Severe Thunderstorm Warning 71, NWS Billings, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
316 PM MDT THU JUL 7 2011

.SHORT TERM...VALID FOR FRI AND SAT...

UPPER LEVEL RIDGE SHIFTS EASTWARD THROUGH TONIGHT AS THE UPPER
TROF CONTINUES TO MOVE THROUGH THE PACIFIC NW. A COUPLE OF STRONG
SHORTWAVES EMBEDDED IN THE SOUTHWEST FLOW AHEAD OF THE MAIN TROF
AXIS WILL WORK WITH UPPER LEVEL DIVERGENCE...PREVIOUSLY GENERATED
OUTFLOW BOUNDARIES...TERRAIN AND AVAILABLE HEATING/LOW LEVEL
MOISTURE TO CONTINUE TO GENERATE AREAS OF CONVECTION THIS EVENING
ACROSS WESTERN/CENTRAL ZONES. EXPECT CONVECTION TO SPREAD EASTWARD
OVERNIGHT AHEAD OF SHORTWAVE ACTIVITY IN AN UNSTABLE ATMOSPHERE.

EFFECTIVE 0-6 KM BULK SHEAR GREATER THAN 30 KTS ACROSS MUCH OF THE
REGION WILL GIVE STORMS A BETTER CHANCE TO BECOME ORGANIZED.
ISOLATED SUPERCELLS ALSO POSSIBLE GIVEN MARGINAL SHEAR VALUES.
MLCAPE VALUES APPROACHING 1500 J/KG IN MANY AREAS SUPPORT SEVERE
HAIL...WHILE DCAPE VALUES UPWARDS OF 1000 J/KG ARE SUPPORTIVE
SEVERE WIND POTENTIAL. PRECIPITABLE WATER VALUES UPWARDS OF AN
INCH ACROSS MUCH OF THE AREA ALSO SUPPORT THE POTENTIAL FOR HEAVY
CONVECTIVE RAINFALL/LOCALIZED FLASH FLOODING.

UPPER TROF BUILDS INTO WESTERN PORTIONS OF THE STATE FRIDAY...WITH
COOLER AND UNSETTLED WEATHER IN WESTERN ZONES. FURTHER EAST
ANOTHER HOT DAY IS IN STORE WITH HIGHS NEAR OR ABOVE 90 DEGREES.
WILL SEE ANOTHER ROUND OF STRONG TO SEVERE STORMS IN CENTRAL AND
EASTERN ZONES AHEAD OF A PRE FRONTAL SURFACE TROF...THEN AHEAD OF
THE SURFACE COLD FRONT. SHEAR PROFILES LOOK FAVORABLE ON FRIDAY
FOR SEVERE CONVECTIVE WINDS AND FORECAST MLCAPES IN THE 750 TO
1500 J/KG LOOK FAVORABLE FOR SEVERE HAIL...ESPECIALLY DURING THE
AFTERNOON/EVENING HOURS.

SATURDAY LOOKS LIKE A MOSTLY DRY AND SOMEWHAT COOLER DAY BEHIND
THE COLD FRONT. WOULD NOT RULE OUT SOME ISOLATED
CONVECTION...ESPECIALLY OVER THE HIGHER TERRAIN WITH MLCAPE VALUES
APPROACHING 500 J/KG.

NO CHANGES TO GOING HYDROLOGIC PRODUCTS. STILL SEEING A MORE OR
LESS STEADY DRAINAGE OF THE BEARTOOTH MOUNTAINS WHICH MEANS
RIVERS WILL CONTINUE NEAR CURRENT LEVELS FOR AT LEAST ANOTHER
COUPLE OF DAYS. GAGES ALONG DRAINAGES OF THE BIG HORN MOUNTAINS
CONTINUE TO SHOW A DOWNWARD DIURNAL TREND THAT IS LEADING TO
DOWNWARD TRENDS ALONG THE TONGUE AND POWDER RIVERS DOWNSTREAM. STC/JKL

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

NEXT WEEK STARTS OFF WARM WITH NICE WEATHER AS AN UPPER LEVEL
RIDGE BUILDS OVER EASTERN MONTANA. A DEEP TROUGH WITH A CLOSED LOW
MOVES OVER THE WASHINGTON COAST MONDAY NIGHT...SETTING UP
SOUTHWEST FLOW OVER THE MOUNTAINS. EXPECT AFTERNOON SHOWERS OVER
THE MOUNTAINS AND FOOTHILLS MONDAY NIGHT. TUESDAY AND WEDNESDAY A
LOW LEVEL EASTERLY JET BRINGS DEWPOINTS IN THE 50S AND LOWER 60S
AND PRECIPITABLE WATER VALUES OVER AN INCH TO EASTERN MONTANA.
SOUNDINGS STILL INDICATING OVER 2000 J/KG AT SOME LOCATIONS IN
EASTERN MONTANA. WILL CONTINUE TO WATCH THIS PERIOD CLOSELY FOR
SEVERE STORM POTENTIAL...ESPECIALLY OVER EASTERN MONTANA.

