Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 190224
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
724 PM MST THU DEC 18 2014

.UPDATE...

MADE A RELATIVELY MINOR UPDATE THIS EVENING TO ADD FLURRIES ACROSS
MUCH OF THE REGION FOR THE OVERNIGHT PERIOD. RADAR IS PAINTING
ECHOES OVER MUCH OF WESTERN AND NORTHWESTERN CWA...WHICH ARE
SLOWLY SHIFTING EASTWARD. ALSO RECEIVED REPORT FROM TFX OF LIGHT
SNOW/FLURRIES ON UPSTREAM WEBCAM. AM NOT CONFIDENT OF MEASURABLE
SNOW...BUT THINK NEED TO HAVE MENTION OF FLURRY POTENTIAL.
OTHERWISE GOING FORECAST APPEARS IN GOOD SHAPE. AAG

&&

.SHORT TERM...VALID FOR FRI AND SAT...

SHORT WAVE TROUGH WILL MOVE ACROSS THE AREA TONIGHT. UPPER LEVEL
FORCING AND MOISTURE LACKING WITH THIS SYSTEM AND WE ONLY EXPECT
ISOLATED SNOW SHOWERS OVER THE MOUNTAINS. AREA DRYING OUT LATE
TONIGHT INTO FRIDAY NIGHT AS SHORT WAVE RIDGING MOVES ACROSS THE
AREA. INCREASED HEIGHTS OVER THE AREA ALONG WITH SOME MIXING ALOFT
WILL COMBINE TO PRODUCE AFTERNOON TEMPERATURES IN THE UPPER 30S
TO LOWER 40S FRIDAY. RIDGE SHIFTING EAST LATE FRIDAY NIGHT AS
ANOTHER TROUGH OF LOW PRESSURE MOVES IN FROM THE WEST. THIS TROUGH
WILL BE SPLITTING AS IT MOVES ACROSS MONTANA ON SATURDAY WITH THE
BEST FORCING STAYING NORTH OF OUR REGION. 850 MB TEMPERATURES
WILL BE WARM WITH A +2C AND WE WILL SEE A MIX OF RAIN AND SNOW
SHOWERS.

FAST ZONAL FLOW SETTING UP SATURDAY NIGHT WITH STRONG 100 KT JET
PUSHING INTO THE REGION. LEE-SIDE TROUGH SETTING UP AHEAD OF
ENERGY MOVING IN FROM THE WEST COAST. THIS ENERGY WILL BRING 700
MB WINDS OF 50 KTS INTO OUR WESTERN AREAS. MODEL CROSS SECTIONS
SHOWING STABLE LAYER TO SET UP AT MOUNTAINS TOP LEVEL AND THIS
WILL BRING GAP FLOW WINDS LATE SATURDAY NIGHT TO THE LIVINGSTON
AND NYE AREAS. PRESSURE GRADIENT WILL BE INCREASING NEAR BIG
TIMBER AND LOCAL WIND GUIDANCE ALSO SHOWING WINDS WILL BE CLOSE TO
ADVISORY LEVEL THERE. HAVE INCREASED WINDS FOR LIVINGSTON/NYE AND
BIG TIMBER SATURDAY NIGHT AND WILL COVER WIND POTENTIAL WITH AN
HWO. MODELS ARE ALL IN GOOD AGREEMENT IN MOVING Q VECTOR
CONVERGENCE ACROSS THE AREA SATURDAY NIGHT. THIS WILL BRING A FEW
SNOW SHOWERS TO THE AREA. STRONGEST LIFT WILL BE OVER OUR
SOUTHWEST MOUNTAINS WITH JET DYNAMICS/Q VECTOR CONVERGENCE AND
OROGRAPHIC LIFTING. SHOULD SEE 3 TO 5 INCHES OF SNOW ABOVE 7000
FEET. PRECIPITATION AMOUNTS WILL BE LIGHT OVER THE PLAINS WITH
STRONG DOWNSLOPE WINDS OVER THE AREA. RICHMOND


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

ACTIVE WEATHER IN STORE FOR THE EXTENDED PERIOD WITH SEVERAL
POTENTIAL IMPACTS TO CONSIDER.

DEEP PACIFIC MOISTURE PLUME WITH A PWAT STANDARDIZED ANOMALY NEAR
+2 EMBEDDED IN WNW FLOW ALOFT WILL IMPACT OUR WESTERN MOUNTAINS
SUNDAY AND MONDAY. THIS WILL RESULT IN A PERIOD OF ACCUMULATING
SNOWFALL AND POTENTIALLY HEAVY AMOUNTS FOR THE WEST ASPECTS OF
THE BEARTOOTH ABSAROKA AND CRAZY MOUNTAINS. LOWER ELEVATIONS WILL
SEE OCCASIONAL SHOWER ACTIVITY...AND CANNOT RULE OUT SOME LIGHT
FREEZING RAIN EAST OF SFC TROF EARLY SUNDAY MORNING AND AGAIN
MONDAY NIGHT.

