Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 250238
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
838 PM MDT TUE MAR 24 2015

.UPDATE...

NO UPDATE TO THE SHORT TERM DISCUSSION THIS EVENING. OVERALL
FORECAST IN GOOD SHAPE...WITH TEMPS IN THE BALLPARK...PRECIP
REMAINING IN WESTERN ZONES...AND WINDS BEHAVING AS EXPECTED. AAG

&&

.SHORT TERM...VALID FOR WED AND THU...

DISTURBANCE IN NORTHWEST FLOW ALOFT OVER WESTERN MONTANA MOVING
THROUGH THE AREA THIS AFTERNOON TURNING THE FLOW CYCLONIC FOR THE
EVENING HOURS BEFORE THE NEXT RIDGE BEGINS MOVING INTO FROM IDAHO
LATE NIGHT. AIRMASS IS UNSTABLE WITH RADAR SHOWING WEAK
CONVECTION DEVELOPING BUT BOUNDARY LAYER DEWPOINTS DRIED
REMARKABLY BEHIND THE EXITING SYSTEM OVER THE DAKOTAS SO
ENTRAINMENT IS LIMITING PRECIPITATION. COLD FRONT IS MOVING SLOWLY
SOUTHWARD FROM NORTHERN MONTANA WHERE TEMPERATURES ARE MUCH COOLER
IN THE 30S.

BEST WINDOW OF PRECIPITATION TONIGHT WILL BE AS THE FRONT BACK IN
TOWARDS THE MOUNTAINS AND FOOTHILLS WHILE THE MOUNTAINS STAY
UNSTABLE. RIDGE AXIS NOSES UP INTO NORTHWEST MONTANA FIRST SO THAT
HELPS MAINTAIN CYCLONIC FLOW OVER SOUTHERN MONTANA FOR A WHILE BUT
RUC SHOWS WAVE DEPARTING THE REGION TO THE SOUTH AROUND 10Z.
MODELS HAVE SHOWING A TREND WHERE BEST PRECIPITATION ONLY LASTS
ALONG THE RED LODGE FOOTHILLS FOR ABOUT 9 HOURS AND SETTING UP
LONGER OVER THE BIG HORN MOUNTAINS. SREF PLUME DIAGRAMS SHOW THIS
BY DECREASING PRECIPITATION AMOUNTS IN THE LIVINGSTON AREA WHILE
RAISING THEM FOR SHERIDAN. ANOTHER LIMITER ON SNOWFALL WILL BE THE
WINDOW FOR PRECIP CHANGE AS EARLY EVENING AIR WILL STILL BE ON THE
MILD SIDE BUT EVAPORATIVE COOLING SHOULD BRING AROUND A QUICK
CHANGE IN AREAS OF HEAVIER PRECIP. FOOTHILLS SHOULD SEE A RAIN
SNOW MIX BY 8 PM BECOMING ALL SNOW BY 10 PM WHILE THE BILLINGS
AREA WILL SEE A RAIN SNOW MIX DEVELOP BY MIDNIGHT. WITHOUT UPSLOPE
INFLUENCES PLAINS WILL SEE LIGHT SNOW AMOUNTS. KEPT WINTER STORM
WARNING AREAS THE SAME AND WILL POST AN ADVISORY FOR THE BIG HORN
MOUNTAINS AS CONDITIONS LOOK MORE FAVORABLE FOR ACCUMULATIONS
THERE.

WEDNESDAY AND THURSDAY THE RIDGE UPSTREAM BEGINS TO BUILD SLOWLY
EASTWARD WITH FLOW ALOFT REMAINING NORTHWESTERLY. SHOWER ACTIVITY
WILL LINGER ON WEDNESDAY BUT TEMPERATURES WARM ENOUGH TO MAKE IT
RAIN SHOWERS WITH ACCUMULATION RATES DECREASING FOR THE MOUNTAINS.
WILL ONLY RUN THE WINTER ADVISORY FOR THE BIG HORN MOUNTAINS UNTIL
18Z. TEMPERATURES WILL BE COOLER WEDNESDAY WITH CLOUDS
REDEVELOPING UNDER ANY SUNBREAKS THAT OCCUR.

THURSDAY A WEAK BACKDOOR COLD FRONT NOSES INTO EASTERN MONTANA
WHICH ALLOWS FOR A CONTINUED CHANCE OF SHOWER ACTIVITY WHILE THE
WESTERN ZONES DRY OUT. WILL SEE A STRONG TEMPERATURE GRADIENT
ACROSS THE AREA WITH 60S IN CENTRAL AND WESTERN ZONES AND 40S IN
SOUTHEAST MONTANA. EXPECT ANY SNOW OVER CARTER AND FALLON COUNTIES
TO BE PRETTY LIGHT DURING THIS TIME FRAME.

WARMUP IN THE WESTERN ZONES ON THURSDAY WILL BE AIDED BY A
DEVELOPING LEESIDE TROUGH. ORIENTATION NOT FAVORABLE FOR GAP FLOW
WINDS BUT IT WILL BE BREEZY FOR AREAS WEST OF AND INCLUDING
BILLINGS THURSDAY NIGHT KEEPING TEMPERATURES MILD. BORSUM


.LONG TERM...VALID FOR FRI...SAT...SUN...MON...TUE...

