847
FXUS65 KBYZ 291943
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
143 PM MDT SAT MAR 29 2025
KEY MESSAGES
- SOME ACCUMULATING WET SNOW TONIGHT & SUNDAY; TEMPS REMAIN COOLER
THAN NORMAL THROUGH THE WEEKEND.
- LOCALIZED FOG TONIGHT AND AGAIN SUNDAY NIGHT TO EARLY MONDAY.
- UNSETTLED CONDITIONS ARE FORECAST TO PERSIST THROUGH NEXT WEEK
WITH MULTIPLE ROUNDS OF PRECIPITATION. THERE IS A MEDIUM TO HIGH
CHANCE (25-75%) FOR GREATER THAN 0.25 INCHES TUESDAY/WEDNESDAY.
DISCUSSION
THROUGH SUNDAY NIGHT...
LIGHT SNOW CONTINUES IN THE FAR SOUTHEAST CORNER OF MT, COURTESY
OF DEPARTING SHORTWAVE OVER WESTERN NE/SD, BUT THE PRECIP WILL BE
ENDING OVER THE NEXT FEW HOURS. ELSEWHERE, THOUGH FORCING IS
BASICALLY NON-EXISTENT, THERE REMAINS AREAS OF LIGHT RAIN/SNOW AS
SHALLOW MOISTURE IS INTERSECTING THE DENDRITIC GROWTH ZONE. IN
FACT, BLX VAD WINDS SHOW EASTERLY FLOW FROM THE SFC THRU ~11KFT
MSL, AND NOTING SOME LARGE DENDRITES FALLING AT BILLINGS IN THE
LATE MORNING, BOTH THE EASTERLY WINDS AND BOUNDARY LAYER MOISTURE
ARE DEEPER THAN ALL MODELS PREDICTED. THE EAST WINDS AND ABUNDANT
CLOUD COVER HAS KEPT A LID ON TEMPS TODAY AND 18Z READINGS ARE
MOSTLY LOWER-MID 30S (THOUGH IT IS IN THE UPPER 30S AT SOME HIGH
ELEVATION RAWS STATIONS).
SATELLITE IMAGERY SHOWS AN UPSTREAM TROF EXTENDING FROM NORTHERN
ID TO UT, MOVING SLOWLY TO THE EAST. THERE ARE ACTUALLY A COUPLE
PV MAXIMUMS IN THIS TROF, ONE OVER CENTRAL ID AND THE OTHER IN
NORTHERN UT. SYNOPTIC SCALE FORCING WILL INCREASE FROM THE WEST AS
THIS TROF ARRIVES, BUT THE PICTURE REMAINS SOMEWHAT COMPLEX IN
WHAT IS OVERALL A LIGHT WIND REGIME OVER THE INTERMOUNTAIN WEST.
THE COOL AIR MASS IN PLACE ISN'T GOING ANYWHERE TODAY, SO AS
PRECIP DEVELOPS TONIGHT FROM THE WEST THE PTYPE WILL BE MOSTLY
SNOW (THOUGH THERE WILL BE A MIX IN SOME PLACES AT THE ONSET). THE
COMBINATION OF ASCENT, DEEP EASTERLY UPSLOPE WINDS AND A NOCTURNAL
START TO THE SNOWFALL ALL POINT TOWARD SOME WET SNOW ACCUMULATION
OVER OUR WESTERN CWA TONIGHT AND EARLY TOMORROW, AND ALL WINTER
HIGHLIGHTS ALREADY ISSUED LOOK GOOD. AS THE TROF MOVES EASTWARD,
WET SNOW WILL DEVELOP OVER CENTRAL PARTS AND IN FAR SOUTHEAST MT
LATE TONIGHT AND SUNDAY. THE PRECIP'S TIMING IN OUR EAST MAKES IT
MORE DIFFICULT TO DETERMINE HOW MUCH WILL ACCUMULATE AS IT WILL BE
COMPETING WITH A LATE MARCH SUN ANGLE, AND DO NOT SEE MUCH RISK
OF HEAVIER MESOSCALE BANDS OF SNOW. THUS, WHEREAS WE ARE EXPECTING
A 2-4" SNOWFALL OVER OUR WEST (GREATEST ALONG THE FOOTHILLS),
ACCUMS FROM BILLINGS EASTWARD SHOULD BE AN INCH OR LESS MOST
PLACES, AND MAYBE 1-2" OVER THE HILLS TO THE SOUTHEAST (E.G. WOLF
MOUNTAINS). PRECIP WILL BECOME LIGHTER IN OUR FAR EAST.
