Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 030413
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
913 PM MST MON MAR 2 2015

.UPDATE...
SNOWING ACROSS MOST OF THE AREA AND JUST RECEIVED A 5 INCHES IN 3
HOUR REPORT FROM 7 MILES SOUTH OF ABSAROKEE IN THE BEARTOOTH
FOOTHILLS ZONE. RADAR IS SHOWING A STEADY STAE TO CURRENT COVERAGE
WHICH SHORT RANGE GUIDANCE FORECASTED BEFORE ACTIVITY BEGINNING TO
DECREASE AFTER MIDNIGHT FOR THE LOWER ELEVATIONS. NO UPDATES AT
THIS TIME AND WILL KEEP CURRENT HIGHLIGHTS GOING. BORSUM

&&

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

RELATIVELY FAST MOVING WEATHER SYSTEM TO INVADE OUR FORECAST AREA
OVERNIGHT LEAVING A VERY COLD AIR MASS OVER US FOR TUESDAY. MY
MAIN CONCERN WITH THIS SYSTEM IS THE POTENTIAL FOR BLOWING/DRIFTING
SNOW LEADING TO VERY POOR TRAVEL CONDITIONS DUE TO SNOWPACKED
ROADS AND SEVERELY REDUCED VISIBILITY AT TIMES. THIS IS PRIMARILY
TRUE IN THE JUDITH GAP AREA BUT ALSO ALONG AND SOUTH OF I-90 INTO
THE BEARTOOTH FOOTHILLS...AND ALSO FROM FORT SMITH TO DAYTON AND
DOWN INTO STORY. LOW LEVEL LAPSE RATES WILL BE STEEP ACCORDING TO
MODEL PROGGS AND PRESSURE GRADIENTS TIGHT AS COLD AIR RUSHES IN
THIS EVENING. THERE IS A VERY DEEP DENDRITIC GROWTH ZONE OVER THE
WESTERN ZONES AT 8 PM THIS EVENING LASTING FOR A FEW HOURS. FURTHER
EAST...MODELS ARE NOT COMING UP WITH MUCH QPF OVER THE PLAINS AND
WE DID LOWER FORECAST AMOUNTS SOME ON THE WSW PRODUCT FOR THE
PLAINS....BUT AREAS OF BLOWING SNOW WILL STILL BE AN ISSUE OVER
THE PLAINS AT TIMES OVERNIGHT...AND DOWN INTO THE SHERIDAN
FOOTHILLS EARLY TUESDAY. THE DYNAMICS AND UPSLOPE GENERALLY END BY
MIDDAY TUESDAY.

CROSS SECTIONS KEEP THE LIFT AND SATURATED LAYERS LOW IN THE
BEARTOOTH/ABSAROKA REGION TONIGHT. SO DESPITE SOME STEEP LAPSE
RATES THE HIGH COUNTRY MAY NOT SEE AS MUCH SNOW AS THE FOOTHILLS.
HOWEVER...RED LODGE MOUNTAIN AND A FEW LOCATIONS COULD STILL SEE
SOME HEAVY SNOW ON THE NORTH FACING SLOPES...SO WILL NOT MESS WITH
DOWNGRADING THE WARNING FOR THE MOUNTAINS BEFORE EVENT EVEN BEGINS
AS THIS WOULD LEAD TO PUBLIC/MEDIA CONFUSION.

WILL GO BELOW GUIDANCE NUMBERS FOR TUESDAY/WEDNESDAY TEMPERATURE
FORECASTS WHERE WE EXPECT TO SEE SNOW. VERY COLD AIR MASS
CERTAINLY FOR TUESDAY WITH 850MB TEMPS ONLY AROUND -15C FOR
BILLINGS. THIS MAY BE A SOLID 30 DEGREES BELOW NORMAL TUESDAY. BT


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

EXTENDED MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH THE PERIOD
WITH THE EXCEPTION OF THE FRIDAY/FRIDAY NIGHT PERIOD. A DRY
NORTHWEST FLOW ALOFT WILL BE OVER THE FORECAST AREA THURSDAY INTO
EARLY FRIDAY. MODELS THEN DIVERGE GREATLY BY LATE IN THE DAY
FRIDAY INTO FRIDAY NIGHT. THE LATEST EC BRINGS A DECENT PIECE OF
ENERGY SOUTH ACROSS WESTERN MONTANA AND EASTER IDAHO CLIPPING OUR
WESTERN ZONES...WHEREAS THE GFS HAS THIS WAVE OVER EASTERN NORTH
AND SOUTH DAKOTA. WILL CONTINUE WITH A SLIGHT POP CHANCE ACROSS
THE WESTERN HALF OF OUR FORECAST AREA AND SEE IF MODELS PHASE
TOGETHER SOMEWHAT OVER THE NEXT DAY OR SO.

