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000
FXUS65 KBYZ 180257
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
857 PM MDT MON JUN 17 2013

.UPDATE...
HAVE MADE SOME MINOR ADJUSTMENTS TO CURRENT FORECAST FOR TONIGHT.
UPPER RIDGE WILL SHIFT SLOWLY EASTWARD OVERNIGHT AS A LOW PRESSURE
TROUGH MOVES ON TO THE WEST COAST. WEAK VORTICITY MOVING UNDER THE
RIDGE THIS EVENING HAS BROUGHT ISOLATED CONVECTION TO THE
MOUNTAINS AND ALONG OUR FAR SOUTHERN ZONES. THIS ACTIVITY HAS
ENDED OVER OUR SOUTHERN ZONES AS INCREASING EASTERLY UPSLOPE FLOW
HAS SETUP A TEMPERATURE INVERSION. DID KEEP A SLIGHT CHANCE OF
ISOLATED SHOWERS AND THUNDERSTORMS ACROSS OUR WESTERN ZONES AS
ANOTHER SHORT WAVE ROTATES ACROSS THAT AREA OVERNIGHT. REMAINDER
OF THE FORECAST ON TRACK AND NO OTHER CHANGES MADE. RICHMOND

&&

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

AFTERNOON INSTABILITY...WEAK SHORTWAVES AND OROGRAPHIC LIFT WERE
CREATING CUMULUS...AS SEEN ON VISIBLE SATELLITE IMAGERY...AS WELL
AS SPOTTY CONVECTION...SEEN ON RADAR. MODELS HAD CAPES AT 1000
J/KG OR LOWER THIS EVENING. HIGHEST SHEAR WAS OVER SE MT AT
00Z...BUT CAPES WILL BE QUITE LOW...SO NOT EXPECTING ANY SEVERE
WEATHER. INHERITED POPS WERE IN GOOD SHAPE...REFLECTING CHANCES
FOR CONVECTION OVER AND NEAR THE MOUNTAINS...AND OVER THE
SE DUE TO UPPER JET.

SHORTWAVES WILL CONTINUE MOVING THROUGH THE UPPER RIDGE TUE AND
TUE NIGHT. THE RIDGE WILL BREAK DOWN TUE NIGHT AS A STRONG UPPER
LOW OVER THE PACIFIC NW ROTATES TOWARD THE AREA. DIFLUENCE WILL
INCREASE OVER THE AREA THROUGH WED AS THE LOW BECOMES NEGATIVELY
TILTED. PRECIPITABLE WATERS WILL AVERAGE AROUND 0.80 INCHES
THROUGH THE PERIOD SO PLENTY OF MOISTURE WAS AVAILABLE FOR
CONVECTION. ON TUE...CAPE INCREASES FROM W TO E ACROSS THE AREA
WITH AROUND 2000 J/KG ALONG THE E MT BORDER. SHEAR WAS NOT OVERLY
STRONG. SOUNDINGS HAD AN INVERTED-V APPEARANCE...MAINLY W OF KBIL.
WILL MENTION POSSIBLE GUSTY WINDS AND SMALL HAIL WITH
THUNDERSTORMS. STORMS WILL BE OVER AND NEAR THE MOUNTAINS ON TUE
AND SPREAD E DURING THE EVENING AS DIFLUENCE INCREASES AND LOW-
LEVEL JET STRENGTHENS OVER THE PLAINS.

Q-VECTOR CONVERGENCE WILL STRENGTHEN OVER THE AREA WED AND WED
NIGHT AS STRONGER SHORTWAVES MOVE INTO THE REGION FROM THE UPPER
LOW TO THE W. SEVERE PARAMETERS LOOKED STRONGER THAN ON TUE...WITH
CAPES GREATER THAN 2000 J/KG E OF KBIL AT 18Z ON THE GFS. GFS
PUSHES THE CAPE TO THE N BY 00Z THU. WRF TAKES LONGER TO MOVE THE
CAPE OUT OF THE AREA WED AFTERNOON. MODELS HAD THE HIGH CAPES
OVER THE FAR E ZONES AT 06Z THU. SHEAR DID NOT LOOK VERY STRONG
WED ON THE GFS. ON THE WRF...HOWEVER...VALUES INCREASED OVER THE W
IN THE AFTERNOON. THE GFS INCREASED THE SHEAR OVER THE AREA WED
NIGHT. GFS ALSO DEVELOPED ALL THE QPF TO THE N OF THE AREA ALONG
THE WARM FRONT ON WED...WHILE THE WRF BROUGHT PRECIPITATION IN
FROM THE W WITH THE SYSTEM/S COLD FRONT. POPS REFLECTED A
COMPROMISE BETWEEN THE TWO MODELS. WILL MENTION POSSIBLE SEVERE
FOR BOTH THE AFTERNOON AND THE OVERNIGHT PERIODS. THE COLD FRONT
WILL CROSS THE AREA WED NIGHT. SEVERE THUNDERSTORMS WILL BE
POSSIBLE OVER THE EASTERN ZONES AHEAD OF THE FRONT AFTER 06Z THU.

