Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 230242
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
842 PM MDT MON SEP 22 2014

.UPDATE...
UPPER TROUGH TRACKING JUST TO OUR SOUTH IS PRODUCING SOME LIGHT
SHOWERS IN OUR SE CORNER ALONG WITH SOME VERY WEAK RETURNS FROM
INSTABILITY OVER OUR CENTRAL ZONES. I AM NOT CONFIDENT THERE IS
ACTUALLY MUCH REACHING THE GROUND EXCEPT IN THE VERY SE CORNER OF
THE STATE. MODELS HAVE ANY ACTIVITY DISAPPEARING AFTER MIDNIGHT.
I WILL ADJUST THE POPS FOR THE REST OF THE EVENING FOCUSING MAINLY
IN THE SE ZONES...AND REMOVE MOST POPS AFTER MIDNIGHT. REST OF
FORECAST ON TRACK. BT

&&

.SHORT TERM...VALID FOR TUE AND WED...

UPPER LOW...SEEN ON WATER VAPOR IMAGERY...WAS ROTATING NE THROUGH
WY THIS AFTERNOON. MODELS WERE IN GOOD AGREEMENT IN BRINGING THE
LOW CENTER TO FAR NE WY THIS EVENING...THEN SHIFTING THE BULK OF
THE SYSTEM INTO SD OVERNIGHT. CONVECTION HAD BEGUN FIRING OVER THE
NE BIG HORNS THIS AFTERNOON PER RADAR IMAGERY. MESOANALYSIS RAP
FORECAST SHOWED INCREASING INSTABILITY FROM S TO N OVER THE
FORECAST AREA THIS AFTERNOON. EXPECT CONVECTION TO INCREASE OVER
THE AREA DUE TO THE INSTABILITY AND PLENTY OF MOISTURE...AS WELL
AS WEAK LIFT FROM THE LOW AND OROGRAPHICS. MODELS WERE SHOWING 2
TO 4 STANDARDIZED DEVIATIONS ABOVE NORMAL IN THE MOISTURE FIELDS
DUE TO THE INCH OF PRECIPITABLE WATER OVER THE AREA. DUE TO WEAK
FORCING...NO SHEAR AND LIMITED INSTABILITY WOULD NOT EXPECT ANY
STRONG STORMS THIS AFTERNOON INTO THIS EVENING...ALTHOUGH SOME
STORMS MAY PRODUCE HEAVY RAINFALL.

KEPT A SLIGHT CHANCE OF EVENING POPS FROM THE CRAZYS TO AROUND
KBIL TO SE MT S PER THE LATEST MODELS...WITH HIGHER POPS IN THE
SOUTHERN MOUNTAINS. DECREASED THE POPS OVERNIGHT AS THE SYSTEM
MOVES OUT. 850 MB TEMPERATURES FROM +16 TO +20 DEGREES C WILL
SUPPORT A WARM NIGHT WITH TEMPERATURES IN THE 50S. LINGERING
ENERGY BEHIND THE LOW WILL BRING A SLIGHT CHANCE OF PRECIPITATION
TO THE MOUNTAINS ON TUE. BASED ON EXPECTED MIXING AND LATEST
GUIDANCE...TEMPERATURES IN THE LOWER TO MID 80S WERE IN GOOD
SHAPE.

WENT MAINLY DRY TUESDAY NIGHT. 850 MB TEMPERATURES WILL BE AROUND
+20 DEGREES C SUPPORTING ANOTHER WARM NIGHT. HIGH AMPLITUDE UPPER
RIDGE WILL BUILD OVER THE AREA WED THROUGH WED NIGHT BRINGING DRY
WEATHER AND WARMER CONDITIONS. HAVE RAISED TEMPERATURES FOR BOTH
PERIODS. ARTHUR

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

THE EXTENDED FORECAST FEATURES NEAR-RECORD HIGH TEMPERATURES BY
WEEK/S END AND A SIGNIFICANT CHANGE IN THE WEATHER PATTERN BY THE
WEEKEND...WITH COOLER TEMPERATURES AND A HIGHER CHANCE OF
PRECIPITATION.

