Special Weather Statement, NWS Missoula, MT

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE MISSOULA MT
820 AM MDT WED MAR 28 2012

.UPDATE...ISSUED A WINTER WEATHER ADVISORY FOR LOST TRAIL PASS.

&&

.DISCUSSION...AS A COLD FRONT CROSSES THE NORTHERN ROCKIES
TODAY...LOST TRAIL PASS WILL BE MOST IMPACTED BY MODERATE TO HEAVY
BURSTS OF SNOWFALL. THIS WILL POSE MANY IMPACTS TO THOSE TRAVELING
OVER LOST TRAIL PASS THROUGHOUT THE DAY...AS VISIBILITIES UNDER
THESE BURSTS OF SNOW WILL DRAMATICALLY REDUCE. ROADWAYS WILL
QUICKLY TURN FROM DRY TO SNOW COVERED AND ICY. IN BETWEEN PERIODS
OF HEAVY SNOWFALL...THE ROADWAYS MAY HAVE TIME TO MELT AND BECOME
WET AGAIN...BUT COULD QUICKLY RETURN TO SNOW AND ICE COVERED. BE
PREPARED FOR QUICK CHANGING CONDITIONS IF PLANNING TO TRAVEL OVER
THE PASS. A WINTER WEATHER ADVISORY HAS BEEN ISSUED TO ADDRESS
THESE POTENTIAL IMPACTS.

&&

.AVIATION...THE FIRST SIGN OF PRECIP AND LOWERING CLOUD COVER IS
IS CURRENTLY BEING OBSERVED IN IDAHO AND WESTERN MONTANA THIS
MORNING AS A TROUGH MOVES INTO THE REGION. A SECOND WAVE OF
MOISTURE AND LIFT WILL SUPPLEMENT THIS FIRST WAVE TO KEEP PRECIP
INTO THIS EVENING. MODEL GUIDANCE AGREE THAT CONDITIONS WILL
BECOME UNSTABLE THROUGH IDAHO AND WESTERN MONTANA THIS AFTERNOON.
SHOWERS AND ISOLATED THUNDERSTORMS WILL BE A RESULT OF THIS
INSTABILITY ESPECIALLY IN SOUTHWEST MONTANA. LIGHTNING STRIKES ARE
ALREADY BEING PRODUCED BY THE SECOND WAVE THAT IS EXPECTED THIS
AFTERNOON WHICH INCREASES THE CONFIDENCE IN THE THUNDERSTORM
POTENTIAL. TERRAIN WILL REMAIN MOSTLY OBSCURED THROUGH THIS
EVENING AND BRIEF PERIODS OF LOWERED CEILINGS AND VISIBILITIES
WILL BE POSSIBLE THROUGH ALL VALLEY LOCATIONS. THE TROUGH WILL
EXIT AND CONDITIONS WILL IMPROVE FOR A SHORT TIME OVERNIGHT.

&&

.PREV DISCUSSION... /ISSUED 356 AM MDT WED MAR 28 2012/

DISCUSSION...LATEST SATELLITE AND RADAR IMAGERY SHOW A WAVE OF
MOISTURE ALONG THE OR/WA/ID BORDERS. THE ASSOCIATED LINE OF
PRECIPITATION WILL MOVE THROUGH IDAHO AND WEST CENTRAL/NORTHWEST
MONTANA THROUGH THIS MORNING. FARTHER WEST IS ANOTHER WAVE OF
MOISTURE AND LIFT THAT IS EXPECTED TO BRING ADDITIONAL PRECIP THIS
AFTERNOON. MODEL GUIDANCE SUGGEST THAT THERE WILL BE ENOUGH LIFT
THIS AFTERNOON FOR ISOLATED LIGHTNING STRIKES ESPECIALLY IN
SOUTHWEST MONTANA...SO THE CHANCE HAS BEEN ADDED THROUGHOUT THE
REGION. LIGHTNING STRIKES ARE ALREADY SHOWING UP IN NORTHERN CA SO
THIS IS A GOOD SIGN FOR OUR CHANCES. SNOW LEVELS ARE LOW ENOUGH
FOR MOUNTAIN PASSES TO HAVE SNOW OR A RAIN/SNOW MIX TODAY.
ROADWAYS WILL MOSTLY REMAIN WET BUT THERE IS A CHANCE FOR LIGHT
ACCUMULATIONS UNDER HEAVIER SHOWERS THAT SHOULD QUICKLY MELT.
SHOWERS WILL LINGER INTO THIS EVENING...AND THE SYSTEM WILL EXIT
OVERNIGHT LEAVING A BRIEF DRY PERIOD EARLY THURSDAY MORNING.

