Severe Thunderstorm Warning 9, NWS Billings, MT

SOUTH CENTRAL AND SOUTHEAST MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BILLINGS MT
235 AM MDT SAT JUN 1 2002

.SHORT TERM...VALID FOR TDY...SUN...MON...
A SMALL BATCH OF CONVECTION CURRENTLY ROLLING ACROSS THE NORTHERN TIER
OF THE SOUTHEAST ZONES. SHORTWAVE RESPONSIBLE FOR THIS WILL EXIT THE
STATE THIS MORNING. COUNTING ON STORMS PUSHING OUT OF THE FORECAST AREA
BY ISSUANCE TIME. NEXT UPSTREAM WAVE IGNITING THUNDERSTORMS OVER IDAHO
THIS HOUR. WAVE GETS TRANSPORTED INTO THE WESTERN AREAS OF SOUTH CENTRAL
MONTANA THIS MORNING. BOTH AVN AND ETA CONSISTENT ON THIS. CONVECTION
SHOULD START EARLY OVER THE SOUTHWEST AND CONTINUE OVER THE PLAINS THIS
AFTERNOON AND TONIGHT. SURFACE LOW PUSHING ACROSS NORTHERN WYOMING
CREATING AN EASTERLY LOW LEVEL FLOW WHICH WAS KEEPING HIGHEST CAPES
SOUTH OF THE FORECAST AREA. THIS LOW LEVEL FLOW WAS ALSO SERVING TO
PRODUCE STRONG SHEAR OVER THE ENTIRE AREA THIS AFTERNOON AND EVENING.
STORMS THAT DO GET GOING WILL HAVE A FAVORABLE ENVIRONMENT TO ROTATE AND
BECOME SEVERE. CONCERNED THAT SUCH HIGH PRECIPITABLE WATER AMOUNTS WITH
TROPICAL MOISTURE COULD LIMIT THE HAIL POTENTIAL WITH FREEZING LEVELS
NEAR 14K FEET THIS AFTERNOON. WITH STRONG SHEAR AND POWERFUL UPPER JET
DIVERGENCE...FEEL THE MENTION OF SEVERE WARRANTED. SECOND SHORTWAVE
PUNCHES INTO SOUTHEAST MONTANA THIS EVENING. WILL MENTION HEAVY RAIN IN
THE ZONES. COULD HAVE TWO ROUNDS OF STRONG STORMS. LIKELY POPS LOOK
GOOD. BROAD SOUTHWEST FLOW SETS UP FOR TONIGHT WITH VORTICITY ADVECTION
700MB CONVERGENCE TO KEEP POPS GOING.

MODELS DIFFER ON SUNDAY ON THE STRENGTH OF TROUGH PUSHING THROUGH THE
FORECAST AREA. THE AVN IS MUCH STRONGER AND ACTUALLY CUTS A LOW OFF
OVER CENTRAL MONTANA SUNDAY NIGHT. THE ETA IS WEAKER AND MUCH MORE
PROGRESSIVE IN SHIFTING THE TROUGH THROUGH. STILL FEEL THAT SCATTERED
POPS LOOK GOOD AS COLD AIR ALOFT TO COMBINE WITH A MOIST ATMOSPHERE AND
CONTINUING 700MB CONVERGENCE...ALONG WITH A MID LEVEL TROUGH WORKING
THROUGH. THE AVN KEEPS THE FORECAST AREA IN A NORTHWEST FLOW MONDAY AS
THE DEEPER TROUGH IS FORECAST TO SLOWLY KICK OUT. MEANWHILE...THE ETA
KEEPS A SOUTHWEST FLOW WITH WEAK WAVES SLIDING THROUGH. WILL KEEP THE
IDEA OF SCATTERED POPS IN THE EAST AND DRY THINGS OUT FROM THE WEST.
MONDAY SHOULD BE THE COOLEST DAY WITH THICKNESSES FALLING TO AROUND
555DM. HUMPHREY

.LONG TERM...VALID FOR TUE...WED...THU...FRI...
THE AVN KEEPS A NORTHWEST FLOW FOR TUESDAY BEHIND THE WAVE. THE AVN IS
DIFFERENT THAN THE EXTENDED ETA IN THIS SOLUTION. THE ETA KEEPS A
SOUTHWEST FLOW AND BRINGS A SPLITTING TROUGH THE FORECAST AREA ON
TUESDAY. EITHER MODEL TAKEN...TUESDAY LOOKS COOLER THAN CURRENTLY
FORECAST. WILL ADJUST TEMPERATURES DOWN ON TUESDAY AND TEMPER THE WARMUP
INTO WEDNESDAY. POSITIVELY TILTED RIDGE SLIDES ACROSS THE AREA WEDNESDAY
AND THIS IS WHERE THE MAJORITY OF THE WARM UP WILL OCCUR. THE REST OF
THE EXTENDED FORECAST LOOKS IN GOOD SHAPE. HUMPHREY

    TDY SUN     MON     TUE     WED     THU     FRI
-------------------------------------------------------
BIL 079 054/065 048/058 044/068 050/071 052/079 053/072
    4/T 84/W    32/W    02/C    20/E    02/C    22/C
LVM 077 050/065 044/058 040/067 046/068 050/076 051/069
    6/T 84/W    32/W    02/C    20/E    02/C    22/C
HDN 081 054/066 046/058 041/069 049/072 052/080 053/073
    4/T 84/W    32/W    02/C    20/E    02/C    22/C
MLS 083 055/066 048/056 045/068 047/073 053/080 054/073
    3/T 84/W    33/W    03/W    33/T    32/C    22/C
4BQ 083 054/066 047/057 043/068 048/072 054/081 055/074
    3/T 84/W    33/W    03/W    30/E    02/C    22/C
BHK 082 053/064 046/056 041/067 047/071 052/078 053/071
    3/T 84/W    33/W    03/W    33/T    32/C    22/C
SHR 083 052/068 045/058 040/069 046/071 048/078 049/071
    4/T 84/W    32/W    02/C    20/E    02/C    22/C

.BYZ...
MT...FLOOD WATCH UNTIL NOON MDT SATURDAY FOR PARK COUNTY.
WY...NONE.