396
FXUS65 KBYZ 132354
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
454 PM MST SAT DEC 13 2025
KEY MESSAGES
- WARMER AND MOSTLY DRIER WEATHER EXPECTED TO RETURN SUNDAY
THROUGH MID WEEK. EXPECT RAPID SNOWMELT THIS COMING WEEK.
- PERIODS OF STRONG WIND FOR FOOTHILLS/GAP LOCATIONS INCLUDING
LIVINGSTON/NYE STARTING TONIGHT AND LASTING THROUGH THE
FORESEEABLE FUTURE. STRONG WINDS ACROSS THE ENTIRE AREA
WEDNESDAY.
- CHANCE OF EXTREME CROSS WINDS ALONG US-191 CORRIDOR (BIG TIMBER
TO JUDITH GAP) WEDNESDAY.
DISCUSSION
TONIGHT THROUGH SATURDAY...
AREAS OF LIGHT SNOW CAME TO AN END EARLIER TODAY WITH UPSLOPE AND
BAROCLINICITY WEAKENING OVER THE AREA AS MID LEVEL FLOW
TRANSITIONED FROM CYCLONIC TO SLIGHTLY ANTI-CYCLONIC. COLD AIR
REMAINS IN PLACE OVER THE HIGH PLAINS AND WILL MEAN ANOTHER COLD
NIGHT FOR MOST LOCATIONS, BUT WARMER AIR OVER THE WESTERN
FOOTHILLS WILL SLOWLY PUSH EASTWARD. SO TEMPS AS FAR EAST AS
YELLOWSTONE COUNTY MAY SLOWLY RISE AFTER MIDNIGHT INTO SUNDAY
MORNING. THIS MAKES THE FORECAST FOR OVERNIGHT LOWS TRICKY, AS
SOME LOCATIONS MAY SEE COLDEST OVERNIGHT TEMPS BEFORE MIDNIGHT.
FOR EXAMPLE, BILLINGS MAY DROP TO SINGLE DIGITS THIS EVENING
BEFORE WARMING INTO THE 20S BY SUNRISE.
TEMPS ARE THEN EXPECTED TO WARM OVER THE REGION FOR SUNDAY RANGING
FROM 50S WEST TO LOWER 40S EAST AS RIDGING ALOFT KICKS IN. HOWEVER,
DUE TO RECENT DEEP SNOWPACK MODELS MAY BE OVER FORECASTING THE
WARM UP IN CENTRAL ZONES. HAVE ADJUSTED TEMPS DOWN A BIT TO
ACCOUNT FOR THIS (USED BLEND OF 10-25-50 PERCENTILES OVER CENTRAL
ZONES). RIDGING TO WESTERLY ZONAL FLOW WILL PREVAIL THROUGH THE
WEEK RESULTING IN GENERALLY ABOVE NORMAL TEMPS.
NO SIGNIFICANT PRECIPITATION EVENTS ARE EXPECTED THIS WEEK.
HOWEVER, A RATHER DYNAMIC CLIPPER SYSTEM MOVING ACROSS THE REGION
AT MIDWEEK MAY BRING A SHOT OF RAIN/SNOW TO LOWER ELEVATIONS (AND
WIND), WITH A BETTER CHANCE OF SNOW ACCUMULATIONS ON WEST FACING
SLOPES IN THE HIGH COUNTRY.
THE PRIMARY WEATHER IMPACT THIS WEEK WILL BE WIND. MODEL
CONSENSUS SUGGEST THE IDAHO FALLS/LEWISTOWN PRESSURE GRADIENT
INCREASES INTO THE 10-15 MB RANGE WITH 700 MB WINDS OF 30-35 KTS
TONIGHT INTO SUNDAY MORNING. LOCAL STUDIES SUGGEST 60% CHANCE OF
GUSTS 50 MPH OR GREATER. WE WILL KEEP SUB-ADVISORY LEVEL WINDS
(45-55 MPH) IN FORECAST FOR NOW LATE TONIGHT/TOMORROW FOR GAP
LOCATIONS (LIVINGSTON/NYE), BUT CANNOT RULE OUT A GUST TO NEAR 60
MPH. BY MONDAY NIGHT THE PRESSURE GRADIENT ACROSS THE PARADISE
VALLEY AND FOOTHILLS REACHES 12-17 MB ON AVERAGE WHICH RAISES
CHANCE OF GUSTS TO 60 MPH PLUS TO 85%. 700 MB WINDS INCREASE
SUBSTANTIALLY MONDAY/MONDAY NIGHT INTO TUESDAY REACHING 50-70 KTS
ACROSS THE WESTERN FOOTHILLS INCLUDING THE US-191 CORRIDOR. LOCAL
STUDIES SHOW THE CHANCE OF GUSTS OVER 60 MPH AVERAGING 70% AT BIG
TIMBER TUESDAY MORNING. IF THESE TRENDS CONTINUE WIND HIGHLIGHTS
WILL BE NECESSARY. AFTER A RELATIVE LULL TUESDAY NIGHT, ANOTHER
PERIOD OF EXTREME 700MB WINDS IS POSSIBLE IN RELATION TO THE
AFOREMENTIONED CLIPPER SYSTEM ON WEDNESDAY WHEN PROGS ARE
DEPICTING SPEEDS OVER 80KTS. THIS IS A SIMILAR SCENARIO TO LAST
TUESDAY MORNING WHEN GUSTS TO 97 MPH WERE RECORDED AT BIG TIMBER
AND GUSTS OVER 50 MPH WERE COMMON FURTHER EAST OVER THE PLAINS.
