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000
FXUS65 KBYZ 200235
AFDBYZ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
835 PM MDT SUN MAY 19 2013

.SHORT TERM...VALID FOR MON AND TUE...

SIGNIFICANT PRECIPITATION CONTINUES TO FALL OVER THE AREA THIS
EVENING. PCPN CAN ACTUALLY BE BROKEN INTO TWO PARTS. WESTERN
SHOWERS ARE DRIVEN BY UPPER LEVEL ASCENT/DEFORMATION AND LOW
LEVEL UNSTABLE UPSLOPE FLOW. BLX RADAR HAS BEEN SHOWING AN OBVIOUS
UPSLOPE SIGNATURE...AND HEAVIEST PCPN IS CURRENTLY ALONG THE NORTH
SLOPES OF THE BEARTOOTHS/PRYORS/BIG HORNS. FORCING IS SHIFTING
WEST SOMEWHAT...AND AS A RESULT THE SHOWERS HAVE BECOME MORE
BROKEN IN THE BILLINGS AREA. NONETHELESS THE INSTABILITY
CONTINUES TO ALLOW FOR SHOWERS TO DEVELOP FROM THE NE...SO OFF AND
ON ACTIVITY EXPECTED FROM THIS POINT ON TONIGHT. SECOND AREA OF
PCPN IS ASSOCIATED WITH TROWAL WRAPPING INTO OUR EAST AS UPPER LOW
DEEPENS OVER THE CENTRAL PLAINS. PCPN HAS SPREAD INTO BAKER AND
EKALAKA AND IS APPROACHING MILES CITY AS OF 8 PM. BOWMAN RADAR
SHOWS LARGE AREA OF MODERATE RAIN...AND SURE ENOUGH BAKER HAS
RECEIVED OVER A TENTH OF AN INCH OVER THE PAST 2 HOURS. PCPN WILL
BE WIDESPREAD ACROSS OUR EAST TONIGHT AS TROWAL CONTINUES TO PUSH
IN FROM THE EAST.

WILL MAKE NO CHANGE TO FLASH FLOOD WATCH FOR OUR BURN SCARRED
AREAS...GIVEN PCPN WILL SPREAD INTO THESE AREAS TONIGHT AND
CONTINUE THRU MONDAY. INTERESTING TO NOTE THAT NEARLY 4 INCHES OF
RAIN HAS FALLEN AT PRYOR MTN RAWS IN THE PAST 24 HOURS...AND OVER
4.50 INCHES SINCE SATURDAY MORNING. THOUGH THERE IS NO FLOODING
YET...CONCERN EXISTS FOR PRYOR CREEK AS THIS RAIN RUNS OFF THE
NORTH SLOPES OF THE PRYOR MOUNTAINS. SODA SPRINGS RAWS JUST SOUTH
OF BILLINGS HAS ALSO RECEIVED ABOUT 2.50 INCHES...INDICATIVE OF
THE UPSLOPE ENHANCEMENT. INCREASED WATER LEVELS COULD IMPACT
RESIDENTS ALONG BLUE CREEK AS WELL. HAVE ISSUED A FLOOD STATEMENT
FOR INCREASED FLOWS ESPECIALLY ON PRYOR CREEK AND ITS
TRIBUTARIES...COVERING FAR WESTERN BIG HORN AND SOUTHWESTERN
YELLOWSTONE COUNTIES.

ELEVATIONS ABOVE 7.5KFT ALONG THE NORTH SLOPES OF THE BEARTOOTHS
HAVE RECEIVED SOME SNOWFALL TODAY...IN FACT COLE CREEK SNOTEL
ABOVE RED LODGE IS REPORTING 5-6 INCHES SINCE MIDDAY TODAY. MID
LEVEL TEMPS ARE CERTAINLY COLDER OVER OUR WEST...SO SNOW LEVELS
ARE LOWER OVER THE BEARTOOTH ABSAROKAS THAN THE PRYORS/BIG HORNS.
NEARLY 2 INCHES OF PCPN HAS FALLEN ON THE NORTH SLOPES OF THE
BEARTOOTHS...BUT GIVEN THE HIGH ELEVATION SNOWFALL THE RUNOFF WILL
NOT BE AS RAPID OR SIGNIFICANT. RIVERS AND STREAM LEVELS WILL
CERTAINLY RISE BUT IMPACTS NOT EXPECTED TO BE SIGNIFICANT AT THIS
TIME.

FOR BILLINGS...OFF AND ON SHOWERS TONIGHT MAY INCREASE INTO
MONDAY IF TROWAL MAKES IT THIS FAR WEST...WHICH IS A TOUGH CALL
RIGHT NOW. EVEN IF TROWAL FORCING STAYS EAST...MOIST AND UNSTABLE
UPSLOPE FLOW WILL ALLOW FOR SHOWERS AT TIMES...BUT WITH PCPN
BECOMING LIGHTER THAN WE EXPERIENCED TODAY.

OVERALL A VERY NICE AND MUCH-NEEDED PRECIPITATION EVENT FOR US...
AND IT IS NOT OVER YET.

