Severe Thunderstorm Warning 40, NWS Missoula, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
616 PM MDT TUE AUG 31 2004

.UPDATE...WILL UPDATE THE FORECAST TONIGHT TO INCLUDE THUNDER AND
SHOWERS FOR THE MOST OF THE FORECAST AREA. THE EXCEPTIONS WILL BE
LEMHI COUNTY IDAHO AND THE FLATHEAD...MISSOULA...AND BITTERROOT
VALLEYS IN MONTANA. MIXING HAS BEGUN LATE TODAY...KEEPING
TEMPERATURES COOLER AT LOWER ELEVATIONS THAN PREVIOUSLY EXPECTED.
INVERTED LAYERS HAVE BEGUN TO BREAK LATE THIS AFTERNOON...ALLOWING
SHOWERS AND THUNDERSTORMS TO DEVELOP. STORMS ARE CURRENTLY MAINLY
OVER THE BITTERROOT AND CLEARWATER MOUNTAINS. MOST OF THESE
THUNDERSTORMS ARE HIGH BASED AND PRODUCING LITTLE PRECIPITATION...SO
WILL KEEP POPS LOW.

&&

.PREVIOUS DISCUSSION...TONIGHT THROUGH FRIDAY...RIDGE CONTINUES
ACROSS THE FORECAST AREA TONIGHT...BUT WITH THE TROUGH DIGGING DOWN
THE PACIFIC COAST...THE RIDGE IS STARTING THE FLATTEN AND SHIFT TO
THE EAST. A WEAK DISTURBANCE IS MOVING FROM THE SOUTHWEST AND
PRODUCING SOME SHOWERS OVER EASTERN WASHINGTON AND NORTHERN IDAHO.
THESE SHOWERS WILL JUST CATCH THE EXTREME NORTHWESTERN CORNER OF THE
FORECAST AREA THIS EVENING. LATER TONIGHT AND EARLY WEDNESDAY THE
TROUGH WILL CONTINUE TO SLIDE TO THE EAST AND PUSH SOME MORE WEAK
DISTURBANCES INTO THE REGION...WILL KEEP SOME LOW POPS ACROSS
MAINLY THE WESTERN HALF OF THE FORECAST AREA THROUGH MORNING...WARM
AND UNSTABLE AIR WILL MOVE INTO THE REGION AHEAD OF THE COLD FRONT.

WEDNESDAY AFTERNOON AS THE COLD FRONT MOVES ACROSS WASHINGTON AND
INTO THE IDAHO PANHANDLE THE ATMOSPHERE GETS MORE UNSTABLE WITH
THUNDERSTORMS DEVELOPING...SOME EARLY STORMS COULD HAVE GUSTY WINDS
WITH THEM. ALSO WITH A TIGHTENING SURFACE PRESSURE GRADIENT OVER
THE REGION...WILL SEE AN INCREASE IN SURFACE WINDS. WIND SPEED
COULD REACH LAKE WIND ADVISORY CRITERIA DURING THE AFTERNOON...WILL
LEAVE THIS FOR THE NEXT FORECAST PACKAGE TO TAKE A CLOSER LOOK AT.
WEDNESDAY NIGHT THE COLD FRONT MOVES ACROSS WESTERN MONTANA...WITH
SHOWERS AND WINDS DECREASING BEHIND THE FRONT. COOLER CONDITIONS
WITH ANOTHER WEAK DISTURBANCE ROTATING IN FROM THE NORTH WILL BE
THE RULE ON THURSDAY AND THURSDAY NIGHT. BY FRIDAY THE TROUGH HAS
MOVED OFF TO THE EAST WITH HIGH PRESSURE BEGINNING TO REBUILD INTO
THE AREA.

