Severe Thunderstorm Warning 35, NWS Great Falls, MT

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
242 PM MDT FRI JUL 13 2001

SYNOPSIS...THUNDERSTORMS EXPECTED ACROSS CWA THIS EVENING WITH SEVERE
THUNDERSTORM WATCHES IN EFFECT UNTIL 700 PM MDT. SCATTERED
THUNDERSTORMS WILL DEVELOP AGAIN SATURDAY AFTERNOON. LITTLE CHANGE
EXPECTED IN TEMPERATURES.

DISCUSSION...PERSISTENT HIGH PRESSURE RIDGE CENTERED OVER THE
SOUTHERN CONUS WITH A LOW PRESSURE TROUGH OFF THE WEST COAST.
RESULTANT SOUTHWEST FLOW OF MOIST...UNSTABLE AIR INTO CWA CREATING
THUNDERSTORMS AGAIN THIS AFTERNOON WITH POSSIBILITY OF SEVERE
THUNDERSTORMS. DYNAMICS IN PLACE...LARGE AREA OF LOWER LEVEL
CONVERGENCE COUPLED WITH UPPER LEVEL DIVERGENCE CENTERED OVER CWA...
DISTURBANCE PUSHING THROUGH...JET MAX PASSING OVER...NEGATIVE LI/S
BLANKETING CWA WITH AREAS BETWEEN -4 AND -6...CAPES 1000 J/KG AND
HIGHER...AND TIME SECTIONS SHOWING STRONG OMEGA AROUND 00Z.
FORECASTED SOUNDINGS ADVERTISE PRECIPITABLE WATER INCREASING FROM
AROUND THREE/QUARTERS OF AN INCH THIS MORNING TO OVER AN INCH THROUGH
THE EVENING. SOME THUNDERSTORMS EXPECTED TO CREATE STRONG WIND...HAIL
AND HEAVY RAIN...THUS TWO SEVERE THUNDERSTORM WATCHES HAVE BEEN
ISSUED FOR THE CWA. ACTIVITY FOR CWA SHOULD DIMINISH AFTER SUNSET AS
DISTURBANCES PUSH INTO EASTERN MT AND DYNAMICS WEAKEN. LITTLE CHANGE
IN PATTERN SATURDAY...WITH SOUTHWEST FLOW CONTINUING. DYNAMICS NOT
QUITE AS IMPRESSIVE HOWEVER...AND WILL PUT POPS IN SCATTERED
CATEGORY. MOS GUIDANCE WANTS TO COOL TEMPERATURES SEVERAL DEGREES
SATURDAY. THOUGH FLOW SLIGHTLY MORE WESTERLY DO NOT EXPECT MUCH
CHANGE AND WILL KEEP FORECASTS WITHIN A DEGREE OR TWO OF TODAY.

.EXTENDED...
ALL OF THE EXTENDED MODELS SUGGEST LITTLE CHANGE TO THE PATTERN
MONDAY THROUGH NEXT FRIDAY.  AN UPPER LOW REMAINS PARKED OVER THE
PAC NORTHWEST AND SOUTHERN BC THRU WED THEN BEGINS SLOWLY FILLING
AND LIFTING NORTHEAST.  HOWEVER...FLOW CONTINUES TO BE OUT OF THE
SOUTHWEST TOWARDS THE END OF THE WEEK.  THEREFORE... EXPECT
SCATTERED THUNDERSTORMS THRU PERIOD WITH NEAR NORMAL TEMPS. MIELKE

CCF NUMBERS
GTF TB 054 084 053 083 054 036334
CTB TB 051 083 050 083 051 035223
HLN zTT 056 085 055 086 055 036345
BZN TT 050 085 051 086 051 036345
WEY TT 053 078 046 080 048 036345
DLN TT 051 084 050 085 050 034344
HVR TB 058 088 059 087 058 036222
LWT TB 054 084 054 085 053 036344

MTZ008-011>015-045-047-049>055-131600-

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREAT FALLS MT
1100 AM MDT FRI JUL 13 2001

...STRONG THUNDERSTORMS POSSIBLE TODAY AND SATURDAY...

AN UPPER LEVEL DISTURBANCE WILL MOVE ACROSS SOUTHWEST MONTANA THIS
AFTERNOON...AND THEN ACROSS CENTRAL MONTANA THIS EVENING. THIS
DISTURBANCE WILL ALLOW FOR THUNDERSTORMS TO DEVELOP BY MID AFTERNOON
FROM NORTHWEST MONTANA EAST OF THE CONTINENTAL DIVIDE INTO
SOUTHWEST MONTANA. THESE THUNDERSTORMS WILL THEN MOVE NORTHEAST...INTO
CENTRAL AND NORTH CENTRAL MONTANA BY THIS EVENING. ANOTHER UPPER
LEVEL DISTURBANCE IS FORECASTED TO TAKE NEARLY THE SAME TRACK ON
SATURDAY.

SOME OF THE STORMS THIS AFTERNOON AND EVENING AND AGAIN SATURDAY
AFTERNOON AND EVENING MAY BECOME SEVERE. THESE SEVERE THUNDERSTORMS
WILL BE CAPABLE OF PRODUCING HAIL TO GOLF-BALL SIZE...WINDS IN
EXCESS OF 60 MPH...AND RAINFALL OF OVER AN INCH IN LESS THAN AN
HOUR.

THEREFORE...IF ANYONE HAS ANY TYPE OF OUTDOOR ACTIVITY PLANNED OVER
THE NEXT TWO DAYS...YOU SHOULD BE PREPARED FOR STRONG THUNDERSTORMS.
LISTEN TO NOAA WEATHER RADIO...OR YOUR FAVORITE SOURCE FOR WEATHER
INFORMATION...FOR ANY WATCHES OR WARNINGS...THAT MAY BE ISSUED.

BLANK