Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 010310
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
910 PM MDT TUE SEP 30 2014

.UPDATE...
COLD ADVECTION HAS TAKEN OVER IN THE EAST AS UPPER CLOSED LOW
LIFTS INTO NORTH DAKOTA THIS EVENING. LOTS OF INSTABILITY YET IN
THIS NW FLOW BEHIND THE SYSTEM WITH THE SPLIT FLOW TROUGH AXIS YET
UPSTREAM. HAVE ADJUSTED POPS FOR CURRENT TRENDS AND KEPT CHANCE
POPS THROUGH THE NIGHT. HIGHEST POPS ARE NEAR NORTH FACING
TERRAIN AROUND THE BIG HORNS AND ASHLAND DIVIDE. STILL LOOKS
COOLER TOMORROW WITH ISOLATED TO SCATTERED SHOWERS WITH -22C 500MB
COLD POOL DRIFTING RIGHT OVER US. BT

&&

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

SLOW MOVING UPPER LOW LIFTING THRU NORTHERN SD CONTINUES TO WRAP
SHOWERS INTO OUR FAR EAST. PCPN AMOUNTS HAVE NOT BEEN AS HIGH AS
PREVIOUSLY THOUGHT...MUCH GREATER AMOUNTS HAVE BEEN CLOSER TO THE
BLACK HILLS...BUT OCCASIONAL SHOWERS WILL PERSIST INTO THE
EVENING. LOW WILL CONTINUE TO MOVE NORTHEAST AND PCPN ASSOCIATED
WITH IT WILL FOR THE MOST PART END IN OUR CWA THIS EVENING.
PACIFIC TROF MOVING INTO WESTERN MT IS HELPING TO PRODUCE SOME
UNORGANIZED AND LIGHT SHOWER ACTIVITY IN OUR WEST. PER THE NW SFC
AND MID LEVEL FLOW...FOCUS OF ANY HEAVIER SHOWERS WILL BE IN OUR
SOUTHERN UPSLOPE AREAS LATE THIS AFTERNOON AND EVENING. 700MB
TEMPS FALLING TO NEAR -4C SUGGEST SOME SNOW IN THE HIGH
COUNTRY...PRIMARILY OVER THE BEARTOOTH ABSAROKAS AND BIG HORNS...
GREATEST ON NW ASPECTS.

INSTABILITY SHOWERS UNDER COLD POOL ALOFT CAN BE EXPECTED ON
WEDNESDAY...GREATEST OVER THE MTNS AS OUR LOWER ELEVATIONS WILL
SEE DOWNSLOPE WINDS AS WELL AS INFLUENCES FROM A DRYING AIRMASS.
TEMPS WILL BE A LITTLE BELOW NORMAL UNDER THE TROF ALOFT...WITH
HIGHS IN THE MID 50S TO NEAR 60. SHOWER ACTIVITY WILL TAPER
QUICKLY BY WEDNESDAY EVENING AS WEAK RIDGING BUILDS IN.

AFTER A BRIEF DRY PERIOD WEDNESDAY NIGHT INTO EARLY THURSDAY...
CLIPPER FROM NW CANADA WILL PUSH ACROSS THE AREA AND BRING A COLD
FRONTAL PASSAGE ALONG WITH ANOTHER PERIOD OF SHOWERS. TIMING OF
FROPA HAS TRENDED FASTER SINCE YESTERDAY. EXPECT HIGH TEMPS ONLY
IN THE 50S WITH COLD ADVECTION BEGINNING SOMETIME DURING THE
MORNING...WITH A DROP IN 850MB TEMPS IN THE LOWER SINGLE DIGITS
AFTER 18Z. THIS WILL BE A TRUE BURST OF FALL WITH COOL TEMPS AND
GUSTY N-NW WINDS. SHOWER ACTIVITY WILL BE BRIEF BUT WITH A LITTLE
MID LEVEL INSTABILITY THROUGH THE DENDRITIC LAYER AND FAIRLY LOW
BOUNDARY LAYER WET BULB TEMPS WE COULD SEE SOME GRAUPEL IN THE
AFTERNOON AND EVENING...AND A POSSIBLE MIX WITH WET SNOW ALONG THE
FOOTHILLS. KEEP IN MIND ANY PCPN WILL BE BRIEF. SFC HIGH WILL
BUILD IN FOR A COOL AND DRY THURSDAY NIGHT...AND COULD SEE ANOTHER
FAIRLY WIDESPREAD FREEZE...THOUGH NW SFC WINDS WILL PERSIST IN OUR
EAST. HAVE TRENDED TEMPS DOWN BOTH THURSDAY AND THURSDAY NIGHT
BASED ON LATEST MODEL TRENDS.

