Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 170112
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
612 PM MST TUE DEC 16 2014

.UPDATE...

WE MADE A COLLABORATIVE FORECAST MOVE LED BY NWS GREAT FALLS THAT
MEANT INCREASING THE CHANCE OF SNOW TONIGHT IN THE LIVINGSTON AND
COOKE CITY AREAS NORTHEAST TOWARD HARLOWTON. WE EVEN ADDED A LOW-
END CHANCE OF SNOW TO THE RYEGATE AND ROUNDUP AREAS AFTER 06 UTC.
THIS CHANGE WAS MADE BASED ON UPSTREAM OBSERVATIONS OF LIGHT SNOW
WITH VISIBILITY BETWEEN 1 AND 3 SM FROM THE ID PANHANDLE AND THEN
INTO SOUTHWEST MONTANA AT DILLON AND BUTTE. FORECAST SOUNDINGS AT
LIVINGSTON ARE NOT ESPECIALLY SATURATED...BUT THERE WAS ENOUGH TO
INCREASE POPS INTO THE 40 PERCENT RANGE THERE AFTER 06 UTC. WE/LL
TAKE A ANOTHER LOOK AT THIS SITUATION BY 9 PM MST.

FOG STILL LOOKS LIKE THE MAIN WEATHER IMPACT TONIGHT...BUT SO FAR
WE HAVE NOT SEEN WIDESPREAD LOW VISIBILITY THAT REQUIRES ADVISORY
ISSUANCE. THAT WILL ALSO BE MONITORED THE NEXT FEW HOURS. SCHULTZ

&&

.SHORT TERM...VALID FOR WED AND THU...

AREAS OF FOG STILL PERSISTING ACROSS PORTIONS OF SC/SE MT THIS
AFTERNOON. MOIST UPSLOPE FLOW OF AIR WITH LIGHT WINDS ALOFT IS
ALLOWING FOG TO CONTINUE OVER THE AREA. VISIBILITY HAS BEEN
IMPROVING OVER OUR WESTERN ZONES LATE THIS AFTERNOON AS A WEAK
DISTURBANCE MOVES TOWARD OUR REGION AND IS SPREADING MID LEVEL
CLOUD DECK ACROSS THE AREA. WILL GO AHEAD AND DROP THE DENSE FOG
ADVISORY FOR OUR WESTERN ZONES WITH IMPROVING VISIBILITIES. HRRR
IS SHOWING MOIST UPSLOPE FLOW TO CONTINUE OVERNIGHT AND FOG WILL
AGAIN BE POSSIBLE OVER MUCH OF OUR FORECAST AREA. MOISTURE NOT
AS DEEP AS THE PREVIOUS NIGHT AND DO NOT EXPECT WIDESPREAD FOG
WITH VISIBILITY BELOW A 1/2 MILE.

UPPER WAVE WILL DRIFT SLOWLY ACROSS THE AREA WEDNESDAY AS 300 MB
JET STAYS WELL SOUTH OF US. WEAK QG FORCING WITH THIS WAVE WILL
BRING SOME LIGHT SNOW TO THE PLAINS TOMORROW BUT NO SNOW
ACCUMULATIONS ARE EXPECTED. DRY WEATHER RETURNING TO THE PLAINS
WEDNESDAY NIGHT THROUGH THURSDAY AS WEAK SHORT WAVE RIDGING
MOVES ACROSS THE REGION. SOME MOUNTAIN SNOW SHOWERS WILL CONTINUE
THROUGH THIS PERIOD BUT AMOUNTS WILL BE LIGHT. WITH INCREASING
HEIGHTS WEDNESDAY AND THURSDAY...TEMPERATURES WILL CLIMB BACK TO
NEAR SEASONAL NORMALS. RICHMOND

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

MODELS CONTINUE TO INCREASE CONFIDENCE IN THE EXTENDED. BOTH THE
OPERATIONAL GFS AND ECMWF GENERALLY FIT WITHIN THE SPREAD OF THE
ENSEMBLE DATA. WEAK PACIFIC RIDGE WILL MOVE IN TO THE STATE
FRIDAY. SATURDAY ANOTHER SHORTWAVE WILL MOVE THROUGH...AS THE FLOW
INCREASES AND BECOMES MORE NORTHWESTERLY. PRECIP CHANCES WILL
INCREASE IN THE MOUNTAINS.

SUNDAY WILL SEE SOME LEESIDE TROUGHING DEVELOP. WINDS WILL PICKUP
AROUND NYE AND LIVINGSTON AS THE PRESSURE GRADIENT TIGHTENS DURING
THE DAY SUNDAY. WINDS WILL BEGIN TO INCREASE SUNDAY NIGHT TO AROUND
BILLINGS. FOR MONDAY...IT STILL LOOKS LIKE A COLD FRONT WILL MOVE
THROUGH AS A SURFACE LOW DROPS OUT OF CANADA...BRING PRECIP TO
MUCH OF THE AREA. AS WITH THE PREVIOUS FORECAST...MODELS CONTINUE
TO DEVELOP AN ATMOSPHERIC RIVER...GIVING THE AREA PLENTY OF
MOISTURE. WITH THIS STILL A LONG WAY OFF...HAVE OPTED TO CONTINUE
SIMILAR POPS TO THE PREVIOUS FORECAST. GIVEN THAT TEMPERATURES
WILL STILL BE WARM...LOOKS LIKE MUCH OF THE CENTRAL ZONES WILL
SEE RAIN THAT WILL SWITCH TO SNOW AS TEMPERATURES DROP MONDAY
NIGHT. REIMER

&&

.AVIATION...

PERSISTENT LOW CIGS WILL KEEP FLIGHT CONDITIONS SUB-VFR IN ALL
LOCATIONS...WITH AS LOW AS VLIFR IN SOME LOCATIONS OVERNIGHT.
AREAS OF FOG ARE AGAIN POSSIBLE ACROSS THE REGION OVERNIGHT...AS
WELL AS SNOW OVER AREA MOUNTAINS AND NEAR FOOTHILLS REGIONS.
WIDESPREAD MOUNTAIN OBSCURATIONS ARE EXPECTED THROUGH THE NIGHT.
FLIGHT CONDITIONS ARE EXPECTED TO IMPROVE THROUGH THE DAY
WEDNESDAY. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    WED     THU     FRI     SAT     SUN     MON     TUE
-----------------------------------------------------------
BIL 020/036 022/039 023/038 027/042 026/044 035/047 030/041
    11/E    01/B    10/U    11/B    13/W    34/W    33/W
LVM 023/040 023/042 023/040 026/043 026/044 036/047 030/043
    42/J    11/E    11/B    11/N    13/W    33/W    33/W
HDN 014/032 015/037 016/037 020/040 019/041 029/044 026/040
    01/E    01/B    10/U    01/B    12/W    33/W    33/W
MLS 014/029 016/036 019/037 019/039 022/041 030/043 026/039
    11/E    01/B    10/U    01/B    11/B    33/W    32/W
4BQ 014/030 016/040 018/040 017/041 020/043 030/045 027/041
    02/J    01/B    11/B    00/B    11/B    33/W    32/W
BHK 011/025 015/035 019/037 017/039 020/040 027/041 024/037
    02/J    11/B    11/B    01/U    01/B    33/W    22/J
SHR 015/038 015/038 016/038 019/040 019/041 028/043 025/040
    01/B    01/B    10/U    01/B    12/J    34/W    43/W

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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