Severe Thunderstorm Warning 63, NWS Billings, MT

SOUTH CENTRAL AND SOUTHEAST MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
235 PM MDT SAT JUN 29 2002

.SHORT TERM...VALID FOR SUN...MON...TUE...
COLD FRONT WILL MAKE FOR ACTIVE EVENING TONIGHT ACROSS CWA...WITH
THUNDERSTORMS ALREADY FIRING IN WESTERN ZONES. AFTER FRONTAL PASSAGE
THROUGH CWA TONIGHT UPPER FLOW WILL BECOME ZONAL...RESULTING IN QUIET
WEATHER THROUGH THE REST OF THE SHORT TERM.

TONIGHT...MAIN CONCERN TONIGHT WILL BE THUNDERSTORMS AND PERIOD OF
STRONG WINDS BEHIND THE FRONT. THUNDERSTORMS ALREADY BEGINNING TO FIRE
IN WEST WHERE APPROACHING SHORTWAVE TROUGH AND FRONT IS BEGINNING TO
ERODE THE CAP. FURTHER EAST VERY WARM 700MB TEMPS STILL IN PLACE. THIS
WILL LIMIT CONVECTIVE ACTIVITY IN THIS AREA...BUT LIFT JUST AHEAD OF
THE FRONT SHOULD BE ENOUGH TO FIRE STORMS AS CAP ERODES. WILL CONTINUE
WITH SEVERE WORDING THIS EVENING AS CONDITIONS MOST FAVORABLE FOR
STRONG WINDS WITH STORMS...AS LARGE DEW POINT DEPRESSIONS AND HIGH WET
BULB ZERO HEIGHTS WILL LIMIT HAIL POTENTIAL. STORMS WILL CLEAR FROM
WEST TO EAST TONIGHT AND SHOULD BE OUT OF EASTERN ZONES BY AROUND 06Z...
AND WILL WORD ACCORDINGLY. BEHIND FRONT WINDS WILL SWITCH TO THE
NORTHWEST AND REACH WINDY CRITERIA OVER CENTRAL AND EAST. WINDS WILL
DIMINISH ACROSS CENTRAL BY MIDNIGHT BUT SHOULD CONTINUE IN EAST MOST
OF THE NIGHT AS COLD AIR ADVECTION/SUBSIDENCE BEHIND FRONT PUSH STRONG
850MB WINDS TOWARD SURFACE.

SUNDAY THROUGH MONDAY...MUCH MORE QUIET PATTERN SETTING UP FOR SUNDAY
AND MONDAY AS UPPER LEVEL ZONAL FLOW SETS UP BEHIND TROUGH. SOME
SHORTWAVE ENERGY PUSHES THROUGH LATE SUNDAY AFTERNOON AND EVENING...AND
ETA DEVELOPS SURFACE LOW WITH THIS FEATURE. SOME INSTABILITY ALSO
EVIDENT IN THIS AREA WITH LOWERING LIS AND SOME CAPE. WILL MENTION
SLIGHT CHANCE OF STORMS FAR WEST AND NORTHWEST FOR THIS PERIOD...EVEN
THOUGH WE ARE NOT INCLUDED IN SPC GENERAL OUTLOOK. TEMPS SUNDAY WILL
MAINLY STAY BELOW THE 90 DEGREE MARK AS SOME COOLING TAKES PLACE...
ESPECIALLY EAST. MONDAY LOOKS TO BE COOLEST DAY OF FORECAST WITH
CONTINUED ZONAL FLOW.

FLOW REMAINS DRY AND ZONAL ON TUESDAY AS THE STRONGEST RIDGE
AMPLIFICATION STAYS OVER SOUTHERN CANADA. A WEAK WAVE DOES ENTER
SOUTHWEST MONTANA TUESDAY AFTERNOON...BUT THE ATMOSPHERE IS FORECAST TO
BE TO DRY TO WARRANT PLACING IN POPS. HIGHS ON TUESDAY SHOULD BE NEAR
THE LEVELS OF MONDAY...SO WILL RAISE GOING HIGHS. JZ/HUMPHREY

.LONG TERM...VALID FOR WED...THU...FRI...SAT...
RIDGE BUILDS UP OVER THE CENTRAL PLAINS AGAIN AND ALLOWS A DEEP UPPER
LOW TO MOVE INTO THE PACIFIC NORTHWEST COAST. THIS WILL SET UP SOUTHWEST
FLOW OVER THE FORECAST AREA. THIS PATTERN IS FAVORABLE FOR CONVECTION.
ATMOSPHERE APPEARS A LITTLE DRY AT FIRST...BUT MOISTENS UP IN TIME. THE
EXTENDED AVN PULLS THE UPPER TROUGH NORTHEAST ON SATURDAY. THIS IS QUITE
A BIT FASTER THAN THE ECMWF. WILL KEEP THE MENTION OF THUNDERSTORMS
WEDNESDAY THROUGH SATURDAY. A COLD FRONT IS PROGGED TO SLIDE THROUGH THE
AREA BY FRIDAY. THIS WILL COOL THINGS DOWN SOME FRIDAY INTO SATURDAY.
HUMPHREY

    SUN     MON     TUE     WED     THU     FRI     SAT
-----------------------------------------------------------
BIL 056/087 059/084 057/084 057/087 059/087 056/082 054/082
    40/B    00/B    00/B    03/T    33/T    33/T    33/T
LVM 053/087 057/083 054/083 054/086 056/086 053/080 051/080
    22/T    20/B    00/B    03/T    33/T    33/T    33/T
HDN 055/089 057/082 055/082 055/088 057/090 054/085 052/083
    40/U    00/B    00/B    03/T    33/T    33/T    33/T
MLS 062/088 062/085 059/085 059/088 061/090 059/085 056/083
    60/U    00/B    00/B    03/T    33/T    33/T    33/T
4BQ 058/089 060/085 058/085 058/088 060/090 059/085 056/083
    40/U    00/B    00/B    03/T    33/T    33/T    33/T
BHK 057/085 057/083 056/083 056/086 058/088 058/083 055/081
    60/U    00/B    00/B    03/T    33/T    33/T    33/T
SHR 056/087 055/084 053/084 053/087 055/089 053/085 051/082
    40/U    00/B    00/B    03/T    33/T    33/T    33/T

.BYZ...
MT...SEVERE THUNDERSTORM WATCH UNTIL 8PM MDT FOR ALL BUT PARK COUNTY.
WY...NONE.