Severe Thunderstorm Warning 77, NWS Great Falls, MT

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
300 PM MDT SUN JUL 9 2000

LOOKS LIKE A TRANSITION TO A LESS ACTIVE CONVECTIVE PATTERN BY TUESDAY.
UPPER TROUGH OVER THE PAC NW SUNDAY AFTERNOON IS FORECAST TO SWING INTO
SRN ALTA AND SW SASK MONDAY AFTERNOON. ON TUE WEAKLY ANTICYCLONIC FLOW
ALOFT IS FORECAST OVER THE AREA. FOR TONIGHT SPC HAS ISSUED SEVERE
THUNDERSTORM WATCH FOR HVR AND LWT ZONES. 19Z SURFACE DATA SHOWS
MOISTURE CONVERGENCE AND LIS DOWN TO MINUS 5 FROM SW MT INTO CENTRAL MT.
NW AREA ALSO HAS MOISTURE CONVERGENCE BUT AIRMASS IS LESS UNSTABLE
THERE.  HAVING SOME TROUBLE PICKING OUT VORTICITY CENTER MODELS FORECAST
S OF MSO AT 18Z. WATER VAPOR IMAGERY GIVING HINTS OF A SHORTWAVE
ANYWHERE FROM FAR SW MT TO SW ID. IN ANY CASE SHOULD HAVE SOME LIFT FROM
DYNAMICS TO HELP DEVELOP STRONG THUNDERSTORMS INTO EARLY THIS EVENING.
MODELS HAVE SHORTWAVES AFFECTING THE AREA LATER TONIGHT INTO MON. THERE
ARE SOME DIFFERENCES ON TIMING. WILL LEAVE IN A THREAT OF
SHOWERS/THUNDERSTORMS LATER TONIGHT AS AIRMASS IS FORECAST TO CONTINUE
TO BE UNSTABLE AND THERE WILL BE LOW LEVEL CONFLUENCE. ON MON AIRMASS IS
FORECAST NOT TO BE AS UNSTABLE AND LOW LEVEL CONFLUENCE SHIFTS E THROUGH
THE FORECAST AREA. WILL LEAVE IN A THREAT OF THUNDERSTORMS BUT GENERALLY
GO WITH A TAD LOWER POPS. FOR TUE AIRMASS IS FORECAST TO BE STABLE AND
MODELS ARE NOT INDICATING ANY SIGNIFICANT SHORTWAVES. EXCEPTION IS THE
SW WHERE ETA HAS BZN ZONE WEAKLY UNSTABLE AND AVN HAS BOTH BZN AND DLN
ZONES WEAKLY UNSTABLE. WAS THINKING OF GOING DRY BUT AFTER COORDINATION
CALL WITH BIL WILL MENTION SOME CONVECTION OVER BZN ZONE. BLANK

EXTENDED DISCUSSION...NEW LONG RANGE PROGS SHOW FAIRLY STRONG UPPER
RIDGE OVER CENTRAL AND EASTERN MONTANA WEDNESDAY...MOVING INTO THE
DAKOTAS ON THURSDAY. HOT TEMPERATURES EXPECTED. SOUTHWEST FLOW ALOFT
WILL CAUSE AREA TO BE VULNERABLE FOR ISOLATED AFTERNOON AND EVENING
THUNDERSTORMS. UPPER TROUGH MOVING INTO THE PACIFIC NORTHWEST AND
BRITISH COLUMBIA FRIDAY FOR INCREASED CHANCE OF DIURNAL THUNDERSTORMS IN
AREA. OARD

CCF NUMBERS
GTF BU 048/080 050/083 055 043210
CTB BU 047/075 048/078 052 042200
HLN BU 050/082 050/085 055 043200
BZN BU 048/082 046/085 050 043321
WEY BU 040/075 038/078 040 043322
DLN BU 046/080 045/083 048 043210
HVR BU 052/081 052/083 057 044310
LWT BU 048/080 048/082 052 044310