Severe Thunderstorm Warning 81, NWS Great Falls, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MONTANA
330 PM MDT TUE AUG 17 2004

.DISCUSSION...

TONIGHT THROUGH THURSDAY...AN UPPER LOW SPINNING OVER NORTHERN UTAH
AND SOUTHEAST IDAHO THIS AFTERNOON WILL CONTINUE TO ROTATE
DISTURBANCES UP INTO SOUTHWEST MONTANA THROUGH MOST OF TONIGHT.
WITH A MOIST AND UNSTABLE AIRMASS IN PLACE...THUNDERSTORMS WILL BE
NUMEROUS ACROSS SOUTHWEST MONTANA...WITH SOME HAVING HEAVY
RAINFALL. STORMS HAVE NOT SHOWN ANY SUSTAINED DEVELOPMENT WITH LIGHT
WINDS ALOFT CAUSING THE STORMS TO JUST PULSE AND COLLAPSE UPON
THEMSELVES. AM EXPECTING ANY PERIODS OF HEAVY RAINFALL TO BE SHORT
IN DURATION AS WELL. THEREFORE...AM NOT GOING TO ISSUE A FLASH FLOOD
WATCH AT THIS TIME...BUT SITUATION WILL NEED TO BE MONITORED. UPPER
LOW WILL SLOWLY MOVE SOUTHEAST OVERNIGHT INTO WEDNESDAY...ALLOWING
STORMS TO DECREASE FROM THE NORTH ACROSS SOUTHWEST MONTANA. FARTHER
NORTH...A COLD FRONT WITH ASSOCIATED DISTURBANCES WILL MOVE SOUTH
OUT OF CANADA TONIGHT...ALLOWING NORTHERLY UPSLOPE WINDS TO DEVELOP.
THIS WILL BRING AT LEAST ISOLATED SHOWERS AND THUNDERSTORMS TO THE
NORTHERN TFX ZONES THROUGHOUT THE NIGHT...WITH A BETTER CHANCE OF
PRECIPITATION ALONG THE ROCKY MOUNTAIN FRONT DUE TO THE UPSLOPE
CONDITIONS. THE RESULTING NORTHWEST FLOW ALOFT WITH EMBEDDED
DISTURBANCES WILL PERSIST OVER THE TFX CWA WEDNESDAY THROUGH
THURSDAY...KEEPING AT LEAST A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS OVER THE CWA. THERE WILL BE A BETTER CHANCE OVER THE
WESTERN MOUNTAINS AND IN THE FAVORED UPSLOPE AREAS. ANOTHER COLD
FRONT WILL PUSH SOUTH OUT OF CANADA THURSDAY AFTERNOON TO HELP
CONTINUE THE UPSLOPE CONDITIONS. HIGHS WEDNESDAY AND THURSDAY WILL BE
IN THE 70S TO LOWER 80S...WHILE LOWS WILL COOL FROM THE MID 40S AND
50S TONIGHT TO THE 40S TO LOWER 50S WEDNESDAY NIGHT.  COULSTON

THURSDAY NIGHT THROUGH TUESDAY...MODELS START OFF IN ACCEPTABLE
AGREEMENT BUT SIGNIFICANT DIFFERENCES EMERGE BY EARLY NEXT WEEK WHICH
WILL HAVE AN IMPACT ON THE SENSIBLE WEATHER. THE ECMWF BRINGS A
SIGNIFICANT TROUGH INTO THE PACIFIC NORTHWEST WHILE THE GFSLR HAS
RIDGING ACROSS THE AREA. GIVEN THE STRONG UPPER RIDGING ACROSS ALASKA
WOULD FAVOR A SOLUTION MORE IN LINE WITH THE ECMWF. PLAN TO MAKE SOME
CHANGES TO THE GRIDS TO ADD SOME POPS AND LOWER TEMPERATURES EARLY
NEXT WEEK.

THURSDAY NIGHT AND FRIDAY...GOOD AGREEMENT THAT AN UPPER RIDGE WILL
STRETCH FROM THE PACIFIC NORTHWEST NORTH INTO ALASKA WITH A CLOSED
UPPER HIGH. CLOSED LOWS WILL BE FOUND IN HUDSON BAY AND OFF THE
BRITISH COLUMBIA COAST. NORTHWEST FLOW ALOFT EXPECTED ACROSS CENTRAL
MONTANA. WOULD EXPECT THAT A FEW OROGRAPHIC SHOWERS MAY LINGER
THURSDAY EVENING...WITH THE BEST CHANCE OF MEASURABLE PRECIPITATION
ALONG THE DIVIDE AND ACROSS OUR SOUTHERN ZONES. POSSIBLE THAT THERE
WILL BE A FEW SHOWERS ACROSS OUR SOUTHERN ZONES AS MODELS IN
REASONABLE AGREEMENT THAT A WAVE WILL PASS ACROSS OUR SOUTHERN ZONES
DURING THE MORNING. A FEW ADDITIONAL SHOWERS AND STORMS MAY AGAIN
FIRE UP FRIDAY AFTERNOON...BUT AS A SURFACE RIDGE SETTLES INTO THE
NORTHERN PLAINS IT SHOULD BE DRY ACROSS THE PLAINS.

