687
FXUS65 KBYZ 161733
AFDBYZ
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
1033 AM MST MON DEC 16 2024
KEY MESSAGES
- ANOTHER PERIOD OF LIGHT SNOW CAN BE EXPECTED LATER TODAY
THROUGH TUESDAY, WITH LIGHT ACCUMULATIONS POSSIBLE 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.
DISCUSSION
TODAY THROUGH TUESDAY NIGHT...
INSTABILITY AND WEAK ENERGY DROPPING THROUGH NW FLOW WAS CAUSING
LIGHT SNOW TO LINGER OVER THE SOUTHERN MOUNTAINS EARLY THIS
MORNING. WEAK SHORTWAVE RIDGING BUILDING INTO THE AREA TODAY WILL
ALLOW TEMPERATURES TO WARM INTO THE UPPER 20S TO UPPER 30S.
HOWEVER, THE RIDGING WILL BE QUICKLY REPLACED BY A PACIFIC WAVE
THAT WILL MOVE THROUGH THE REGION LATER TODAY/TONIGHT INTO
TUESDAY. SNOW WILL STEADILY INCREASE OVER THE WESTERN ASPECTS IN
THE SOUTHWEST MOUNTAINS DURING THE DAY TODAY, WITH SOUTHWEST FLOW
BRINGING AN INCREASE IN MOISTURE AHEAD OF THE WAVE. EXPECT SNOW
TO SPREAD OUT ONTO PORTIONS OF THE LOWER ELEVATIONS FROM WEST TO
EAST LATE TODAY/THIS EVENING AND INTO TUESDAY. A REINFORCING SHOT
OF COOLER AIR AND LIGHT UPSLOPE WINDS FROM THE NORTHEAST WILL
BRING HIGHS IN THE 20S OVER THE EAST, TO THE UPPER 30S OVER
CENTRAL AND WESTERN AREAS. PRECIPITATION AMOUNTS WILL RANGE FROM
A FEW HUNDREDTHS TO NEAR 0.10 INCHES OVER THE LOWER ELEVATIONS,
HIGHEST IN THE NORTH. THE WESTERN MOUNTAINS LOOK TO PICK UP 0.30
TO 0.75 INCHES, WITH AROUND 0.10 INCHES IN THE BIGHORNS AND
PRYORS. THIS TRANSLATES TO AN INCH OR LESS OF SNOW FOR THE LOWER
ELEVATIONS, WITH 4-10 INCHES OF SNOW OVER THE WESTERN MOUNTAINS,
GREATEST ON WEST FACING ASPECTS. THE PROBABILITY FOR 4 OR MORE
INCHES OF SNOWFALL RANGES FROM 40-100% IN THE CRAZY AND
BEARTOOTH/ABSAROKA MOUNTAINS, HIGHEST IN THE MOUNTAINS NEAR COOKE
CITY. THE BIGHORNS AND PRYORS WILL SEE ONLY AN INCH OR TWO OF
SNOW.
HEADING INTO TUESDAY NIGHT, HEIGHTS BUILDING IN FROM THE WEST WILL
CAUSE PRESSURE GRADIENTS TO BEGIN TIGHTENING ALONG THE WESTERN
FOOTHILLS, WITH WINDS INCREASING FOR THE GAP AREAS. FOR MORE ON
THE WINDS, SEE THE LONG TERM DISCUSSION. STP
WEDNESDAY THROUGH MONDAY...
