Flood Watch 2, NWS Missoula, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
251 PM MDT SAT JUN 5 2010

.DISCUSSION...THE BRIEF BREAK IN PRECIPITATION WILL CONTINUE
THROUGH THE NIGHT TONIGHT AS A SHORTWAVE RIDGE REMAINS OVER THE
NORTHERN ROCKIES. CLOUD COVER WILL INCREASE AFTER MIDNIGHT AHEAD
OF THE NEXT WEATHER SYSTEM.

YET ANOTHER WET PACIFIC WEATHER SYSTEM WILL AFFECT WESTERN
MONTANA AND NORTH CENTRAL IDAHO SUNDAY AND SUNDAY NIGHT. WHILE THE
MOISTURE CONTENT WITH THIS APPROACHING SYSTEM IS NOT AS IMPRESSIVE
AS THE PREVIOUS TWO...WIDESPREAD SOAKING RAINS ARE EXPECTED. THE
HIGHEST PRECIPITATION AMOUNTS WILL BE FOCUSED MAINLY IN NORTH
CENTRAL IDAHO AND ALONG THE BITTERROOT CREST...WITH UP TO AN INCH
AND A HALF OF RAIN EXPECTED BY SUNDAY NIGHT OVER THE HIGHER
TERRAIN. FORECAST MODELS HAVE STRUGGLED A BIT WITH THE PLACEMENT
OF THESE PRECIPITATION BULLSEYES...SO SOME UNCERTAINTY REMAINS IN
TERMS OF PLACEMENT. IN ADDITION...THE ATMOSPHERE IS EXPECTED TO
DESTABILIZE TOMORROW AFTERNOON ALLOWING FOR THE POTENTIAL OF SOME
ISOLATED THUNDERSTORMS...PARTICULARLY ACROSS NORTH CENTRAL IDAHO
AND SOUTHWEST MONTANA. THIS WILL FURTHER ENHANCE THE POTENTIAL FOR
HEAVY RAIN IN THESE AREAS. ANOTHER RISE IN AREA RIVERS AND STREAMS
IS EXPECTED TOMORROW AFTERNOON AND EVENING...PARTICULARLY OVER
NORTH CENTRAL IDAHO AND RAVALLI COUNTY IN MONTANA. PLEASE SEE THE
HYDROLOGY SECTION BELOW FOR FURTHER INFORMATION.

MONDAY...PLENTY OF MOISTURE AND INSTABILITY WILL BE IN PLACE TO
PRODUCE AREAS OF SHOWERS...ESPECIALLY IN THE MOUNTAINS. EXPECT
SEASONAL TO SLIGHTLY BELOW SEASONAL TEMPERATURES UNDER A WEST-
SOUTHWEST FLOW.

TUESDAY AND WEDNESDAY...THE OVERALL FLOW BECOMES SOUTHWEST AHEAD
OF AN APPROACHING UPPER LEVEL LOW. ABUNDANT LOW LEVEL MOISTURE
WILL BE IN PLACE TO PRODUCE WIDESPREAD SHOWERS WEDNESDAY AS THE
FRONT NEARS THE REGION.  INSTABILITY AND DYNAMICS ALSO INCREASE
SUFFICIENTLY TO BRING A POTENTIAL FOR THUNDER EACH AFTERNOON AND
EVENING WITH THESE SHOWERS.

THURSDAY THROUGH SATURDAY...LATE SPRING STORM POSSIBLE LATE NEXT
WEEK. SIGNIFICANT CHANGE EXPECTED AS A LARGE UPPER LEVEL LOW
MOVES INTO THE PACIFIC NORTHWEST AND NORTHERN ROCKIES. ONCE IN
PLACE A MID LEVEL CLOSED LOW WILL DEVELOP AND MOVE SLOWLY ACROSS
THE REGION. SIGNIFICANT MOISTURE IS EXPECTED TO BE ENTRAINED
AROUND THIS LOW FROM THE EAST AND PRODUCE WIDESPREAD
PRECIPITATION. TEMPERATURES ARE EXPECTED TO DROP TO WELL BELOW
NORMAL READINGS IN THE LOWER 60S WITH THE COLDEST DAY EXPECTED ON
FRIDAY WITH TEMPERATURES STRUGGLING TO REACH 60 DEGREES. TIMING OF
THESE UPPER LOWS MAY DIFFER SEVERAL DAYS OUT SO STAY TUNED TO
FURTHER FORECAST DISCUSSIONS AS THIS MAY CHANGE. BUT MODELS ARE IN
AGREEMENT AND HAVE BEEN FOR SEVERAL RUNS THUS CONFIDENCE IS HIGH
ON A SIGNIFICANT LATE SPRING STORM LATE NEXT WEEK.

&&

.AVIATION...BREEZY SURFACE CONDITIONS WILL PERSIST UNTIL SUNSET
ACROSS THE NORTHERN ROCKIES AS THE UPPER LEVEL JET CONTINUES TO
STREAM OVER THE AREA. ALONGSIDE SURFACE WINDS...MOSTLY TERRAIN
LOCKED SHOWERS WILL LINGER THROUGHOUT THE EVENING.
OTHERWISE...PARTLY CLOUDY SKIES WILL REMAIN THROUGH EARLY
SUNDAY...BEFORE THE NEXT PACIFIC WEATHER DISTURBANCE INCREASES
CLOUDS AND PRECIPITATION CHANCES ACROSS THE REGION FOR LATE SUNDAY
INTO MONDAY.

&&

.HYDROLOGY...RIVER LEVELS HAVE BEGUN TO DROP ACROSS THE AREA TODAY
AS THE REGION ENJOYS A BRIEF BREAK IN PRECIPITATION. THE ONE
EXCEPTION IS THE SALMON RIVER NEAR WHITEBIRD WHICH CONTINUES TO
SLOWLY RISE DUE TO A LATE RESPONSE TO YESTERDAYS PRECIPITATION.
A WET PERIOD IS EXPECTED AGAIN FOR SUNDAY AND SUNDAY EVENING
BRINGING ANOTHER ROUND OF FLOODING CONCERNS...PARTICULARLY FOR THE
SMALL STREAMS AND RIVERS OF NORTH CENTRAL IDAHO AND RAVALLI
COUNTY. IN ADDITION...ISOLATED THUNDERSTORMS TOMORROW COULD
INITIATE SOME MORE INTENSE DOWNPOURS IN THE AFTERNOON. THIS WOULD
FURTHER EXACERBATE THE FLOODING CONCERNS AND LEAD TO THE POTENTIAL
FOR MUD AND ROCK SLIDES IN AREAS OF UNSTABLE SOILS. PLEASE
CONTINUE TO MONITOR OUR WEBSITE FOR FURTHER INFORMATION.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...NONE.
&&

SHORT TERM...PALLISTER
LONG TERM....RPN
AVIATION...NOLTE