Severe Thunderstorm Warning 46, NWS Glasgow, MT

NORTHEAST MONTANA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE GLASGOW MT
233 PM MDT WED JUL 3 2002

.SHORT TERM...BLENDED AVN AND ETA FAMILY FOR THETA E RIDGE POSITION
AND GRADIENT...LOW LEVEL JET INTRUSION...PRECIP AND QPF...CAPE...AND
SHORTWAVE POSITION.  SHORTWAVE INITIALIZED OVER IDAHO THIS MORNING
IS STEADILY MOVING NORTHEAST INTO MONTANA.  SATELLITE AND RADAR
IMAGERY CONFIRM MOTION AND PROGRESS OF SHORTWAVE IS CONSISTENT WITH
THE MODELS.  LOW LEVEL JET IS PUSHING MOISTURE FROM THE GULF INTO
THE REGION FROM THE SOUTH AND EAST AS THE THETA E RIDGE PROGRESSES
TOWARD THE AREA.  THETA E RIDGE GRADIENT AND HIGHER CAPE (1000+
J/KG) WILL MEET THE SHORTWAVE ABOUT VALLEY COUNTY AND NORTH OF THE
MISSOURI RIVER THIS EVENING AT 04Z FOR ENHANCED DYNAMICS OVERNIGHT.

SPECIAL UPPER AIR LAUNCH FOR 18Z SHOWS INCREASE PRECIPITABLE WATER
BUT CAP REMAINS FOR NOW.  THIS IS CONSISTENT WITH THE FORECAST
SOUNDINGS OF THE CURRENT MODELS RUNS.  EXPECT THE CAP TO BREAK ABOUT
SUNSET (04Z) WHEN THE LOW LEVEL MOISTURE AND JET COME INTO PROXIMITY
OF THE TROUGH/SHORTWAVE FROM THE WEST.  SOUNDING SHOWS THE GREATEST
POTENTIAL FOR ANY SEVERE THUNDERSTORMS SHOULD BE AS WIND EVENTS
RATHER THAN HEAVY RAIN OR LARGE HAIL.

ETA FAMILY CARRIES THE QPF CORE NORTH OF A LINE FROM PETROLEUM
COUNTY TO SHERIDAN COUNTY WITH MOST ACTIVITY OCCURRING BETWEEN 4-12Z
OVERNIGHT.  AT THE SAME TIME THE ETA FAMILY SHOWS A CAPE CORE (2000+
J/KG) OVER NW SOUTH DAKOTA WHICH MAY INFLUENCE THE SOUTHEASTERN
ZONES OF THE CWA.  MEANWHILE THE AVN CARRIES THE QPF CORE OVER THE
CENTRAL PORTION OF THE CWA WITH PRECIP COVERING ALL ZONES.  FORECAST
WILL HAVE LIKELY POPS NORTH AND WEST WITH CHANCE TO LIKELY POPS
SOUTHEAST ZONES FOR TONIGHT...CENTERED AFTER MIDNIGHT FOR THE
GREATEST ACTIVITY.

PATTERN APPEARS TO HAVE A 24 HOUR PERIODICITY FOR THE RETURN OF
THUNDERSTORMS.  MODELS ARE HINTING THAT TOMORROW HAS A POTENTIAL FOR
SEVERE CONDITIONS SINCE IT WILL NOT BE NECESSARY TO ADVECT THE
DYNAMIC ELEMENTS INTO THE REGION.  THIS IS ALSO REFLECTED IN THE
METEOGRAMS AND TIME HEIGHTS.  EXPECT SUFFICIENT SURFACE HEATING AND
INSTABILITY DEVELOPMENT TOMORROW AFTER THE STORMS DECREASE IN THE
MORNING TO SMALL RUMBLES AND SCATTERED TO ISOLATED SHOWERS.
THUNDERSTORMS WILL AGAIN FIRE IN THE LATE AFTERNOON THURSDAY AND
PERSIST PAST MIDNIGHT AS THE THETA E RIDGE RESURGES INTO THE CWA
UNDER THE INFLUENCE OF GRADIENT DEVELOPING AHEAD OF BUILDING WESTERN
RIDGE.

.LONG TERM...BUILDING UPPER LEVEL RIDGE REFLECTED AT SURFACE WILL
DRY THE REGION.  STRONG THERMAL TROUGHS OVER THE SOUTHWEST MAY ACT
AS MOISTURE FUNNELS TO DIRECT THE SW MONSOON INTO THE WESTERN
STATES...POSSIBLY REACHING MONTANA LATE IN THE EXTENDED PERIOD.
WILL CONTINUE THE PRESENT FORECAST FOR NOW.  MCNULTY

KGGW TTB 062/085 063/080 060/087 81636311
     BBBB 059/087 060/088 059/086 059/089 8111222222
KGDV TTB 066/088 066/085 062/086 81435311
     BBBB 061/087 062/090 060/088 057/086 8111222222

.GGW...NONE.