BILLINGS.
WE NUDGED THE FORECAST IN THAT DIRECTION...BUT THE 12 UTC ECMWF IS
STILL QUICKER WITH THAT PROGRESSION...SO THERE ARE SOME DETAILS ON
THE TABLE FOR DEBATE YET. REGARDLESS...EVEN WHERE SNOWFALL ENDS UP
CLOSER TO 2 INCHES INSTEAD OF 5 INCHES...SLIPPERY ROADS AND TRAVEL
IMPACTS SUPPORTED ISSUING A WINTER WEATHER ADVISORY IN MANY AREAS.
WE WENT WITH A WINTER STORM WARNING IN THE MOUNTAINS WHERE PACIFIC
MOISTURE WILL SUPPORT HIGHER TOTALS BETWEEN 10 AND 20 INCHES. NOTE
THAT THERE IS A LOW PROBABILITY OF SOME FREEZING RAIN LATER IN THE
EVENT...WEDNESDAY AFTERNOON OR EVENING AS THE FRONTAL ZONE FINALLY
LIFTS NORTHEAST. HOWEVER...MID-LEVEL DRYING MAY OUTPACE THE WARMER
AIR ALOFT AS 12 UTC GFS SOUNDINGS SUGGEST...SO WE CHOSE TO HOLD ON
MENTIONING THAT IN THE FORECAST FOR NOW. SCHULTZ

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

WARMER TEMPERATURES FROM THURSDAY WILL BLEED OVER INTO FRIDAY WITH
STRONG ZONAL FLOW OVER THE AREA. EXPECT ANOTHER PERIOD OF STRONG
FOOTHILLS WINDS FRIDAY NIGHT INTO EARLY SATURDAY. A SYSTEM DROPS
SOUTHWARD OUT OF SOUTHWEST CANADA PUSHING AN AREA OF ENHANCED
VORTICITY OVER THE AREA SATURDAY INTO SUNDAY. THIS SYSTEM PUSHES
THE JET TO THE SOUTH ALLOWING COLDER AIR TO DROP BACK INTO THE
REGION FOR SATURDAY AND SUNDAY. IN ADDITION TO COLDER AIR A GOOD
CHANCE FOR PRECIPITATION SHOULD DEVELOP SATURDAY INTO
SUNDAY...ESPECIALLY OVER MOUNTAIN LOCATIONS FOR THE FIRST SKI
WEEKEND OF THE SEASON. ZONAL FLOW REDEVELOPS MONDAY WHICH SHOULD
SCOUR OUT COLDER AIR AND BEGIN TO WARM TEMPERATURES BACK UP GOING
INTO EARLY NEXT WEEK. OVERALL THIS NEXT 7 TO 10 DAYS WILL SEE
SOME VERY BIG TEMPERATURE SWINGS DAY TO DAY ALONG WITH PERIODS OF
WET/SNOWY CONDITIONS. CHAMBERS

&&

.AVIATION...

BIGGEST CONCERN OVERNIGHT WILL BE THE DEVELOPMENT OF WINDS GUSTING
OVER 50KTS...ALONG THE WESTERN FOOTHILLS ALONG WITH MOUNTAIN WAVE
ACTIVITY AND LOW LEVEL WIND SHEAR FURTHER INTO THE PLAINS AND EAST
OF THE BIG HORN MOUNTAINS. THERE WILL BE SOME SNOW SHOWER ACTIVITY
LINGERING INTO THE EARLY EVENING WITH LOCAL MVFR CONDITIONS BUT
MUCH OF THIS WILL DISSIPATE WITH SUNSET. MORE PRECIPITATION WILL
MOVE INTO THE AREA BEFORE SUNRISE FOR WESTERN AREAS...MAINLY
IMPACTING THE MOUNTAINS AND FOOTHILLS INITIALLY. LOCAL MVFR
CONDITIONS CAN BE EXPECTED WITH THIS ACTIVITY. FOR AREAS FROM
HARLOWTON TO LIVINGSTON AND NYE THE COMBINATION OF STRONG WINDS
AND SNOW COULD CREATE SOME AREAS OF VISIBILITY ISSUES DUE TO
BLOWING SNOW. SNOW SHOULD BECOME MORE WIDESPREAD DURING THE DAY
TUESDAY WITH DETERIORATING FLIGHT CONDITIONS ALL AREAS. CHAMBERS

&&

.PRELIMINARY POINT TEMP/POPS...

    TUE     WED     THU     FRI     SAT     SUN     MON
-----------------------------------------------------------
BIL 031/040 027/036 025/044 034/044 014/014 004/019 013/032
    24/W    89/O    31/E    11/B    24/J    42/J    11/B
LVM 030/038 030/041 032/046 034/042 020/021 009/031 025/037
    36/W    83/O    21/N    12/W    45/J    42/J    22/W
HDN 025/039 022/035 019/043 028/043 014/017 004/020 011/029
    24/W    89/O    31/E    11/B    23/J    31/B    11/B
MLS 026/037 021/028 016/039 029/039 010/011 903/017 009/025
    57/W    48/S    62/O    11/B    23/J    21/B    11/B
4BQ 025/037 021/031 017/046 027/041 014/016 002/023 015/035
    47/W    46/S    41/E    11/B    23/J    31/B    11/B
BHK 019/033 017/024 014/034 027/038 012/013 903/015 010/029
    37/J    36/S    52/S    11/B    23/J    21/B    11/B
SHR 021/037 022/036 020/044 028/043 017/022 007/027 017/036
    24/W    67/O    21/E    11/B    13/J    31/B    11/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY IN EFFECT FROM NOON TUESDAY TO NOON
      MST WEDNESDAY FOR ZONES 28-40-41-56-63>66.
     WINTER WEATHER ADVISORY IN EFFECT FROM 6 PM TUESDAY TO 6 PM
      MST WEDNESDAY FOR ZONES 29>31-34-35-38-39-42-57-58.
     WIND ADVISORY IN EFFECT UNTIL NOON MST TUESDAY FOR ZONES
      65-66.
     WINTER STORM WARNING IN EFFECT FROM MIDNIGHT TONIGHT TO NOON
      MST WEDNESDAY FOR ZONES 67-68.
WY...WINTER WEATHER ADVISORY IN EFFECT FROM 6 PM TUESDAY TO 6 PM
      MST WEDNESDAY FOR ZONE 99.
     WINTER WEATHER ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO 6
      PM MST WEDNESDAY FOR ZONE 98.

&&

$$
WEATHER.GOV/BILLINGS


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.