Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 301033
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
333 AM MST FRI JAN 30 2015

.SHORT TERM...VALID FOR TDY AND SAT...

LIGHT WINDS ALOFT AND AT THE SURFACE TODAY AS MAIN FLOW PATTERN IS
SPLIT UPSTREAM OVER THE IDAHO PANHANDLE. COMBINATION OF PLENTIFUL
SUNSHINE AND A BIT OF A WARM START WILL HELP TEMPERATURES CLIMB
THROUGH THE 40S WITH A FEW 50S POSSIBLE. WARM AIR LINGERS OVER
SOUTHERN MONTANA AND NORTHERN WYOMING TONIGHT AS SURFACE PRESSURES
FALL IN RESPONSE TO DIFFLUENCE ALOFT MOVING INTO THE AREA AND SOME
COMPRESSIONAL WARMING AHEAD OF THE COLD FRONT MOVING INTO NORTHERN
MONTANA.

COLD FRONT EXPECTED TO SHIFT THROUGH THE REGION FROM NORTH TO
SOUTH BETWEEN 16Z AND 22Z SATURDAY WITH A SHORTWAVE TRACKING OVER
SOUTHEAST MONTANA DURING THIS TIME. FORCING WILL PUSH THE FRONT
FASTER THROUGH SOUTHEAST MONTANA SO AIRMASS CHANGE WILL BE MORE
DRAMATIC THERE SATURDAY AFTERNOON. FRONT MAY PROGRESS SLOWER
THROUGH SOUTH CENTRAL MONTANA WHERE WESTERLY WINDS AT 700MB WILL
PROMOTE SOME DOWNSLOPE INITIALLY BUT THIS EFFECT DECREASES IN THE
LATE AFTERNOON AS MID LEVEL WINDS VEER. SNOWFALL WITH THIS PUSH
CAN BE BROKEN INTO 3 AREAS OF EMPHASIS. SOUTHEAST MONTANA WILL SEE
BETTER LIFT WITH THE SHORTWAVE AND LESS DOWNSLOPE INFLUENCE BUT
ITS NOT A REAL DEEP ARCTIC PUSH SO PROBABILITY OF LIGHT SNOW IS
STRONG SATURDAY AFTERNOON AND EVENING BUT AMOUNTS SHOULD BE
LIGHT. FURTHER WEST THE FRONTAL BOUNDARY WILL BEGIN TO BE AIDED BY
UPSLOPE SO AREAS CLOSER TO BILLINGS WILL SEE SLIGHTLY HIGHER
AMOUNTS BUT SNOW WILL ARRIVE MORE IN THE SATURDAY EVENING
TIMEFRAME. FURTHER WEST SOME AREAS OF THE FOOTHILLS MAY BE LIMITED
AS THE COLD AIR STRUGGLES TO DEEPEN AND MIDLEVEL NORTHWEST FLOW
CAUSES SOME DOWNSLOPE. THERE IS UNCERTAINTY AS TO HOW DEEP THE
COLD AIR WILL GET BUT THE BOTTOM LINE SHOULD BE THE SNOWFALL WILL
BE GENERALLY LIGHT AND THE WINDOW IS NOT VERY LONG. BY LATE
SATURDAY NIGHT THE SURFACE HIGH DRIVING THE COLD AIR IS ALREADY
DIVING THROUGH THE EASTERN DAKOTAS AND 700MB FLOW BEGINS TO BACK
AND BECOME MORE WESTERLY BRINGING A DRYING DOWNSLOPE TO THE
WESTERN AREAS. BORSUM


.LONG TERM...VALID FOR SUN...MON...TUE...WED...THU...

OVERALL FORECAST APPEARS IN PRETTY GOOD SHAPE...WITH GENERALLY
COOLER AND UNSETTLED WEATHER ON TAP THROUGH THE BULK OF THE
PERIOD. THE DIFFICULTY CONTINUES TO BE REST IN THE DETAILS...WHICH
CONTINUE TO VARY FROM RUN TO RUN...AND MODEL TO MODEL.
FLUCTUATIONS HAVE RESULTED IN RELATIVELY MINOR CHANGES FOR THE
THE EXTENDED FORECAST PERIOD ONCE AGAIN.

