Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 012151
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
251 PM MST SUN FEB 1 2015

.SHORT TERM...VALID FOR MON AND TUE...

AN ACTIVE WEATHER PATTERN IS IN STORE THE NEXT FEW DAYS AS SEVERAL
DISTURBANCES CROSS THE REGION AND INTERACT WITH A FRONT THAT WILL
SLOSH BACK AND FORTH WITH EACH PASSING WAVE. HIGHS WILL BE IN THE
40S F ON THE WARM SIDE OF THE FRONT...BUT WILL BE MUCH COOLER TO
ITS NORTH AND EAST.

OUR CONFIDENCE IN FORECAST DETAILS IS INCREASING...BUT REMAINS AT
A LEVEL WHICH IS LOWER THAN NORMAL FOR THE SHORT TERM SINCE SMALL-
SCALE NUANCES IN FRONTAL POSITION AND SHORTWAVE TROUGH TIMING WILL
DRIVE THE DETAILS AND MODEL GUIDANCE IS ONLY STARTING TO DEVELOP A
COMMON CONSENSUS TO BOTH. IN GENERAL...WE EXPECT LIGHT SNOW ACROSS
SOUTHEASTERN MT MONDAY MORNING AND AGAIN MONDAY NIGHT INTO TUESDAY
WITH LIGHT ACCUMULATIONS...AND THEN A HEALTHIER BATCH OF SNOWFALL
/WITH ACCUMULATIONS OF SEVERAL INCHES POSSIBLE/ OVER SOUTH CENTRAL
MT AND NORTH CENTRAL WY CENTERED ON TUESDAY NIGHT.

AFTERNOON MOISTURE CHANNEL IMAGERY SHOWS A STRONG SHORTWAVE TROUGH
MOVING INTO BRITISH COLUMBIA SOUTH OF KETCHIKAN. THE 12 UTC MODEL
RUNS PICKED UP WELL ON THE STRENGTH OF THIS WAVE AND ALL TAKE IT
INTO SOUTHEASTERN MT MONDAY. A WARM FRONT WILL MOVE EAST AS THIS
SHORTWAVE APPROACHES THE REGION AND THAT WILL LIKELY LEAD TO
WARMING TEMPERATURES OVERNIGHT IN MANY AREAS...AS SUPPORTED BY ALL
OF THE 12 UTC MOS-BASED GUIDANCE. QG-FORCING WITH THAT WAVE WILL
LINK WITH THE FRONTAL ZONE IN SOUTHEASTERN MT MONDAY MORNING AND
SO WE BELIEVE SOME LIGHT SNOW COULD OCCUR THEN. CYCLONIC FLOW IN
THE IMMEDIATE WAKE OF THE WAVE IS SUPPORTIVE OF A LOW CHANCE OF
SNOW SHOWERS EVEN INTO MONDAY AFTERNOON THERE. ANOTHER SURGE OF
LOW- AND MID-LEVEL WARM AIR ADVECTION IS EXPECTED MONDAY NIGHT AND
THE 12 UTC GFS...ECMWF AND NAM ALL AGREE THAT THE MID-LEVEL FRONT
WILL STAY NORTH AND EAST OF BILLINGS...SO WE HAVE FOCUSED POPS FOR
MONDAY NIGHT AND INTO TUESDAY FROM ROUNDUP TO HYSHAM...MILES CITY
AND BAKER. WE GAVE CONSIDERATION TO THE RISK OF FREEZING RAIN NEAR
THE FRONTAL ZONE GIVEN THE WARMING ALOFT...BUT IT/S NOT CLEAR THAT
PRECIPITATION WILL OCCUR WHERE MID-LEVEL TEMPERATURES ARE ACTUALLY
WARM ENOUGH TO MELT HYDROMETEORS GIVEN SUBTLE DIFFERENCES IN THE
PLACEMENT OF THE MID-LEVEL FRONTAL ZONE. THAT IS REFLECTED IN LOW
PROBABILITIES OF FREEZING RAIN IN THE 09 UTC SREF PRECIPITATION-
TYPE GUIDANCE...WHICH WAS ENOUGH FOR US TO KEEP FREEZING RAIN OUT
OF THE FORECAST AT THIS POINT.