THE PROBABILITY OF 2+ INCHES OF SNOW IS 20% AT BILLINGS, 30-50%
ALONG THE WESTERN FOOTHILLS, 10-20% NEAR SHERIDAN, AND 0-5%
EVERYWHERE NORTH OF BILLINGS-HARDIN AND EAST OF ROSEBUD COUNTY.
ONE OTHER ITEM THAT NEEDS TO BE MONITORED IS FOG. FULLY EXPECT
UPSLOPE FOG TO REMAIN ALONG THE FOOTHILLS TONIGHT INTO SUNDAY,
WITH MORE LOCALIZED FOG POSSIBLE EAST OF THE FOOTHILLS LATE
TONIGHT (HIGH UNCERTAINTY AS STRATUS MAY/SHOULD DOMINATE). AS THE
SHORTWAVE EXITS TO THE EAST TOMORROW AFTERNOON AND EVENING, PRECIP
WILL END BUT EASTERLY SURFACE WINDS WILL PERSIST. THUS, SUNDAY
NIGHT MAY OFFER A MORE FAVORABLE PERIOD OF FOG DEVELOPMENT IF
THERE IS ENOUGH CLEARING. AGAIN, NOT SURE HOW EXACTLY THIS WILL
EVOLVE BUT IT IS SOMETHING TO WATCH. THERE COULD BE FOG IMPACTS
FOR THE MONDAY MORNING COMMUTE.
TEMPERATURES WILL REMAIN COOLER THAN NORMAL THROUGH THE REMAINDER
OF THE WEEKEND. HIGHS SUNDAY SHOULD HOLD IN THE MID 30S TO LOWER
40S ACROSS MOST LOWER ELEVATIONS, WITH NIGHTTIME LOWS BELOW
FREEZING.
JKL
MONDAY THROUGH FRIDAY...
MODELS ARE SLOWLY COMING INTO MORE AGREEMENT WITH THE MIDWEEK
SYSTEM. THE GFS AND GEM HAVE TRENDED MORE TOWARDS THE ECMWF
SOLUTION IN RECENT RUNS WITH A TOUGH MOVING ONSHORE INTO THE PNW
LATE MONDAY INTO EARLY TUESDAY. DUE TO THE VARYING MODELS, AND
EVEN THE ENSEMBLE MEMBERS, COMING MORE INTO AGREEMENT THE QPF
VALUES HAVE ALSO BECOME FAR MORE CLEAR AS WELL. WHEN IT COMES TO
THE ACTUAL FORECAST FOR THE EVENT NOT TOO MUCH HAS CHANGED FROM
THE PREVIOUS TWO OFFICIAL FORECASTS. SNOWFALL TOTALS HAVE COME UP
TO OVER A FOOT FOR MUCH OF THE BIGHORN MOUNTAINS DUE A SURFACE
LOW DEVELOPING IN THE LEE OF THE CO FRONT RANGE ALLOWING FOR
UPSLOPE FLOW TO OCCUR ALL ALONG THE BIGHORN RANGE. THE GREATEST
PERIOD OF MOISTURE ADVECTION FROM THE GULF WILL BE OVERNIGHT
BETWEEN TUESDAY AND WEDNESDAY WHERE DEW POINTS NEAR KSHR COULD BE
IN THE UPPER 30'S. THIS IS SIGHTLY OFFSET IN TIME FROM THE BEST
PERIOD OF UPSLOPE FLOW WHICH WILL OCCUR TUESDAY AFTERNOON INTO
THE EVENING. THIS MEANS THAT THIS PARTICULAR EVENT WILL NOT BE A
MASSIVE SNOW PRODUCER IN THE MOUNTAINS, BUT WILL STILL BRING
ANOTHER ROUND OF HEALTHY MOUNTAIN SNOW.