WITH NO MAJOR WINTER STORM IN SIGHT AT THIS TIME, THE MAIN
WEATHER OF CONCERN DURING THE LONG-TERM FORECAST IS INCREASED
WINDS WEDNESDAY INTO THURSDAY MORNING. AT THIS TIME, THE STRONGEST
WINDS ARE EXPECTED OVER THE USUAL WESTERN FOOTHILL LOCATIONS OF
LIVINGSTON TO NYE, BIG TIMBER, AND HARLOWTON, WEDNESDAY INTO
WEDNESDAY NIGHT. A COLD FRONT PASSAGE WILL THEN PUSH THE STRONG
WINDS OVER THE PLAINS OF SOUTH-EASTERN MONTANA WEDNESDAY NIGHT
INTO THURSDAY MORNING. AROUND LIVINGSTON TO NYE, FAVORABLE
INGREDIENTS FOR GAP WINDS DEVELOP EARLY WEDNESDAY MORNING AND LAST
UP UNTIL THE COLD FRONT PASSAGE WEDNESDAY EVENING. DURING THIS
TIME, THERE IS A HIGH, 90 PERCENT CHANCE OF SEEING WIND GUSTS OF
50 MPH OR GREATER. AS FOR WIND GUSTS OF 58 MPH OR GREATER (WIND
ADVISORY THRESHOLD), THERE IS A MODERATE TO HIGH CHANCE AROUND 70
PERCENT. FOR BIG TIMBER TO HARLOWTON, THERE IS MORE UNCERTAINTY IN
THE WIND FORECAST, BUT INCREASED TO STRONG WINDS ARE FORECAST.
THE DETERMINISTIC GFS AND ECMWF BOTH SHOW A PERIOD OF STRONG 50 TO
65 KNOT 700MB WINDS WEDNESDAY EVENING WHEN THE SHORTWAVE MOVES
THROUGH. THE UNCERTAINTY LIES IN THE EXACT TIMING OF THESE WINDS
THOUGH, WHICH PLAYS A ROLE IN THE ABILITY FOR THE STRONGEST WINDS
TO MAKE IT TO THE SURFACE. THIS WILL BE SOMETHING TO WATCH AS WE
PROGRESS THROUGH THE WEEK. OVER THE PLAINS, THERE IS A HIGH CHANCE
OF NORTHWEST WIND GUSTS OF 25 MPH OR GREATER WEDNESDAY NIGHT INTO
THURSDAY MORNING. THE CURRENT FORECAST HAS WINDS OF 25 TO 45 MPH
COMMON, STRONGEST OVER THE HIGHER HILLS.
OUTSIDE OF WINDS, THERE IS A LOW CHANCE OF PRECIPITATION WITH THE
SHORTWAVE WEDNESDAY INTO THURSDAY. AS WE GET INTO THE WEEKEND,
RIDGING LOOKS TO BUILD OVER THE WESTERN UNITED STATES. WITH THIS,
GENERALLY WARMER AND DRIER CONDITIONS WILL PREVAIL. BECAUSE THERE
IS UNCERTAINTY IN THE EASTWARD EXTENT OF THE RIDGE AXIS, THE
FORECAST FOR EASTERN MONTANA IS MORE UNCERTAIN AS COOLER AND
SLIGHTLY WETTER CONDITIONS COULD REMAIN INTO THE WEEKEND. ON
SUNDAY, A SHORTWAVE LOOKS TO ROUND THE RIDGE, POTENTIALLY BRINGING
LIGHT PRECIPITATION CHANCES BACK TO PORTIONS OF THE AREA. ARENDS
AVIATION
18Z TAFS...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
TDY TUE WED THU FRI SAT SUN
-------------------------------------------------------
BIL 037 023/038 022/048 031/044 026/050 030/052 032/052
0/B 52/S 11/E 00/N 00/B 00/B 01/B
LVM 039 026/040 028/050 032/048 032/052 033/055 034/051
3/S 73/S 11/N 10/N 00/B 00/B 11/B
HDN 039 023/037 017/047 028/042 020/047 024/049 027/052
0/B 62/S 11/B 10/U 01/B 00/B 01/B
MLS 033 020/028 014/037 018/031 010/036 017/038 022/043
0/U 54/S 11/E 20/U 01/B 00/B 01/B
4BQ 036 021/034 018/042 026/038 017/044 023/046 026/047
0/U 33/S 00/B 10/U 00/B 00/B 01/B
BHK 029 013/027 009/034 013/028 002/031 011/033 016/038
0/U 24/S 11/E 30/N 01/B 00/B 00/B
SHR 039 019/039 018/051 027/045 022/054 027/056 027/054
0/B 22/S 00/B 10/U 00/B 00/U 01/B
BYZ WATCHES/WARNINGS/ADVISORIES
MT...NONE.
WY...NONE.
WEATHER.GOV/BILLINGS
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