940
FXUS65 KBYZ 182117
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
217 PM MST WED DEC 18 2024
KEY MESSAGES
- STRONG AND GUSTY WINDS WILL CONTINUE THROUGH THE EVENING HOURS.
EXPECT THE STRONGEST GUSTS IN ADVISORY AND WARNING AREAS. WIND
GUSTS WILL APPROACH THE UPPER 50S MPH IN THE FAR EAST TONIGHT.
- LOW TO MODERATE CHANCE FOR PRECIP IN THE EAST TONIGHT, EXPECTED
TO BE A RAIN TO RAIN/SNOW MIX, VERY LOW CHANCE FOR FREEZING
RAIN.
- ABOVE NORMAL TEMPERATURES WITH OCCASIONAL CHANCES OF
PRECIPITATION ARE IN THE FORECAST FRIDAY INTO THE MIDDLE OF NEXT
WEEK.
DISCUSSION
TODAY THROUGH THURSDAY NIGHT...
A SHORTWAVE TROUGH AND SURFACE COLD FRONT WILL DROP THROUGH THE
REGION, THIS AFTERNOON INTO THE OVERNIGHT HOURS. VERY STRONG WINDS
WILL CONTINUE INTO THE OVERNIGHT HOURS AS WELL, FOR THE WESTERN
COUNTIES AS WELL AS MUSSELSHELL AND SOUTHERN YELLOWSTONE COUNTIES.
THE HIGH WIND WARNING FOR BIG TIMBER AND HARLOWTON WILL CONTINUE,
WITH GUSTS AS HIGH AS 75 MPH. THE HIGH WIND WARNING FOR
MUSSELSHELL AND SOUTHERN YELLOWSTONE COUNTIES GOES INTO EFFECT AT
2 PM, WITH GUSTS UP TO 60 MPH POSSIBLE. WIND ADVISORY FOR THE
BEARTOOTH FOOTHILLS, LIVINGSTON, AND NYE CONTINUES, WITH OBSERVED
GUSTS IN THE LOW 70S MPH.
THE FAVORABLE PRESSURE GRADIENT OF BETWEEN IDAHO FALLS AND
LEWISTOWN HAS PEAKED AROUND 18-20MB. THE SW-NE ORIENTATION OF THIS
GRADIENT HAS FAVORED STRONG WINDS IN LIVINGSTON AND NYE, WITH THE
APPROACHING SHORTWAVE, THE GRADIENT IS SHIFTING TO A W-E
ORIENTATION WHICH FAVORS BIG TIMBER, HARLOWTON AND THE CENTRAL
COUNTIES. STRONG 700-500MB WINDS OF 70-100 KNOTS ARE MIXING DOWN
WITH STRONG SUBSIDENCE AND HAVE RESULTED IN POTENTIAL MOUNTAIN
WAVE ACTIVITY ATOP THE BEARTOOTH PLATEAU, WITH A GUST OF 94 MPH
OBSERVED AT THE QUAD CREEK RAWS.
THIS EVENING, THE COLD FRONT WILL REACH THE NORTH-EASTERN
COUNTIES, BRINGING A 15-50% CHANCE FOR PRECIPITATION. THERE HAS
BEEN CONCERN WITH PRECIP TYPE IN THE EAST TONIGHT, WITH A PREVIOUS
MODEL RUNS DEPICTING MIXED PRECIPITATION. LATEST MODELS HAVE
LARGELY THROWN THIS OUT, NOW SHOWING JUST RAIN OR RAIN/SNOW MIX.
THE CHANCE FOR FREEZING RAIN IS VERY LOW, LESS THAN 15%. SLICK
ROADS ARE POSSIBLE OVERNIGHT IN THE EAST WHERE PRECIPITATION
OCCURS, AS TEMPERATURES DROP BELOW FREEZING. ALONG WITH PRECIP,
STRONG WINDS GUSTING INTO THE 50S MPH ARE FORECAST. WHILE WINDS
WILL APPROACH CRITERIA, I DECIDED TO NOT ISSUE A HIGH WIND WARNING
FOR FALLON AND CARTER COUNTIES, DUE TO LACK OF CONFIDENCE IN
WIDESPREAD GUSTS BEING OBSERVED FOR AN EXTENDED DURATION.
ALONG WITH THE CHANCE FOR PRECIP IN THE EAST, THERE IS A 25-70%
CHANCE IN THE ABSAROKA/BEARTOOTHS THROUGH THE EVENING HOURS.
ADDITIONAL SNOW ACCUMULATIONS UP TO 6 INCHES IS POSSIBLE FOR THE
W-SW FACING SLOPES, INCLUDING COOKE CITY. FOR THE REST OF THE
FORECAST AREA, EXPECT LESS THAN A 20% CHANCE FOR PRECIPITATION FOR
THE DURATION OF THE SHORT TERM FORECAST PERIOD.