MODELS PRETTY CONSISTENT OF LATE IN ADVERTISING AN AMPLIFIED
RIDGE FOR FRIDAY...BREAKING DOWN ON SATURDAY. THIS WILL LEAD TO A
COUPLE OF MILD AND DRY DAYS...FOLLOWED BY A CHANCE OF SHOWERS AND
SLIGHTLY COOLER WEATHER INTO NEXT WEEK.

A STRONG COLD FRONT IS PROGGED FOR SATURDAY...BUT THE MODELS
STILL DIFFER ON TIMING. THE GFS WAS QUICKER WITH THE FRONT AND
BRINGS IT THROUGH BY MID DAY. THIS WOULD BE COOLER THAN THE ECMWF
WHICH KEEPS THE FRONT NORTH UNTIL LATE AFTERNOON. THE ECMWF LOOKS
TO HAVE SPED UP A LITTLE BIT...SO THE TREND MAY BE FOR A QUICKER
FRONTAL PASSAGE. WILL CHOOSE TO WAIT THIS ONE OUT AND MAKE SURE
THE FRONTAL TIMING IS CONSISTENT BEFORE MAKING ANY FURTHER CHANGES
ON THE SATURDAY TEMPERATURE GRID. SATURDAY COULD BE A FIRE WEATHER
CONCERN...BASED ON HOW WARM AND DRY IT GETS AHEAD OF THE FRONT AND
HOW STRONG THE NORTHWEST WINDS ARE BEHIND THE FRONT.

PRECIPITATION WILL NOT BE A HUGE FACTOR WITH THE FRONTAL PASSAGE
ON SATURDAY AS DEWPOINTS WILL BE LOW AND THE MAIN MID LEVEL
FORCING CROSSES NORTHERN MONTANA. WILL KEEP LOW POPS IN. SUNDAY
LOOKS MAINLY DRY WITH WEAK ZONAL FLOW BEHIND THE SHORTWAVE OF
SATURDAY...BUT THERE ARE HINTS OF MID LEVEL MOISTURE AND WEAK
ENERGY STREAMING INTO THE MOUNTAINS.

MONDAY LOOKS TO BE DRY BEFORE THE NEXT TROUGH ARRIVAL FOR
TUESDAY. MODELS HAVE COME INTO BETTER AGREEMENT ON THIS.
DIFFERENCES STILL EXIST WITH THE ECMWF BEING COOLER AND WETTER BUT
THE MODELS ARE COMING CLOSER TOGETHER...SO CONFIDENCE IS GROWING A
LITTLE BIT ON A COOLER AND MORE UNSETTLED PATTERN MOVING IN FOR
NEXT WEEK. TWH

&&

.AVIATION...

THERE WILL BE AREAS OF MVFR/IFR AND LOCALLY LOWER CONDITIONS
OVERNIGHT FROM W OF A ROUNDUP TO KBIL TO KSHR LINE...IN A MIX OF
RAIN AND SNOW SHOWERS THAT WILL CHANGE TO ALL SNOW SHOWERS. THE
LOWEST CONDITIONS WILL BE NEAR THE MOUNTAINS INCLUDING THE KLVM
AREA. GUSTY N TO NE WINDS BEHIND A COLD FRONT MOVING THROUGH THE
AREA THIS EVENING WILL DIMINISH OVERNIGHT...AS THE FRONT MOVES
INTO THE RED LODGE AND BEARTOOTH FOOTHILLS. THE MOUNTAINS WILL BE
OBSCURED OVERNIGHT. EXPECT GRADUALLY IMPROVING CONDITIONS DURING
THE DAY ON WED. ARTHUR
&&

.PRELIMINARY POINT TEMP/POPS...

    WED     THU     FRI     SAT     SUN     MON     TUE
-----------------------------------------------------------
BIL 031/052 038/061 043/071 048/076 040/065 041/070 044/064
    63/W    32/W    10/B    02/W    22/W    11/B    23/W
LVM 028/049 035/061 042/071 048/071 038/065 040/068 040/056
    73/W    22/W    10/B    02/W    22/W    21/B    23/W
HDN 029/054 034/062 038/073 040/078 035/066 035/072 039/067
    43/W    32/W    10/B    02/W    22/W    11/B    13/W
MLS 027/049 032/055 037/067 040/075 034/061 037/068 038/066
    11/B    22/W    10/B    02/W    21/B    00/U    12/W
4BQ 026/049 031/054 035/068 040/077 035/064 036/070 039/069
    11/B    23/W    20/B    02/W    22/W    11/B    12/W
BHK 023/043 025/048 031/061 036/073 032/059 033/065 037/064
    11/B    22/W    21/E    02/W    21/U    00/U    12/W
SHR 028/048 031/056 037/068 039/076 036/065 035/070 040/067
    54/W    34/W    20/B    02/W    22/W    21/B    13/W

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...WINTER STORM WARNING IN EFFECT UNTIL 9 AM MDT WEDNESDAY FOR
      ZONES 56-67.
WY...WINTER WEATHER ADVISORY IN EFFECT FROM MIDNIGHT TONIGHT TO
      NOON MDT WEDNESDAY FOR ZONE 98.

&&

$$
WEATHER.GOV/BILLINGS



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