Area Forecast Discussion
Issued by NWS Billings, MT

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FXUS65 KBYZ 160259
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
859 PM MDT FRI AUG 15 2014

.UPDATE...
BUSY AS EVENING AS WE HAVE HAD IN AWHILE AS DECENT FORCING
AND DIFFLUENT FLOW WORKED ACROSS OUR WESTERN SECTIONS THIS
EVENING. SHEAR WAS EVIDENT ON MESOSCALE ANALYSIS AND LED TO SOME
SUSTAINED STORM UPDRAFTS. THERE HAVE ALSO BEEN MANY OUTFLOW
BOUNDARIES FLOATING AROUND...TWO OF WHICH COLLIDED RIGHT OVER THE
BILLINGS AREA LEADING TO SOME ENHANCED ACTIVITY. WE EVEN HAD A
NICE MICROBURST SIGNATURE ON RADAR OVER THE BILLINGS
HEIGHTS/LOCKWOOD AREA.

THE LOBE OF ENERGY EJECTING ACROSS THE AREA IS NOW BASICALLY
MOVING EAST/NORTHEAST AND PRODUCING A LINE OF CONVECTION. THE BEST
FORCING IS HEADED NORTH OF OUR FORECAST AREA AND OUTRACING SOME OF
THE SHEAR TO THE WEST AS WELL. I HAVE UPDATED POPS FOR CURRENT
TRENDS AND EXPECT MUCH OF OUR CONVECTION TO DIMINISH OVER THE NEXT
COUPLE OF HOURS...THOUGH AN ISOLATED STRONG CELL OR TWO MAY LINGER
AFTER MIDNIGHT. BT

&&

.SHORT TERM...VALID FOR SAT AND SUN...

TO OUR WEST...UPPER LOW CONTINUES TO MOVE SLOWLY OVER EASTERN
WA...WITH A 70KT H3 JET NOSING FROM OR INTO CENTRAL ID. THIS HAS
ALLOWED FOR STRONG CONVECTION TO DEVELOP IN DIFFLUENT REGION OVER
CENTRAL MT...IE WEST OF OUR CWA. SHEAR/FORCING AND THUS SEVERE
POTENTIAL WILL REMAIN MUCH GREATER TO OUR NW OVER THE NEXT
SEVERAL HOURS...BUT WE MAY SEE SOME STRONGER STORMS GET INTO OUR
W/NW PARTS WITH EFFECTIVE SHEAR ON THE ORDER OF 30 KTS AND
1000-1500 J/KG OF SBCAPE. COULD SEE AN ISOLATED TSTM GET INTO
BILLINGS AS WELL. ONE ITEM TO NOTE...LIVINGSTON HAS MIXED A DEWPT
TO 33F...SO WERE ARE BEGINNING TO SEE EFFECTS OF DRIER AIR FROM
THE GREAT BASIN. TO OUR EAST...WEAK CUT OFF LOW OVER SOUTHWEST ND
CONTINUES TO SPREAD SOME SHOWERS INTO OUR NE...AND THERE IS SOME
DEVELOPMENT BACK INTO NORTHERN ROSEBUD COUNTY AS WELL. WILL KEEP
SCATTERED POPS TO COVER THIS BUT WITHOUT TOO MUCH LIGHTNING. COULD
BE SOME FOG IN OUR FAR EAST TOO TONIGHT GIVEN THE RECENT PCPN AND
CURRENT DEWPTS IN THE MID 60S.

LATER TONIGHT...OUR REGION BECOMES IN A MORE FAVORED AREA OF A
MORE WESTERLY ORIENTED 60-70 KT JET IN CENTRAL ID...SO WILL KEEP
SOME SHOWERS MENTIONED THROUGH THE NIGHT...THOUGH AGAIN THE
GREATER DIFFLUENCE ALOFT WILL EXIST TO OUR NORTH.

UPPER LOW WILL TRACK ACROSS NORTH CENTRAL MT TOMORROW...AND AS A
RESULT OF THIS UPPER LEVEL ASCENT AND WIND SHEAR WILL INCREASE
ACROSS OUR EAST. LOW LEVEL MOISTURE WILL NOT HAVE ERODED WITH
PWATS STILL TO AN INCH OR MORE...SO FEEL THERE IS AT LEAST A
SLIGHT CHANCE OF STRONGER STORMS IN OUR EAST BY SATURDAY AFTN AND
EVNG. LATEST GFS/ECMWF KEEP SFC TROF ON OUR SIDE OF THE DAKOTAS
BORDER...AND THIS WILL HELP OUR CONVECTIVE CHANCES...SO WILL KEEP
SCATTERED POPS. FURTHER WEST WE WILL SEE MORE DOWNSLOPE INFLUENCE
AND THUS LOWER CHANCES.

ON SUNDAY...UPPER LOW WILL DROP TOWARD ND AS IT PARTIALLY PHASES
WITH ANOTHER PIECE OF PV EMERGING FROM THE GREAT BASIN. MODELS
HAVE TRENDED A BIT STRONGER WITH WNW FLOW ENERGY...SO HAVE
EXPANDED SLIGHT POPS A LITTLE FURTHER WEST...WITH GREATEST
COVERAGE EXPECTED AGAIN IN OUR EAST WHERE PWATS WILL BE HIGHEST.
ANY SEVERE RISK WILL HAVE SHIFTED EAST OF OUR CWA INTO THE
DAKOTAS. W-NW WINDS WILL ALSO BE A LITTLE GUSTY ON SUNDAY WITH THE
MIXING OF INCREASED MID LEVEL WINDS.