MODELS REMAIN IN EXCELLENT AGREEMENT ABOUT A MORE AMPLIFIED
PATTERN BY THE END OF THE WEEK. DEEP TROUGHING DEVELOPS OFF THE
PACIFIC COAST WEDNESDAY INTO THURSDAY...WHICH ENHANCES RIDGING
AND SOUTHWESTERLY FLOW OVER THE FORECAST AREA. THIS WILL RESULT IN
HIGH TEMPERATURES SOARING TO AROUND 90 DEGREES BY
THURSDAY/FRIDAY...WHICH WILL BE NEAR RECORD VALUES FOR THAT TIME
OF THE YEAR.

MODELS DIVERGE IN HOW THEY HANDLE THE FORWARD MOTION OF THE
UPPER-LEVEL LOW BY THE WEEKEND. THE EC REMAINS THE SLOWEST
SOLUTION...THE GFS REMAINS THE FASTEST SOLUTION AND THE GEM IS
TAKING THE MIDDLE GROUND. GIVEN THE HIGHLY AMPLIFIED
PATTERN...TYPICAL EVOLUTION OF THESE SYSTEMS SUGGESTS THAT A
SLOWER SOLUTION SHOULD BE FAVORED...AND IN FACT...THE GFS HAS
TRENDED SLOWER WITH EACH OF ITS LAST 5 MODEL RUNS. EXPECT SATURDAY
WILL LIKELY BE A TRANSITION DAY WHERE SLIGHTLY COOLER TEMPERATURES
START TO WORK INTO THE FORECAST AREA AS HEIGHTS DECREASE...BUT
SUNDAY MAY BE THE FIRST TRUE COOLER DAY WITH THE BETTER CHANCE OF
PRECIPITATION. AS FAR AS TEMPERATURES GO WITH THIS SYSTEM...850
MB TEMPERATURES ARE NEVER PROGGED TO BE COOLER THAN ABOUT +5 OR +6
C...WHICH WOULD LIKELY TRANSLATE TO HIGHS IN THE 50S TO AROUND 60.
GIVEN THE CUT-OFF NATURE OF THIS LOW...DO NOT ANTICIPATE
TEMPERATURES TRENDING MUCH COOLER. 700 MB TEMPERATURES COOL TO
AROUND 0 TO -2 C WITH THIS SYSTEM...WHICH INDICATES THE POTENTIAL
FOR SNOW IN THE HIGH COUNTRY...INCLUDING THE BEARTOOTH PASS.

CHURCH

&&

.AVIATION...

A WEAK DISTURBANCE OVER NORTHEAST WYOMING WILL BRING A SLIGHT
CHANCE FOR A SHOWER OR THUNDERSTORM AND ASSOCIATED MVFR CONDITION
FROM KSHR EASTWARD ALONG THE MONTANA/WYOMING BORDER THROUGH 06Z.
SKIES WILL GRADUALLY CLEAR LATE TONIGHT BUT THE MOUNTAINS WILL
CONTINUE TO BE OBSCURED AT TIMES. OTHERWISE...VFR CONDITIONS WILL
PREVAIL THROUGHOUT THE NIGHT. HOOLEY
&&

.PRELIMINARY POINT TEMP/POPS...

    TUE     WED     THU     FRI     SAT     SUN     MON
-----------------------------------------------------------
BIL 056/083 057/087 058/091 058/087 055/066 048/064 046/060
    11/U    00/U    00/U    01/U    12/T    34/T    33/T
LVM 051/082 050/087 051/088 051/085 048/066 046/062 041/063
    01/N    10/U    00/U    11/B    23/T    44/T    32/T
HDN 053/084 054/089 056/091 055/088 052/070 048/067 046/064
    11/B    00/U    00/U    01/U    12/T    34/T    33/T
MLS 054/085 056/089 058/092 060/090 055/074 051/069 048/063
    11/U    00/U    00/U    01/U    11/B    34/T    33/T
4BQ 055/083 053/089 057/092 059/091 056/077 051/069 047/063
    21/B    00/U    00/U    01/U    11/B    23/T    34/T
BHK 051/081 051/088 054/088 057/089 054/078 050/070 046/063
    11/B    00/U    00/U    01/U    11/B    23/T    34/T
SHR 050/081 049/087 051/089 052/089 052/073 049/066 045/062
    21/B    10/U    00/U    01/U    12/T    34/T    33/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS


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