EXTENDED MODELS GENERALLY AGREE WELL UP TO MID WEEK NEXT WEEK. THE
00Z RUN OF THE ECMWF CHANGED FROM THE PREVIOUS SOLUTION TO MAKE
THE UPPER LOW NEXT WEEK MUCH MORE PROGRESSIVE. ENSEMBLE GUIDANCE
ALSO INDICATES MORE UNCERTAINTY WITH THE SPEED OF THE LOW...WITH
MORE MEMBERS HOLDING IT BACK OFF THE WEST COAST THAN BEING
PROGRESSIVE. OTHERWISE THERE WERE NO SIGNIFICANT CHANGES TO MODEL
GUIDANCE IN THE EXTENDED. RNL.

&&

.AVIATION...

SCATTERED THUNDERSTORMS WILL CONTINUE TO DEVELOP ACROSS WEST AND
CENTRAL REGIONS OVER THE NEXT FEW HOURS...THEN SPREAD EASTWARD
OVERNIGHT. KLVM...KBIL..KSHR...AND KMLS MAY BE IMPACTED BY THE
THUNDERSTORMS. EXPECT MVFR TO IFR CONDITIONS IN ANY THUNDERSTORM
WITH HAIL AND HEAVY RAINS POSSIBLE. THUNDERSTORMS WILL DIE DOWN
LATE TONIGHT...WITH WINDS SWITCHING TO MORE OF A WESTERLY
DIRECTION FROM KBIL WESTWARD. A COLD FRONT MOVING THROUGH THE AREA
WILL GENERATE MORE SHOWERS AND THUNDERSTORMS BY TOMORROW
AFTERNOON. STC

&&

.PRELIMINARY POINT TEMP/POPS...

    FRI     SAT     SUN     MON     TUE     WED     THU
-----------------------------------------------------------
BIL 062/089 057/086 057/083 060/088 063/093 063/092 062/089
    43/T    42/T    12/T    22/T    22/T    23/T    22/T
LVM 052/084 046/081 047/081 050/088 052/091 052/090 052/087
    53/T    22/T    12/T    23/T    32/T    23/T    22/T
HDN 060/090 057/085 055/085 059/089 062/093 061/094 062/091
    43/T    42/T    12/T    22/T    32/T    23/T    22/T
MLS 064/090 058/083 056/083 060/087 064/091 064/092 064/090
    44/T    41/B    12/T    23/T    32/T    23/T    22/T
4BQ 063/090 060/083 056/084 060/085 063/088 063/091 064/090
    44/T    42/T    12/T    23/T    32/T    23/T    22/T
BHK 061/089 059/081 055/080 057/082 061/083 061/087 062/087
    34/T    41/B    12/T    23/T    32/T    23/T    22/T
SHR 059/087 057/084 053/083 057/086 058/090 059/089 059/088
    43/T    42/T    22/T    23/T    32/T    23/T    22/T

&&

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

&&

WEATHER.GOV/BILLINGS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE BILLINGS MT
331 PM MDT THU JUL 7 2011

MTZ028>042-056>058-063>068-WYZ098-099-082145-
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-
331 PM MDT THU JUL 7 2011

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 ARE EXPECTED THROUGH LATE TONIGHT. SOME
OF THESE STORMS WILL BE CAPABLE OF PRODUCING LARGE HAIL. SOME
STORMS MAY ALSO PRODUCE HEAVY RAINFALL...WHICH MAY RESULT IN
LOCALIZED FLASH FLOODING.

RIVERS AND AREA STREAMS WILL REMAIN AROUND OR ABOVE FLOOD STAGE.
STREAM FLOWS WILL BE STRONGER THAN NORMAL. PAY CLOSE ATTENTION TO
RIVER LEVELS IF YOU ARE ON OR NEAR THE WATER.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

ANOTHER CHANCE OF THUNDERSTORMS WILL OCCUR FRIDAY AND FRIDAY
NIGHT AS A COLD FRONT MOVES THROUGH THE AREA. THERE IS THE
POTENTIAL FOR A FEW SEVERE STORMS WITH LARGE HAIL AND LOCALLY
HEAVY RAINFALL ALONG AND EAST OF A ROUNDUP TO LAUREL TO RED LODGE
LINE.

FLOODING AND HIGH WATER DUE TO SNOW MELT WILL CONTINUE AS THE
WEATHER REMAINS WARM. TAKE STEPS TO PROTECT PROPERTY AND
LIVESTOCK IF LOCATED NEAR LOCAL WATERWAYS OR IN AREAS PRONE TO
FLOODING FROM SNOW MELT.

