144
FXUS65 KBYZ 201510
AFDBYZ
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
910 AM MDT TUE OCT 20 2020
UPDATE
FAIRLY STRONG PRESSURE RISES MOVING ACROSS OUR EAST ARE STARTING
TO PRODUCE BREEZY NW WINDS, WITH GUSTS 20-35 MPH MANY LOCATIONS.
RAIN/SNOW SHOWER ACTIVITY IS ON THE DECREASE BUT WILL LINGER FOR A
COUPLE MORE HOURS. BUILDING SURFACE HIGH OVER EASTERN MT WILL
BRING A MOSTLY DRY DAY ONCE WE GET TO THE AFTERNOON. TEMPS WILL BE
WARMER THAN THE PAST FEW, BUT STILL WELL BELOW NORMAL. HAVE
TWEAKED POPS, SKY AND WIND PER CURRENT TRENDS...BUT OVERALL
FORECAST IS IN GOOD SHAPE. JKL
DISCUSSION
TODAY THROUGH WEDNESDAY NIGHT...
WE HAVE CANCELLED THE WEATHER ADVISORY FOR CUSTER COUNTY AS LOW
LEVEL TEMPERATURES HAVE WARMED ABOVE FREEZING IN THIS AREA. WE
WILL LET THE OTHER ONES FOR FALLON AND CARTER RIDE FOR NOW UNTIL 6
AM AS SOME POCKETS OF COLD AIR MAY BE LINGERING IN THIS AREA YET.
SOME RAIN/SNOW SHOWERS ARE STILL POSSIBLE, BUT SHOULD NOT AMOUNT
TO MUCH AS MOST OF ENERGY ALOFT EXITS TO THE EAST THIS MORNING.
STRONG JET OVER THE AREA TODAY, BUT SOUNDINGS SUGGEST AN INVERSION
WILL PREVENT THE BULK OF MID LEVEL FLOW FROM REACHING SURFACE.
THAT SAID, STRONG PRESSURE RISES WILL LEAD TO BRISK NORTHWEST
WINDS, ESPECIALLY IN THE FAR EASTERN SECTIONS OF THE CWA. TEMPS
WILL BE WARMER, BUT HINDERED BY EXISTING SNOW COVER. LOOK FOR
READINGS TO BE MOSTLY UPPER 30S TO MID 40S WHICH IS WELL BELOW THE
SEASONAL AVERAGES.
BACKING WINDS ALOFT AND ISENTROPIC ASCENT WILL INTRODUCE OUR NEXT
CHANCE OF LIGHT PRECIP BY TONIGHT. PRECIP TYPE WILL AGAIN BE
DIFFICULT TO CALL. WE WILL MENTION SOME LIGHT FREEZING RAIN AGAIN
AS SURFACE TEMPS ARE LIKELY TO FALL BELOW FREEZING, BUT
PRECIPITATION MAY BE SORTA PATCHY OVERALL WITH LITTLE ACCUMULATION
EXPECTED.
WEDNESDAY/WEDNESDAY NIGHT...WINDS CONTINUE TO BACK EARLY WEDNESDAY
AS UPPER TROF MOVES INTO THE ROCKIES. MOISTURE SLOWLY ENCROACHES
ON OUR AREA FROM THE WEST WITH STRONG FRONTOGENESIS ACROSS OUR
CWA BY EVENING SUPPORTED BY OVERRUNNING AND UPSLOPE. SOME AREAS OF
RAIN ON WEDNESDAY WILL INCREASE AND TURN TO SNOW WEDNESDAY
NIGHT. SNOW WEDNESDAY NIGHT MAY APPROACH 6-10 INCHES OR MORE IN
THE MOUNTAINS WITH 3-6 INCHES IN THE NEARBY WESTERN LOWER
ELEVATIONS AND A COUPLE OF INCHES IN THE EAST. ADDITIONAL SNOWFALL
IS THEN EXPECTED THURSDAY). WHILE THE LAST SYSTEM DID NOT HAVE
MUCH WIND INVOLVED, IT DOES LOOK LIKE BLOWING SNOW MAY BE AN ISSUE
WITH THIS ONE. WE WILL ISSUE A WINTER STORM WATCH FOR AREAS WE
BELIEVE WILL BE HARDEST HIT (SW MOUNTAINS AND FOOTHILLS ALONG WITH
A LARGE PORTION OF SOUTH CENTRAL MONTANA). THE WATCH WILL START
AT NOON WEDNESDAY FOR THE SOUTHWEST MOUNTAINS, AND AT 6 PM
WEDNESDAY FOR THE LOWER ELEVATIONS. END TIME FOR ALL LOCATIONS IS
6 PM THURSDAY. WE ANTICIPATE OTHER AREAS TO THE EAST WILL
EVENTUALLY NEED WINTER WEATHER ADVISORIES AS WELL. BT
THURSDAY THROUGH MONDAY...
