Severe Thunderstorm Warning 69, NWS Great Falls, MT

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
300 PM MDT SAT JUL 21 2001

ACCORDING TO MODELS LOOKS LIKE THERE WILL BE A CHANGE TO CURRENT
PATTERN OF SW FLOW ALOFT WITH SEVERE WEATHER EPISODES E OF THE
CONTINENTAL DIVIDE. FOR TONIGHT...AIRMASS IS UNSTABLE ONCE AGAIN
OVER AREA AND EVEN A LITTLE MORE UNSTABLE THAN EARLY FRI AFTERNOON.
MSAS DATA INDICATES A MOISTURE CONVERGENCE AREA FROM SW TO N
CENTRAL MT AT 19Z. APPEARS TO BE ENOUGH SHEAR FOR ORGANIZED STORMS
BUT NOT NECESSARILY SUPERCELLS. THE PROBLEM LIKE FRIDAY NIGHT IS
THAT MODELS DO NOT INDICATE ANY SIGNIFICANT SHORTWAVES AFFECTING
FORECAST AREA. STILL WITH QUITE AN UNSTABLE AIRMASS WILL GO WITH HIGH
SCATTERED TO LOW LIKELY POPS OVER MOST OF AREA. IN THE FAR NW
WILL GO WITH SLIGHT CHANCE POPS AS THAT AREA IS FORECAST TO BE
IN A DRIER AIRMASS. FOR SUNDAY...ETA AND AVN DIFFER SIGNIFICANTLY
WITH REMNANTS OF PAC NW UPPER TROUGH MOVING THROUGH THE AREA. PREFER
THE SLOWER AND WEAKER ETA AS THE AVN/MRF HAS HAD A TENDENCY TO BE TOO
STRONG AND FAST WITH SHORTWAVES MOVING TOWARDS AN UPPER RIDGE. WILL
GO WITH 20 AND 30 PCT POPS AS MOISTURE AND LIFT AHEAD OF FEATURE ARE
NOT VERY IMPRESSIVE. FORECAST SOUNDINGS STILL INDICATE SOME
INSTABILITY DURING THE AFTERNOON BUT IT IS QUITE A BIT LESS THAN THAT
OF TODAY. FOR MONDAY...BOTH ETA AND AVN FORECAST A STRONGLY
POSITIVELY TILTED SHORTWAVE FROM SW SASK THROUGH NW MT TO ERN OREGON.
AREA IS MAINLY UNDER WLY CONFLUENT FLOW ALOFT WITH LITTLE IN THE WAY
OF SHORTWAVE ACTIVITY. AIRMASS IS ALSO NOT ALL THAT MOIST. WAS
TEMPTED TO GO DRY BUT MODELS DO INDICATE SOME WEAK INSTABILITY SO
WILL GO WITH BROADBRUSH 20 PCT POPS. AVN QPF FOR MON LOOKS OVERDONE.
BLANK

.EXTENDED...
ON TUESDAY THE TROUGH CONTINUES OVER THE WESTERN US WITH MINOR SHORT
WAVES MOVING THROUGH THE MEAN SW FLOW. THE TROUGH LOOKS LIKE IT
WILL MOVE EAST ON WEDNESDAY WITH YET ANOTHER TROUGH MOVING THROUGH
SOUTHERN CANADA ON THU/FRI. THOUGH THE FLOW ALOFT BECOMES MORE
WESTERLY BY THURSDAY...THE SHORTWAVE MOVING THROUGH ON THU/FRI WILL
KEEP A CHANCE OF AFTERNOON/EVENING STORMS IN FORECAST THROUGH FRI.
WITH NORTHWEST FLOW BY SAT...SHOULD BE DRYING OUT THEN.

CCF NUMBERS
GTF BB 055/078 050/078 048 04522
CTB BB 050/075 047/075 045 04221
HLN BB 054/080 051/080 050 04522
BZN BB 051/080 047/080 047 04431
WEY BB 046/075 042/076 042 04432
DLN BB 049/077 043/077 044 04421
HVR EB 060/088 054/088 052 04532
LWT EB 056/077 048/077 046 04632=

LOCAL STORM REPORT
NATIONAL WEATHER SERVICE GREAT FALLS MT
610 PM MDT SAT JUL 21 2001

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

0315 PM    3 E ILIAD                 MT   1.50 INCH HAIL
07/21/01   CHOUTEAU

0330 PM    10 NE STANFORD            MT   0.75 INCH HAIL
07/21/01   JUDITH  BASIN

0420 PM    7 NE DENTON               MT   1 INCH HAIL
07/21/01   FERGUS

0445 PM    8 N STANFORD              MT   1 INCH HAIL
07/21/01   JUDITH  BASIN

0505 PM    SUFFOLK                   MT   1 INCH HAIL
07/21/01   FERGUS

BRUSDA
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