Severe Thunderstorm Warning 81, NWS Great Falls, MT

SOUTHWEST AND NORTH CENTRAL MONTANA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
230 AM MDT MON JUL 10 2000

.SHORT TERM...ALL MODELS ARE SIMILAR IN THE SHORT TERM WITH RESPECT TO
POSITION OF MAJOR PLAYERS. THE AVN IS A BIT STRONGER WITH REGARDS TO THE
SHORTWAVE ROTATING AROUND THE BASE OF THE BC LOW AT THE MOMENT. MODELS
DIVERGE SOMEWHAT AFTER 24 HOURS BUT NOT A GREAT DEAL. SOLUTION WILL BE
BASED ON A BLEND OF THE AVN/ETA WITH A SLIGHT LEAN TOWARDS THE AVN DUE
TO ITS PAST PERFORMANCE AND THE FACT IT IS A LITTLE BIT STRONGER THAN
THE OTHER MODELS.

LARGE SCALE PATTERN CHANGE IS IN STORE AS A MUCH LESS ACTIVE PATTERN
TAKES SHAPE. THE CLOSED LOW OVER BC IS SHUNTED NORTHEASTWARD THRU THE
PERIOD AND THE ENTIRE WEST COAST TROF WEAKENS. AFOREMENTIONED TROF MOVES
ACROSS SOUTHERN ALTA AND THEN SWINGS NORTHEASTWARD INTO SASK BY TUESDAY
MORNING...SLIGHTLY SLOWER THAN PREVIOUS RUNS.

SLOW PROGRESSION OF THE TROF STILL LEADS ME TO BELIEVE SOME CONVECTION
IS POSSIBLE TODAY ESPECIALLY ACROSS THE HIGH LINE IN THE VICINITY OF THE
LOW. ANOTHER AREA OF CONCERN WILL BE OVER THE CENTRAL ZONES AS STABILITY
INDICES ARE STILL QUITE HIGH...REACHING -2 TO -4 BY AFTERNOON. SEVERAL
WEAK SHORTWAVES WILL BE THE TRIGGERS FOR SAID CONVECTION BUT NO SEVERE
WEATHER IS EXPECTED. ONE SHORTWAVE SEEN ON WATER VAPOR IMAGERY IS
GENERATING SOME ACTIVITY FROM BLAINE COUNTY SOUTHEAST TO BROADWATER
COUNTY. TIMING OF THESE FEATURES WILL BE TRICKY AT BEST. FEEL THE BEST
OPTION WILL BE TO MENTION A CHANCE OF MORNING ACTIVITY FOLLOWED BY
ANOTHER CHANCE DURING THE LATE AFTERNOON. REGARDLESS ONLY MINIMAL POPS
WILL BE MENTIONED AS BEST DYNAMICS WILL BE OVER FAR EASTERN MONTANA.

UPPER FLOW BECOMING MORE WESTERLY DURING THE NIGHT WITH UPPER RIDGE
EXPANDING WESTWARD ON TUESDAY. RIDGE CRESTS OVER THE REGION LATE ON
TUESDAY WITH DRY...HOT AND STABLE CONDITIONS EXPECTED. I LIKE THE
THINKING OF THE PREVIOUS SHIFTS REGRADING THE SLIGHT CHANCE OF PRECIP
FOR THE BOZEMAN ZONE. ETA MODEL SOUNDINGS SHOWING THAT AREA IS SLIGHTLY
UNSTABLE DURING THE AFTERNOON WHILE THE AVN DOES NOT. MINIMAL POPS STILL
SEEM WARRANTED. AS FAR AS TEMPS ARE CONCERNED...THE MOSS AND FAN
GUIDANCE ARE BASICALLY SIMILAR THROUGH 48 HOURS AND ARE GENERALLY
ACCEPTED WITH THE USUAL TWEEKING.

.EXTENDED...RIDGE IS THE PREDOMINATE WEATHER MAKER THROUGH THE PERIOD
ALTHOUGH THE AXIS DOES SHIFT EASTWARD WITH TIME. WARM AND DRY CONDITIONS
ARE EXPECTED THROUGH DAYS 3 AND 4 AS 700MB TEMPS WARM CONSIDERABLY.
SHOWERS AND THUNDERSTORMS ARE POSSIBLE ON DAY 5 AS ANOTHER TROF STARTS
TO SWING THROUGH BC INCREASING THE SW FLOW OVER THE AREA ONCE AGAIN.
CURRENT EXTENDED LOOKS GOOD WITH ONLY MINIMAL CHANGES.

GOUDSWARD

CCF NUMBERS
GTF BU 082/052 084/055 091 052000
CTB BU 077/048 080/050 087 053100
HLN BU 084/050 086/055 092 052000
BZN BU 083/048 086/050 090 052020
WEY BU 077/040 080/044 086 052020
DLN BU 082/048 084/050 088 052010
HVR BU 082/054 085/056 093 053100
LWT BU 080/052 084/052 091 053100