THE NEXT SYSTEM TO MOVE THROUGH THE AREA COULD OCCUR TOWARDS THE
END OF THE WEEK INTO NEXT WEEKEND. THERE IS A MASSIVE DISAGREEMENT
IN THE MODELS IN REGARDS TO THIS EVENT. THE GFS AND GEM WANT TO
MOVE THE MIDWEEK TROUGH OFF TO THE EAST AND BEGIN TO BUILD IN A
RIDGE BY FRIDAY THUS HAVING US MISS OUT ON A SYSTEM ALMOST
ENTIRELY, WHEREAS THE ECMWF WANTS TO DEVELOP A SHORTWAVE ON THE
BACKSIDE OF THE TROUGH AND HAVE THAT ZIP THROUGH MT ON FRIDAY. DUE
TO THAT FACT THAT THE GFS HAS DONE A COMPLETE 180 DEGREE TURN ON
ITS DETERMINISTIC SOLUTIONS OVER THE PAST ~6 RUNS TO FALL IN
AGREEMENT WITH THE ECMWF SOLUTIONS WITH THE MIDWEEK STORM, I AM
MORE INCLINED TO BELIEVE THE SOLUTION OF THE ECMWF AT THIS TIME.
REGARDLESS OF WHAT HAPPENS WITH THE SYSTEM AT THE END OF NEXT
WEEK, ALL OF THE LONG RANGE MODELS ARE IN AGREEMENT THAT A HIGH
AMPLITUDE FLOPPED OVER RIDGE SHOULD BUILD IN TOWARDS THE END OF
NEXT WEEKEND.
WMR
AVIATION
FLYING WEATHER WILL REMAIN POOR (MVFR-LIFR) THROUGH THE REMAINDER
OF THE DAY. DUE TO AREAS OF LIGHT RAIN AND SNOW, LOW CLOUDS AND
LOCALIZED FOG, AND PERSISTENT EASTERLY SURFACE WINDS. SLIGHT
IMPROVEMENT MAY OCCUR DURING THE LATE AFTERNOON, BUT ANOTHER ROUND
OF MOSTLY WET SNOW WILL SPREAD IN FROM THE WEST TONIGHT AND
CONTINUE THROUGH SUNDAY, KEEPING CIGS AND VSBYS ON THE LOW SIDE.
EXPECT WIDESPREAD MVFR TO LIFR TONIGHT AND SUNDAY, WITH ALL TAF
SITES BEING AFFECTED. MOUNTAINS WILL REMAIN OBSCURED THROUGH THE
PERIOD. PRECIP WILL SLOWLY TAPER OFF SUNDAY AFTERNOON AND EARLY
EVENING. JKL
PRELIMINARY POINT TEMP/POPS
SUN MON TUE WED THU FRI SAT
-----------------------------------------------------------
BIL 030/039 029/055 034/050 035/053 032/053 031/046 029/053
69/O 24/W 37/W 64/W 23/W 34/W 21/U
LVM 030/040 029/050 031/044 029/046 028/046 028/044 026/049
99/S 26/W 58/J 63/J 24/J 44/J 21/B
HDN 030/040 027/057 031/050 033/051 029/054 029/047 026/053
58/O 23/W 47/W 55/W 24/W 34/W 32/J
MLS 029/040 028/052 032/053 033/051 031/054 029/048 029/054
23/S 11/E 23/W 52/W 12/W 22/W 21/U
4BQ 029/037 027/051 031/052 033/048 029/052 029/047 028/050
46/O 21/B 24/W 74/W 12/W 22/W 32/J
BHK 023/039 023/045 029/049 029/046 027/053 026/049 025/049
32/S 11/N 33/W 53/W 12/W 22/W 21/U
SHR 028/037 024/053 026/049 028/046 024/049 024/044 023/048
59/O 23/W 38/W 66/W 24/W 24/W 32/W
BYZ WATCHES/WARNINGS/ADVISORIES
MT...WINTER WEATHER ADVISORY IN EFFECT FROM 6 PM THIS EVENING TO 6
PM MDT SUNDAY FOR ZONES 34-56-63-65-66-141-228.
WINTER STORM WARNING IN EFFECT UNTIL 6 PM MDT SUNDAY FOR ZONE
68.
WINTER WEATHER ADVISORY IN EFFECT UNTIL 6 PM MDT SUNDAY FOR
ZONE 172.
WY...NONE.
WEATHER.GOV/BILLINGS
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