Area Forecast Discussion
Issued by NWS Billings, MT

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000
FXUS65 KBYZ 271538
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
938 AM MDT MON JUL 27 2015

.UPDATE...
MORNING SURFACE ANALYSIS WAS A BIT AMORPHOUS WITH LOCATION OF COLD
FRONT WHICH WAS LIKELY CROSSING THE DIVIDE. THERE WAS A PREFRONTAL
TROUGH WITH AREAS OF LOW PRESSURE ALONG IT FROM SE MT EXTENDING SW
THROUGH WY. RADAR SHOWED BAND OF SHOWERS AND THUNDERSTORMS FROM
KTFX/S AREA SSW THROUGH KBTM INTO S ID. OTHER WEAKER THUNDERSTORMS
WERE OBSERVED MOVING N THROUGH NE WY. ADJUSTED MORNING POPS TO
MATCH CAM MODELS WHICH DID NOT BRING MUCH PRECIPITATION EASTWARD
INTO THE AREA BY 18Z. DID ADD LOW POPS TO THE SE CORNER OF THE
AREA. CAM MODELS SHOWED TIMING OF CONVECTION TO BE AROUND 20Z
INITIATING OFF THE BEARTOOTHS/ABSAROKAS...THEN PROGRESSING E INTO
KBIL AREA AROUND 21Z THROUGH 00Z THEN MOVING FURTHER E INTO KMLS
AREA/SE MT BEFORE MOVING N OUT OF AREA AROUND 03Z OR SO. NOTED THE
NMM AND ARW HAD SLOWER TIMING THAN OTHER MODELS. PUSHED LIKELY
POPS A BIT FURTHER E THIS AFTERNOON.

VISIBLE SATELLITE AND SURFACE OBSERVATIONS SHOWED A STRATUS LAYER
EXPANDING AROUND KBIL DUE TO N FLOW INTO THE PRYORS. RAP HAD THIS
LAYER SCATTERING OUT AROUND 16Z-17Z...SO WILL SEE IF THIS PANS
OUT. WILL HAVE STRONG LIFT TODAY FROM A COUPLED JET AND Q-VECTOR
CONVERGENCE. PRECIPITABLE WATERS WILL BE 1 TO 1.5 INCHES FROM
CENTRAL TO E ZONES. SHEAR WILL BE 40 TO 50 KT OVER THESE AREAS AND
CAPES WILL BE 500-1000 J/KG WITH HIGHER VALUES ALONG THE DAKOTAS
BORDER. CAM MODELS ALSO SHOWED FAIRLY HIGH UPDRAFT HELICITY VALUES
OVER CENTRAL AND E. THUS SEVERE WEATHER IS A POSSIBILITY...ESPECIALLY
OVER SE MT. STRATUS MAY INHIBIT POTENTIAL SOMEWHAT OVER CENTRAL
ZONES.

FRONT WILL BECOME BETTER DEFINED THIS AFTERNOON AS IT COMBINES
WITH COLD POOLS FROM CONVECTION. WINDS WILL BE ON THE INCREASE
BEHIND THE FRONT IN A TIGHT PRESSURE GRADIENT. WILL REVISIT HIGH
WIND WATCH FOR TUE IN NEXT PACKAGE.

UPPER TROUGH WILL CONTINUE MOVING ACROSS THE AREA THROUGH
TUE...ALTHOUGH TUE LOOKED MOSTLY DRY. HIGHEST WINDS WILL BE
FOCUSED OVER THE E AND NE ZONES TUE.

NO CHANGES NEED TO RED FLAG WARNING IN THE PREFRONTAL ENVIRONMENT.
ARTHUR

&&

.SHORT TERM...VALID FOR TDY AND TUE...

ACTIVE WEATHER THROUGH THE SHORT TERM WITH THUNDERSTORMS...A
STRONG COLD FRONT PASSAGE AND FIRE WEATHER CONCERNS TODAY WITH
WIND AND FIRE WEATHER CONCERNS FOR TUESDAY. WATER VAPOR SHOWING A
A DEEP TROUGH AND UPPER LOW MOVING ONTO THE PACIFIC NORTHWEST
COAST WITH TWO VORT MAXES...ONE CENTERED OVER OREGON AND THE
SECOND MOVING INTO NEVADA. THIS WILL PROVIDE A DEEP SOUTHWEST FLOW
ALOFT ACROSS OUR FORECAST AREA TODAY. AS THIS TROUGH MOVES
EAST...IT WILL SWEEP A STRONG COLD FRONT ACROSS THE AREA. TIMING
LOOKS TO BE EARLY THIS MORNING FOR OUR FAR WESTERN AREAS...LATE
MORNING/EARLY AFTERNOON FOR THE CENTRAL AREAS AND LATE
AFTERNOON/EARLY EVENING FOR THE FAR EAST. AS A RESULT...A LARGE
TEMPERATURE DIFFERENCE FOR HIGHS WILL EXIST TODAY RANGING FROM 60S
WEST TO THE LOWER 90S EAST. SHOWERS AND THUNDERSTORMS WILL DEVELOP
AHEAD OF AND ALONG THE FRONT WITH NUMEROUS SHOWERS INCREASING IN
COVERAGE BEHIND THE FRONT. THE STORM PREDICTION CENTER HAS ADDED A
SLIGHT RISK FOR SEVERE THUNDERSTORMS FROM YELLOWSTONE COUNTY
EASTWARD AND AN ENHANCED RISK ACROSS THE EXTREME EASTERN AREAS OF
THE STATE. BEST DYNAMICS WILL BE FROM CUSTER AND POWDER RIVER
COUNTIES EASTWARD BUT ESPECIALLY NEAR THE DAKOTA BORDER. SEVERE
THUNDERSTORMS WILL BE POSSIBLE FOR THESE AREAS AND HAVE ADDED THIS
MENTION TO THE GRIDS.