THE 12 UTC MODEL SUITE GENERALLY AGREED THAT A STRONGER SHORTWAVE
TROUGH WILL ENABLE A STRONGER SOUTHWARD PUSH OF THE FRONT TUESDAY
NIGHT SUCH THAT ARCTIC AIR WILL PUSH ACROSS THE ENTIRE AREA. MEAN
LIQUID-EQUIVALENT MOISTURE VALUES FROM A MULTI-MODEL CONSENSUS AND
THE EXPECTATION OF INCREASING SNOW-TO-LIQUID RATIOS WITH TIME PER
VISUALIZATION OF THERMAL AND OMEGA PROFILES IN BUFKIT YIELDED SOME
2 TO 5 INCHES OF SNOW IN THE FORECAST TUESDAY NIGHT ACROSS MUCH OF
SOUTH CENTRAL MT AND NORTH CENTRAL WY. HOWEVER...THE 12 UTC GFS IS
STRONGER WITH THE QG-FORCING AND THUS HAS HIGHER MOISTURE THAN THE
CONSENSUS...AND IF LATER TRENDS SUPPORT THIS IDEA THAN SNOW TOTALS
COULD BE HIGHER THAN CURRENTLY ADVERTISED...ESPECIALLY ACROSS THE
FOOTHILLS. THIS COULD INDEED BE A HEADLINE-WORTHY SNOW EVENT OVER
PARTS OF THE AREA AND IF GUIDANCE STAYS STEADFAST IN ITS DEPICTION
OF THIS SCENARIO WE WILL BE FOCUSING ON TUESDAY NIGHT FOR POSSIBLE
TRAVEL IMPACTS IN THE NEXT FEW FORECAST CYCLES. SCHULTZ

.LONG TERM...VALID FOR WED...THU...FRI...SAT...SUN...

THE EXTENDED FORECAST LOOKS RATHER MILD AND MOSTLY DRY AS A MEAN
RIDGE REMAINS IN TACT OVER THE SOUTHERN ROCKIES.

WEDNESDAY SHOULD BE THE COLDEST DAY AS A SHORTWAVE TROUGH EXITS
THE AREA AND SLIDES INTO THE DAKOTAS. 850MB TEMPERATURES FROM -12C
TO -18C WILL BE OVER THE FORECAST AREA AT 12Z WEDNESDAY. WARM AIR
ADVECTION QUICKLY ENSUES BY WEDNESDAY AFTERNOON AS HEIGHTS BUILD
AND THIS WILL SHOVE THE COLD AIR EAST. SNOW SHOWERS WILL LINGER IN
THE MORNING OVER THE MOUNTAINS AND WESTERN FOOTHILLS.

RIDGING WILL TAKE OVER FOR THURSDAY ONWARD FOR A WARMING TREND.
WEAK ENERGY WILL RIDE OVER THE RIDGE AND PROVIDE SOME ASCENT BUT
WILL KEEP THE POP FOCUS OVER THE MOUNTAINS AND NEARBY FOOTHILLS
AS DOWNSLOPE FLOW WILL LIMIT PRECIPITATION POTENTIAL. A STRONGER
SHORTWAVE WILL CRASH THE RIDGE FRIDAY NIGHT INTO SATURDAY NIGHT
FOR A BETTER CHANCE OF PRECIPITATION.

WINDS WILL CRANK UP OVER THE WEST FROM THURSDAY NIGHT ONWARD...SO
BUMPED WINDS UP QUITE A BIT FROM LIVINGSTON TO NYE. THURSDAY NIGHT
INTO FRIDAY MORNING LOOKS LIKE THE WINDIEST PERIOD AT THE MOMENT
BUT THERE WILL BE STRONG WIND POSSIBILITIES IN A NUMBER OF PERIODS
THROUGH SATURDAY. TWH

&&

.AVIATION...

VFR CONDITIONS ARE EXPECTED TONIGHT. A WEAK SYSTEM WILL MOVE INTO
WESTERN LOCATIONS EARLY THIS EVENING...AND INTO THE EAST
OVERNIGHT. THIS SYSTEM WILL PROVIDE A SLIGHT CHANCE OF SNOW
SHOWERS. SNOW SHOWERS SHOULD BE LIGHT...BUT LOCAL MVFR CONDITIONS
ARE NOT OUT OF THE QUESTION. MOUNTAINS WILL BECOME OBSCURED. TWH

&&

.PRELIMINARY POINT TEMP/POPS...

    MON     TUE     WED     THU     FRI     SAT     SUN
-----------------------------------------------------------
BIL 022/046 029/039 011/031 026/046 037/055 038/056 035/053
    21/N    24/O    62/J    10/B    01/N    11/N    11/N
LVM 027/048 033/046 016/039 029/050 038/056 041/055 037/053
    41/N    32/R    74/W    22/W    11/N    23/W    11/N
HDN 020/043 024/036 007/027 018/045 030/051 031/053 029/051
    22/S    35/O    62/J    10/B    01/B    11/B    11/B
MLS 010/032 017/024 002/023 012/040 027/047 028/052 031/050
    35/S    66/S    41/B    11/B    01/B    11/B    11/B
4BQ 014/043 022/034 007/027 019/045 030/054 035/056 033/055
    25/S    35/O    51/B    10/B    01/B    11/B    11/B
BHK 004/030 013/022 901/020 012/039 026/047 028/049 031/048
    25/S    66/S    21/B    10/B    11/B    12/W    11/N
SHR 018/045 024/041 012/029 020/045 029/056 032/054 028/052
    21/E    12/W    63/J    10/B    00/B    11/B    11/B

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
WY...NONE.

&&

$$
WEATHER.GOV/BILLINGS


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