RAISED HIGH TEMPERATURES AHEAD OF THE COLD FRONT ON WED. ARTHUR


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

ONLY MINOR ADJUSTMENTS TO THE FORECAST THIS AFTERNOON. AREA WILL
BE UNDER THE INFLUENCE OF A PACIFIC LOW THURSDAY INTO SUNDAY. MOST
MODEL SOLUTIONS KEEP CORE OF THE LOW JUST TO THE WEST PUTTING THE
FORECAST AREA IN SOUTHERLY DIVERGENT FLOW WHICH IS A GOOD
PRECIPITATION PATTERN. THUNDERSTORMS LOOK LIKE A GOOD BET EACH DAY
WITH STRENGTH OF THE STORMS DEPENDING ON LOW LEVEL PLAINS MOISTURE
ADVECTION AS WELL AS THE AMOUNT OF HEATING. WITH PROXIMITY TO THE
LOW THERE WILL BE A GOOD DEAL OF CLOUD COVER THAT MAY HOLD
TEMPERATURES DOWN MINIMIZING STORM STRENGTH...BUT CERTAINLY LOOKS
LIKE AT LEAST SOME THREAT FOR SEVERE STORMS THURSDAY AND FRIDAY.
CURRENT SCATTERED PRECIPITATION CHANCES LOOK REASONABLE AND AS
MODELS MERGE ON A SOLUTION WILL BE ABLE TO BETTER PINPOINT AREAS
OF HIGHER POPS AND STRONGER STORMS. AS THE CORE OF THE UPPER LOW
MOVES OVER THE AREA SATURDAY INTO SUNDAY EXPECT COOLER
TEMPERATURES AND MORE SHOWER ACTIVITY AS OPPOSED TO THUNDERSTORMS.
WEAK RIDGING WILL DEVELOP MONDAY FOR DRIER AND WARMER CONDITIONS.
&&

.AVIATION...

VFR CONDITIONS WILL PREVAIL ACROSS THE AREA TONIGHT AND TUESDAY.
A LOW PROBABILITY OF THUNDERSTORMS EXISTS OVER THE MOUNTAINS AND
NEARBY LOCATIONS THOUGH. ANOTHER CHANCE OF STORMS WILL RETURN TO
SOUTH CENTRAL MT AND NORTH CENTRAL WY BY LATE TUESDAY AFTERNOON.
HOWEVER...CONFIDENCE IN THAT POTENTIAL WAS TOO LOW TO MENTION IN
ANY OF THE 00 UTC TERMINAL FORECASTS. SCHULTZ

&&

.PRELIMINARY POINT TEMP/POPS...

    TUE     WED     THU     FRI     SAT     SUN     MON
-----------------------------------------------------------
BIL 056/086 060/088 053/077 050/073 050/075 051/074 051/079
    12/T    23/T    32/T    33/T    22/T    22/T    22/T
LVM 046/085 049/089 047/072 040/070 042/074 047/076 046/081
    24/T    33/T    23/T    33/T    22/T    23/T    32/T
HDN 053/088 059/090 053/078 053/074 050/076 051/075 051/079
    12/T    22/T    33/T    33/T    22/T    22/T    22/T
MLS 056/087 060/090 058/081 055/074 055/077 055/077 055/080
    11/U    22/T    33/T    33/T    33/T    33/T    22/T
4BQ 051/087 059/092 055/081 055/075 052/077 052/077 051/080
    11/U    21/U    23/T    33/T    33/T    33/T    22/T
BHK 053/083 056/086 057/080 054/075 053/074 052/074 052/076
    11/U    22/T    32/T    44/T    43/T    33/T    32/T
SHR 054/085 052/088 050/078 050/073 048/075 047/074 048/078
    23/T    22/T    23/T    33/T    22/T    22/T    22/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS