Severe Thunderstorm Warning 113, NWS Billings, MT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE BILLINGS MT
407 PM MDT MON JUL 8 2013

.UPDATE...

UPDATED FORECAST FOR NEW SEVERE THUNDERSTORM WATCH COVERING
SOUTHEAST MONTANA. SEVERE STORMS ONGOING OVER NORTHWEST AREAS WITH
GOLFBALL HAIL AND 60 MPH WINDS REPORTED. THIS ACTIVITY IS
APPROACHING YELLOWSTONE COUNTY AND WILL SEE STORMS IN THE BILLINGS
AREA BEFORE 5 PM IF CURRENT TRENDS CONTINUE. CHAMBERS

&&

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

UPPER LEVEL TROUGH OF LOW PRESSURE WILL MOVE ACROSS NORTHERN
MONTANA LATE THIS AFTERNOON AND EVENING. MODELS CONTINUE TO KEEP
THE STRONGEST FORCING ACROSS OUR NORTHERN ZONES FROM WHEATLAND
COUNTY EASTWARD THROUGH FALLON COUNTY. THE REMAINDER OF THE
FORECAST AREA ALSO UNDER THE GUN FOR SEVERE WEATHER AS UPPER
TROUGH DRAGS A COLD FRONT ACROSS THE AREA.

STRONG MOISTURE ADVECTION CONTINUE OVER THE AREA THIS AFTERNOON
AND EVENING AS EASTERLY WINDS ADVECT IN HIGHER DEW POINTS. THIS
MOISTURE COMBINED WITH STRONG AFTERNOON HEATING HAS CREATED
SURFACE BASED CAPES OF 1000 TO 2400 J/KG. JET DYNAMICS ALONG WITH
STRONG MID LEVEL WESTERLY FLOW ALSO MOVING INTO THE REGION AND IS
CREATING EFFECTIVE BULK SHEAR OF 30 TO 50 KTS ACROSS THE AREA. THE
COMBINATION OF STRONG INSTABILITY AND THE PASSAGE OF A COOL FRONT
THIS AFTERNOON...THE POTENTIAL EXIST FOR SEVERE THUNDERSTORMS WEST
OF A LINE FROM ROUNDUP...BILLINGS TO HARDIN. THE MAIN THREAT FROM
THESE STORMS WILL BE WINDS AND LARGE HAIL. SEVERE THUNDERSTORM
WATCH NUMBER 398 HAS ALREADY BEEN ISSUED AND IS IN EFFECT THROUGH
7 PM FOR THE ABOVE AREAS.

THE THREAT OF SEVERE WEATHER INCREASES FURTHER EAST THIS EVENING
AS STRONG SURFACE CONVERGENCES/FAVORABLE DIRECTIONAL AND SPEED
SHEAR/CAPES 2500 J/KG AND LI'S NEAR -8C EXIST. STEEP LAPSE RATES
AROUND 8 C/KM ALSO SETTING. ROTATING UPDRAFTS WILL DEVELOP IN THIS
ENVIRONMENT AND SUPERCELLS WILL BE LIKELY. HAVE INCREASED POPS TO
LIKELY FOR THE NORTHERN ZONES OF SOUTHEAST MONTANA AND HIGH
SCATTERED FOR THE REMAINDER AREAS. THESE STORMS WILL PRODUCE LARGE
HAIL/DAMAGING WINDS AND AN ISOLATED TORNADO CANNOT BE RULED OUT. A
WATCH WILL MORE THAN LIKELY BE ISSUED LATER THIS EVENING FOR
ROSEBUD COUNTY EAST TO THE DAKOTA BORDER.

CONVECTION WILL DIE DOWN LATE TONIGHT AS MAIN FORCING MOVES EAST.
A FEW LINGERING SHOWERS AND THUNDERSTORMS WILL CONTINUE TUESDAY
MORNING FROM BAKER TO ALZADA BUT WILL BE ENDING BY NOON TIME.
MODELS ALL IN GOOD AGREEMENT IN BUILDING ANOTHER RIDGE OF HIGH
PRESSURE ACROSS THE AREA FOR DRY WEATHER AND A RETURN TO ABOVE
NORMAL TEMPERATURES. RICHMOND

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

EXTENDED FORECAST LOOKS TO BE IN GOOD SHAPE WITH MODELS BEING IN
DECENT AGREEMENT FOR MOST PERIODS. AS A RESULT...DID NOT MAKE ANY
SIGNIFICANT CHANGES WITH THIS ISSUANCE. AN UNSETTLED SOUTHWEST
FLOW ALOFT RETURNS FOR THURSDAY. BOTH THE GFS AND ECMWF BRING A
DISTURBANCE NORTHEAST OUT OF THE GREAT BASIN AREA AND ACROSS
SOUTHERN MONTANA THURSDAY AFTERNOON AND EVENING. THE GFS IS QUITE
A BIT STRONGER WITH THIS WAVE RESULTING IN THE POSSIBILITY OF
STRONGER THUNDERSTORMS THAN WHAT THE ECMWF IS SHOWING. AFTER
THURSDAY...MAINLY A ZONAL FLOW ALOFT WILL BE OVER THE FORECAST
AREA INTO NEXT WEEKEND. MAIN UPPER LEVEL DYNAMICS WILL BE MOVING
ACROSS THE CANADIAN BORDER KEEPING MOST OF THE ACTIVITY TO OUR
NORTH. STILL CAN'T RULE OUT AN ISOLATED THUNDERSTORM SO WILL KEEP
A SLIGHT MENTION FRIDAY THROUGH THE WEEKEND. TEMPERATURES ARE
EXPECTED TO BE ABOVE NORMAL THROUGH THE PERIOD. HOOLEY

&&

.AVIATION...

