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000
FXUS65 KBYZ 151616
AFDBYZ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
1016 AM MDT WED MAY 15 2013

.UPDATE...

UPDATED FORECAST TO INCREASE PRECIPITATION CHANCES THIS AFTERNOON
THROUGH TONIGHT. CONVECTION YESTERDAY WAS MORE THAN EXPECTED AND
LOOKING BACK AT MODELS THERE WAS A RIBBON OF 850-700MB MOISTURE
ADVECTION FROM THE PLAINS THAT SNAKED NORTH ALONG THE BIG HORNS
AND THEN GOT PULLED EAST INTO THE BEARTOOTH FOOTHILLS. A WEAK
DISTURBANCE WAS ALL THAT WAS NEEDED TO FORCE CONVECTION FROM THIS
MOISTURE POOL AND SAW THUNDERSTORMS EVEN DURING THE OVERNIGHT
HOURS ALONG THIS MOISTURE AXIS OVER POWDER RIVER AND CARTER
COUNTIES. EXPLAINED ALL THIS BECAUSE SIMILAR SET UP IS IN PLACE
TODAY WITH A BIT BETTER MOISTURE ADVECTION SNAKING ITS WAY UP FROM
THE SOUTHEAST. MODELS CATCHING ON TO THIS WITH CONVECTIVE
SIGNATURES SHOWING UP IN THE MID LEVELS STARTING OVER WESTERN
ZONES MID AFTERNOON AND CONTINUING THROUGH THE NIGHT AS THIS
ACTIVITY MOVES WEST TO EAST. DO NOT EXPECT A BUNCH OF
PRECIPITATION WITH THIS ACTIVITY OVER WESTERN AND CENTRAL ZONES
GIVEN PW VALUES UNDER .75 INCHES...BUT IN EASTERN ZONES COULD SEE
LOCAL QUARTER TO HALF INCH AMOUNTS WITH SOME OF THESE CONVECTIVE
COMPLEXES AS PW VALUES PUSH UP TO AN INCH DUE TO LOW LEVEL
MOISTURE ADVECTION. OUTSIDE OF PRECIPITATION AND THUNDERSTORM
CHANCES REST OF THE FORECAST LOOKS REASONABLE. CHAMBERS

&&

.SHORT TERM...VALID FOR TDY AND THU...

OVERALL PATTERN TO BECOME MORE UNSETTLED DURING THE NEXT COUPLE
OF DAYS AND ESPECIALLY INTO THE WEEKEND WITH COOLER TEMPERATURES
IN STORE. ZONAL FLOW ALOFT WILL BE OVER OUR FORECAST AREA TODAY
WITH NO STRONG DISTURBANCES MOVING ACROSS THE FORECAST AREA. SKIES
WILL BE PARTLY SUNNY WITH TEMPERATURES REMAINING ABOVE NORMAL WITH
READINGS IN THE MIDDLE TO UPPER 70S FOR MOST LOCATIONS. A WEAK
DISTURBANCE WILL APPROACH THE MOUNTAIN AREAS LATE THIS AFTERNOON
AND EVENING BRINGING A SLIGHT CHANCE FOR A SHOWER/THUNDERSTORM TO
THE MOUNTAINS AND ADJACENT FOOTHILLS.

AN UPPER LEVEL TROUGH BEGINS TO MOVE ONTO THE PACIFIC NORTHWEST
COAST LATE TONIGHT AND INTO THE DAY THURSDAY RESULTING IN A
SOUTHWEST FLOW ALOFT TO OUR AREA. SEVERAL DISTURBANCES WILL EJECT
NORTHEAST ACROSS MONTANA INCREASING THE CHANCES FOR SHOWERS AND
ISOLATED THUNDERSTORMS. IN ADDITION...A SURFACE LOW DEVELOPS
ACROSS NORTHEAST WYOMING LATE TONIGHT AND INTO THE DAY THURSDAY.
MODELS SHOW THIS LOW DRAWING GULF MOISTURE NORTHWARD INTO THE
CENTRAL AND WESTERN HIGH PLAINS THURSDAY AND THURSDAY NIGHT
RESULTING IN HIGH CHANCE POPS FOR THE WESTERN DAKOTAS AND EASTERN
MONTANA. THE UPPER LEVEL DISTURBANCES MOVING IN FROM THE SOUTHWEST
COMBINED WITH THE ABOVE MENTIONED SURFACE LOW WILL BRING BETTER
CHANCES FOR SHOWERS AND ISOLATED THUNDERSTORMS ACROSS OUR ENTIRE
AREA THURSDAY AND THURSDAY NIGHT. THE BEST CHANCES WILL BE CLOSER
TO THE DAKOTA BORDER...AS WELL AS OUR FAR WESTERN AREAS TOWARD THE
MOUNTAINS. GIVEN HOW MODELS HAVE BEEN OVERDOING PRECIP THE PAST
WEEK...WILL LEAVE PRECIP IN THE HIGH CHANCE CATEGORY AND NOT GO
LIKELY AT THIS TIME. HOOLEY

