Tornado Warning 1, NWS Glasgow, MT

NORTHEAST MONTANA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GLASGOW MT
220 PM MDT WED JUN 7 2000

MDLS IN AGRMNT WITH TRENDS THRU FRI. AVN/ETA ON TARGET THRU 18Z.
STRONG UPR RIDGE OVR MT WILL SHARPEN WITH TIME AS TROF OFF PAC NW
CST DIGS SE BACKING FLOW TO SSW BY THURS. UPR LOW OFF CA CST WILL
KICK NE THRU MT LATE FRI. WEAK S/WS CONTINUE TO MOVE THROUGH UPR
RIDGE ACRS RGN THRU THURS. ONE SUCH FTR MOVING INTO SW MT ATTM SEEMS
TO BE HANDLED RELATIVELY BE MDLS. RESULTING PATTN COULD PRODUCE
STRONG/SEVERE CONVCTN ACRS CWA MAINLY THURS EVNG.

FOR TONIGHT...UPR RIDGE WARMING MID LEVELS KEEPING MOST OF ERN MT
CAPPED. CONVECTION WILL FIRE OVER WRN MT ASSOC WITH S/W IN DEVLOPING
SWLY FLOW ALOFT. DEVELOPING SFC LOW WILL ENHANCE MOIST LOW LEVEL
EASTERLY FLOW TONIGHT AND THURSDAY. MDLS INDICATE CONVECTION
PROPOGATING OUT ONTO PLAINS THIS EVENING MOVING ENE INTO NRN CWA AND
SASK OVERNIGHT. 06Z ETA INDICATES NICE CONVECTIVE FEEDBACK COUPLET
WITH THIS FTR. THE 18Z ETA ALSO INDICATES THIS COUPLET ALSO...BUT IT
IS WEAKER AND FURTHUR SE. CAPE/LI NOT TOO IMPRESSIVE...BUT ENOUGH
INSTABILITY...ESPECIALLY IN MID LEVELS OVERNIGHT...TO MAINTAIN AN
AREA OF CONVECTION DURING THE OVERNIGHT HOURS. THE POTENTIAL EXISTS
FOR HIGH WINDS AND HAIL...BUT MAINLY EVENING HOURS OVER NW PORTN OF
CWA.  WITH STG CAP...EXPECT NOTHING MORE THAN A FEW ISOLD CELLS S
AND SE.

FOR THURS...STG SFC LOW WILL CONT TO ENHANCE INCRSG ELY FLOW OVER
NEMONT.  TO THE SOUTH OF THIS FTR...DRY LOW LEVEL SWLYS WILL DVLP
EXTRM SW CWA. THIS WILL RESULT IN A PSEUDO WARM FRONT/DRY LINE
BOUNDARY...WITH SIGNIFICANT CAPE ALONG AND NORTH OF BOUNDARY.  THE
WIND PROFILE INDICATES STG SHEAR WITH VEERING LOW LEVEL WINDS. CONV
WILL BE TRIGGERED BY AN UPPER LVL S/W IN WEAKLY DIFLUENT SWLY FLOW
ALOFT. THUS THE INGREDIENTS ARE IN PLACE FOR A SIG CONVECTIVE EVENT
FOR NEMONT THURS EVNG. WOULD LIKE TO SEE A BIT STRG FORCING THOUGH.

BY FRI...MAIN SFC LOW SHIFTS E IN DAKOTAS WILL COOLER NELY LOW LEVEL
FLOW INTO NE CWA. INVERTED TROF WILL EXTEND SE NW ACRS REGION.  THIS
WILL PROVIDE A MODEST ENVIRONMENT FOR SCATTERED CONVECTION WITH SOME
POTENTIAL FOR STRONG CONVECTION EXTREME SE...ESPECIALLY IF PATTN
SLOWS. PETRESCU

.EXTENDED...MODELS START OFF THE EXTENDED PERIOD IN GOOD
AGREEMENT...THEN RAPIDLY DIVERGE BY MONDAY. ECMWF AND MRF PRESENT
SIGNIFICANTLY DIFFERENT SOLUTIONS FOR SURFACE AND THICKNESS PATTERNS
MONDAY. MRF SHOWS A COLD POOL ALOFT MOVING INTO NEMONT SUNDAY AND
MONDAY. COLD AIR ADVECTION AT H7 AND H5 SHOULD DESTABILIZE THE
ATMOSPHERE ENOUGH FOR SOME CONVECTIVE DEVELOPMENT. THE ECMWF SHOWS
SOME INSTABILITY OVER NEMONT AS WELL...SO WILL USE A MIX AND KEEP A
CHANCE OF SHOWERS IN THE FORECAST THROUGH THE PERIOD.   POHL

GGW TWWWW 061/090 059/073 050/077 051/075 050/072 912254/87222
GDV TWWWW 062/092 059/077 052/078 053/075 050/074 910144/87222