064
FXUS65 KBYZ 010258
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
858 PM MDT MON MAR 31 2025
KEY MESSAGES
- PERIODS OF HEAVY MOUNTAINS SNOW WILL BEGIN TO IMPACT THE WESTERN
MOUNTAINS THIS EVENING THROUGH WEDNESDAY. TOTALS WILL BE BETWEEN
8-16".
- PERIODS OF HEAVY SNOW POSSIBLE IN THE BIGHORNS BEGINNING
TUESDAY EVENING, WITH 7-14 INCHES OF SNOW POSSIBLE.
- CLIPPER SYSTEM BRINGS NEXT SHOT OF LOWER ELEVATION SNOW AND
COLDER TEMPS THURSDAY NIGHT AND FRIDAY; ACCUMULATIONS AT LOWER
ELEVATIONS OF 1-3" EXPECTED, GREATEST NEAR FOOTHILLS.
- HIGH CONFIDENCE OF BUILDING HIGH PRESSURE THIS WEEKEND; EXPECT
WARMER AND DRY CONDITIONS INTO NEXT WEEK.
UPDATE
UPDATED THE FORECAST TO ADD SOME FOG OVERNIGHT INTO TUESDAY. THE
CHANCE OF FOG IS GREATEST ON THE HILLTOPS OF MUCH OF OUR AREA
(12Z HREF SHOWS A 30-40% CHANCE THERE) AND IN AND NEAR CARTER
COUNTY (NEAR 50% CHANCE). FURTHERMORE, LATEST DETERMINISTIC MODELS
SUGGEST THE FOG IN/NEAR CARTER COUNTY LOOKS TO BE MORE WIDESPREAD
AND PERSISTENT INTO TUESDAY MORNING. THESE SOLUTIONS ALIGN WITH
SATELLITE IMAGERY WHICH SHOWS A POCKET OF LARGER SCALE CLEARING
MOVING INTO EASTERN MT. THE CLEARING ALOFT SHOULD HELP THE LOWER
LEVELS REACH SATURATION AND PRODUCE THE AREAS OF FOG. IN THE FOG,
VISIBILITY CAN DROP TO 1/4 MILE...SO PLEASE ALLOW EXTRA TIME TO
REACH YOUR DESTINATION. REST OF FORECAST IS IN GOOD SHAPE. RMS
DISCUSSION
TONIGHT THROUGH WEDNESDAY...
A DIGGING TROUGH WILL CONTINUE TO MOVE ITS WAY INTO THE
INTERMOUNTAIN WEST OVERNIGHT TONIGHT WITH EXCELLENT DIFFLUENCE
OUT AHEAD OF IT. THIS INCREASED LIFT AIDED BY EXCELLENT MID-LEVEL
LAPSE RATES >8C/KM IS CURRENTLY PRODUCING CONVECTIVE SNOW SHOWERS
OVER THE WESTERN THIRD OF THE CWA. THE KLVM ASOS RECORDED A DROP
FROM 10SM VISIBILITY DOWN TO 1/4SM WITHIN A SPAN OF JUST 15
MINUTES AND THIS WILL LIKELY BE THE TREND WITH ALL OF THESE
SHOWERS.
AS THE TROUGH CONTINUES TO DIG AND WE LOOSE THE DAYTIME
INSTABILITY, THESE SHOWERS WIL FADE AND MAY WAY FOR THE SYNOPTIC
PRECIPITATION TO MOVE IN FROM WEST TO EAST OVERNIGHT TONIGHT. WITH
THE MID-LEVEL FLOW HAVING ORIGINS OVER THE PACIFIC, THIS SYSTEM
SHOULD HAVE NO TROUBLE BRINGING A DECENT AMOUNT OF MOISTURE INTO
THE WESTERN MOUNTAINS. WITH THIS FLOW ALSO BEING SOUTHWESTERLY,
UPSLOPE ALONG WEST AND SOUTHWEST FACING ASPECTS COULD HELP LOCALLY
RAISE SNOWFALL TOTALS IN THOSE AREAS. ALONG THE SAME LINES, IT IS
STILL UNCERTAIN HOW MUCH SNOW WILL MAKE IT INTO PLACES SUCH AS
MELVILLE DURING THE FIRST HALF OF THE SYSTEM DUE TO THE LEE SIDE
DOWNSLOPING, HOWEVER, HI-RES MODELS ARE NOT SHOWING THIS TAS AN
ISSUE FOR THEM. IT IS WORTH NOTING THAT THIS EVENT HAS NOT BEEN
HANDLED BY MODELS PARTICULARLY WELL THOUGH.
