Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 250041
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
641 PM MDT SUN AUG 24 2014

.UPDATE...
HEIGHT RISES BECOMING MORE NOTICEABLE IN OUR WEST AS UPPER LOW
CONTINUES TO MOVE SLOWLY EAST. SHOWERS REMAIN UNDER TROWAL FROM
MUSSELSHELL COUNTY ACROSS OUR EAST...BUT DRYING HAS OCCURRED IN
OUR WEST. HAVE REDUCED POPS FROM BILLINGS WEST AND SOUTH BASED ON
LATEST RADAR TRENDS. SHOWERS WILL DECREASE ELSEWHERE THRU THE
EVENING. WILL BE INTERESTING TO SEE HOW COOL WE GET TONIGHT. WE
WILL KEEP SOME NW WINDS GOING ACROSS OUR EAST...BUT WINDS SHOULD
BECOME LIGHT IN OUR WEST AS SFC HIGH SETTLES IN FROM THE NW. CLOUD
COVER AND POTENTIAL FOR STRATUS/FOG FORMATION WILL KEEP LOWS FROM
GOING TOO FAR...BUT GIVEN WE ARE STARTING TO SEE A FEW CLOUD
BREAKS HAVE DROPPED EXPECTED LOWS JUST A BIT. SHOULD SEE LOW TO
MID 40S MOST PLACES...MAYBE UPPER 30S IN SPOTS...THE COOLEST NIGHT
FOR SOME LOCATIONS SINCE EARLY JUNE. RECORDS ARE UNACHIEVABLE AS
WE ARE COMPETING WITH THE HISTORIC COOL SPELL AT THIS TIME OF YEAR
IN 1992. JKL

&&

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

OUR STORM CONTINUES TO PRODUCE A GOOD DEAL OF PRECIPITATION
ACROSS OUR FORECAST AREA AT MID AFTERNOON AS MOISTURE AND FORCING
FROM A TROWAL PATTERN AFFECT OUR NORTHERN AND CENTRAL ZONES. THIS
AREA OF MODERATE RAIN IS GRADUALLY ROTATING AROUND THE UPPER LOW
AND MODELS AGREE WILL EVENTUALLY SHIFT NE OUT OF OUR FORECAST
AREA. THE EFFECTS OF THE TROWAL HAVE MANAGED TO PUSH FURTHER SOUTH
THAN ORIGINALLY ANTICIPATED. MESOSCALE MODELS ARE PICKING UP ON
THIS TO SOME EXTENT AND THUS I HAVE USED THEM AS A GUIDE FOR
EXPANDING POPS A LITTLE FURTHER SOUTH AND WEST FOR THE EVENING.
I DO EXPECT ANY MEASURABLE PRECIPITATION TO BE PRETTY MUCH DONE
FOR MOST AREAS AFTER MIDNIGHT. WE WILL CONTINUE TO MENTION FOG
OVERNIGHT INTO MONDAY MORNING...BUT IT MAY TURN OUT WE JUST SEE
A GOOD DEAL OF LOW CLOUD COVER RATHER THAN AREAS OF WIDESPREAD FOG
TONIGHT.

FOR MONDAY...TROUGH DIGGING INTO THE DESERT SW WILL BEGIN TO
SLOWLY SHIFT EAST AND DRAG THE SPLIT FLOW AXIS INTO OUR WESTERN
ZONES BY MONDAY EVENING. MODELS AGREE IN SOME LIGHT QPF OVER THE
BEARTOOTH MOUNTAINS SO WILL PULL BACK POPS TO MAINLY THE HIGH
COUNTRY FOR TOMORROW...AND SOME LOW POPS ACROSS OUR SOUTHERN
BORDER INTO TUESDAY. I SEE NO REASON THE TEMPS WILL NOT GRADUALLY
WARM OVER THE NEXT COUPLE OF DAYS AS SUGGESTED BY
GUIDANCE...THOUGH CLOUD COVER MAY BE AN ISSUE WITH ALL THE GROUND
MOISTURE...SO GOING A LITTLE BELOW GUIDANCE SEEMS PRUDENT. BT

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

ECMWF ENSEMBLES SHOWED SOME UNCERTAINTY WITH THE PATTERN THROUGH
THE EXTENDED PERIOD...WHILE GFS ENSEMBLES HAD BETTER CONFIDENCE
EARLY IN THE PERIOD. REGARDLESS...THE DETERMINISTIC GFS AND ECMWF
WERE SIMILAR WITH THE PATTERN THROUGH THU NIGHT. SOME DIFFERENCES
THEN EMERGED BETWEEN THE MODELS LATE IN THE PERIOD.