IN ADDITION...VERY WARM TEMPERATURES...LOW
HUMIDITIES...INCREASING THUNDERSTORM RISK AND STRONG WINDS WITH
THE FRONTAL PASSAGE WILL RESULT IN RED FLAG CONDITIONS ACROSS OUR
EASTERN AREAS WHERE A REG FLAG WARNING IS IN PLACE. PRECIPITATION
CHANCES WILL INCREASE FROM WEST TO EAST THROUGH THE DAY INTO THIS
EVENING WITH LIKELY POPS ALONG AND NORTH OF A MILES CITY-BILLINGS-
LIVINGSTON LINE. THE BULK OF THE PRECIP WILL MOVE INTO NORTHEAST
MONTANA AND NORTH DAKOTA LATE THIS EVENING INTO TUESDAY.
HOWEVER...THE DEEP SURFACE LOW WILL PROVIDE FOR WRAP AROUND
SHOWERS ACROSS MOST OF OUR AREA TUESDAY WITH THE BEST CHANCES EAST
AND NORTH OF BILLINGS.

LASTLY...850MB WINDS TUESDAY ACROSS THE EAST WILL BE AROUND
45-50KTS AND LATEST GUIDANCE HAS 35-40KT WINDS FOR MILES CITY AND
BAKER. WILL ISSUE A HIGH WIND WATCH FOR TUESDAY MORNING AND
AFTERNOON FOR NORTHERN ROSEBUD...CUSTER...FALLON AND CARTER
COUNTIES AS THESE AREAS LOOK TO HAVE THE TIGHTEST PRESSURE
GRADIENTS FROM THE SURFACE LOW WHICH IS PROGGED TO BE OVER
NORTHERN NORTH DAKOTA DURING THAT TIME PERIOD. HOOLEY


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

MAINLY DRY EXTENDED PERIOD WITH SLIGHTLY ABOVE NORMAL
TEMPERATURES. MODELS ARE MAINTAINING GOOD AGREEMENT SHOWING ZONAL
FLOW OVER THE REGION WITH A DRY AIRMASS. WEAK INTRUSION OF
MONSOONAL FLOW INTRODUCES SOME CONVECTION OVER THE MOUNTAINS
FRIDAY NIGHT. MODELS SHOWED A BACKDOOR COLD FRONT APPROACHING BUT
WASHING OUT ON SATURDAY NIGHT. CURRENT FORECAST IN GOOD SHAPE.
BORSUM &&

.AVIATION...

AS OF 15Z A COLD FRONT IS ENTERING WESTERN ZONES NEAR LVM AND
NORTHERLY WINDS ARE GENERATING AN UPSLOPE 1400FT STRATUS DECK
OVER BIL. THIS STRATUS DECK THAT IS GENERATING MVFR CIGS SHOULD
ERODE BY 18-20Z AS THE FRONT GETS CLOSER TO BIL. THROUGH THE
AFTERNOON A LINE OF SHOWERS AND STORMS WILL PROGRESS EAST AND
GENERATE MVFR/IFR CONDITIONS WITH MOUNTAIN OBSCURATIONS AROUND LVM
FROM 18-20Z...BIL 21-23Z...SHR 22-01Z...AND MLS 23-02Z. AFTER THE
INITIAL LINE OF STORMS VCSH...WITH POSSIBLE MVFR CONDITIONS...AND
INCREASING WESTERLY WINDS AROUND 25 TO 35 KNOTS WILL AFFECT ALL
TERMINALS FOR THE REMAINDER OF THE TAF PERIOD.

DOBBS

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY TUE     WED     THU     FRI     SAT     SUN
-------------------------------------------------------
BIL 077 051/075 052/085 057/092 060/094 061/090 061/090
    6/T 42/W    11/U    00/U    01/U    11/U    11/B
LVM 067 048/074 045/083 051/089 053/092 054/089 055/088
    6/T 43/T    11/U    00/U    01/U    11/U    22/T
HDN 083 051/076 051/087 055/094 058/096 059/092 059/091
    6/T 62/W    11/U    00/U    01/U    11/U    11/B
MLS 090 055/072 052/086 058/093 061/095 061/092 061/089
    3/T 83/T    21/U    00/U    01/U    11/U    11/B
4BQ 094 053/074 051/086 056/093 060/095 061/093 060/089
    3/T 42/W    11/U    00/U    01/U    11/U    11/B
BHK 095 056/071 050/084 055/090 057/092 058/090 058/086
    4/T 73/T    21/U    00/U    01/U    11/U    11/B
SHR 087 047/074 045/083 053/091 055/093 056/091 056/088
    3/T 32/W    00/U    00/U    00/U    01/U    12/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...RED FLAG WARNING IN EFFECT UNTIL MIDNIGHT MDT TONIGHT FOR
      ZONES 30>33-36>38-57-58.
     HIGH WIND WATCH IN EFFECT FROM TUESDAY MORNING THROUGH
      TUESDAY AFTERNOON FOR ZONES 31>33-37.
WY...RED FLAG WARNING IN EFFECT UNTIL MIDNIGHT MDT TONIGHT FOR
      ZONES 98-99.

&&

$$
WEATHER.GOV/BILLINGS



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