.SPOTTER INFORMATION STATEMENT...

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

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BILLINGS MT
523 PM MDT THU JUL 7 2011

MTZ028-041-042-080015-
GOLDEN VALLEY MT-NORTHERN SWEET GRASS MT-SOUTHERN WHEATLAND MT-
523 PM MDT THU JUL 7 2011

...SIGNIFICANT WEATHER ADVISORY FOR SOUTHEASTERN WHEATLAND...
SOUTHWESTERN GOLDEN VALLEY AND NORTHEASTERN SWEET GRASS COUNTIES
UNTIL 615 PM MDT...

AT 518 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
STRONG THUNDERSTORM 12 MILES SOUTH OF HARLOWTON...MOVING NORTHEAST AT
20 MPH.

HAIL UP TO THE SIZE OF PENNIES IS EXPECTED WITH THIS STORM...ALONG
WITH HEAVY RAIN. THE HEAVY RAIN WILL CAUSE A REDUCTION OF VISIBILITY
AND QUICK PONDING OF WATER ON ROADS MAKING TRAVEL DIFFICULT. QUICK
RISES ON SMALL STREAMS AND CREEKS ARE ALSO EXPECTED.

THIS STORM WILL BE NEAR...
HARLOWTON AROUND 530 PM MDT.
SHAWMUT AROUND 600 PM MDT.
HEDGESVILLE AROUND 610 PM MDT.

LAT...LON 4604 10943 4604 11004 4645 11001 4654 10932
TIME...MOT...LOC 2322Z 243DEG 18KT 4627 10976

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE BILLINGS MT
640 PM MDT THU JUL 7 2011

MTZ029-034-035-039-041-042-066>068-080145-
ABSAROKA/BEARTOOTH MOUNTAINS MT-BEARTOOTH FOOTHILLS MT-CRAZY
MOUNTAINS MT-EASTERN CARBON MT-GOLDEN VALLEY MT-MUSSELSHELL
MT-NORTHERN STILLWATER MT-NORTHERN SWEET GRASS MT-YELLOWSTONE MT-
640 PM MDT THU JUL 7 2011

...SIGNIFICANT WEATHER ADVISORY FOR EXTREME NORTHERN CARBON...
SOUTHERN GOLDEN VALLEY...STILLWATER...SWEET GRASS...WESTERN
YELLOWSTONE AND SOUTHERN MUSSELSHELL COUNTIES UNTIL 745 PM MDT...

AT 700 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING A
CLUSTER OF THUNDERSTORMS IMPACTING MUCH OF SWEET GRASS AND
STILLWATER COUNTIES...AND MOVING INTO EASTERN YELLOWSTONE COUNTY
OVER THE NEXT HOUR...MOVING NORTHEAST AT 15 MPH.

HEAVY RAIN IS EXPECTED WITH THIS STORM...ALONG WITH HAIL UP TO THE
SIZE OF PENNIES

AREAS AFFECTED BY THIS STORM INCLUDE...BIG TIMBER...COLUMBUS...
BILLINGS...ABSAROKEE...LAUREL...BILLINGS WEST END...BILLINGS
HEIGHTS...LOCKWOOD...SHEPHERD...HUNTLEY...GREYCLIFF...REED POINT...
SOURDOUGH...RAPELJE...HALFBREED LAKE WILDLIFE...HAILSTONE WILDLIFE
REFUGE...PARK CITY...MOLT...BROADVIEW AND COMANCHE.

THIS INCLUDES INTERSTATE 94 BETWEEN MILE MARKERS 10 AND 9.

THIS INCLUDES HIGHWAY 212 BETWEEN MILE MARKERS 55 AND 58.

THIS INCLUDES INTERSTATE 90 BETWEEN MILE MARKERS 354 AND 468.

THIS INCLUDES MONTANA HIGHWAY 87 BETWEEN MILE MARKERS 10 AND 9.

THIS INCLUDES MONTANA HIGHWAY 310 BETWEEN MILE MARKERS 47 AND 54.

THIS INCLUDES MONTANA STATE HIGHWAY 78 BETWEEN MILE MARKERS 31 AND
47.

THIS STORM MAY INTENSIFY...SO BE CERTAIN TO MONITOR LOCAL RADIO AND
TV STATIONS...AS WELL AS LOCAL CABLE TV OUTLETS...FOR ADDITIONAL
INFORMATION AND POSSIBLE WARNINGS FROM THE NATIONAL WEATHER SERVICE.

LAT...LON 4625 10838 4567 10813 4538 11020 4578 11022
      4579 11025 4605 11028
TIME...MOT...LOC 0038Z 237DEG 7KT 4560 10982

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