TEMPS THE NEXT COUPLE DAYS WILL REMAIN NEAR NORMAL WITH HIGHS
MAINLY IN THE 80S TO AROUND 90F.

JKL

.LONG TERM...VALID FOR MON...TUE...WED...THU...FRI...

MINIMAL CHANGES TO THE EXTENDED FORECAST PERIOD THIS
AFTERNOON...WITH MODELS IN PRETTY GOOD AGREEMENT THROUGHOUT THE
EXTENDED PERIOD. THERE IS SOME VARIATION BETWEEN THE MODELS WITH
REGARD TO THE TIMING OF THE UPPER TROF INTO THE AREA MID
WEEK. THIS WILL NEED TO BE WATCHED CLOSELY IN COMING SHIFTS TO GET
BETTER HANDLE ON TIMING.

EXPECT TO SEE SHALLOW RIDGING TO ZONAL FLOW FOR MONDAY AND
TUESDAY...WITH A TRANSITION TO MORE SOUTHWEST FLOW BY TUESDAY
NIGHT/WEDNESDAY AHEAD OF THE APPROACHING UPPER LEVEL TROF. EXPECT
TO SEE MAINLY DRY AND WARM CONDITIONS PREVAIL THROUGH THIS
PERIOD...WITH HIGHS AT OR SLIGHTLY ABOVE SEASONAL NORMAL. THERE
WILL BE A CHANCE FOR ISOLATED SHOWERS/THUNDERSTORMS IN AREA
MOUNTAINS...BUT LITTLE CHANCE FOR STORMS TO MOVE INTO THE PLAINS.

IMPACTS OF THE TROF INTO THE REGION IS VARYING A BIT. THE ECMWF
BRINGING MULTIPLE WAVES OF ENERGY THROUGH THE REGION BEGINNING
TUESDAY NIGHT...AND SLOWLY BRINGING MAIN TROF THROUGH THE REGION
THROUGHOUT THE REMAINDER OF THE PERIOD. THE GFS SEEMS TO CONTINUE
TO FAVOR DRY CONDITIONS THROUGH WEDNESDAY...WITH SLIGHTLY BETTER
POTENTIAL FOR THE HIGH TERRAIN WEDNESDAY...AND HOLDING OF PRECIP
ACROSS THE REGION UNTIL WEDNESDAY EVENING/NIGHT. GFS THEM FOLLOWS
SUIT WITH ECMWF WITH SLOW PROGRESSION OF THE TROF THROUGH THE
REMAINDER OF THE PERIOD. HAVE OPTED AT THIS TIME TO CONTINUE WITH
INHERITED FORECAST...WITH ISOLATED POPS INTO PLAINS BEGINNING
TUESDAY NIGHT...INCREASING TO SCATTERED POTENTIAL THURSDAY
EVENING THROUGH THE REMAINDER OF THE PERIOD.

IN ADDITION TO THE POTENTIAL FOR AN EXTENDED PERIOD PRECIP ACROSS
THE REGION...THIS SLOW MOVING TROF SHOULD RESULT IN DAYTIME HIGHS
REMAINING SLIGHTLY BELOW NORMAL FROM THURSDAY THROUGH THE END OF
THE EXTENDED PERIOD. DID TREND TEMPERATURES SLIGHTLY LOWER FOR
FRIDAY AND SATURDAY IN RESPONSE TO PERSISTENT IMPACTS OF TROF. AAG

&&

.AVIATION...

A LINE OF SHOWERS AND THUNDERSTORMS WILL PUSH EAST THIS EVENING
BETWEEN KBIL AND KMLS AS WELL AS DOWN BETWEEN KBIL AND KSHR THIS
EVENING. SOME LOCALIZED MVFR/IFR CONDITIONS ARE POSSIBLE IN
STRONGER CELLS. LOCAL WIND GUSTS TO 35 MPH ARE POSSIBLE WITH SOME
OF THE SHOWER ACTIVITY. BT


&&

.PRELIMINARY POINT TEMP/POPS...

    SAT     SUN     MON     TUE     WED     THU     FRI
-----------------------------------------------------------
BIL 061/087 061/088 060/087 061/091 062/090 061/083 060/078
    32/T    22/T    21/B    11/U    22/T    23/T    33/T
LVM 052/084 052/088 052/087 053/090 053/088 052/081 050/075
    22/T    21/B    11/B    11/U    22/T    23/T    33/T
HDN 058/089 058/090 058/089 059/093 060/092 059/086 058/083
    52/T    22/T    21/B    11/U    22/T    23/T    33/T
MLS 062/090 061/088 061/087 062/091 063/092 061/084 060/082
    43/T    33/T    21/B    11/U    22/T    23/T    33/T
4BQ 060/089 060/088 060/087 060/091 061/093 060/086 061/084
    23/T    23/T    31/B    11/B    22/T    22/T    33/T
BHK 059/087 057/086 058/084 055/088 057/089 056/082 055/081
    35/T    43/T    32/T    21/B    22/T    23/T    33/T
SHR 054/086 054/088 054/086 055/090 056/091 055/084 055/081
    22/T    21/B    11/U    11/U    22/T    23/T    33/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS



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