A WEAK RIDGE WILL BE OVER THE REGION ON WED WHILE A WEAK UPPER LOW
PASSES THROUGH THE FOUR CORNERS AREA. THE RIDGE WILL PERSIST OVER
THE AREA THU AND FRI. MODELS SHOWED SOME QPF OVER THE FAR SOUTHERN
TIER OF THE FORECAST AREA INTO WED EVENING DUE TO THE SOUTHERN LOW...SO
HAD LOW POPS OVER THESE AREAS. THU INTO FRI LOOKED DRY...EXCEPT
THE ECMWF SHOWED SOME QPF OVER THE WEST HALF OF THE REGION FRI
AFTERNOON. HAD SOME POPS IN THE SW MOUNTAINS TO ADDRESS THIS
POSSIBILITY. THE FLOW THEN TURNS SW AHEAD OF A PACIFIC SYSTEM FRI
NIGHT AND SAT...THEN THE UPPER TROUGH SWINGS THROUGH THE AREA
DURING THE SAT NIGHT/SUN TIME FRAME...WITH MODELS DIFFERING ON THE
TIMING. SPREAD LOW POPS OVER MUCH OF THE AREA FRI NIGHT THROUGH
SUN.

THE AREA WILL BE UNDER A WARMING TREND THROUGH SAT...BEFORE THE
NEXT TROUGH COOLS OFF THE REGION ON SUN. MADE SOME SLIGHT
TEMPERATURE ADJUSTMENTS BASED ON LATEST GUIDANCE AND EXPECTED
MIXING. ARTHUR
&&

.AVIATION...

SHOWERS CONTINUE TO GRADUALLY END FROM SW TO NE...WITH SHOWERS
MAINLY EAST OF A LINE FROM KSHR TO KBIL AT THIS TIME. MVFR TO IFR
CONDITIONS WILL STILL BE POSSIBLE IN SHOWERS...OTHERWISE VFR
CONDITIONS WILL PREVAIL WEST OF THE SHOWERS. GUSTY NORTHWEST WINDS
CONTINUE ACROSS MUCH OF THE REGION...BUT ARE EXPECTED TO DIMINISH
FROM WEST TO EAST LATER THIS EVENING.

PATCHY FOG AND AREAS OF LOW STRATUS ARE EXPECTED OVERNIGHT INTO
EARLY MONDAY MORNING...BRINGING AREAS OF IFR TO LIFR CONDITIONS.
ISOLATED SHOWERS AND THUNDERSTORMS ARE POSSIBLE WEST AND SOUTH OF
KBIL MONDAY...WITH LOCALIZED MVFR CONDITIONS EXPECTED WITH ANY
PRECIP THAT DOES DEVELOP. PERIODIC MOUNTAIN OBSCURATION OVER THE
BEARTOOTHS...ABSAROKAS AND CRAZYS ARE EXPECTED ON MONDAY. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    MON     TUE     WED     THU     FRI     SAT     SUN
-----------------------------------------------------------
BIL 044/065 048/075 052/080 057/085 060/086 061/085 061/073
    11/B    11/B    11/U    01/U    11/U    22/T    22/T
LVM 040/066 045/076 046/081 051/084 051/086 053/083 052/071
    12/T    32/T    20/U    10/U    01/U    22/T    33/T
HDN 044/067 048/076 051/081 055/086 057/089 059/087 060/078
    21/B    11/B    11/U    11/U    11/U    22/T    22/T
MLS 047/066 050/076 052/080 057/085 061/089 062/088 061/082
    61/E    11/B    11/U    11/U    11/U    22/T    22/T
4BQ 046/066 051/075 052/079 056/085 058/089 062/089 060/084
    31/B    22/T    22/T    11/U    11/U    11/U    22/T
BHK 044/062 044/072 048/076 053/081 057/086 058/085 059/083
    41/E    12/T    11/U    11/U    11/U    22/W    22/T
SHR 042/066 046/074 048/079 051/085 054/089 056/087 056/080
    21/B    22/T    22/W    10/U    01/U    21/U    22/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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