JKL

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

OVERALL EXTENDED FORECAST IN GOOD SHAPE...WITH A SLOWER
PROGRESSION TO DRY WEATHER THAN PREVIOUSLY ADVERTISED. MODELS
ARE IN PRETTY GOOD AGREEMENT...SLOW TO MOVE CURRENT SYSTEM
EAST...AND SUPPRESSING RIDGE DEVELOPMENT IN BETWEEN AT THIS TIME
AS THE PACIFIC LOW PUSHES EASTWARD. THE EXTENDED FORECAST PERIOD
APPEARS RELATIVELY UNSETTLED OVERALL...ALTHOUGH MARKEDLY DRIER
THAN THE CURRENT WEATHER ACROSS THE REGION. TEMPS THROUGH THE
PERIOD ARE EXPECTED TO BE AROUND SEASONAL AVERAGE...WITH ONLY A
FEW DEGREES ABOVE OR BELOW.

PRECIP FROM DEPARTING SYSTEM STILL APPEARS TO LINGER IN EXTREME
EASTERN MONTANA ON WEDNESDAY...WITH THE TROF SLOW TO MOVE
EASTWARD. SOUTHWEST FLOW ALOFT SETS UP ACROSS THE REGION AS THE
STRONG UPPER LEVEL PACIFIC LOW CONTINUES PUSH EASTWARD...AND SENDS
A STRONG SHORTWAVE THROUGH THE REGION WEDNESDAY. THIS WAVE
APPEARS THAT IT WILL MAINLY IMPACT THE HIGH TERRAIN AND WESTERN
PLAINS...BUT PRECIP WILL ALSO BE POSSIBLE ACROSS THE EAST.
MEANWHILE LOW LEVEL EASTERLY FLOW APPEARS TO SET UP ACROSS THE
REGION...BRINGING MORE LOW LEVEL MOISTURE INTO THE AREA. THE UPPER
LEVEL LOW REMAINS CENTERED OVER WASHINGTON THROUGH
FRIDAY...MAINTAINING UNSETTLED SOUTHWEST FLOW ACROSS THE AREA.
THE LOW FINALLY KICKS NORTHEAST FRIDAY NIGHT...TAKING MOST ENERGY
NORTH OF THE CWA...BUT SOUTHWEST FLOW ALOFT IN PLACE...WITH
POSSIBLE GULF SFC MOISTURE INFLUX THROUGH THE REMAINDER OF THE
PERIOD. AT LEAST SLIGHT POPS CANNOT BE RULED OUT THROUGHOUT THE
REMAINDER OF THE PERIOD...IF ONLY DUE TO DIURNAL HEATING AND
AVAILABLE SURFACE MOISTURE...NOT TO MENTION POTENTIAL WEAK
SHORTWAVES THROUGH THE SOUTHWEST FLOW. AAG
&&

.AVIATION...

PERIODS OF WIDESPREAD RAIN WILL CONTINUE ACROSS MUCH OF THE
REGION...WITH AREAS OF MVFR TO IFR CONDITIONS. MOUNTAINS WILL BE
OBSCURED INTO MONDAY. NORTHERLY SURFACE WINDS WILL INCREASE
OVERNIGHT AND INTO MONDAY OVER SOUTHEAST MONTANA AND NORTHERN
WYOMING. AVIATION INTERESTS SHOULD EXPECT GUSTS BETWEEN 35 AND
40 KTS MONDAY AT KMLS...KBHK AND KSHR. BT
&&

.PRELIMINARY POINT TEMP/POPS...

    MON     TUE     WED     THU     FRI     SAT     SUN
-----------------------------------------------------------
BIL 048/061 044/069 046/069 049/072 049/074 050/075 050/074
    +8/W    41/B    02/T    42/T    22/T    22/T    22/T
LVM 045/059 038/065 040/067 040/067 041/069 042/069 041/068
    +6/W    41/B    14/T    44/T    43/T    33/T    32/T
HDN 049/061 045/070 044/071 049/074 048/077 050/077 050/076
    ++/W    51/B    02/T    32/T    22/T    22/T    22/T
MLS 050/059 046/064 046/068 050/071 050/074 052/076 053/076
    ++/W    73/W    12/T    22/T    22/T    22/T    22/T
4BQ 048/056 044/062 044/068 048/072 049/074 051/076 052/077
    ++/W    74/W    22/T    22/T    22/T    22/T    22/T
BHK 047/056 042/058 044/064 047/067 048/070 051/074 052/073
    ++/W    84/W    22/T    22/T    22/T    22/T    22/T
SHR 046/056 041/062 040/069 046/072 046/075 048/075 048/074
    9+/W    52/W    12/T    32/T    22/T    22/T    22/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...FLASH FLOOD WATCH IN EFFECT THROUGH LATE MONDAY NIGHT FOR
      ZONES 29>31-36>38-57-58.
WY...NONE.

&&

$$
WEATHER.GOV/BILLINGS