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000
FXUS65 KBYZ 152137
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
337 PM MDT WED MAY 15 2013

.SHORT TERM...VALID FOR THU AND FRI...

DEVELOPING TROF TO THE WEST OF THE AREA IS BEGINNING TO IMPACT THE
WEATHER PATTERN ACROSS EASTERN MONTANA AND NORTHERN WYOMING.
COOLER AIR ALOFT IS HELPING TO CREATE INSTABILITY WHILE PLAINS
MOISTURE IS BEING ADVECTED NORTHEAST INTO THE AREA ON EASTERLY
SURFACE WINDS. THIS COMBINATION OF INSTABILITY AND MOISTURE WILL
RESULTIN IN SCATTERED SHOWER AND THUNDERSTORM CHANCES ACROSS THE
REGION GOING INTO THE WEEKEND.

HAVE BEEN WATCHING PUSH OF MOISTURE FROM EASTERN WYOMING MOVE
NORTHWARD INTO THE AREA WITH DEW POINTS MOVING BACK INTO THE 30S
FROM THE LOWER 20S THIS MORNING. THIS MOISTURE WILL COMBINE WITH A
DISTURBANCE CROSSING THE AREA TONIGHT TO PRODUCE AN AREA OF
SHOWERS AND THUNDERSTORMS THAT IS EXPECTED TO DEVELOP OVER WESTERN
MOUNTAIN ZONES AND PROGRESS ACROSS THE FORECAST AREA TONIGHT. MOST
AREAS FROM BILLINGS WEST HAVE A CHANCE AT A TENTH OF AN INCH OF
RAIN FROM THIS ACTIVITY WHILE FURTHER EAST MORE MOISTURE
AVAILABILITY IN THE ATMOSPHERE WILL BRING THE CHANCE FOR A QUARTER
OF AN INCH. CONVECTIVE PARAMETERS ARE WEAK AND DO NOT EXPECT ANY
SEVERE THUNDERSTORMS TONIGHT BUT COULD SEE SOME WIND GUSTS IN THE
45 MPH RANGE NEAR ANY THUNDERSTORMS.

CONVECTION LOOKS TO PRESS EAST OF THE AREA AROUND
SUNRISE...POSSIBLY LINGERING IN THE BAKER AND EKALAKA AREAS INTO
THE MID MORNING HOURS. SIMILAR SET UP TO THIS AFTERNOON DEVELOPS
THURSDAY AFTERNOON WITH SCATTERED SHOWERS AND THUNDERSTORMS
DEVELOPING. MODELS TRENDING TOWARD HIGHER COVERAGE WITH THIS ROUND
OF STORMS BUT WANT TO SEE HOW TONIGHT WORKS OUT BEFORE GOING
LIKELY OR BETTER POPS. TEMPERATURES TOMORROW WILL BE SIMILAR TO
TODAY FOR ALL BUT WESTERN ZONES WHERE CLOUD COVER MAY KEEP
TEMPERATURES IN THE 60S. ONCE AGAIN AREAS EAST OF BILLINGS WILL BE
FAVORED FOR HEAVIER PRECIPITATION BASED ON BETTER MOISTURE
PROFILES IN THESE AREAS.

FRIDAY LOOKS LIKE IT COULD BRING THE FIRST SEVERE THUNDERSTORM
THREAT TO THE AREA. STRONG MOISTURE ADVECTION AS WELL AS
TEMPERATURES IN THE MID 70S TO LOWER 80S WILL PUSH CAPE VALUES
INTO THE 1500 J/KG RANGE FROM ROSEBUD COUNTY EAST FRIDAY
AFTERNOON/EVENING. SHEAR PROFILES LOOK FAVORABLE FOR SEVERE STORMS
WITH SOUTHEASTERLY LOW LEVEL WINDS VEERING TO A 50KT SOUTHWEST
WIND IN THE MID LEVELS. UPPER LEVEL SOUTHERLY FLOW MAY ALSO BRING
A PUSH OF DRIER AIR INTO THE AREA FROM THE SOUTH THAT WOULD
PROVIDE ADDITIONAL CONVERGENCE TO INITIATE STORMS. ADDED MENTION
OF SEVERE STORMS TO THE FORECAST AND WILL MONITOR THIS POTENTIAL
CLOSELY FOR THE NEXT FEW DAYS. ELSEWHERE ACROSS THE AREA EXPECT
ADDITIONAL STORMS TO DEVELOP BUT RIGHT NOW THESE LOOK TO REMAIN
BELOW SEVERE LEVELS UNLESS STRONGER DYNAMICS SHIFT FURTHER WEST.