FRIDAY NIGHT AND SATURDAY...THE NEW 12Z GFS COMING IN MORE IN LINE
WITH THE 00Z/17TH ECMWF WITH THE IDEA THAT AN UPPER TROUGH BEGINS TO
PUSH INTO THE PACIFIC NORTHWEST. THE GFSLR MAINTAINED MORE OR LESS
ZONAL FLOW INTO THE PACIFIC NORTHWEST AT THIS TIME WHICH DOES NOT
LOOK REASONABLE GIVEN THE RIDGING TO THE NORTH. EXPECT THAT THERE
WILL BE SOME DOWNSTREAM RIDGING ACROSS THE NORTHERN ROCKIES AHEAD OF
THE UPPER TROUGH WHICH SHOULD MAKE FOR DRY WEATHER FRIDAY NIGHT INTO
EARLY SATURDAY. MAY SEE A FEW SHOWERS POP UP DURING THE AFTERNOON
ALONG THE DIVIDE.

SUNDAY...THE UPPER TROUGH CONTINUES TO PUSH EAST AND ACROSS THE
NORTHERN ROCKIES WHICH WILL PUSH A COLD FRONT ACROSS THE CWA. IT
LOOKS LIKE THERE SHOULD BE ENOUGH MOISTURE AND LIFT TO GENERATE A
FEW SHOWERS AND STORMS. IT ALSO APPEARS THAT THERE SHOULD BE A PUSH
OF COOLER AIR WORKING INTO THE AREA IN THE WAKE OF THE COLD FRONT.
ADDED IN SOME LOW POPS DURING THIS TIME PERIOD AND ALSO COOLED
MAXIMA BY A FEW DEGREES.

EARLY NEXT WEEK...CONFIDENCE BEGINS TO DROP OFF A BIT...BUT NOW THAT
THE LATEST RUN OF THE GFS80 IS MORE IN LINE WITH THE ECMWF AND
ENSEMBLES WOULD SUSPECT THAT AN UPPER TROUGH REMAINS IN PLACE
ACROSS THE WESTERN CONUS. EXPECT THAT THERE WILL AT LEAST THE CHANCE
OF A FEW SHOWERS ALONG WITH COOLER THAN AVERAGE TEMPERATURES. MADE
CHANGES TO THE DATABASE TO ADD IN SOME POPS ACROSS MOST OF THE CWA
AND ALSO LOWERED MAXIMA JUST A BIT MONDAY AND TUESDAY. CB

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF BB 056/079 052/081 048 10322
    BBBBB 078/048 079/051 077/049 078/048 080 33000022222
CTB BB 050/077 050/078 047 10322
    BBBBB 076/048 076/049 071/047 072/046 074 33002222222
HLN BB 057/078 055/082 053 10222
    BBBBB 083/052 083/055 079/053 080/052 082 22212222222
BZN BB 057/078 050/082 046 10322
    BBBBB 081/047 083/045 079/045 081/044 083 22220022222
WEY TB 047/073 041/074 040 10553
    BBBBB 077/039 075/041 071/041 075/040 077 33220021222
DLN BB 057/077 050/079 048 10422
    BBBBB 080/048 080/048 076/046 078/045 080 22212222222
HVR BB 051/078 049/083 046 10222
    BBBBB 078/050 079/051 075/051 077/050 079 22000021122
LWT BB 054/075 047/077 044 10222
    BBBBB 074/045 078/045 077/045 078/044 080 22110022222

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREAT FALLS MT
505 AM MDT TUE AUG 17 2004

MTZ008>015-044>055-181105-
BEAVERHEAD-NORTHERN ROCKY MOUNTAIN FRONT-EASTERN
GLACIER-HILL-CASCADE-CHOUTEAU-CENTRAL AND SOUTHERN LEWIS AND
CLARK-MADISON-TOOLE-LIBERTY-EASTERN PONDERA-BLAINE-SOUTHERN ROCKY
MOUNTAIN FRONT-EASTERN TETON-JUDITH
BASIN-FERGUS-JEFFERSON-BROADWATER-MEAGHER-GALLATIN-
505 AM MDT TUE AUG 17 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL AND SOUTHWEST
MONTANA

.DAY ONE...TODAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

NO WATCHES, WARNINGS, OR ADVISORIES CURRENTLY IN EFFECT

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

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