SUNDAY WILL BEGIN WITH STRONG SW WINDS ALONG THE WESTERN FOOTHILLS
PER 50+ KTS OF 700MB FLOW AND FAIRLY DEEP LEE SIDE SFC TROFFING.
HAVE RAISED WIND SPEEDS FROM LIVINGSTON TO BIG TIMBER AND
HARLOWTON SUNDAY MORNING...WITH A DECREASE EXPECTED BY AFTERNOON
WITH CAA BEHIND MID LEVEL SHORTWAVE...THOUGH SHOULD BE NOTED THAT
W-NW WINDS WILL BECOME GUSTY ACROSS THE LOWER ELEVATIONS. THERE IS
A POSSIBILITY OF ANOTHER PERIOD OF STRONG FOOTHILLS WINDS BY
TUESDAY NIGHT BUT MODELS IN MORE DISAGREEMENT HERE.

TEMPERATURES SUNDAY THROUGH TUESDAY WILL STAY ABOVE NORMAL PER THE
WEST FLOW ALOFT AND PERSISTENT DOWNSLOPE GRADIENTS. HIGHS ON
SUNDAY WILL ACTUALLY PUSH 50F...WITH A BIT OF COOLING MONDAY AND
TUESDAY.

PATTERN SHIFT IS EXPECTED FOR THE MIDDLE OF THE WEEK AS RIDGE
BUILDS OVER THE NW PACIFIC AND TROF SLIDES FROM THE GULF OF AK
THROUGH THE NORTHERN ROCKIES...INTRODUCING NW FLOW TO OUR CWA BY
CHRISTMAS. CONFIDENCE IS HIGH IN THE OVERALL THEME HERE...COLDER
TEMPS AND A GOOD CHANCE OF SNOW...BUT MODELS ARE STILL EVOLVING IN
THE DETAILS. LATEST RUNS SUGGEST STRONGEST FORCING WILL STAY TO
OUR SOUTH WEDNESDAY AND WEDNESDAY NIGHT. THIS WOULD KEEP GREATEST
PCPN TO OUR SOUTH BUT STILL WITH SNOW SHOWERS IN OUR CWA PER THE
CYCLONIC FLOW AND WEAKER SHORTWAVE ACTIVITY. PREVIOUS ECMWF RUNS
HAD DEVELOPED A DEEP UPPER TROF OVER THE GREAT BASIN BUT THE
LATEST RUN HAS SHIFTED TOWARD THE GFS WITH LESS AMPLIFICATION
OVERALL. DIFFERENCES SEEM TO EMERGE FROM HANDLING OF WEAK LOW NEAR
30N 145W...SO EXPECT MORE MODEL CHANGES OVER THE NEXT COUPLE DAYS.
AS FOR THE ACTUAL FORECAST FOR OUR REGION...LOOKS LIKE A GREATER
THAN CLIMO CHANCE OF SNOW AND BELOW NORMAL TEMPS FOR CHRISTMAS...
WITH POTENTIAL FOR ADDITIONAL COOLING BY NEXT WEEKEND.

ANYONE PLANNING TO TRAVEL ANYTIME FROM CHRISTMAS EVE THROUGH NEXT
WEEKEND WILL WANT TO MONITOR THE FORECAST CLOSELY.

JKL
&&

.AVIATION...

VFR CONDITIONS WILL PREVAIL TONIGHT AND FRIDAY WITH PASSING MIDDLE
AND HIGH-LEVEL CLOUDS. A FEW FLURRIES ARE POSSIBLE OVER THE PLAINS
TONIGHT...WHILE THE MOUNTAINS WILL BE OBSCURED AT TIMES WITH A FEW
SNOW SHOWERS. SOUTHWEST WINDS WILL BE GUSTY ALONG THE FOOTHILLS...
WITH GUSTS OF 25 TO 35 KT IN PLACES LIKE KLVM. SCHULTZ

&&

.PRELIMINARY POINT TEMP/POPS...

    FRI     SAT     SUN     MON     TUE     WED     THU
-----------------------------------------------------------
BIL 025/041 029/040 029/049 037/046 028/042 022/034 016/026
    10/B    31/B    34/W    32/W    22/W    22/J    44/J
LVM 025/042 029/043 030/048 039/046 028/043 021/038 016/027
    11/N    31/N    35/W    44/W    32/W    34/J    44/J
HDN 015/037 020/039 020/049 031/044 019/040 017/034 015/027
    10/B    22/J    24/W    33/W    22/J    22/J    33/J
MLS 018/038 022/040 023/044 029/041 023/037 019/030 013/023
    10/U    13/J    25/W    22/W    22/J    22/J    22/J
4BQ 017/040 019/041 021/046 030/040 021/038 019/033 013/024
    10/B    12/J    14/W    23/W    22/J    22/J    33/J
BHK 017/037 019/041 020/043 025/037 021/035 017/028 011/019
    10/B    03/J    05/W    22/J    22/J    11/B    22/J
SHR 015/038 020/039 019/045 032/043 019/040 017/036 015/027
    01/U    12/J    23/W    33/W    22/J    22/J    44/J

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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