395
FXUS65 KTFX 060853
AFDTFX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
253 AM MDT SUN JUL 6 2008
DISCUSSION
SUNDAY THROUGH TUESDAY...AN UPPER LEVEL LOW PRESSURE TROF IS MOVING
THROUGH THE PACIFIC NORTHWEST AND WILL APPROACH THE ROCKIES THIS
MORNING. SATELLITE CURRENTLY INDICATES A SPLIT IN THE FLOW WITH
ENHANCED CLOUD TOPS MOVING ACROSS SOUTHERN IDAHO AND ALBERTA. MOST
OF THE DYNAMICS WILL BE TO THE NORTH OF THE ZONES BUT THE WEAK
VORTICITY TO THE SOUTH WILL AID IN AFTERNOON THUNDERSTORM
DEVELOPMENT ACROSS SOUTHWEST MONTANA. AFTERNOON INSTABILITY WILL
DEVELOP ACROSS THE CWA BUT STRONGEST OVER THE SOUTHWEST ZONES.
CONVECTIVE TEMPS LOOK RATHER LOW FARTHER TO THE NORTH ALTHOUGH A
SECOND WEAK SHORTWAVE CROSSES THE ROCKIES BY EARLY EVENING AND MAY
HELP INITIATE SOME CONVECTION OVER THE NORTHERN AND CENTRAL ZONES. A
PUSH OF COOLER CANADIAN AIR CROSSES THE BORDER MONDAY MORNING AND
SHOULD BE THROUGH THE CENTRAL ZONES BY AFTERNOON. THIS WILL HELP
MODERATE HIGH TEMPS IN THIS AREA. OVERALL...THE BUILDING OF THE HIGH
PRESSURE RIDGE BEGINS TO DOMINATE THE WEATHER AND THE AIRMASS WARMS
AND DRIES...A HIGH PRESSURE RIDGE WILL BE OVER THE CWA BY 12Z
TUESDAY. TEMPS BEGIN THE PERIOD NEAR NORMALS BUT BEGIN TO TREND
HIGHER ON TUESDAY. ZELZER
TUESDAY NIGHT THROUGH FRIDAY NIGHT...A WEAK UPPER LEVEL RIDGE OF
HIGH PRESSURE WILL GENERALLY KEEP A DRY WESTERLY FLOW ALOFT OVER
NORTH CENTRAL...CENTRAL...AND SOUTHWEST MONTANA INTO THURSDAY.
TEMPERATURES WILL GENERALLY BE ABOUT 5 TO 10 DEGREES ABOVE NORMAL. A
WEAK UPPER LEVEL SHORTWAVE TROUGH WILL THEN MOVE THROUGH THE AREA
THURSDAY THROUGH FRIDAY NIGHT. JUST AHEAD OF THE SHORTWAVE AND AN
ASSOCIATED SOUTHEAST-MOVING COLD FRONT...THERE WILL BE A SLIGHT
CHANCE OF THUNDERSTORMS THURSDAY AFTERNOON AND EVENING IN THE
MOUNTAINS OF SOUTHWEST AND CENTRAL MONTANA. AS THE SHORTWAVE AND
COLD FRONT MOVE SOUTHEAST THROUGH MONTANA AND SHIFT THE FLOW ALOFT
MORE NORTHWESTERLY...THEY WILL BRING A SLIGHT CHANCE OF SHOWERS AND
THUNDERSTORMS TO MOST OF THE AREA FRIDAY AND FRIDAY NIGHT...EXCEPT
FOR SOUTHWEST MONTANA. OVERNIGHT LOWS WILL REMAIN NEAR NORMAL DURING
THIS TIME...AS DAYTIME HIGHS ON FRIDAY COOL TO NEAR OR SLIGHTLY
BELOW SEASONAL AVERAGES.
SATURDAY AND SUNDAY...EXTENDED RANGE MODEL SOLUTIONS BRING AN UPPER
LEVEL LOW PRESSURE SYSTEM INTO THE REGION FROM CANADA. A CHANCE FOR
SHOWERS AND THUNDERSTORMS FOR MUCH OF THE REGION AS THE TROUGH
SWINGS THROUGH. TEMPERATURES ARE EXPECTED TO BE NEAR SEASONAL
AVERAGES THROUGH THE PERIOD. SAUCIER
AVIATION
UPDATED 0430Z.
ALL SHOWERS AND ISOLD THUNDERSTORMS FROM EARLIER THIS EVE HAVE
DISSIPATED ACROSS SW AND NORTH CENTRAL MT BUT WILL PERSIST FOR A FEW
MORE HOURS BETWEEN KBIL AND KLVM. CLEAR TO SCT SKIES EXPECTED DURING
THE OVERNIGHT HOURS. ANOTHER WEAK UPPER LEVEL SYSTEM WILL MOVE INTO
THE REGION ON SUNDAY AFTN WITH SLIGHTLY WIDER COVERAGE OF SHOWERS
AND THUNDERSTORMS ACROSS BEGINNING 20Z. VFR CONDITIONS WILL BE
THE RULE ACROSS THE FLYING AREA BUT SOME SITES MAY BRIEFLY SEE MVFR
CIGS NEAR ANY PRECIP ACTIVITY. WARANAUSKAS
PRELIMINARY POINT TEMPS/POPS
GTF 83 54 80 50 / 10 10 10 10
CTB 79 49 76 47 / 10 10 10 10
HLN 84 56 84 53 / 20 10 10 10
BZN 82 51 85 48 / 20 20 10 10
WEY 75 45 77 44 / 30 20 10 10
DLN 80 48 82 46 / 20 10 10 10
HVR 84 56 78 51 / 10 10 10 10
LWT 80 52 77 48 / 20 20 10 10
TFX WATCHES/WARNINGS/ADVISORIES
NONE.
WEATHER.GOV/GREATFALLS
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