302
FXUS65 KMSO 042037
AFDMSO
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
237 PM MDT SAT JUL 4 2009
DISCUSSION
TONIGHT THROUGH MONDAY...AN UPPER LEVEL RIDGE OF HIGH
PRESSURE...THAT HAS BROUGHT SEASONALLY WARM TEMPERATURES AND
AFTERNOON THUNDERSTORM ACTIVITY TO THE REGION DURING THE PAST
SEVERAL DAYS...WILL MOVE EAST OF THE CONTINENTAL DIVIDE DURING THE
NEXT 24 HOURS. THUNDERSTORM ACTIVITY FOR THE REMAINDER OF THIS
EVENING WILL EXIST MAINLY OVER SOUTHWEST MONTANA AND THE SALMON
RIVER CORRIDOR IN IDAHO...WHERE COOL AIR ALOFT IS ANTICIPATED TO BE
PRESENT THROUGH TONIGHT. THE INSTABILITY IN THIS AREA MAY ALLOW A
FEW STRONGER STORMS TO DEVELOP TOWARD SUNSET...WITH THE MAIN THREAT
BEING HAIL AND HEAVY RAIN. HOWEVER...THE CHANCE OF SEVERE WEATHER
APPEARS MARGINAL AT THE PRESENT TIME. BY SUNDAY...SOUTHWESTERLY FLOW
ALOFT IS EXPECTED TO DEVELOP OVER THE NORTHERN U.S. ROCKIES IN
ADVANCE OF A CLOSED LOW PRESSURE CIRCULATION. THIS CLOSED LOW WILL
INTRODUCE COLD AIR ALOFT AND THE PACIFIC JET STREAM TO THE AREA BY
MONDAY...WITH THUNDERSTORM ACTIVITY MOST PRONOUNCED ACROSS NORTHWEST
MONTANA. A SURFACE COLD FRONT IS ANTICIPATED DURING MONDAY...WITH
AFTERNOON TEMPERATURES COOLING 10 DEGREES OR GREATER AS COMPARED
TO SUNDAY AFTERNOON.
MONDAY NIGHT THROUGH FRIDAY...THIS PERIOD IS EXPECTED TO BE SIGNIFICANTLY
COOLER WITH A GOOD THREAT OF PRECIPITATION AS A TROUGH PATTERN
DEVELOPS OVER THE WESTERN U.S. THERE IS GOOD MODEL AGREEMENT ON THIS
THROUGH MIDWEEK. A GENERAL SOUTHWEST FLOW WILL PERSIST BEHIND THIS
FIRST WAVE MONDAY NIGHT THROUGH TUESDAY NIGHT MAINTAINING A SOMEWHAT
MOIST AND UNSTABLE AIR MASS. A MORE MOIST SHORTWAVE IS EXPECTED
WEDNESDAY. THIS WILL LIKELY BE THE COOLEST DAY WITH THE BEST SHOWER
COVERAGE THROUGHOUT THE REGION. MEDIUM RANGE MODELS BEGIN TO DIVERGE
THURSDAY AND FRIDAY WITH THE ECMWF SLOWLY TRANSITIONING TO A DRIER
LOW AMPLITUDE RIDGE AND THE GS HOLDING ONTO SOME TROUGHINESS ALONG
THE WEST COAST AND A WEST-SOUTHWEST FLOW OVER THE NORTHERN ROCKIES.
GIVEN THE STRENGTH AND AMPLITUDE OF THE LONG WAVE TROUGH...THINK THE
GFS MAY BE THE BETTER SOLUTION. THE CURRENT FORECAST OF TRENDING
LATE WEEK PRECIP CHANCES BACK TOWARD CLIMATOLOGY LOOKS GOOD.
AVIATION
AN UPPER LEVEL RIDGE OF HIGH PRESSURE WILL CONTINUE TO EXIST OVER
THE REGION DURING THE NEXT 24 HOURS. THUNDERSTORM ACTIVITY WILL
EXIST NEAR KBTM AND KSMN THROUGH 05/0300Z. OCCASIONALLY GUSTY
WINDS WILL BE POSSIBLE IN THE VICINITY OF THUNDERSTORMS. A FEW OF
THESE STORMS MAY CONTAIN SMALL HAIL AS WELL. AFTER 05/0300Z...NO
SIGNIFICANT AVIATION WEATHER IMPACTS ARE ANTICIPATED.
MSO WATCHES/WARNINGS/ADVISORIES
MT...NONE.
ID...NONE.
SHORT TERM...ZUMPFE
LONG TERM....KOLATA
AVIATION...ZUMPFE
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