THE UPPER TROUGH THAT IS EXPECTED TO MOVE INTO THE NORTHERN
ROCKIES WEDNESDAY-WEDNESDAY NIGHT LOOKS TO PRODUCE MORE SNOW ON
THURSDAY. MUCH OF THE AREA COULD RECEIVE ANOTHER 1 TO 4 INCHES OF
SNOW DURING THE DAY. THE SNOW WILL GRADUALLY LIGHTEN IN THE
AFTERNOON AS THE LARGE SCALE ASCENT WEAKENS. NORTHERLY LOW LEVEL
WINDS WILL KEEP TEMPERATURES NEARLY STEADY IN THE 20S.
CONDITIONS SHOULD DRY OUT THURSDAY NIGHT AS THE UPPER TROUGH MOVES
AWAY FROM MONTANA AND A 1036 MB SURFACE HIGH MOVES INTO MONTANA.
TEMPERATURES WILL DROP TO THE SINGLE DIGITS ABOVE ZERO BY FRIDAY
MORNING.
ON FRIDAY, THE SURFACE HIGH PRESSURE WILL MOVE EASTWARD AWAY FROM
MONTANA AS ANOTHER UPPER TROUGH MOVES INTO THE PACIFIC NORTHWEST.
THIS UPPER TROUGH SHOULD BEGIN TO SPREAD SNOW OVER SOUTH CENTRAL
MT IN THE AFTERNOON AND OVER THE WHOLE AREA FRIDAY NIGHT. SNOW
LOOKS TO CONTINUE THROUGH SATURDAY AND POSSIBLY SATURDAY NIGHT.
MODEL DATA ARE SUGGESTING A 70%+ CHANCE OF AT LEAST 4 INCHES OF
SNOW OVER SOUTH CENTRAL MT AND NORTH CENTRAL WY FROM THIS SYSTEM.
STRONG SURFACE HIGH PRESSURE OVER ALBERTA SHOULD SUPPLY PLENTY OF
COLD AIR FOR THIS WINTER STORM, KEEPING PRECIPITATION AS SNOW,
AND TEMPERATURES FRIDAY NIGHT IN THE TEENS AND SINGLE DIGITS AND
TEENS AND 20S ON SATURDAY. SATURDAY NIGHT LOOKS REMARKABLY COLD
WITH LOW TEMPERATURES BELOW ZERO NORTHWEST OF BILLINGS, AND SINGLE
DIGITS ABOVE ZERO FOR THE REST OF THE AREA.
SUNDAY, UPPER RIDGING AND THE SURFACE HIGH WILL SLIDE
SOUTHEASTWARD INTO MONTANA AND CAUSE SNOW TO TAPER OFF FROM NORTHWEST
TO SOUTHEAST. TEMPERATURES WILL CLIMB TO THE TEENS TO LOWER 20S
IN THE AFTERNOON. THE SURFACE HIGH WILL MOVE SOUTHEASTWARD FURTHER
INTO THE CENTRAL PLAINS ON MONDAY, WHICH SHOULD CAUSE LOW LEVEL
WINDS TO TURN SOUTH/SOUTHWESTERLY AND BRING INCREMENTALLY WARMER
AIR INTO THE REGION WITH HIGH TEMPERATURES WELL INTO THE 20S. RMS
AVIATION
MVFR-IFR IN AREAS OF RAIN/SNOW AND LOW CEILINGS WILL IMPROVE TO
VFR FROM NORTH TO SOUTH TODAY AS DRIER AIR MOVES IN. NORTHWEST
WINDS GUSTING TO 25-30 KT ARE EXPECTED OVER SOUTHEAST MT AND NORTH
CENTRAL WY THIS MORNING INTO THE AFTERNOON, WITH LOCALLY HIGHER
GUSTS AIDED BY RAIN SHOWERS. GILSTAD
PRELIMINARY POINT TEMP/POPS
TDY WED THU FRI SAT SUN MON
-------------------------------------------------------
BIL 041 028/040 021/027 008/024 013/020 005/018 001/022
2/W 36/O +8/S 22/S 88/S 74/S 21/B
LVM 049 031/047 017/029 007/029 011/022 000/020 901/029
2/W 47/O 96/S 14/S 89/S 63/S 21/B
HDN 040 026/043 021/029 007/027 013/023 004/019 901/022
3/J 34/O 98/S 21/E 77/S 74/S 21/B
MLS 041 023/044 022/029 010/025 013/023 008/020 001/020
2/W 23/O 97/S 11/E 67/S 64/S 21/B
4BQ 041 026/046 023/031 011/028 016/026 009/021 001/022
3/W 22/O 88/S 31/E 67/S 74/S 21/B
BHK 041 021/042 021/028 007/025 010/023 007/020 001/020
3/W 05/O 98/S 21/B 56/S 64/S 21/B
SHR 044 025/048 018/030 008/030 013/027 004/020 901/025
5/W 22/R 99/S 31/B 57/S 85/S 32/S
BYZ WATCHES/WARNINGS/ADVISORIES
MT...WINTER STORM WATCH IN EFFECT FROM WEDNESDAY EVENING THROUGH
THURSDAY AFTERNOON FOR ZONES
34-40-42-56-57-63>66-138-139-141-169>172-228-235.
WINTER STORM WATCH IN EFFECT FROM WEDNESDAY AFTERNOON THROUGH
THURSDAY AFTERNOON FOR ZONES 67-68.
WY...NONE.
WEATHER.GOV/BILLINGS
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