NORTHWEST FLOW WILL DOMINATE THE PATTERN THROUGH WEDNESDAY.
SATURDAY SYSTEM WILL COMPLETE PASSAGE THROUGH THE REGION
SUNDAY...WITH SOME POTENTIAL FOR A SHORT PERIOD OF CLEARING. THE
NEXT SURGE OF PACIFIC MOISTURE WILL MOVE QUICKLY INTO THE REGION
SUNDAY EVENING...INITIALLY IMPACTING THE WESTERN MOUNTAINS.
ANOTHER SHORTWAVE WILL MOVE INTO THE AREA SPREADING PRECIP
POTENTIAL ACROSS THE REGION. CURRENT MODEL RUNS FOR SUNDAY NIGHT
THOUGH MONDAY LOOK MUCH LESS IMPRESSIVE WITH REGARD TO PRECIP THAN
DID IN PREVIOUS RUNS. THE BEST ENERGY APPEAR TO SKIRT THE BULK OF
THE CWA TO THE NORTH. ADDITIONALLY...THE WAVE SEEMS TO FLATTEN
UPPER LEVEL FLOW...MAKING DOWNSLOPE FLOW A DEFINITE POSSIBILITY
TO DRY THINGS A OUT A BIT MORE QUICKLY. THESE ARE SIGNIFICANT
DEPARTURES FROM PREVIOUS RUNS. HAVE OPTED TO KEEP INHERITED POPS
AT THIS TIME...AS STILL THINK THAT THERE SHOULD BE SOME POTENTIAL
FOR PRECIP...BUT JUST DOES NOT LOOK AS GOOD. THIS WILL DEFINITELY
BE WORTH FURTHER ATTENTION IN FUTURE SHIFTS.

ANOTHER DISTURBANCE CROSSES THROUGH THE REGION TUESDAY...BUT
AGAIN...MODELS SEEM TO KEEP BEST ENERGY ACROSS THE NORTHERN TIER.
STILL THINK THE ENTIRE REGION WILL SEE A FAIR CHANCE AT SOME
SNOW...BUT WITH SHIFTY LOCATION...FELT NEED TO TAPER BACK POPS
SLIGHTLY FOR TUESDAY. IT DOES APPEAR THAT THIS WAVE SHIFTS SOUTH
LATE TUESDAY AND INTO WEDNESDAY...SETTING UP A PROLONGED PERIOD OF
OVERRUNNING ACROSS THE SOUTHERN TIER OF THE REGION THROUGH
WEDNESDAY. TIMING VARIES A BIT ON THE DURATION OF THIS SNOW...WITH
GFS CLEARING A BIT MORE QUICKLY. DID RAISE POPS AGAIN ACROSS THE
SOUTHERN TIER FOR WEDNESDAY.

A RIDGE APPEAR TO TAKE OVER ACROSS THE REGION FOR THE REMAINDER OF
THE PERIOD...BRINGING AN END TO THE COOLER AND UNSETTLED PATTERN.

AS FOR TEMPERATURES...EXPECT SLIGHTLY BELOW SEASONAL AVERAGE TEMPS ON
SUNDAY UNDER THE CONTINUED COLD AIRMASS FROM SAT. TEMPS ARE A BIT
TRICKY FOR MONDAY...WITH POTENTIAL FOR A QUICK WARMUP BEFORE
COLDER AIR FILTERS BACK INTO THE AREA. EXPECT BELOW AVERAGE TEMPS
TO RETURN FOR TUESDAY AND WEDNESDAY...THEN MODERATING FOR THURSDAY
AND FRIDAY. THAT SAID...THERE ARE SOME INDICATIONS THAT THESE
TEMPS COULD BE MUCH COLDER THAN WHAT THE MODELS ARE INDICATING
BASED ON TEMPERATURES READINGS CURRENTLY BEING RECORDED IN
ALASKA...WHERE THE COLD AIRMASS ORIGINATES. A SHALLOW AND VERY
COLD AIRMASS MAY NOT BE HANDLED WELL BY MODELS. THE COLDER
TEMPERATURES WOULD ALSO MAKE SENSE CLIMATOLOGICALLY FOR THIS TIME
OF YEAR...SO MAY BE WORTH KEEPING IN MIND. AAG

&&

.AVIATION...

VFR CONDITIONS ARE EXPECTED TO PREVAIL TODAY UNDER CLEAR TO
PARTLY CLOUDY SKIES. AG

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY SAT     SUN     MON     TUE     WED     THU
-------------------------------------------------------
BIL 050 029/040 017/032 028/045 021/028 009/027 021/043
    0/U 02/O    63/J    43/W    44/J    32/J    11/N
LVM 050 024/045 019/037 031/047 025/030 017/035 027/046
    0/U 01/B    43/W    43/W    66/J    32/J    22/W
HDN 047 023/038 013/030 022/043 017/025 007/025 012/040
    0/U 02/S    42/J    43/W    44/J    32/J    11/B
MLS 046 023/033 009/025 019/035 013/018 902/018 006/038
    0/U 05/S    32/J    33/J    44/J    22/J    01/B
4BQ 051 024/043 012/028 023/043 019/026 006/023 012/042
    0/U 03/O    32/J    33/W    34/J    32/J    11/B
BHK 045 022/028 004/021 014/033 011/016 905/014 004/032
    0/U 16/S    72/J    23/J    44/J    21/B    11/B
SHR 046 020/041 013/029 022/044 018/029 006/028 015/041
    0/B 01/U    32/J    22/W    35/J    32/J    21/B

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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