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

FRIDAY THROUGH SUNDAY SEE INCREASING MOISTURE OVER THE REGION BUT
RELATIVELY WEAK DYNAMICS. THIS WILL SUPPORT LARGELY DIURNAL
SHOWER ACTIVITY AND PERIODS OF SUNSHINE IN THE MORNINGS SHOULD
HELP TEMPERATURES BE NEAR NORMAL. ONE BETTER PERIOD OF FOCUS MAY
BE FRIDAY NIGHT INTO EARLY SATURDAY WHERE A STRONGER DISTURBANCE
IS HINTED AT.

LARGER QUESTIONS LOOM AFTER SUNDAY AS BOTH ECMWF AND GFS DEVELOP A
CUTOFF LOW BUT ITS LOCATION VARIES FROM NORTHEAST WYOMING TO
SOUTHWEST MINNESOTA. GFS POSITION WOULD BE A PRETTY WET SCENARIO
FOR THE REGION WHILE THE ECMWF WOULD MAINTAIN THE SAME TREND OF
SHOWERY WITH NO STRONG FOCUSING MECHANISMS.

CONFIDENCE INCREASING FOR CHANGES OF MOISTURE ACROSS THE REGION
AND RAISED CHANCES OF PRECIPITATION ACROSS THE BOARD FOR FRIDAY
THROUGH SUNDAY. FEW OTHER CHANGES MADE. BORSUM
&&

.AVIATION...

MOSTLY CLEAR SKIES THIS MORNING WILL GIVE WAY TO INCREASING CLOUD
COVER OVER WESTERN AREAS THIS AFTERNOON. ISOLATED TO SCATTERED
SHOWERS AND THUNDERSTORMS WILL DEVELOP OVER THE MOUNTAINS THIS
AFTERNOON. ACTIVITY WILL SPREAD EAST TO THE ADJACENT PLAINS THIS
EVENING...AND ACROSS THE REGION OVERNIGHT. LOCALIZED MVFR/IFR
CONDITIONS CAN BE EXPECTED IN AND AROUND PRECIP. AAG/BORSUM

&&

.PRELIMINARY POINT TEMP/POPS...

    TDY THU     FRI     SAT     SUN     MON     TUE
-------------------------------------------------------
BIL 076 052/073 050/071 050/069 051/064 048/064 042/067
    2/T 33/T    34/T    45/T    55/T    53/T    32/T
LVM 075 044/069 044/067 042/066 044/063 041/062 036/067
    3/T 33/W    34/T    45/T    54/T    44/T    33/T
HDN 079 052/076 051/074 051/071 051/067 047/065 041/069
    2/T 33/T    34/T    44/T    45/T    54/T    32/T
MLS 078 052/075 052/075 054/072 049/067 048/066 043/068
    0/B 34/T    44/T    45/T    55/T    54/T    32/T
4BQ 078 051/075 051/075 054/070 050/065 046/063 041/065
    2/T 34/T    34/T    45/T    55/T    54/T    32/T
BHK 076 048/073 050/071 052/070 045/064 046/063 040/066
    0/B 34/T    44/T    56/T    55/T    54/T    32/T
SHR 076 047/074 047/072 048/067 046/061 043/060 036/064
    3/T 33/T    33/T    45/T    55/T    54/T    32/T

&&

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

&&

$$
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