Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 130248 AAA
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
848 PM MDT SAT APR 12 2014

.UPDATE...
UPGRADED THE ADVISORY FOR SOUTHERN BIG HORN COUNTY AND SHERIDAN
COUNTY TO A WINTER STORM WARNING. OBSERVATIONS WERE INDICATING
THAT MODERATE TO HEAVY SNOW STARTED DOWN THERE AROUND 6 PM. WEB
CAMS WERE SHOWING ROAD SURFACES BECOMING SLUSH COVERED WITH A
LAYER OF WHITE ON THE GRASS. TAIL END OF A JET MAX WAS SWINGING
RIGHT OVER SOUTHERN MONTANA THIS HOUR AND WILL ENHANCE THE
SNOWFALL THERE INTO EARLY MORNING. RAPID REFRESH PRODUCTS WERE
POINTING TO VISIBILITIES BELOW A MILE IN SHERIDAN ITSELF FOR A
LARGE PORTION OF THE NIGHT AND AS TEMPERATURES FALL...ACCUMULATION
WILL BE EASIER TO COME BY. THE HEAVIEST SNOW WILL BE ALONG THE
FOOTHILLS TOWARD DAYTON AND STORY...WITH ACCUMULATIONS OF 4 TO 8
INCHES OFF THE SLOPES TOWARD SHERIDAN. AREAS ALONG THE FOOTHILLS
COULD PICK UP 8 TO 12 INCHES.

THE REST OF THE WARNINGS AND ADVISORIES LOOK IN GOOD SHAPE. OVER
RUNNING IN PLACE WITH THE AFOREMENTIONED JET STREAK OVER HEAD AND
DEEP UPSLOPE TO AROUND 600MB. SNOW HAS BEEN LIGHT IN BILLINGS BUT
WAS FILLING IN TO THE WEST...SO COULD GET A SLUSHY INCH BY
MORNING. THE HEAVIEST SNOW CERTAINLY DOES LOOK TO THE SOUTH OF
BILLINGS FOR THIS EVENT. UPDATE ALREADY SENT. TWH

&&

.SHORT TERM...VALID FOR SUN AND MON...

NO MAJOR CHANGES TO THE GOING FORECAST THIS AFTERNOON...AND NO
CHANGES TO WINTER STORM WARNINGS OR ADVISORIES. ROADS WILL
PROBABLY BE SLICK SUNDAY MORNING...EVEN IN AREAS THAT DON`T HAVE
WINTER HIGHLITES IN PLACE.

COLD CANADIAN AIR IS WORKING INTO THE AREA AT THIS TIME.
TEMPERATURES HAVE DROPPED INTO THE 30S ALONG AND NORTH OF
I-90/I-94...AS WELL AS ALONG THE BEARTOOTH FOOTHILLS. RADAR IS
SHOWING STRONG RETURNS NORTH/WEST AND SOUTH OF THE RADAR BUT STILL
SEEING A GOOD DEAL OF THIS ACTIVITY NOT QUITE REACHING THE GROUND
BASED ON OBSERVATIONS. DID GET A REPORT OF 0.03 INCHES OF RAIN SO
FAR IN NYE WITH A TEMPERATURE OF 37 DEGREES SO SHOULD SEE SNOW
BEGINNING FROM RED LODGE TO MCLEOD SHORTLY. AS THE COLD AIR
DEEPENS UP WILL SEE PRECIPITATION FILL IN ACROSS THE REST OF THE
AREA LATE THIS AFTERNOON. SHORT RANGE MODELS ARE ALL HITTING THE
WARNING AREAS VERY HARD WITH SNOW OVER THE NEXT 8 HOURS WITH HRRR
SHOWING ALMOST 18 INCHES IN RED LODGE BY 10 PM THIS EVENING. THINK
THESE MODELS MAY BE A BIT FAST WITH TIMING AND MAY BE OVERDOING
THE SNOW RATES...BUT WILL NOT BE SURPRISED TO SEE SOME FOOTHILLS
AREAS GOING OVER A FOOT OF ACCUMULATION TONIGHT.

