515
FXUS65 KBYZ 162101
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
201 PM MST MON DEC 16 2024
KEY MESSAGES
- SNOW MOVES THROUGH TONIGHT WITH ACCUMULATIONS UNDER AN INCH
OVER THE LOWER ELEVATIONS AND SEVERAL INCHES OF SNOW IN THE
MOUNTAINS.
- PERIOD OF INCREASED TO STRONG WINDS WEDNESDAY INTO THURSDAY
MORNING, FIRST OVER THE WESTERN FOOTHILLS THEN OVER THE PLAINS
WEDNESDAY NIGHT INTO THURSDAY MORNING.
- ABOVE NORMAL HIGH TEMPERATURES OVER MUCH OF THE AREA FROM
WEDNESDAY THROUGH NEXT MONDAY.
DISCUSSION
TONIGHT THROUGH TUESDAY NIGHT...
TONIGHT WILL SEE ONGOING LIGHT SNOW SHOWERS OVER MUCH OF THE
REGION. LOWER ELEVATIONS FROM ROSEBUD COUNTY AND LOCATIONS TO THE
WEST GENERALLY HAVE A 10-30% CHANCE OF GETTING 1 INCH OF SNOWFALL.
MODELS ARE IN GOOD AGREEMENT IN SHOWING LITTLE POTENTIAL FOR
SNOWFALL OVER 2 INCHES. 500MB WINDS WILL BE OUT OF THE
WEST/SOUTHWEST BRINGING A GOOD SETUP FOR THE SOUTHWEST MOUNTAINS
AND A 60-80% CHANCE FOR >4 INCHES OF SNOW.
SOUNDINGS INDICATE MOIST LOW LEVELS, SURFACE INVERSIONS, AND
LIGHT WINDS TOMORROW MORNING. THIS WILL LEAD TO THE POTENTIAL FOR
PATCHY FOG FOR MANY LOW LYING VALLEYS ACROSS THE REGION. THIS FOG
IS EXPECTED TO START TO DISSIPATE IN THE LATE MORNING HOURS.
TOMORROW WILL BE A TRANSITION DAY BEFORE THE NEXT TROUGH MOVES
INTO THE REGION. HIGH TEMPERATURES WILL SIMILAR TO TODAY WITH
HIGH 20S IN THE EAST TO HIGH 30S ACROSS THE WEST. THE APPROACHING
UPPER LEVEL TROUGH WILL CREATE LEE SIDE TROUGHING LOWERING
PRESSURES ACROSS THE PLAINS. THIS WILL SET THE STAGE FOR A
SIGNIFICANT IDAHO FALLS TO LEWISTOWN GRADIENT WITH THE GFS
INDICATING A GRADIENT OF OVER 20MB BY WEDNESDAY MORNING. THIS WILL
COINCIDE WITH 700MB WINDS INCREASING INTO THE 40-50KT RANGE. FOR
LIVINGSTON, THIS WILL CREATE INCREASING STRONG WIND PROBABILITIES
TUESDAY NIGHT WITH THE CHANCE FOR A WIND GUST OVER 50KTS BEING
90% BY WEDNESDAY MORNING. THE REST OF THE STRONG WINDS, INCLUDING
THOSE FOR BIG TIMBER AND HARLOWTON WILL BE COVERED IN THE LONG
TERM DISCUSSION. TORGERSON
WEDNESDAY THROUGH MONDAY...
MAIN IMPACT DURING THE EXTENDED PERIOD WILL BE WINDS IN THE
WESTERN FOOTHILLS. RIDGE OVER THE AREA SHIFTS E DURING WEDNESDAY
AND A SHORTWAVE MOVES IN DURING THE AFTERNOON. SHORTWAVE MOVES OUT
OF THE AREA WED. NIGHT. PATTERN IS FAVORABLE FOR STRONG WINDS IN
THE WESTERN FOOTHILLS, INCLUDING KLVM, NYE, K6S0 AND K3HT. NAEFS
HAD 50-60 KT WSW 700 MB WINDS MOVING E ON WEDNESDAY. GFS HAD
SIMILAR WINDS. GFS SURFACE PRESSURE GRADIENT INCREASES TO AROUND
15 MB OVER THE W WITH AN ORIENTATION THAT FAVORS GAP WINDS FOR
KLVM/NYE, AS WELL AS HYBRID GAP/MIX-DOWN WINDS FOR K6S0 AND K3HT.
WENT WITH HIGH-END ADVISORY WINDS FOR THESE AREAS WITH SOME
QUESTIONS DUE TO THE WSW DIRECTION OF 700 MB WINDS, WHICH COULD
KEEP WINDS BELOW WARNING CRITERIA. CONTINUED THE STRONG WINDS WED.
