Severe Thunderstorm Warning 25, NWS Great Falls, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
600 PM MDT TUE JUN 13 2006

UPDATED AVIATION SECTION ONLY

.DISCUSSION...

TONIGHT THROUGH THURSDAY...UPPER TROF OVER THE PACIFIC NORTHWEST
CONTINUES TO PUSH SLOWLY EAST. STRONG SOUTHERLY FLOW ALOFT OUT
AHEAD OF THE TROF BRINGING MOISTURE TO THE AREA. THE AIRMASS IS
VERY UNSTABLE AND CONVECTIVE ACTIVITY EXPECTED TO DEVELOP LATE
THIS AFTERNOON AND INTO EVENING. AREA OF GREATEST CONCERN
CONTINUES TO BE WEST AND NORTH OF GREAT FALLS AND ALONG THE ROCKY
MOUNTAIN FRONT. 19Z SOUNDING INDICATES THE PRESENCE OF A STRONG
CAP AROUND 750MB OVER GREAT FALLS. WILL TAKE QUITE A BIT OF ENERGY
TO BREAK THIS CAP. ANYTHING THAT GETS GOING LIKELY TO BE ISOLATED
IN NATURE. HEAVIEST PRECIPITATION WILL OCCUR OVERNIGHT AND WEDNESDAY
AS THE MAIN TROF DYNAMICS MOVE CLOSER TO THE AREA. TROF LIFTS OUT
THURSDAY. SURFACE GRADIENT TIGHTENS THURSDAY WITH GUSTY SURFACE
WINDS DEVELOPING. SHOULD BE ENOUGH DOWNSLOPE TO INHIBIT MOST
PRECIPITATION BUT WILL KEEP MENTION WITH LOW POPS. TEMPERATURES
WILL BE NEAR SEASONAL AVERAGES. EMANUEL

THURSDAY NIGHT THROUGH TUESDAY...MODELS IN GENERAL AGREEMENT
THROUGH FRIDAY NIGHT...BUT DIFFER SLIGHTLY (NOT ENOUGH TO MAKE A
SIGNIFICANT DIFFERENCE IN THE FORECAST) SATURDAY THROUGH TUESDAY.
AN UPPER LEVEL TROUGH WILL LIFT NORTHEAST OUT OF THE AREA THURSDAY
NIGHT AND FRIDAY. WEAK DISTURBANCES AND MOISTURE WILL MOVE OVER
NORTH CENTRAL AND SOUTHWEST MONTANA DURING THIS TIME TO KEEP A
CHANCE OF SHOWERS AND THUNDERSTORMS OVER THE MOUNTAINS AND A
SLIGHT CHANCE OVER THE PLAINS AND IN THE VALLEYS. BREEZY WESTERLY
SURFACE WINDS WILL ALSO ACCOMPANY THE SYSTEM PASSAGE. WEAK UPPER
LEVEL RIDGING WILL THEN KEEP FRIDAY NIGHT DRY. FROM SATURDAY
FORWARD...THE GFS KEEPS A SLIGHTLY MORE UNSETTLED WESTERLY FLOW
ALOFT OVER THE AREA THAN THE ECMWF. HAVE DECIDED TO ERR ON THE
SIDE OF CAUTION AND LEAVE THE FORECAST AS IS...CONTINUING THE
TREND OF A CHANCE OF SHOWERS AND THUNDERSTORMS OVER THE MOUNTAINS
AND A SLIGHT CHANCE OVER THE PLAINS AND VALLEYS. BREEZY WESTERLY
WINDS WILL CONTINUE THROUGH SUNDAY...BUT THEN DECREASE AFTER THAT.
TEMPERATURES WILL COOL TO SLIGHTLY BELOW NORMAL WITH THE PASSAGE
OF THE SYSTEM EARLY IN THE PERIOD...BUT THEY WILL WARM BACK UP TO
NEAR TO ABOVE NORMAL BY TUESDAY. COULSTON

&&

.AVIATION...
UPDATED 0000Z.
SHOWERS AND THUNDERSTORMS ARE DEVELOPING WEST OF THE DIVIDE THIS
EVENING...A FEW OF THESE STORMS WILL AFFECT AN AREA BETWEEN KGTF AND
KCTB THIS EVENING. MORE ISOLATED THUNDERSTORM ACTIVITY IS POSSIBLE
SOUTH OF KHLN. EXPECT THE PRECIPITATION TO BECOME MORE WIDESPREAD ON
WEDNESDAY MORNING AS THE UPPER LEVEL TROF MOVES THROUGH. CONDITIONS
SHOULD REMAIN ABOVE IFR CONDITIONS...BUT IF THE PRECIP EVENT FOR
WEDNESDAY BECOMES MORE STRATIFORM...THERE IS A CHANCE CEILINGS COULD
LOWER TO NEAR IFR CONDITIONS. BRUSDA

&&

.HYDROLOGY...
WITH SHOWERS AND THUNDERSTORMS EXPECTED OVER THE NEXT FEW DAYS...A
FEW RIVERS AND STREAMS MAY RISE BACK UP TO NEAR BANKFUL. SOME RIVERS
THAT WILL BE WATCHED CLOSELY INCLUDE THE SUN RIVER AS WELL AS THE
DEARBORN AND GALLATIN RIVERS.

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  55  73  51  72 /  40  60  30  20
CTB  53  68  48  67 /  60  50  30  20
HLN  57  71  52  73 /  50  60  40  30
BZN  52  72  45  72 /  50  50  40  20
WEY  42  66  37  63 /  40  40  30  20
DLN  50  70  44  68 /  50  50  30  20
HVR  58  77  54  73 /  30  50  40  20
LWT  56  74  48  72 /  30  40  40  20

&&

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

&&

SHORT TERM...EMANUEL
LONG TERM...COULSTON
AVIATION...THOMSON

WEATHER.GOV/GREATFALLS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREAT FALLS MT
517 AM MDT TUE JUN 13 2006

MTZ011>013-045-047-050-051-054-141130-
HILL-CASCADE-CHOUTEAU-LIBERTY-BLAINE-JUDITH BASIN-FERGUS-MEAGHER-
517 AM MDT TUE JUN 13 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
MONTANA...NORTH CENTRAL MONTANA AND SOUTHWEST MONTANA.

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON
AND THIS EVENING. THE SLIGHT RISK WILL BE MAINLY WEST OF THIS AREA.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS WEDNESDAY AFTERNOON
AND EVENING.

.SPOTTER INFORMATION STATEMENT...

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

MTZ008>010-014-015-044-046-048-049-052-053-055-141130-
BEAVERHEAD-NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-
CENTRAL AND SOUTHERN LEWIS AND CLARK-MADISON-TOOLE-
EASTERN PONDERA-SOUTHERN ROCKY MOUNTAIN FRONT-EASTERN TETON-
JEFFERSON-BROADWATER-GALLATIN-
517 AM MDT TUE JUN 13 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
MONTANA AND SOUTHWEST MONTANA.

.DAY ONE...TODAY AND TONIGHT

THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON
AND THIS EVENING. THIS SLIGHT RISK WILL BE MAINLY OVER
GLACIER...PONDERA...TETON AND TOOLE COUNTIES FROM 400 PM MDT TO
900 PM MDT.

.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.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
717 PM MDT TUE JUN 13 2006

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0715 PM     HAIL             BROWNING                48.56N 113.01W
06/13/2006  E0.50 INCH       GLACIER            MT   TRAINED SPOTTER

&&

BRUSDA