Severe Thunderstorm Warning 112, NWS Great Falls, MT

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
300 PM MDT TUE SEP 5 2000

SLOW BUT STEADY MOVEMENT OF TROF TOWARDS THE EAST. A SECOND TROF OVER
BRITISH COLUMBIA MOVES ACROSS THE HI LINE AND JOINS WITH NORTHERN BRANCH
OF TROF...LEAVING THE SOUTHERN END OF THE TROF BEHIND. TROF SHOULD BE
ACROSS THE ROCKIES IN THE NORTH BY 12Z WEDNESDAY...OVER EXTREME ERN MT
BY EVENING.  MID-HI LVL CLOUD COVER ASSOCIATED WITH THE AXIS...AND QUITE
A BIT OF LOW LVL MOISTURE ACROSS THE STATE CAUSING SOME LOWER LEVEL
CLOUDS. SEVERAL WEAK VORT LOBES MOVING THRU SWLY FLOW AHEAD OF
TROF...HOWEVER MOSTLY SHEAR VORT AND VERY LITTLE VERTICAL VELOCITY IS
CREATED. SO COMBINATION OF MOISTURE AND INSTABILITY AGAIN APPEARS TO BE
SOURCE OF ACTION...AND NOTICED THAT BUTTE IS REPORTING TCU ALL QUADS.
ONE ITEM OF CONCERN IS WHETHER THE SHORT WAVE IN BRITISH COLUMBIA WILL
CONTINUE TO MOVE QUICKLY TO THE EAST OR GET CAUGHT UP WITH THE SLOWER
MOVING TROF OVER THE ROCKIES. AT THE MOMENT ONLY LOOKING AT A PERIOD OF
ENHANCED DYNAMICS ALONG THE NORTHERN ZONES. ALSO...A SECONDARY COLD
FRONT IS ASSOCIATED WITH THE FASTER MOVING SHORT WAVE. THIS MAY DRIFT
FURTHER SOUTH THAN THE CURRENT PROGS DEPICT...ALTHO THE LATEST MESO DOES
BRING THE 552 THICKNESS SOUTH OF THE CANADIAN BORDER. RIDGING OVER THE
PAC NW BY WEDNESDAY AFTN...AND EXCEPT FOR SOME AREAS IN THE SOUTH WILL
BE IN A DRIER AND COOLER AIRMASS.  WIND NEEDS TO BE MENTIONED AS THE
TROF MOVES EAST AND WINDS GO WESTERLY...NOT ANYTHING OUT OF THE ORDINARY
THOUGH. ZELZER

EXTENDED DISCUSSION...IT SEEMS LIKE EVERY VERSION OF THE MRF HAS A
DIFFERENT SHORT WAVE PATTERN...ALTHOUGH THE LONG WAVE FEATURES ARE
FAIRLY CONSISTENT. THE MAIN MESSAGE ON THE PROGS IS THAT THE WESTERLIES
WILL BE BREAKING INTO MONTANA DURING THE 3 TO 5 DAY PERIOD. SHORT WAVE
DETAILS BETWEEN MRF...72HOUR AVN...72HOUR UKMET AND ECMWF ARE ALL
DIFFERENT. ALL BUT THE MRF HINT AT MORE DIGGING OF MAIN LONG WAVE
TROUGH...ESPECIALLY ECMWF. WILL FORECAST MOSTLY DRY AND WINDY WITH
SHOWERS IN THE NORTHERN MOUNTAINS IN THE 3 TO 5 DAY FORECAST. OARD

CCF NUMBERS
GTF EB 050/070 045/076 048 133111
CTB BB 0i49/065 045/072 044 132111
HLN EB 050/070 045/076 042 134111
BZN EB 040/075 036/077 038 134111
WEY EB 032/066 028/068 030 134111
DLN EB 038/072 036/074 038 134111
HVR EB 050/070 046/076 046 133111
LWT EB 050/065 044/070 044 133111