Severe Thunderstorm Warning 87, NWS Great Falls, MT

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
300 PM MDT THU JUL 13 2000

AVN/ETA/NGM LOOK OK WITH VORTICITY CENTER THAT THEY FORECAST OVER OR
NEAR SW ID AT 18Z HOWEVER ETA EASILY HAS THE BEST FORECAST POSITION. ETA
TRACKS THIS VORTICITY CENTER OVER SW MT LATE THIS AFTERNOON AND INTO
CENTRAL MT LATER THIS EVENING. SURFACE DATA INDICATING MOST UNSTABLE
AIRMASS IS OVER CENTRAL MT. ALREADY BEGINNING TO SEE CONVECTION FIRE UP
OVER SW AND CENTRAL MT AND EXPECT THESE AREAS TO BE THE MAIN FOCUS OF
CONVECTION INTO THIS EVENING. ONCE AGAIN WILL BE MENTIONING GUSTY WINDS
WITH THE THUNDERSTORMS. AIRMASS RELATIVELY DRY SO AM NOT EXPECTING MUCH
THREAT FOR HAIL. MOISTURE STREAM FROM CA WILL BRING A THREAT OF SHOWERS
OR THUNDERSTORMS TO THE NW ZONES THOUGH THE AIRMASS IS NOT AS UNSTABLE
AS OVER CENTRAL MT. FOR FRI...ALTHOUGH MODELS DIFFER ON DETAILS MODELS
DO BRING A WEAKER SHORTWAVE THROUGH THE AREA DURING THE MORNING AND INTO
THE ERN PLAINS DURING THE AFTERNOON. ALTHOUGH SHORTWAVE MAY BE EAST OF
AREA DURING PRIME HEATING TIME AIRMASS IS STILL FORECAST TO BE UNSTABLE.
WILL GO WITH A SLIGHT CHANCE OF SHOWERS/THUNDERSTORMS. LOOKING AHEAD TO
SAT...STRONGLY POSITIVELY TILTED SHORTWAVE IS FORECAST TO MOVE ACROSS
SRN ALTA AND SRN SASK WITH CONFLUENT WLY FLOW ALOFT OVER MUCH OF
FORECAST AREA. THIS LEADS TO A MORE STABLE AIRMASS OVER THE PLAINS ALONG
WITH DOWNSLOPE WINDS. ON THE FENCE ABOUT WHETHER TO MENTION ANY THREAT
FOR PRECIPITATION OVER THE SRN ZONES. MODELS HAVE AIRMASS LESS STABLE IN
THAT AREA BUT NOT REALLY UNSTABLE. MODELS ALSO HAVE SOME VERY WEAK LIFT
AND AIRMASS IS PRETTY DRY. AFTER COORD WITH BIL WILL MENTION A SLIGHT
CHANCE OF SHOWERS OVER THE FAR SRN ZONES. FIRE WEATHERWISE ONE THING TO
WATCH FOR ON SAT IS GUSTY WINDS OVER THE PLAINS. HUMIDITIES MAY ALSO
LOWER TO 15 TO 20%. BLANK

EXTENDED...MRF AND EUROPEAN MODELS IN FAIRLY GOOD AGREEMENT WITH 3 TO 5
DAY FORECAST. ALSO AGREE WITH HPC DISCUSSION REGARDING THE PERSISTENCE
OF THE UPPER RIDGE AND CONTINUATION OF HOT AND DRY CONDITIONS ACROSS
CWA. FLOW ALOFT WILL REMAIN GENERALLY ZONAL WITH WEAK IMPULSES MOVING
THROUGH WITH LITTLE IMPACT FOR THE CWA.

CCF NUMBERS
GTF BN 060/093 055/083 051 042221
CTB NN 056/085 050/078 046 041221
HLN BB 060/094 058/085 054 042221
BZN BB 056/094 053/088 050 043221
WEY BB 042/086 038/082 036 042222
DLN BB 055/091 050/087 048 042221
HVR BN 060/095 058/083 053 042221
LWT BB 060/093 055/082 050 043331

LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
700 PM MDT THU JUL 13 2000

TIME(MDT)  .....EVENT  LOCATION..... ST   ...EVENT/REMARKS...........
           .....COUNTY LOCATION.....

0635 PM    6 N BIG SANDY             MT   60 TO 65 MPH TSTM GUST
07/13/00   CHOUTEAU                       WINDS ESTIMATED

0645 PM    6 N BIG SANDY             MT   80 TO 85 MPH TSTM GUST
07/13/00   CHOUTEAU                       WINDS ESTIMATED

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