Severe Thunderstorm Warning 45, NWS Great Falls, MT

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
300 PM MDT SUN JUL 15 2001

SYNOPSIS...THUNDERSTORMS EXPECTED ACROSS MUCH OF CWA THIS AFTERNOON
AND EVENING AS DISTURBANCES PUSH NORTHEAST. POTENTIAL EXISTS FOR SOME
SEVERE THUNDERSTORMS AND A WATCH IS IN EFFECT FOR JUDITH BASIN AND
FERGUS COUNTIES. COOLER TEMPERATURES AND SCATTERED AFTERNOON
THUNDERSTORMS EXPECTED MONDAY AS A LOW PRESSURE TROUGH BEGINS WORKING
INLAND. COOLER TEMPERATURES PERSIST INTO TUESDAY.

DISCUSSION...ACTIVITY PICKING UP ACROSS CWA WITH ONE LINE OF
THUNDERSTORMS MOVING INTO THE CENTRAL CWA...ANOTHER AREA APPROACHING
THE SOUTHWEST CWA...AND SOME ISOLATED STORMS OVER THE NORTHEAST CWA.
ALL ARE ASSOCIATED WITH A SHORT WAVE THAT IS PUSHING THROUGH COUPLED
SOME MODERATELY HIGH INSTABILITY AND A MOIST AIR MASS. THE 18Z
MESOETA SHOWS A LINE OF ENERGY EXTENDING FROM THE NORTHERN ROCKIES TO
SOUTHEAST MT AT 00Z WITH A TRAIN OF DISTURBANCES WORKING UP INTO
CENTRAL AND NORTHERN CWA THIS EVENING. BEST STEERING WINDS FOUND
ACROSS SOUTH...STORMS ACROSS NORTHERN CWA MAY BE SLOW MOVING AND
CREATE AREAS OF HEAVY RAIN. TRAIN OF DISTURBANCES OVER SOUTHWEST AND
CENTRAL CWA COULD ALSO RESULT IN SOME SIGNIFICANT ACCUMULATED
RAINFALL. EASTERN CWA WITH HIGHEST INSTABILITIES...MOISTURE AND WIND
SHEAR HAS A CHANCE OF SEVERE THUNDERSTORMS. TROUGH THEN PUSHES IN
ALONG WA/CANADA BORDER MONDAY. SEVERAL EMBEDDED DISTURBANCE WITH THIS
AS WELL...HOWEVER THEY SEEM TO BE STAYING CLOSER TO THE LOW...
SWEEPING OVER AREAS WEST OF THE DIVIDE AND JUST BRUSHING THE
NORTHWEST CWA FOR ISOLATED TO SCATTERED SHOWERS. HAVE DROPPED TEMPS
MONDAY AND TUESDAY A FEW DEGREES AS TROUGH BRINGS IN COOLER AIR.

EXTENDED...MRF HAS UPPER TROUGH OVER THE PACIFIC NW ROTATING INTO
ALBERTA ON DAY3. ECMWF MODEL NOT AS STRONG AS THE MRF WITH
THE PORTION OF THE UPPER TROUGH MOVING OVER MT. BY DAY 5...MRF
HAS WEAK UPPER RIDGE BUILDING...WHILE SHORT WAVE TROF SCOOTS
ACROSS SOUTHERN CANADA. MRF/ECMWF HAS WEAK TROUGH HANGING BACK TO
THE WEST. DAY6 AND DAY7 SHOWS UPPER RIDGE BUILDING BACK OVER MT...
WHILE KEEPING WEAK UPPER LOW OFF THE PACIFIC NORTHWEST COAST. IN
SHORT...WED LOOKS COOL AND UNSETTLED WITH A RETURN TO WARM
TEMPERATURES BY FRIDAY. WILLIAMSON DC

CCF NUMBERS
GTF EE 051 079 049 077 049 034231
CTB EE 049 077 047 075 047 036211
HLN TE 054 079 051 077 052 032432
BZN TE 049 082 047 079 049 033432
WEY TE 043 078 045 075 046 032432
DLN TE 048 078 045 076 046 032433
HVR EE 055 085 053 081 050 037231
LWT TE 052 081 050 076 048 037342