Severe Thunderstorm Warning 9, NWS Great Falls, MT

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
215 PM MDT SUN MAY 25 2003

.SHORT TERM...SW FLOW ALOFT WILL DOMINATE TONIGHT THROUGH MON NIGHT
AS A SERIES OF SHORTWAVES MOVES THROUGH THE AREA. TUE FLOW ALOFT WILL
VEER TO NWLY ON TUE AS AN UPPER RIDGE BUILDS OVER WRN MT AND ID. THIS
RIDGE THEN MOVES OVER THE FORECAST AREA TUE NIGHT AND SHIFTS E OF
AREA ON WED WITH AREA RETURNING TO SW FLOW ALOFT. MAIN FOCUS DURING
THE PERIOD IS TONIGHT. AIRMASS IS BECOMING MODERATELY UNSTABLE AND
LOOKS LIKE SHORTWAVE WILL MOVE THROUGH THE AREA LATER THIS AFTERNOON
AND EARLY EVENING. TSTMS ALREADY FIRING OVER SW MT. PER MORNING
DISCUSSION WILL ADD A THREAT OF STRONGER STORMS INTO THIS EVENING.
EVEN AS EARLY AS LATE THIS EVENING ETA/GFS DIFFER ON SHORTWAVE
ACTIVITY. GFS BRINGS A WAVE THROUGH AFTER MIDNIGHT WHILE ETA HOLDS
OFF UNTIL MEMORIAL DAY MORNING. DUE TO MODEL DIFFERENCES HAVE BACKED
OFF ON INHERITED LIKELY POPS FOR CERTAIN AREAS FOR TONIGHT. MON/MON
EVENING STILL LOOKING UNSETTLED WITH AN UNSTABLE AIRMASS AND MORE
SHORTWAVE ACTIVITY. WILL CONTINUE WITH MAINLY SCATTERED POPS. AIRMASS
DOES NOT LOOK AS UNSTABLE MEMORIAL DAY AFTERNOON AS SUN AFTERNOON SO
AM NOT EXPECTING ANY SEVERE TSTMS. AIRMASS SHOULD BE STABLE AND DRIER
ON TUE SO WILL CONTINUE WITH ZERO POPS. WED GFS HAS AN UNSTABLE
AIRMASS DURING THE AFTERNOON BUT APPEARS TRIGGER TEMPERATURES ARE
HIGHER THAN FORECASTED HIGH TEMPERATURES. A LITTLE RELUCTANT TO
INTRODUCE ISOLATED TSTMS AT THIS POINT BUT LATER SHIFTS WILL WANT TO
TAKE A CLOSER LOOK. BLANK

EXTENDED...WEDNESDAY NIGHT THROUGH SUNDAY...COLD FRONT TO BE MOVING
ACROSS THE FORECAST AREA.WEDNESDAY NIGHT. WILL ADD A SLIGHT CHANCE
OF SHOWERS AND THUNDERSTORMS TO THE FORECAST FOR THIS. AN UPPER
LEVEL LOW WILL MOVE OVER SOUTHERN ALBERTA THURSDAY CREATING A STRONG
WESTERLY FLOW OVER THE STATE. WILL DROP THE MENTION OF PRECIPITATION
AND ADD WINDY FOR THE NORTHERN ZONES THURSDAY AFTERNOON WITH THE
DOWNSLOPE CONDITIONS. A DIRTY WESTERLY FLOW WILL THEN BE THE MAIN
FEATURE THROUGH THE WEEKEND. EXPECTING ONLY A FEW MOUNTAIN SHOWERS
AND TEMPERATURES NEAR NORMAL TO SLIGHTLY ABOVE WITH THIS PATTERN.
MEIER