MODELS THEN CONTINUE A NORTHWEST FLOW ALOFT GOING INTO THE
WEEKEND AND EARLY NEXT WEEK. HOWEVER...DIFFERENCES EXIST BETWEEN
THE GFS AND ECMWF IN THAT THE EC PERIODICALLY BRINGS SOME WEAK
DISTURBANCES ACROSS THE AREA WHEREAS THE GFS DOES NOT. AT THIS
TIME...MODELS AGREE TO THE POINT THAT NEITHER IS BRINGING ANY COLD
AIR INTO THE AREA. HOWEVER...THERE IS ABOUT A 10 DEGREE DIFFERENCE
IN THE TEMPERATURES WITH THE ECMWF SHOWING MAINLY MIDDLE AND UPPER
40S WHEREAS THE GFS IS SHOWING MOSTLY UPPER 50S. HOOLEY
&&

.AVIATION...

A STRONG COLD FRONT HAS SWEPT ACROSS THE FORECAST AREA THIS
EVENING...BRINGING GUSTY NORTHWEST WINDS AND FALLING TEMPERATURES
TO THE REGION. SNOW HAS SPREAD ALONG AND WEST OF A LINE FROM
ROUNDUP TO SHERIDAN....WITH LIFR TO VLIFR CIGS AND VIS COMMON IN
SNOW.

IFR CONDITIONS OR LOWER CAN BE EXPECTED ALONG AND WEST OF
THIS LINE INTO MID MORNING TUESDAY. AREAS EAST OF THE LINE WILL
ALSO SEE SIMILAR CONDITIONS...BUT LESS FREQUENTLY...AND CONDITIONS
SHOULD BE IMPROVING BY EARLY TUESDAY MORNING. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    TUE     WED     THU     FRI     SAT     SUN     MON
-----------------------------------------------------------
BIL 004/016 901/028 010/045 028/052 030/053 032/054 031/056
    83/S    00/B    00/B    01/B    21/B    01/U    10/U
LVM 000/014 904/028 015/045 028/052 030/053 032/054 031/056
    +4/S    00/B    00/N    11/N    21/B    01/B    10/B
HDN 007/019 901/027 008/047 022/055 026/052 026/055 027/057
    73/S    00/B    00/B    01/B    11/B    01/U    10/U
MLS 003/013 907/017 901/043 023/050 026/048 027/047 026/049
    41/N    20/B    00/B    01/B    11/B    01/B    10/U
4BQ 005/015 905/017 000/041 018/049 021/047 022/050 023/052
    72/S    20/B    00/U    00/B    11/B    01/B    10/U
BHK 001/011 909/011 903/040 021/046 023/046 025/044 022/046
    32/J    20/B    00/U    00/B    11/B    01/B    10/B
SHR 004/009 910/018 005/041 019/049 023/048 025/050 024/052
    96/S    00/B    00/U    01/B    21/B    01/B    10/U

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER WEATHER ADVISORY IN EFFECT UNTIL 9 AM MST TUESDAY FOR
      ZONES 28-29-42.
     WINTER STORM WARNING IN EFFECT UNTIL NOON MST TUESDAY FOR
      ZONES 34-38>41-56-64>67.
     WINTER WEATHER ADVISORY IN EFFECT UNTIL NOON MST TUESDAY FOR
      ZONES 35>37-57-58.
     WINTER STORM WARNING IN EFFECT UNTIL 9 AM MST TUESDAY FOR
      ZONE 63.
WY...WINTER STORM WARNING IN EFFECT UNTIL NOON MST TUESDAY FOR
      ZONES 98-99.

&&

$$
WEATHER.GOV/BILLINGS



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