Areal Flood Warning 5, NWS Missoula, MT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MISSOULA MT
337 AM MDT TUE APR 24 2012

...MODERATE TO HEAVY RAINFALL AND COOLER TEMPERATURES EXPECTED
THURSDAY INTO FRIDAY...
...RIVERS AND STREAMS EXPECTED TO RUN HIGH THROUGH THE WEEK...

.DISCUSSION...NOCTURNAL THUNDERSTORMS HAVE ONCE AGAIN DEVELOPED
WITH SOME STRENGTH TO OUR WEST IN WASHINGTON AND IDAHO...AND HAVE
CONTINUED TO MOVE INTO WESTERN MONTANA EARLY THIS MORNING. CURRENT
RADAR REFLECTIVITY SHOWS PLENTY OF LIGHTNING ASSOCIATED WITH THE
STORMS...WITH PERIODIC WIND GUSTS AND BURSTS OF RAIN BEING
REPORTED FROM WEATHER SPOTTERS. THESE STORMS SHOULD WEAKEN THROUGH
THE MORNING AS THEY MOVE FURTHER ACROSS NORTHWEST MONTANA...WITH A
STRAY LIGHTNING STRIKE POSSIBLE ACROSS WEST CENTRAL AND SOUTHWEST
MONTANA.

THERE MAY BE A SHORT BREAK IN PRECIPITATION LATER IN THE MORNING
INTO EARLY AFTERNOON AS THE ATMOSPHERE GATHERS ITSELF ONCE MORE
AND BECOMES UNSTABLE ONCE AGAIN. EXPECT MUCH MORE CLOUD COVER
TODAY COMPARED TO MONDAY...WITH AN INCREASED COVERAGE OF
THUNDERSTORM DEVELOPMENT. TEMPERATURES ARE STILL EXPECTED TO BE A
FEW DEGREES COOLER AS A RESULT OF CLOUD COVER AND RAINFALL...AND
THUS THE COOLER AND WETTER TREND FOR THE REMAINDER OF THE WEEK
BEGINS.

FORECAST MODELS ARE STILL HINTING AT THE DEVELOPMENT OF STRONG
SHOWERS AND THUNDERSTORMS NEAR THE OREGON/IDAHO BORDER LATE
WEDNESDAY NIGHT AND SUGGEST THAT THEY WILL TRACK ACROSS WESTERN
MONTANA THROUGH EARLY THURSDAY MORNING. HOWEVER PLACEMENT OF THIS
FOCUS FOR CONVECTIVE INITIATION AND THE SUBSEQUENT PATH OF THESE
POTENTIALLY INTENSE STORMS IS VARIED AMONGST THE MODELS AND WILL
LIKELY REMAIN VERY CHALLENGING TO FORECAST. SO BASICALLY THERE IS
HIGH CONFIDENCE IN DEVELOPING STRONG STORMS DURING THE OVERNIGHT
HOURS...BUT LOW CONFIDENCE IN EXACTLY WHERE THESE STORMS WILL
TRACK WITH THE LATEST FORECAST THINKING PLACING THE FOCUS OVER
CENTRAL IDAHO AND ALONG THE IDAHO/MONTANA BORDER.

A SECOND FOCUS OF INTENSE PRECIPITATION WILL COME THURSDAY
AFTERNOON AS A STRONG COLD FRONT MOVES THROUGH THE NORTHERN
ROCKIES. A BURST OF HEAVY PRECIPITATION IS EXPECTED ALONG WITH
VERY GUSTY WINDS AS THE FRONT QUICKLY MOVES ACROSS THE AREA. SNOW
LEVELS WILL FALL OVERNIGHT AS A DRAMATICALLY COLDER ATMOSPHERE
BECOMES ESTABLISHED AND THE POTENTIAL DOES EXIST FOR A FEW SLUSHY
INCHES TO ACCUMULATE ATOP MOUNTAIN PASSES BY FRIDAY MORNING.
COLDER...SHOWERY CONDITIONS SHOULD PREVAIL THROUGH THE WEEKEND
WITH ONLY MINIMAL WARMING EACH DAY. TEMPERATURES WILL START OFF
SOME 10 DEGREES BELOW NORMAL ON FRIDAY BUT RISE TO NEAR NORMAL BY
SUNDAY WITH SEASONAL CONDITIONS EXPECTED TO PREVAIL INTO THE FIRST
WEEK OF MAY.

&&

.AVIATION...SHOWERS AND WEAK ISOLATED THUNDERSTORMS HAVE DEVELOPED
ACROSS WESTERN MONTANA AND CENTRAL IDAHO THIS MORNING. LIGHTNING
AND A PERIODIC WIND GUST HAVE BEEN THE ONLY REPORTS FROM THESE
STORMS...BUT A FEW COULD IMPACT KGPI THROUGH THE REMAINDER OF THE
MORNING. EXPECT INTERMITTENT RAIN SHOWERS AND THE REDEVELOPMENT OF
WIDESPREAD THUNDERSTORMS TO IMPACT ALL TERMINALS THROUGH THIS
AFTERNOON AND EVENING.

&&

.HYDROLOGY...CONFIDENCE IS HIGH REGARDING CONTINUED SNOW MELT AND
RAINFALL HAVING A MAJOR IMPACT ON WATER LEVELS ON SMALL
STREAMS...CREEKS...AND LARGER RIVERS THROUGH THE WEEK. WITH
MODERATE TO HEAVY RAINFALL AMOUNTS FORECASTED LATER IN THE
WEEK...SMALL STREAMS AND RIVERS WILL HAVE THE POTENTIAL TO EXCEED
THEIR BANKS AND CAUSE MINOR FLOODING. FLOODING IS ALSO POSSIBLE ON
MANY LARGER RIVERS ACROSS WESTERN MONTANA AND CENTRAL IDAHO. FLOOD
WATCHES/WARNINGS ARE CURRENTLY IN EFFECT.

&&

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

&&

SHORT TERM/HYDROLOGY/AVIATION...ALLEGRETTO
LONG TERM....DICKERSON