DURING THE DAY TUESDAY A SURFACE LOW DEVELOPS OVER EASTERN WY AND
MOVES OFF TO THE NORTHEAST. THERE IS STILL SOME DISAGREEMENT
REGARDING WHERE EXACTLY THE INITIAL CYCLOGENESIS WILL TAKE PLACE
(N-S) AND THUS THERE IS UNCERTAINTY IN THE PRECIPITATION FOR MUCH
OF THE EASTERN 2/3 OF THE CWA. IF THIS LOW DEVELOPS FATHER NORTH
IT WILL NOT ONLY ALLOW FOR THERE TO BE MORE GULF MOISTURE
TRANSPORTED INTO THE REGION, BUT ALSO AID IN UPSLOPE FOR THE
BIGHORN AND PRYOR MOUNTAINS. ADDITIONALLY A TROWEL COULD DEVELOP
ON THE BACKSIDE OF THE LOW WHICH WOULD INDUCE A BAND OF HEAVIER
SNOWFALL RATES. THIS THIS STILL EVEN UNCERTAIN IF IT WILL HAPPEN
AT ALL, BUT IF IT DOES OCCUR THE PLACEMENT IS ANYONE'S GUESS AT
THIS POINT STILL. THIS LOW WILL ALSO HAVE LINGERING BACKSIDE SNOW
ACROSS ALL OF THE CWA WHICH WILL BE THE SECOND MAIN ROUND OF
PRECIPITATION FOR THE EVENT.
DUE TO THERE BEING TWO MAIN FORCING MECHANISMS WITH THIS EVENT
(THE INITIAL CVA AND DIFFLUENCE FOLLOWED BY THE SURFACE LOW)
THERE WILL BE TWO PERIODS OF PRECIP WHERE MOST LOCATIONS OUTSIDE
OF THE MOUNTAINS WILL SEE, AT THE MINIMUM, A FEW HOUR BREAK AT
SOME POINT TUESDAY.
EARLY WEDNESDAY THE SURFACE LOW PUSHES OFF TO THE NORTHEAST AND
THE PARENT TROUGH CONTINUES TO DIG WHICH SHOULD BE THE END TO THE
BULK OF THE PRECIP. WMR
WEDNESDAY THROUGH MONDAY...
THE EVOLUTION OF THE DEVELOPING LOW OVER THE REGION THE NEXT 36
HOURS IS STILL SOMEWHAT UNCERTAIN, BUT WE ARE CONFIDENT THE LOW
WILL BE TO OUR EAST BY WEDNESDAY, WITH A WEAK TROWAL WRAPPING OVER
OUR FORECAST AREA. THIS WILL YIELD HEAVIEST PRECIP IN N-NW FLOW
UPSLOPE AREAS AND MUCH OF OUR EAST, BEFORE THE LOW EXITS WEDNESDAY
NIGHT. SURFACE TEMPS SHOULD BE SUFFICIENTLY COLD FOR SOME WET
SNOW ACCUMULATION ALONG THE SOUTHERN FOOTHILLS, AND OVER THE
HIGHER HILLS OF OUR SOUTHEAST ZONES. CURRENT WINTER HIGHLIGHTS FOR
OUR WEST AND THE BIGHORNS LOOK GOOD. AS CONFIDENCE INCREASES WE
MAY NEED ADDITIONAL HIGHLIGHTS FOR THE AFOREMENTIONED AREAS. ALONG
WITH BREEZY NW WINDS (GUSTS TO 30 MPH), CONDITIONS WILL BE
HAZARDOUS FOR YOUNG LIVESTOCK SO PLEASE TAKE PRECAUTIONS.
LATE WEDNESDAY NIGHT AND THURSDAY MORNING SHOULD OFFER A DRY
PERIOD BETWEEN SYSTEMS. BY THURSDAY AFTERNOON WE WILL BEGIN TO SEE
IMPACTS FROM A CLIPPER SYSTEM DROPPING THROUGH AB. THERE IS STILL
MODEL SPREAD WITH THE EXACT TRAJECTORY OF THE SHORTWAVE, BUT
RECENT GFS RUNS HAVE TRENDED TOWARD THE EC/GEM IN SHOWING ENERGY
DIGGING SOUTHWARD TO OUR WEST, SUCH THAT DIFFLUENT SOUTHERLY FLOW
ALOFT REMAINS UNTIL MIDDAY-ISH ON FRIDAY. THIS TRACK SEEMS VERY
PLAUSIBLE GIVEN THE PRE-EXISTING LOW NEAR THE 4-CORNERS. OTHER
THAN THE ASCENT, WE WILL SEE A SHIFT BACK TO UPSLOPE N-E WINDS AND
COLD ADVECTION THAT IS MORE SIGNIFICANT THAN WHAT WE HAVE SEEN
THE PAST FEW DAYS. MODELS SHOW 850MB TEMPS FALLING TO -5C TO -9C.
