Severe Thunderstorm Warning 18, NWS Missoula, MT

WESTERN MONTANA AND NORTH CENTRAL IDAHO FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
210 PM MDT THU JUN 19 2003

.SHORT TERM...AN ACTIVE EVENING SHAPING UP AS STALLED BOUNDARY
BETWEEN MODIFIED PACIFIC AIRMASS AND THERMAL TROF REMAINS FROM
SOUTHWEST IDAHO THROUGH MISSOULA TO CUTBANK MONTANA. THIS BOUNDARY
COMBINED WITH THE ENTRANCE REGION OF A 60KT JET AND INCREASED WIND
SPEED AND DIRECTIONAL SHEAR IN THE MID LEVELS IS SETTING OFF
SCATTERED SHOWERS AND THUNDERSTORMS OVER CENTRAL IDAHO AND SOUTHWEST
MONTANA THIS AFTERNOON. A SHORTWAVE MOVING UP IN THE SOUTHWEST FLOW
AHEAD OF THE TROUGH OFF THE WEST COAST WILL KEEP THESE STORMS GOING
INTO THE EVENING. THE MAIN THREAT ALONG AND JUST NORTH OF THIS
BOUNDARY IS LARGE HAIL DAMAGING WINDS AND HEAVY DOWNPOURS...SOUTH
OF THE BOUNDARY WINDS AND HAIL WILL BE THE MAIN THREATS. AS THE
LOWER ATMOSPHERE BEGINS TO MOISTEN IN THE SOUTHERN PORTION OF THE
AREA...HEAVY RAIN WILL BECOME MORE WIDESPREAD THROUGH THE REMAINDER
OF THE AFTERNOON AND EVENING. AS A RESULT A WATCH HAS BEEN ISSUED
FOR MUCH OF THE MISSOULA FORECAST AREA THROUGH 700 PM MST THIS
EVENING. THE SHOWERS AND THUNDERSTORMS WILL CONTINUE THROUGH THE
EVENING...THEN THE THUNDERSTORMS WILL TAPPER FROM THE NORTH AS THE
ATMOSPHERE STABILIZES. A SURFACE COLD FRONT AND UPPER LEVEL TROUGH
WILL MOVE INTO THE PACIFIC NORTHWEST OVERNIGHT KEEPING MOST OF
THE SHOWERS GOING OVERNIGHT. THE COLD FRONT IS EXPECTED TO BE
THROUGH THE FORECAST AREA BY EARLY SATURDAY MORNING...AND WILL
LOWER TEMPERATURES ANOTHER 10-15 DEGREES FROM TODAY. THE ATMOSPHERE
WILL BE QUITE A BIT MORE STABLE FRIDAY...BUT WITH COLD AIR MOVING
IN AT THE UPPER LEVELS...LAPSE RATES WILL BE IN THE 6.0-7.5 C/KM
RANGE SO ISOLATED AFTERNOON THUNDERSTORMS CAN NOT BE RULED OUT. MEAD

.SATURDAY AND SUNDAY...TROF PATTERN WILL CONTINUE THROUGH THE
WEEKEND AND BRING COOL UNSTABLE AIR. TEMPERATURES WILL BE
UNSEASONABLY COOL THIS WEEKEND. THIS COOL UNSTABLE AIR WILL TRANSLATE
INTO MAINLY RAIN SHOWERS WITH SOME SNOW SHOWERS POSSIBLE AT THE
HIGHER ELEVATIONS.
.LONG TERM...CLOSED UPPER LEVEL LOW PRESSURE SYSTEM DIGS INTO THE
NORTHERN ROCKIES MONDAY AND TUESDAY.  THIS LOW WILL BRING COOL
UNSTABLE AIR AND CHANCE OF RAIN AND SNOW TO THE HIGHEST MOUNTAIN
PEAKS. TEMPERATURES WILL ONLY RISE INTO THE MID 60S FOR HIGHS.
WEDNESDAY AND THURSDAY THE LOW WILL MOVE EAST AND LEAVE BEHIND A
CONTINUED COOL NORTHWESTERLY FLOW...THOUGH TEMPERATURES WILL RISE
SLIGHTLY. THIS COOL AIR WILL CONTINUE TO BRING A CHANCE OF SHOWERS.
RPN

.MSO...SEVERE THUNDERSTORM WATCH IN EFFECT UNTIL 700 PM IDZ006>010
MTZ003>007-043...

...7-DAY SPOT TEMPS AND POPS...
LIB EEB 049/063 044/063 045/066 27544332
     EEBB 048/065 045/065 047/068 049/072 4024443222
FCA WEB 050/063 044/061 040/063 27455332
     EEEB 043/061 041/063 042/067 045/071 4024443322
POL WEB 052/064 048/062 047/064 27565333
     EEEB 045/063 043/064 044/067 046/071 4024443322
MSO WEB 057/067 045/064 043/066 27766233
     EEEB 045/064 044/066 045/070 048/074 4034443322
HMM WEB 052/064 044/064 042/065 27765333
     EEEB 043/064 043/066 044/069 047/073 4034443422
BTM WEB 049/067 040/062 038/063 27766333
     EEEE 039/060 038/062 039/065 042/069 4034433422
ORO EEB 051/069 049/068 049/068 27433221
     BEBB 051/069 051/069 052/074 055/078 4024443222
GRV EEB 047/062 044/065 042/062 27555222
     BEBB 044/063 044/065 046/069 048/073 4024443222
SMN WEB 053/069 044/067 042/066 27775222
     EEEB 043/065 041/067 042/072 044/076 4033443322

MTZ001>007-043-IDZ005>010-201200-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE MISSOULA MT
108 PM MDT THU JUN 19 2003

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

.DAY ONE... TODAY

A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR PORTIONS OF
WESTERN MONTANA AND NORTH CENTRAL IDAHO. SCATTERED THUNDERSTORMS ARE
EXPECTED ACROSS THE AREA THIS AFTERNOON THROUGH EARLY THIS EVENING.
SOME STORMS MAY BECOME SEVERE PRODUCING LARGE HAIL AND DAMAGING
WINDS.

.DAYS TWO THROUGH SEVEN... FRIDAY THROUGH WEDNESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME. PROGRESSIVELY COOLER
WEATHER SYSTEMS WILL MOVE ACROSS THE REGION THROUGH THE WEEKEND AND
EARLY NEXT WEEK. TEMPERATURES WILL BE 10 TO 15 DEGREES BELOW NORMAL
BY SATURDAY. MOUNTAIN SNOW LEVELS MAY LOWER TO ABOUT 7000 FEET...
NEAR THE SAME ELEVATION AS LOGAN PASS IN WEST GLACIER PARK...DURING
THE PERIOD.

.SPOTTER INFORMATION STATEMENT...

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