Severe Thunderstorm Warning 83, NWS Great Falls, MT

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
315 PM MDT MON JUL 10 2000

ON THE SYNOPTIC SCALE MODELS IN LINE WITH ONE ANOTHER IN FORECASTING SW
FLOW ALOFT LATE THIS AFTERNOON TO TRANSITION TO WEAK RIDGE ON TUE AND
THEN TO A LITTLE STRONGER RIDGE ON WED. MODELS NOT INDICATING ANY
SIGNIFICANT SHORTWAVES FOR THE FORECAST AREA OVER THE NEXT COUPLE OF
DAYS. FOR TONIGHT...EARLY AFTERNOON SURFACE DATA INDICATING AIRMASS
STILL QUITE UNSTABLE OVER ERN SECTIONS OF THE FORECAST AREA. ALSO WINDS
SHOW SOME CONFLUENCE OVER SRN ZONES AND FERGUS COUNTY. WILL GO WITH
SCATTERED POPS IN THESE AREAS. SPC HAS ISSUED SEVERE THUNDERSTORM WATCH
FOR FERGUS AND BLAINE COUNTIES. ALTHOUGH WOULD BE SURPRISED TO SEE
SEVERE THUNDERSTORMS OVER THESE COUNTIES DO NOT DOUBT THERE WILL BE
STORMS WITH SMALL HAIL AND POSSIBLY GUSTY WINDS. FOR TUE WITH WEAK
RIDGING AIRMASS IS FORECAST TO BECOME STABLE EXCEPT IN THE FAR S. IN
THAT AREA WEAK INSTABILITY IS FORECAST AND CAME UP WITH A CAPE OF AROUND
500 JOULES PER KG AT BZN. ETA FORECASTS SOME LOW LEVEL CONFLUENCE OVER
SAME AREA. ALTHOUGH DO NOT SEE ANY SHORTWAVES TO SPEAK OF WILL GO WITH A
SLIGHT CHANCE OF THUNDERSTORMS OVER THE FAR SRN ZONES. LOOKING AHEAD TO
WED...ETA FORECASTS AIRMASS TO BECOME MORE UNSTABLE IN THAT REGION WITH
ROUGHLY DOUBLE THE CAPE VALUES. INSTABILITY ALSO IS FORECAST TO SPREAD A
LITTLE FARTHER N. WILL ADD HLN ZONE TO THREAT OF THUNDERSTORMS. ALTHOUGH
ETA HAS GTF AND LWT ZONES WITH WEAK INSTABILITY BETTER CONFLUENCE IS
FARTHER S SO AT THIS TIME HAVE ELECTED NOT TO MENTION THUNDERSTORMS IN
GTF AND LWT ZONES. BLANK

EXTENDED...MODELS ARE IN CLOSE AGREEMENT BUILDING UPR RDG OVER INTER
MOUNTAIN RGN WED EVE AND THU...THEN SHIFTING RDG AXIS OVER ERN MT FRI
WITH BACKING FLOW BECOMING MORE PRONOUNCED OVER WRN SECTIONS.
DIFFERENCES OCCUR WITH MOVEMENT OF UPR LOW MOVING THE WRN CANADA.
CURRENT MRF DEEPENING UPR LOW ALONG BC COAST MORE THAN PREVIOUS MRF
RUN... WHILE UKMET AND ECMWF ARE MORE PROGRESSIVE WITH THIS FEATURE.
WILL KEEP WARM TEMPS AND ISOLATED AFTN THRU EVE CONVECTION THU AND
FRI...WITH BETTER CHC DEVELOPING ON SAT. EYSSAUTIER

GTF UU 052/085 052/090 058 041001
CTB UU 048/080 048/084 055 040000
HLN UB 050/086 052/091 058 041002
BZN UB 048/086 048/090 054 043112
WEY BB 040/080 038/084 042 044222
DLN UB 048/084 047/089 054 042112
HVR UU 054/085 054/090 060 042000
LWT UU 052/084 050/089 056 043001