EXPECT STRONG WINDS TO DIMINISH FROM WEST TO EAST OVERNIGHT,
GIVING WAY TO CALM AND DRY CONDITIONS, THURSDAY. HIGH TEMPERATURES
RANGE FROM THE UPPER TEENS TO MID 40S (COLDEST TEMPERATURES IN
FALLON COUNTY) AND THE CHANCE FOR PRECIPITATION ACROSS THE AREA
WILL BE LESS THAN 15%.
MATOS
THURSDAY NIGHT THROUGH WEDNESDAY...
MAIN FORECAST CONCERNS IN THE LONG TERM ARE ON ABOVE NORMAL HIGH
TEMPERATURES THROUGH THE WEEKEND, FOCUS THEN TURNS TO THE POTENTIAL
FOR A MORE ACTIVE WEATHER PATTERN BY THE MIDDLE OF NEXT WEEK.
RIDGING WITH EMBEDDED WEAK SHORTWAVES WILL BE THE DOMINANT WEATHER
FEATURES THROUGH SATURDAY THEN OUR NEXT STRONGER SHORTWAVE IS
EXPECTED TO MOVE OVER THE FORECAST AREA SATURDAY NIGHT INTO SUNDAY.
THIS FEATURE LOOKS TO BRING A SHOT OF SNOW TO THE MOUNTAINS WITH A
MEDIUM CHANCE FOR RAIN/SNOW MIX ACROSS LOWER ELEVATIONS. IT WILL BE
RATHER WARM FOR THIS TIME OF YEAR WITH HIGHS CLIMBING INTO THE MID
40S TO LOWER 50S, IN FACT, THE NBM IS SHOWING NEAR A 50 PERCENT
CHANCE OF EXCEEDING 50 DEGREES FOR HIGHS AT KBIL SATURDAY THROUGH
TUESDAY. A POTENTIALLY MORE ACTIVE WEATHER PATTERN COULD SET UP
ACROSS THE REGION BY THE MIDDLE OF NEXT WEEK. HALF OF THE WPC
CLUSTER MEMBERS ARE SHOWING A TROUGH FEATURE AT 500 MB MOVING INTO
THE WESTERN CONUS BUT THERE IS CONSIDERABLE UNCERTAINTY REGARDING
THE DEPTH AND TIMING OF THE TROUGH.
JW
AVIATION
EXPECT STRONG WESTERLY WINDS AT THE TAF SITES INTO THE OVERNIGHT
WITH GUSTS OF 40 TO 50 KTS, STRONGEST AT KLVM AND KBIL. KSHR WILL
BE MORE SHELTERED FROM THE STRONGEST SURFACE WINDS BUT EXPECT LLWS
AT TIMES. WINDS WILL GRADUALLY SUBSIDE AFTER 09Z. ISOLATED RAIN
OR SNOW SHOWERS ARE POSSIBLE THIS EVENING, MAINLY EAST OF KBIL.
VFR CONDITIONS WILL PREVAIL AT THE TAF SITES BUT EXPECT SNOW
SHOWERS OVER THE MOUNTAINS OBSCURING THE HIGHER TERRAIN.
JW
PRELIMINARY POINT TEMP/POPS
THU FRI SAT SUN MON TUE WED
-----------------------------------------------------------
BIL 031/043 024/051 032/053 035/050 029/047 030/049 034/048
00/U 00/B 00/B 22/R 01/B 01/B 32/R
LVM 029/047 030/053 033/054 035/046 029/047 030/050 031/045
00/N 00/B 00/U 52/O 02/O 02/R 52/O
HDN 025/039 021/046 025/052 029/049 025/047 026/049 030/048
10/U 00/B 00/B 24/O 01/B 01/B 33/O
MLS 012/022 010/038 020/043 025/041 024/043 026/044 028/043
20/U 00/B 00/B 13/O 00/U 00/U 22/O
4BQ 023/033 017/043 025/050 029/044 026/046 027/049 029/043
20/U 00/B 00/U 13/O 00/U 00/U 23/O
BHK 004/018 001/030 016/040 021/038 021/040 022/042 023/038
40/N 00/E 00/B 02/O 00/U 00/U 12/O
SHR 026/043 020/052 027/057 029/048 023/049 025/052 027/046
00/U 00/B 00/U 13/O 01/B 00/B 34/O
BYZ WATCHES/WARNINGS/ADVISORIES
MT...HIGH WIND WARNING IN EFFECT UNTIL 2 AM MST THURSDAY FOR ZONES
29-34-42-63-141-172-228-235.
WIND ADVISORY IN EFFECT UNTIL 2 AM MST THURSDAY FOR ZONES
65-66.
WY...NONE.
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