RIVERS AND STREAMS ACROSS THE AREA HAVE SEEN SIGNIFICANT RISES
OVER THE PAST WEEK DUE TO THE RECENT HOT TEMPERATURES...HOWEVER
FLOODING IS NOT EXPECTED ON ANY AREA RIVERS. WITH THE COOLER
CONDITIONS OF THE PAST COUPLE OF DAYS EXPECTED TO CONTINUE INTO
NEXT WEEK SNOWMELT WILL SLOW CONSIDERABLY. THIS WILL ALLOW RIVERS
TO STABILIZE NEAR CURRENT LEVELS. PLEASE USE CAUTION NEAR ANY
RIVERS OR STREAMS FOR THE NEXT FEW WEEKS AS WATER IS FLOWING FAST.
CHAMBERS

.LONG TERM...VALID FOR SAT...SUN...MON...TUE...WED...

SEVERAL RELATIVELY MINOR CHANGES TO THE EXTENDED PERIOD THIS
MORNING...AS CONFIDENCE INCREASES AND MODELS REMAIN IN AGREEMENT
FOR A PERIOD OF INCREASED MOISTURE ACROSS THE REGION.

SOUTHWEST FLOW REMAINS IN PLACE ACROSS THE REGION SATURDAY AHEAD
OF A BROAD SLOW MOVING UPPER LEVEL TROF APPROACHES. SEVERAL
DISTURBANCES AND GOOD MOISTURE AVAILABILITY ARE PROGGED THROUGH
THE AREA...WITH DECENT DYNAMICS AND UPPER LEVEL SUPPORT. RAISED
POPS ACROSS THE REGION THROUGH SATURDAY AND SATURDAY NIGHT. MANY
VARIABLES STILL EXIST AS TROF PROCEEDS EASTWARD THROUGH THE
WEEKEND...BUT GENERALLY KEEPS PRECIP CHANCES ACROSS THE REGION
THROUGHOUT THE PERIOD. A CUT OFF LOW DEVELOPS LATE SUNDAY INTO
MONDAY...BUT POSITIONING IS QUITE VARIABLE AS WELL...WITH MOST
RECENT GFS PLACING CENTER OF CIRCULATION OVER NORTHWEST SOUTH
DAKOTA...OPENING THE DOOR FOR FURTHER PRECIP POTENTIAL FROM WRAP
AROUND TYPE SHOWERS AND THUNDERSTORMS. THIS CIRCULATION THEN
PROCEEDS SLOWLY EAST...EXITING THE CWA MONDAY NIGHT/TUESDAY.
ALTHOUGH SOME RIDGING IS PROGGED BETWEEN SYSTEMS...TUESDAY AND
WEDNESDAY...HAVE CONTINUED WITH CLIMO TYPE POPS AT THIS TIME
THROUGH THE END OF THE EXTENDED PERIOD...WEDNESDAY NIGHT...BASED
IN LARGE PART ON EARLY PERIOD PRECIP POTENTIAL.

AS FOR TEMPERATURES...THE EXTENDED PERIOD WILL BEGIN WITH SEASONAL
TYPE TEMPERATURES...FALLING A FEW DEGREES BELOW NORMAL FOR SUNDAY
AND MONDAY...UNDER THE BROAD UPPER LEVEL TROF. TEMPS ARE EXPECTED
TO CLIMB TO A FEW DEGREES ABOVE SEASONAL AVERAGES FOR TUESDAY AND
WEDNESDAY...AS MINOR UPPER LEVEL RIDGING DEVELOPS. AAG

&&

.AVIATION...

ISOLATED TO SCATTERED SHOWERS AND THUNDERSTORMS ARE POSSIBLE OVER
THE MOUNTAINS LATE THIS AFTERNOON. ACTIVITY IS EXPECTED TO SPREAD
EAST TO THE ADJACENT PLAINS THROUGH THIS EVENING...AND ACROSS THE
REGION OVERNIGHT. LOCALIZED MVFR/IFR CONDITIONS CAN BE EXPECTED IN
AND AROUND PRECIP. AAG

&&

.PRELIMINARY POINT TEMP/POPS...

    THU     FRI     SAT     SUN     MON     TUE     WED
-----------------------------------------------------------
BIL 051/074 052/071 053/069 050/063 048/064 042/072 049/072
    33/T    44/T    55/T    55/T    54/T    42/T    22/T
LVM 043/069 045/065 043/067 043/062 041/062 036/067 043/072
    35/T    55/T    55/T    54/T    44/T    33/T    33/T
HDN 051/075 052/075 053/071 049/066 047/065 041/072 043/075
    33/T    44/T    54/T    55/T    55/T    32/T    12/T
MLS 053/074 053/076 055/071 049/066 048/066 043/070 044/073
    34/T    55/T    65/T    55/T    55/T    42/T    12/T
4BQ 051/075 052/079 054/070 047/064 046/063 041/067 042/074
    43/T    45/T    55/T    55/T    55/T    53/T    11/B
BHK 049/072 050/075 053/069 047/063 046/063 040/068 040/070
    45/T    55/T    56/T    55/T    55/T    53/T    12/T
SHR 047/073 048/075 048/068 044/060 043/060 036/066 037/075
    34/T    43/T    55/T    55/T    55/T    42/T    23/T

&&

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

&&

$$
WEATHER.GOV/BILLINGS