EVENING, THEN DECREASED THEM A BIT OVERNIGHT DUE TO EVOLUTION OF
PRESSURE GRADIENT. THE NBM 24 HOUR MAX PROBABILITY FOR WIND GUSTS
HIGHER THAN 58 MPH WAS 70-90% FOR THESE AREAS THROUGH WED.
EVENING. FOR THURSDAY, NW FLOW WILL GIVE WAY TO UPPER RIDGING, AND
A BACK DOOR FRONT PUSHES W INTO THE AREA. 700 MB WINDS OF AT LEAST
50 KT TURN NW AND SHIFT E IN THE MORNING. GIVEN THE FAVORABLE 700
MB WINDS AND A DECENT PRESSURE GRADIENT, KEPT ADVISORY WINDS IN
THE FOOTHILLS THRU 18Z. THERE WILL ALSO BE STRONG 850 MB WINDS
OVER THE PLAINS WED. NIGHT, BUT THESE WILL HAVE LIMITED MIX DOWN
POTENTIAL. WILL ISSUE A HIGH WIND WATCH FROM JUDITH GAP TO K6S0,
AND FOR KLVM/BEARTOOTH FOOTHILLS FROM 12Z WED.-18Z THURSDAY.
PWAT'S CLIMB TO 0.50 IN ON WEDNESDAY AND THERE WILL BE A LOW
CHANCE OF RAIN AND SNOW OVER THE NORTHERN AND WESTERN ZONES.
CHANCE DOES NOT INCLUDE KBIL. CHANCES OF RAIN LINGER E OF KBIL
WED. EVENING WITH SNOW OVER THE MOUNTAINS. ANOTHER SHORTWAVE IS
POSSIBLE OVER THE AREA THU. NIGHT PER THE DETERMINISTICS, BUT
FORECAST IS DRY FOR NOW. HIGHS ON WED. WILL BE IN THE 40S AND
MANY AREAS WILL BE IN THE 40S ON THU., EXCEPT IN THE 20S AND 30S
OVER THE E.
AREA WILL BE UNDER NW FLOW PER THE CLUSTERS ON FRIDAY AND THEN
RIDGING OR NW FLOW ON SATURDAY. SUNDAY WILL HAVE RIDGING OR SW
FLOW AND MONDAY WILL BE SIMILAR TO SUNDAY. TEMPS WILL BE IN THE
40S AND 50S...COOLER IN THE E. EFI HAD A .8-.9 FOR SATURDAY'S
HIGHS, SHOWING THEY WERE UNUSUALLY ABOVE NORMAL WHEN COMPARING
THE MODEL FORECAST TO THE MODEL CLIMATE. OTHER THAN LOW PRECIP.
CHANCES OVER PARTS OF THE AREA ON SUNDAY, AND MOUNTAIN POPS SUN.
THROUGH MONDAY, THE FORECAST WAS DRY. ARTHUR
AVIATION
VFR CONDITIONS WILL PREVAIL TODAY. A DISTURBANCE MOVING THROUGH
THE REGION WILL BRING INCREASING SNOW CHANCES, FIRST TO THE
SOUTHWEST MOUNTAINS TODAY, SPREADING E OVER THE LOWER ELEVATIONS
THIS EVENING AND OVERNIGHT TONIGHT. CHANCES FOR SNOW WILL
CONTINUE TUESDAY MORNING. MVFR TO IFR CONDITIONS ARE POSSIBLE WITH
THE SNOW. EXPECT AREAS OF MOUNTAIN OBSCURATION. ARTHUR
PRELIMINARY POINT TEMP/POPS
TUE WED THU FRI SAT SUN MON
-----------------------------------------------------------
BIL 024/040 022/049 028/042 026/049 030/052 033/050 031/051
52/J 11/E 10/U 00/B 00/B 01/B 01/B
LVM 025/041 028/049 030/047 032/051 035/054 035/049 031/050
71/B 12/R 20/N 00/B 00/B 12/R 12/O
HDN 023/038 020/048 024/040 020/047 024/049 026/050 026/050
52/J 01/E 20/U 00/B 00/B 02/O 01/B
MLS 020/029 016/041 014/022 011/036 016/038 022/042 025/044
21/E 02/O 20/U 01/B 00/B 01/B 00/B
4BQ 023/034 018/045 022/032 017/043 022/046 027/047 027/048
31/B 00/B 20/U 00/B 00/B 01/B 10/B
BHK 012/027 010/040 008/020 002/031 011/034 017/038 022/040
12/J 01/E 40/N 01/B 00/B 01/B 10/B
SHR 019/040 017/052 025/042 022/053 027/055 029/050 025/052
21/B 00/B 10/U 00/B 00/B 02/O 01/B
BYZ WATCHES/WARNINGS/ADVISORIES
MT...HIGH WIND WATCH IN EFFECT FROM LATE TUESDAY NIGHT THROUGH
THURSDAY MORNING FOR ZONES 63-65-66-141-172-228.
WY...NONE.
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