WAS TEMPTED TO BUMP THE ADVISORY FOR THE SHERIDAN FOOTHILLS AND
SOUTHERN BIG HORN TO A WARNING...BUT TIMING OF SNOW BEGINNING LOOKS
TO BE JUST A BIT LATE TO GENERATE FOR SURE SNOW ACCUMULATIONS
HEAVY ENOUGH TO WARRANT THAT. IT WILL DEFINITELY BE NASTY TRAVEL
CONDITIONS AT TIMES TONIGHT ON I-90 OVER ABERDEEN HILL AND OVER
THE HILLS SOUTH OF SHERIDAN THOUGH AND MAY NEED TO UPGRADE LATER
THIS EVENING DEPENDING ON HOW QUICKLY SNOW DEVELOPS. ALSO THOUGHT
ABOUT GOING WITH AN ADVISORY FOR SOUTHERN ROSEBUD AND WESTERN
POWDER RIVER COUNTIES BASED ON THIS AREA SEEING GOOD UPSLOPE FLOW.
HOWEVER MODELS ALL CONSISTENT WITH KEEPING HEAVIER QPF WEST OF
THIS AREA AS UPPER LOW DROPS STRAIGHT SOUTH THROUGH WESTERN
WYOMING. SO KEPT CURRENT SNOW ACCUMULATIONS AROUND 3 INCHES IN
THERE WITHOUT AN ADVISORY FOR NOW. FOR OTHER AREAS THERE WILL BE
SOME LOCATIONS ON THE PERIFERY OF THE ADVISORY AREA THAT SEE 2 TO
4 INCHES OF SNOW BUT IMPACTS IN THESE AREAS ARE EXPECTED TO BE
MINOR AS SNOW WILL MELT ON AREA ROADS FOR MUCH OF THE EVENT AND BY
THE TIME TEMPERATURES GET COLD ENOUGH FOR SNOW TO REALLY STICK AND
CAUSE TRAVEL ISSUES THE PRECIPITATION WILL BE ENDING.

BASED ON THE CURRENT TEMPERATURES OVER NORTHERN MONTANA AND
SOUTHERN CANADA UNDER THE CANADIAN HIGH PRESSURE WHICH IS SLIDING
SOUTH...LOWS IN THE LOW TO MID 20S SEEM REASONABLE TONIGHT.

FOR TOMORROW...STORM SYSTEM QUICKLY DIVES SOUTH TOWARD COLORADO
LEAVING IMPROVING CONDITIONS FOR OUR AREA...ESPECIALLY BY
AFTERNOON. INSTABILITY SHOWERS UNDER NORTHWEST FLOW ALOFT WILL
KEEP LOW POPS IN THE FORECAST BUT ACCUMULATING SNOW SHOULD END
BEFORE NOON. TEMPERATURES WILL BE QUITE COOL TOMORROW WITH MOD TO
UPPER 30S COMMON IN THE AFTERNOON. SUNDAY NIGHT WILL BE COLD WITH
TEMPERATURES IN THE TEENS AND LOWER 20S AS CANADIAN HIGH PRESSURE
SITS OVER THE AREA AND SKIES CLEAR ALLOWING GOOD RADIATIONAL
COOLING TO COMMENCE.

RIDGING BUILDS INTO THE AREA FOR MONDAY WITH TEMPERATURES PUSHING
BACK TOWARD 50 DEGREES UNDER SUNNY SKIES. COULD BE A BIT OF FOG IN
THE MORNING GIVEN THE SIGNIFICANT PRECIPITATION IN THE PREVIOUS 36
HOURS. CHAMBERS

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

ACTIVE WEATHER COMING MIDWEEK AND ALL MODELS CONTINUE TO TREND IN
THIS DIRECTION. HIGH CONFIDENCE EXISTS IN A CUT OFF HIGH FORMING
IN NW CANADA...ALLOW FOR LOWER THAN NORMAL HEIGHTS OVER THE
NORTHERN ROCKIES...WITH A PHASING BETWEEN PACIFIC ENERGY AND
COLDER NW FLOW OVER CENTRAL CANADA.

CHANCES OF PCPN WILL INCREASE BY TUESDAY AFTERNOON IN OUR WEST AS
PAC TROF MOVES INTO THE NORTHERN ROCKIES. HAVE RAISED POPS TO
LIKELY OVER THE MTNS TO COVER THIS. OTHERWISE TUESDAY ITSELF WILL
BE A WARMER DAY WITH SOME DOWNSLOPE WARMING AHEAD OF THIS TROF AND
SHOULD SEE 60F IN PLACES.