A COLD FRONT WILL MOVE ACROSS THE FORECAST AREA THIS AFTERNOON
AND EVENING TRIGGERING ANOTHER ROUND OF THUNDERSTORMS. THE
THUNDERSTORMS WILL BEGIN BY EARLY TO MID AFTERNOON WEST OF KBIL
AND MOVE EAST TOWARD KMLS BY EARLY EVENING AND THE DAKOTA BORDER
BY LATE EVENING. LARGE HAIL...DAMAGING WINDS AND VERY HEAVY RAIN
WILL BE LIKELY WITH THE THUNDERSTORMS. EXPECT IFR TO VLIFR
CONDITIONS IN AND NEAR THE THUNDERSTORM ACTIVITY. OTHERWISE...VFR
CONDITIONS WILL PREVAIL THROUGH THIS EVENING. HOOLEY

&&

.PRELIMINARY POINT TEMP/POPS...

    TUE     WED     THU     FRI     SAT     SUN     MON
-----------------------------------------------------------
BIL 061/084 059/094 064/093 064/092 061/092 061/090 059/091
    51/B    01/U    11/B    22/T    22/T    22/T    22/T
LVM 051/085 050/093 056/093 052/092 051/092 051/090 049/091
    41/B    11/U    11/B    22/T    22/T    22/T    22/T
HDN 061/084 058/095 064/094 064/093 061/093 061/091 059/092
    52/T    01/U    11/B    22/T    22/T    22/T    22/T
MLS 063/082 059/095 066/094 065/092 062/092 062/090 060/091
    62/T    01/U    11/B    22/T    22/T    22/T    22/T
4BQ 059/083 056/093 062/092 065/091 061/091 061/089 059/090
    32/T    01/U    11/U    22/T    12/T    22/T    22/T
BHK 060/078 054/089 061/088 068/091 062/087 062/085 060/086
    63/T    01/U    11/U    22/T    22/T    22/T    22/T
SHR 056/082 055/092 059/092 058/091 056/091 056/089 054/090
    31/B    11/U    11/U    12/T    22/T    22/T    22/T

&&

.BYZ WATCHES/WARNINGS/ADVISORIES...
MT...SEVERE THUNDERSTORM WATCH 398 IN EFFECT UNTIL 7 PM MDT THIS
      EVENING FOR ZONES 28-29-34-35-38>42-56-57-63>68.
     SEVERE THUNDERSTORM WATCH 401 IN EFFECT UNTIL 11 PM MDT THIS
      EVENING FOR ZONES 30>33-36-37-58.
WY...SEVERE THUNDERSTORM WATCH 401 IN EFFECT UNTIL 11 PM MDT THIS
      EVENING FOR ZONES 98-99.

&&

WEATHER.GOV/BILLINGS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BILLINGS MT
231 PM MDT MON JUL 8 2013

MTZ028>042-056>058-063>068-WYZ098-099-092045-
SOUTHERN WHEATLAND-MUSSELSHELL-TREASURE-NORTHERN ROSEBUD-CUSTER-
FALLON-NORTHERN STILLWATER-YELLOWSTONE-POWDER RIVER-CARTER-
SOUTHERN BIG HORN-EASTERN CARBON-NORTHERN PARK-
NORTHERN SWEET GRASS-GOLDEN VALLEY-RED LODGE FOOTHILLS-
NORTHERN BIG HORN-SOUTHERN ROSEBUD-JUDITH GAP-PARADISE VALLEY-
LIVINGSTON AREA-BEARTOOTH FOOTHILLS-ABSAROKA/BEARTOOTH MOUNTAINS-
CRAZY MOUNTAINS-NORTHEAST BIG HORN MOUNTAINS-SHERIDAN FOOTHILLS-
231 PM MDT MON JUL 8 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
MONTANA...SOUTH CENTRAL MONTANA...SOUTHEAST MONTANA AND NORTH
CENTRAL WYOMING.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED THUNDERSTORMS WILL MOVE WEST TO EAST THIS AFTERNOON AND
OVERNIGHT. SOME STORMS MAY BECOME SEVERE WITH DAMAGING
WINDS...LARGE HAIL AND VERY HEAVY RAIN POSSIBLE. WINDS IN EXCESS
OF 60 MPH WILL BE POSSIBLE WITH THESE STORMS. THE SEVERE
THUNDERSTORMS WILL SPREAD EAST OF BILLINGS THIS EVENING AND THE
THREAT OF DAMAGING WINDS...LARGE HAIL AND HEAVY RAIN CAN BE
EXPECTED OVER SOUTHEAST MONTANA. THOSE WITH OUTDOOR ACTIVITIES
SHOULD KEEP A CLOSE EYE ON THE SKY...MONITOR LOCAL WEATHER UPDATES
AND HAVE A PLAN TO GET TO SHELTER SHOULD STORMS APPROACH.

.DAYS TWO THROUGH SEVEN...TUESDAY THROUGH SUNDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

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