FRIDAY NIGHT THROUGH TUESDAY NIGHT...A RIDGE OF
HIGH PRESSURE CONTINUES TO BUILD ALONG THE WEST COAST FRIDAY
NIGHT AND SATURDAY. THIS RIDGE WILL DRAG IN WARMER AND DRIER AIR INTO
THE REGION. THERE ARE A FEW WEAK SHORTWAVES EMBEDDED IN THE
NORTHWEST FLOW...SO KEPT A SLIGHT CHANCE OF SHOWERS ALONG THE
CONTINENTAL DIVIDE FOR FRIDAY NIGHT AND SATURDAY NIGHT. THEN THE
RIDGE GETS PUSHED TO THE SOUTHEAST A BIT...PUTTING WESTERN MONTANA
AND NORTH CENTRAL IDAHO IN WESTERLY FLOW FOR THE REMAINDER OF THE
FORECAST PERIOD. THIS ZONAL FLOW WILL CAUSE THE AREA TO HAVE MILD
TEMPERATURES. WILL HAVE TO KEEP WATCH OF WEAK SHORTWAVES MOVING
THROUGH THE THIS ZONAL FLOW FOR CHANCES OF PRECIP THROUGHOUT NEXT
WEEK...BUT HAVE KEPT THE FORECAST DRY AT THIS TIME.
&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...NONE.
&&

UPDATE/STEGEMILLER
PREVIOUS/KOLATA/SMITH/WHITMORE

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE MISSOULA MT
300 PM MDT (200 PM PDT) TUE AUG 31 2004

MTZ001>004-043-011300-
KOOTENAI/CABINET REGION-WEST GLACIER REGION-FLATHEAD/MISSION VALLEYS-
LOWER CLARK FORK REGION-BLACKFOOT REGION-
300 PM MDT TUE AUG 31 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL IDAHO AND WESTERN
MONTANA

.DAY ONE... REST OF TODAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN... WEDNESDAY THROUGH MONDAY

A PACIFIC WEATHER SYSTEM WILL MOVE INTO WESTERN MONTANA WEDNESDAY
AFTERNOON. THE SURFACE PRESSURE GRADIENT WILL TIGHTEN AHEAD OF AND
WITH THIS FRONT INCREASING THE WIND SPEEDS. A LAKE WIND ADVISORY
MAY NEED TO BE ISSUED WEDNESDAY MORNING. ALONG WITH THE WINDS...
THUNDERSTORMS AND COOLER TEMPERATURES CAN BE EXPECTED.

.SPOTTER INFORMATION STATEMENT...

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

IDZ005>008-011300-
NORTHERN CLEARWATER MOUNTAINS-SOUTHERN CLEARWATER MOUNTAINS-
OROFINO/GRANGEVILLE REGION-LOWER HELLS CANYON/SALMON RIVER-
200 PM PDT TUE AUG 31 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL IDAHO AND WESTERN
MONTANA

.DAY ONE... REST OF TODAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN... WEDNESDAY THROUGH MONDAY

A PACIFIC WEATHER SYSTEM WILL MOVE INTO NORTHERN IDAHO ON WEDNESDAY.
THIS SYSTEM WILL BRING GUSTY WINDS AND THUNDERSTORMS INTO THE AREA.
SOME OF THE FIRST THUNDERSTORMS COULD HAVE STRONG DOWNBURST WINDS
ASSOCIATED WITH THEM. COOLER TEMPERATURES WILL MOVE INTO THE REGION
BY WEDNESDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

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

IDZ009-010-MTZ005>007-011300-
WESTERN LEMHI COUNTY-EASTERN LEMHI COUNTY-
MISSOULA/BITTERROOT VALLEYS-BITTERROOT/SAPPHIRE MOUNTAINS-
BUTTE/PINTLAR REGION-
300 PM MDT TUE AUG 31 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL IDAHO AND WESTERN
MONTANA

.DAY ONE... REST OF TODAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN... WEDNESDAY THROUGH MONDAY

A PACIFIC WEATHER SYSTEM WILL MOVE ACROSS WESTERN MONTANA AND IDAHO
ON WEDNESDAY. THIS SYSTEM WILL BRING GUSTY WINDS AND THUNDERSTORMS
INTO THE AREA BY WEDNESDAY AFTERNOON. COOLER TEMPERATURES WILL MOVE
INTO THE REGION ON THURSDAY.

.SPOTTER INFORMATION STATEMENT...

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