EVEN WITH THE WARMER SOLUTIONS WE WILL SEE ALMOST ALL PRECIP FALL
AS SNOW. CURRENT INDICATIONS ARE FOR A 1-3" SNOWFALL AT LOWER
ELEVATIONS, GREATEST CLOSE TO THE WESTERN AND SOUTHERN FOOTHILLS,
AND 3-8" OVER THE MOUNTAINS. THE PROBABILITY OF EXCEEDING 2" IS
ABOUT 30% AT BILLINGS AND 45-50% ALONG THE FOOTHILLS. MORE
IMPORTANTLY, GIVEN THE TEMPS EXPECTED TO FALL WELL INTO THE 20S
THURSDAY NIGHT, THERE MAY BE TRAVEL IMPACTS FOR THE FRIDAY MORNING
COMMUTE. SOMETHING TO KEEP IN MIND. PRECIP SHOULD TAPER OFF
FRIDAY AFTERNOON. FRIDAY ITSELF WILL BE CHILLY WITH HIGHS IN THE
30S MOST PLACES. CLEARING ASSOCIATED WITH A 1035+ MB CANADIAN
SURFACE HIGH SHOULD YIELD A CHILLIER FRIDAY NIGHT WITH LOWS IN THE
UPPER TEENS AND LOWER 20S.
CONFIDENCE IS HIGH FOR A STRONG UPPER LEVEL RIDGE TO BUILD OVER
THE WESTERN CONUS THIS WEEKEND INTO NEXT WEEK. INITIALLY, THE
RIDGE AXIS WILL BE TO OUR WEST LEAVING US PRONE TO EPISODES OF
BACKDOOR COOLING, BUT OVER TIME THE RIDGE WILL SPREAD WARMER THAN
NORMAL TEMPS FOR OUR REGION, ALONG WITH A STRING OF SEVERAL DRY
DAYS. AS FOR TEMPS, WE ARE LOOKING AT A RETURN OF 50S FOR THE
WEEKEND THEN 60S BY MONDAY. LOOKING FURTHER AHEAD, THERE IS A
HIGH CHANCE (>50%) OF SEEING 70F AT SOME POINT NEXT WEEK. THIS
WOULD RESULT IN SOME MID ELEVATION SNOW MELT AND RISES ON STREAMS
NEAR THE FOOTHILLS.
JKL
AVIATION
AREAS OF LOW STRATUS WITH MVFR-IFR CEILINGS CONTINUE TO IMPACT THE
REGION. LOW CLOUDS HAVE GREATEST COVERAGE IN SOUTHEAST MT (KMLS-
KBHK). THERE IS A RISK OF FOG/STRATUS CAPABLE OF PRODUCING IFR-
LIFR OVER SOUTHEAST MT TONIGHT INTO TUESDAY MORNING. TAF SITES
AFFECTED BY THIS WOULD INCLUDE KMLS & KBHK.
SCATTERED SHOWERS, AND PERHAPS A FEW WEAK THUNDERSTORMS, WILL
IMPACT WESTERN AND CENTRAL AREAS THIS EVENING. LOCALIZED MVFR AND
GUSTY WINDS ARE POSSIBLE WITH THE STRONGEST ACTIVITY. LATER
TONIGHT AND TUESDAY, THE POTENTIAL FOR RAIN/SNOW INCREASES AS THE
NEXT WEATHER SYSTEM MOVES IN FROM THE WEST. EXPECT AREAS OF
MVFR TOMORROW. MOUNTAINS WILL BE FREQUENTLY OBSCURED THROUGH THE
PERIOD.
JKL/ARCHER
PRELIMINARY POINT TEMP/POPS
TUE WED THU FRI SAT SUN MON
-----------------------------------------------------------
BIL 034/048 034/045 029/047 026/039 024/051 029/058 035/065
26/W 77/O 24/R 74/S 11/U 10/U 00/U
LVM 032/042 031/043 027/044 026/039 020/050 028/055 033/062
66/J 75/S 35/S 74/S 11/U 00/U 00/U
HDN 034/049 031/046 027/050 026/040 021/051 026/058 030/067
25/W 88/O 24/R 74/S 11/U 10/U 00/U
MLS 035/046 031/044 028/048 026/040 021/051 028/055 030/065
26/W 65/O 12/R 52/S 11/U 00/U 00/U
4BQ 035/045 032/042 028/047 027/040 021/048 027/054 030/062
26/W 78/O 12/R 44/S 11/U 10/U 00/U
BHK 032/041 026/039 023/043 024/038 017/045 023/050 025/059
26/W 67/S 12/O 53/S 11/U 00/U 00/U
SHR 031/048 027/042 022/045 024/038 017/047 023/053 027/062
24/W 89/O 25/O 66/S 21/U 10/U 00/U
BYZ WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO 6
PM MDT WEDNESDAY FOR ZONES 40-63>66-141-172-228.
WINTER STORM WARNING IN EFFECT UNTIL 6 PM MDT WEDNESDAY FOR
ZONES 67-68.
WINTER STORM WATCH IN EFFECT FROM TUESDAY EVENING THROUGH
WEDNESDAY AFTERNOON FOR ZONE 171.
WY...WINTER STORM WATCH IN EFFECT FROM TUESDAY EVENING THROUGH
WEDNESDAY AFTERNOON FOR ZONE 198.
WEATHER.GOV/BILLINGS
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