.CCF NUMBERS
GTF EB 054/077 050/078 047 04443
    BBBBB 087/048 071/045 071/045 075/045 071 00120000000
CTB EB 051/073 047/074 046 04332
    BNBBB 084/049 066/044 064/044 068/045 068 00120000000
HLN TB 056/078 050/080 048 04653
    BBBBB 090/051 073/046 071/046 075/046 074 00120022222
BZN EB 048/078 046/080 044 04433
    BBBBB 086/049 075/045 074/045 078/044 070 00120022222
WEY EB 040/072 038/072 036 04333
    UBBBB 080/039 072/038 065/038 069/038 063 00120022222
DLN EB 050/076 045/079 045 04422
    UBBBB 087/047 074/045 074/045 078/043 069 00120022222
HVR EB 056/080 052/080 048 04433
    BBBBB 086/053 072/049 074/049 078/049 074 00120000000
LWT EB 052/078 049/077 046 04534
    BBBBB 084/052 070/045 072/045 076/046 067 00120000000

.TFX...SMALL STREAM AND CREEK FLOOD ADVISORY FOR MOST OF NORTH
       CENTRAL AND SOUTHWEST MONTANA THROUGH MEMORIAL DAY.

MTZ008>015-044>055-260010-
HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREAT FALLS MT
1000 AM MDT SUN MAY 25 2003

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL AND SOUTHWEST
MONTANA

.DAY ONE...TODAY

...A SMALL STREAM AND CREEK FLOOD ADVISORY REMAINS IN EFFECT THROUGH
MEMORIAL DAY FOR MUCH OF NORTH CENTRAL AND SOUTHWEST MONTANA...
FOR THE FOLLOWING ZONES: BEAVERHEAD -NORTHERN ROCKY MOUNTAIN FRONT
-EASTERN GLACIER-CASCADE-SOUTHERN LEWIS AND CLARK-MADISON-LIBERTY
-SOUTHERN ROCKY MOUNTAIN FRONT-EASTERN TETON-JUDITH
BASIN-FERGUS-MEAGHER -BROADWATER-JEFFERSON-GALLATIN

A SLIGHT RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EARLY
EVENING FOR THE FOLLOWING ZONES: BEAVERHEAD -CASCADE-SOUTHERN LEWIS
AND CLARK-MADISON-LIBERTY -EASTERN TETON-JUDITH BASIN-FERGUS-MEAGHER
-BROADWATER-JEFFERSON-GALLATIN-HILL-BLAINE-CHOUTEAU

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

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.

MTZ008-011>015-045-047-050>055-252145-

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE GREAT FALLS MT
945 AM MDT SUN MAY 25 2003

...STRONG THUNDERSTORMS POSSIBLE THIS AFTERNOON AND EVENING...

A MOIST AND UNSTABLE AIRMASS IN COMBINATION WITH A WEAK WEATHER
DISTURBANCE ALOFT WILL CAUSE SCATTERED THUNDERSTORMS THIS AFTERNOON.
SOME OF THESE THUNDERSTORMS WILL CONTAIN SMALL HAIL AND GUSTY WINDS.
THERE IS A RISK THAT A FEW OF THEM WILL BE SEVERE WITH WIND GUSTS TO
OF 60 MPH AND HAIL NEAR AN INCH IN DIAMETER. BRIEF HEAVY RAIN OF A
HALF INCH IN LESS THAN A HALF HOUR IS ALSO POSSIBLE.

THUNDERSTORMS ARE EXPECTED TO DEVELOP OVER SOUTHWEST MONTANA AS WELL
AS ALONG THE EAST SLOPES OF THE ROCKY MOUNTAINS BY MID-AFTERNOON
THEN SPREAD TO CENTRAL AND NORTHCENTRAL MONTANA BY LATE AFTERNOON.
THE THREAT OF STRONG THUNDERSTORMS WILL END BY MID-EVENING.

PERSONS INVOLVED IN OUTDOOR ACTIVITIES SHOULD KEEP A CLOSE WATCH ON
THE SKY THIS AFTERNOON AND HAVE READY ACCESS TO WEATHER FORECASTS
SHOULD ANY SEVERE WEATHER WATCHES OR WARNINGS BE ISSUED.