THIS WILL NEED TO BE CLOSELY MONITORED AND MESSAGING RAMPED UP.
CURRENT DETERMINISTIC FORECASTS DO NOT INDICATE THIS LEVEL OF WIND
GUSTS YET, BUT BASED ON THE PATTERN WE SUSPECT WIND GUSTS
FORECASTS WILL INCREASE AS WE MOVE FORWARD. PERIODS OF STRONG
WINDS MAY CONTINUE THROUGH THE END OF THE WEEK. BT
AVIATION
00Z TAF DISCUSSION...
SHALLOW COLD AIRMASS SITS OVER THE AREA THIS EVENING. RIDGING IS
BUILDING IN FROM THE WEST ALOFT AND PRESSURE FALLS ARE DEVELOPING
OVER THE NORTHERN PLAINS WHERE THE JET STREAM IS LOCATED. THIS
COMBINATION WILL WORK TO PULL THE ARCTIC AIR EASTWARD TONIGHT INTO
TOMORROW. LATEST KBLX VWP SHOWS SW WINDS @25KT LESS THAN 1KFT
ABOVE THE SURFACE. AS A RESULT EXPECT WARMER AIR AND GUSTY
SOUTHWEST WINDS TO DEVELOP OVER THE WESTERN FOOTHILLS OVERNIGHT AS
WELL AS POKING INTO AT LEAST THE HIGHER HILLS ACROSS CENTRAL
ZONES. THIS WILL INCLUDE KBIL THOUGH HAVE KEPT WIND GUSTS AT THE
LOWER END OF WHATS POSSIBLE FOR NOW. KLVM WILL SEE GUSTS
INCREASING STEADILY OVERNIGHT TOWARD 40KTS BY SUNRISE. LOW LEVEL
WIND SHEAR IS IN THE TAFS FOR KBIL/KSHR/KMLS AT VARIOUS TIMES
THROUGH TOMORROW MORNING. WARM ADVECTION USUALLY LEADS TO SOME LOW
LYING FOG DEVELOPMENT THIS TIME OF YEAR, BUT THE CURRENT
SITUATION SHOWS STRONG ENOUGH WINDS JUST OFF THE SURFACE THAT
MECHANICAL MIXING WILL LIKELY INHIBIT FOG DEVELOPMENT FOR ALL BUT
HE LOWEST RIVER VALLEY LOCATIONS ACROSS THE EASTERN HALF OF THE
FORECAST AREA. OTHERWISE VFR CONDITIONS WILL PREVAIL THROUGH
SUNDAY. CHAMBERS
PRELIMINARY POINT TEMP/POPS
SUN MON TUE WED THU FRI SAT
-----------------------------------------------------------
BIL 011/041 031/046 038/049 035/048 023/039 029/047 027/043
00/B 00/B 01/B 16/O 11/B 24/O 42/S
LVM 032/053 035/055 042/052 038/049 025/040 030/047 027/041
00/N 00/N 01/N 28/O 12/S 56/O 42/S
HDN 007/039 020/045 034/048 031/048 016/037 024/047 023/042
00/B 00/U 01/B 27/O 21/B 24/O 42/S
MLS 002/038 023/042 034/046 030/045 012/027 018/041 017/035
00/U 00/B 01/B 24/O 21/B 22/O 31/B
4BQ 013/043 025/044 035/049 032/050 017/035 025/047 024/041
00/U 00/U 01/B 14/O 20/B 12/O 31/B
BHK 904/039 023/043 032/046 025/042 007/023 011/040 013/032
00/U 00/U 01/B 24/O 20/B 12/O 31/B
SHR 015/047 027/052 033/053 030/053 018/040 023/050 022/042
00/U 00/U 01/B 15/O 21/B 12/O 42/S
BYZ WATCHES/WARNINGS/ADVISORIES
MT...NONE.
WY...NONE.
WEATHER.GOV/BILLINGS
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