JKL

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

ENSEMBLES AND DETERMINISTIC MODELS SHOWED HIGH CONFIDENCE IN A
MILD AND DRY EXTENDED FORECAST. FORECAST AREA WILL BE ON THE FRONT
SIDE OF AN UPPER RIDGE THROUGH THE PERIOD. GFS DID BRING SOME WEAK
ENERGY THROUGH THE AREA ON SAT...BUT MOISTURE WILL BE CONFINED TO
THE HIGHER LEVELS OF THE ATMOSPHERE AND DOWNSLOPE FLOW WILL KEEP
ANY CHANCES FOR PRECIPITATION AT BAY.

LEE TROUGHING WILL CREATE WINDY CONDITIONS OVER CENTRAL AND
WESTERN PARTS OF THE AREA FRI NIGHT AND SAT. ECMWF ALSO HINTED AT
WINDY CONDITIONS SUN NIGHT THROUGH MON NIGHT IN THESE AREAS. AT
THIS TIME...THE FORECAST PRESSURE GRADIENTS DID NOT LOOK
SUPPORTIVE OF ANY WIND HIGHLIGHTS. GOOD MIXING AND DOWNSLOPE FLOW
WILL COMBINE TO MAKE SAT AND MON THE WARMEST DAYS OF THE PERIOD
WITH HIGHS IN THE LOWER 70S. ARTHUR

&&

.AVIATION...

EXPECT ISOLATED TO SCATTERED SHOWERS ACROSS THE AREA TONIGHT. THE
PRECIPITATION WILL BE ACCOMPANIED BY MVFR TO IFR CONDITIONS.
MOUNTAIN OBSCURATION WILL BE WIDESPREAD OVERNIGHT. GUSTY W TO NW
SURFACE WINDS WILL CONTINUE TONIGHT AND WED. SHOWERS WILL BE
MAINLY ISOLATED OVER THE REGION ON WED WITH MVFR TO IFR
CONDITIONS. EXPECT AREAS OF MOUNTAIN OBSCURATION ON WED.
ARTHUR/CHURCH

&&

.PRELIMINARY POINT TEMP/POPS...

    WED     THU     FRI     SAT     SUN     MON     TUE
-----------------------------------------------------------
BIL 044/059 042/055 033/068 049/073 047/069 047/071 048/069
    32/W    12/W    00/U    00/U    11/U    10/U    11/B
LVM 039/056 035/058 030/068 042/071 040/067 041/070 044/069
    32/W    12/W    00/B    00/U    11/U    10/U    11/B
HDN 043/061 039/057 030/069 045/074 046/070 044/071 047/070
    52/W    12/W    10/U    00/U    11/U    10/U    11/B
MLS 047/060 041/054 030/065 045/073 046/067 044/068 045/065
    52/W    02/W    00/U    00/N    11/U    10/B    11/B
4BQ 044/060 039/056 030/065 044/072 047/067 043/069 045/066
    42/W    12/W    20/U    00/N    11/U    10/U    11/B
BHK 045/059 038/053 030/058 039/068 042/062 041/064 040/061
    72/W    03/W    10/U    00/U    11/U    10/B    11/B
SHR 044/057 035/056 028/067 041/071 044/067 040/070 043/066
    32/W    12/W    20/U    00/U    11/U    10/U    11/B

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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