LOOKS LIKE A PERIOD OF WET WEATHER IN THE FORM OF RAIN TO WET
SNOW COMING LATE TUESDAY THRU WEDNESDAY. ALTHOUGH MODELS ARE ALL
TRENDING THIS WAY THEY CONTINUE TO DIFFER IN DETAILS...WITH THE
CANADIAN BEING COLDEST/WETTEST AND ECMWF WARMEST/DRIEST AND LEAST
AMPLIFIED. WILL RIDE THE MIDDLE HERE...WHICH STILL SUGGESTS HIGHER
POPS AND A MENTION OF SNOW ACROSS THE LOWER ELEVATIONS LATE
TUESDAY NIGHT THROUGH WEDNESDAY AS 850MB TEMPS FALL BELOW ZERO.
COLD ADVECTION PER NE SFC WINDS SUPPORTED BY THE SHARP SOUTH
CENTRAL CANADIAN TROF/CYCLONIC FLOW SAGGING INTO THE NORTH CENTRAL
CONUS. POTENTIAL EXISTS FOR SOME SNOWFALL ACROSS THE LOWER
ELEVATIONS BUT NOT SURE IF THE FOOTHILLS OUR OUR EAST WILL BE
FAVORED...THIS WILL DEPEND ON HOW AMPLIFIED THE PAC TROF BECOMES
AND HOW DEEP THE CANADIAN COLD SURGE WILL BE. FOR NOW...HAVE
RAISED POPS TUESDAY NIGHT AND WEDNESDAY AND MENTIONED A CHANCE OF
SNOW ACROSS THE LOWER ELEVATIONS. THIS WILL NEED TO BE WATCHED.

LATEST MODEL TRENDS...WITH THE EXCEPTION OF ECMWF...ALSO SUGGEST
CANADIAN LOW TO OUR NORTH WILL BE SLOWER TO EJECT...AND THIS
COULD KEEP COLDER AIR AND CHANCES FOR PCPN LINGERED THROUGH
THURSDAY. HAVE ADJUSTED THE FORECAST TO ACCOUNT FOR THIS BY
LOWERING TEMPS A FEW DEGREES ON THURSDAY...WHILE KEEPING NEAR
CLIMO POPS. LOTS OF UNCERTAINTY HERE. NEXT PAC TROF LOOKS TO PUSH
INLAND BY FRIDAY. THIS WOULD ALLOW FOR DOWNSLOPE WINDS AND A
WARMING TREND ALONG WITH A CHANCE OF SHOWERS BY THE END OF THE
WEEK. OVERALL THE WEATHER WILL REMAIN ACTIVE. JKL

&&

.AVIATION...

SNOW WILL CONTINUE OVER MUCH OF SOUTH CENTRAL MONTANA AND
NORTHERN WYOMING THIS EVENING. EXPECT MVFR TO IFR FLIGHT
CONDITIONS ESPECIALLY ALONG THE EAST SLOPES OF THE
MOUNTAINS...INCLUDING LIVINGSTON...WITH ACCUMULATING SNOWFALL IN
THESE AREAS. LOCATIONS NEAREST THE SLOPES...LIKE AROUND RED LODGE
AND SHERIDAN... WILL EXPERIENCE VLIFR CONDITIONS MOST OF THE NIGHT
WITH MODERATE TO OCCASIONALLY HEAVY SNOWFALL. THE MOUNTAINS WILL
BE OBSCURED IN HEAVY SNOW. SNOW AND SUB-VFR CONDITIONS WILL
PERSIST INTO SUNDAY MORNING WITH A TRANSITION TO VFR AND DRY
WEATHER BY AFTERNOON. NORTH TO EAST WINDS WILL PERSIST TONIGHT.
WINDS WILL GUST TO 20-30 KTS AT LIVINGSTON AND SHERIDAN. TWH

&&

.PRELIMINARY POINT TEMP/POPS...

    SUN     MON     TUE     WED     THU     FRI     SAT
-----------------------------------------------------------
BIL 027/038 026/052 034/061 031/038 027/049 034/059 037/061
    84/O    10/B    03/W    55/W    22/W    22/W    21/B
LVM 027/037 021/050 033/059 032/042 027/050 034/057 033/058
    +6/S    10/B    05/W    55/W    22/W    23/W    32/W
HDN 028/038 024/052 031/064 031/039 025/051 031/061 033/062
    84/O    10/B    02/W    55/W    22/W    22/W    21/B
MLS 026/039 023/050 031/059 028/037 024/048 028/059 033/061
    32/O    10/B    02/W    44/J    11/B    12/W    21/B
4BQ 027/036 022/048 029/062 029/038 024/046 028/059 032/061
    62/O    10/B    02/W    55/W    22/W    12/W    21/B
BHK 023/035 020/042 026/053 025/032 020/042 024/054 032/057
    22/O    10/B    01/B    44/J    11/B    12/W    31/B
SHR 026/031 018/045 028/062 031/040 025/048 030/059 032/060
    +9/S    10/U    02/W    55/W    22/W    12/W    21/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY IN EFFECT UNTIL NOON MDT SUNDAY FOR
      ZONES 34-39>41-65.
     WINTER STORM WARNING IN EFFECT UNTIL NOON MDT SUNDAY FOR
      ZONES 38-56-66-67.
WY...WINTER STORM WARNING IN EFFECT UNTIL NOON MDT SUNDAY FOR
      ZONES 98-99.

&&

$$
WEATHER.GOV/BILLINGS



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