A STEADY STREAM OF PACIFIC MOISTURE WILL MOVE INTO THE NORTHERN
ROCKIES STARTING LATE THURSDAY. WIDESPREAD RAIN CAN BE EXPECTED
WITH THE HEAVIEST RAINFALL AMOUNTS LIKELY IN CENTRAL IDAHO AND
ALONG THE MONTANA BORDER WITH THE IDAHO PANHANDLE. WITH RAIN
EXPECTED TO CONTINUE INTO SATURDAY EVENING ROCK/MUDSLIDES..PONDING
OF WATER...AND POSSIBLY SMALL STREAM FLOODING BECOME A CONCERN.
SNOW LEVELS WILL REMAIN FAIRLY HIGH LIMITING SNOWFALL TO ONLY THE
HIGHEST TERRAIN THROUGH LATE SATURDAY. IF SNOW DOES FALL AT THE
PASS LEVEL IT WILL BE SLUSHY AND NOT STICK WELL TO ROADWAYS. HIGH
TEMPERATURES WILL BE WARMEST ACROSS LEMHI COUNTY AND SOUTHWEST
MONTANA WHILE FARTHER NORTH COOLER TEMPERATURES CAN BE EXPECTED
WHERE CLOUD COVER AND RAIN COOLED AIR AFFECT WARMING. UNSTABLE AIR
AHEAD OF AN APPROACHING COLD FRONT WILL INCREASE THE CHANCE OF
THUNDERSTORMS SATURDAY AFTERNOON ACROSS CENTRAL IDAHO AND WESTERN
MONTANA. HEAVIER RAIN SHOWERS CAN BE EXPECTED FROM ANY
THUNDERSTORMS THAT DO DEVELOP. THE FRONT WILL MOVE THROUGH THE
REGION SATURDAY NIGHT LOWERING SNOW LEVELS TO NEAR VALLEY FLOORS
HOWEVER THE BULK OF THE MOISTURE WILL HAVE FALLEN BY THIS TIME.
THE POTENTIAL DOES STILL EXIST FOR MINOR SNOW ACCUMULATIONS IN THE
VALLEYS AND ENOUGH SNOW TO IMPACT MOUNTAIN PASSES. LINGERING SNOW
SHOWERS ON SUNDAY WILL BE ACCOMPANIED BY BELOW AVERAGE
TEMPERATURES.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...NONE.
ID...WINTER WEATHER ADVISORY UNTIL 3 PM MDT THIS AFTERNOON EASTERN
     LEMHI COUNTY.

&&

UPDATE/AVIATION...ALLEGRETTO
PREVIOUS DISCUSSION....KITSMILLER/LOEFFELBEIN

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MISSOULA MT
130 PM MDT WED MAR 28 2012

MTZ001>004-043-282030-
BLACKFOOT REGION-FLATHEAD/MISSION VALLEYS-KOOTENAI/CABINET
REGION-LOWER CLARK FORK REGION-WEST GLACIER/BOB MARSHALL REGION-
130 PM MDT WED MAR 28 2012

...SIGNIFICANT WEATHER ADVISORY FOR CENTRAL FLATHEAD...SOUTHEASTERN
SANDERS...LAKE AND NORTHEASTERN MISSOULA COUNTIES UNTIL 230 PM MDT...

AT 119 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM 26 MILES SOUTHWEST
OF KALISPELL TO 10 MILES WEST OF DIXON...AND MOVING EAST AT 35 MPH.

WIND GUSTS UP TO 45 MPH ARE EXPECTED WITH THESE STORMS...ALONG WITH
HEAVY RAIN.  IN ADDITION...SMALL HAIL AND OCCASIONAL LIGHTNING CAN
BE EXPECTED.

LOCATIONS NEAR THE PATH OF THESE STORMS INCLUDE...FLATHEAD
LAKE...POLSON...DIXON...RAVALLI...BIG ARM...SAINT IGNATIUS...
RONAN...PABLO...BIGFORK...WOODS BAY...MOIESE...ROUND
BUTTE...KILA...LAKE MARY RONAN...ELMO...CHARLO...PROCTOR...
DAYTON...FORT CONNAH...ALLENTOWN AND KICKING HORSE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IF THREATENING WEATHER APPROACHES YOUR AREA...GO INDOORS AND STAY
AWAY FROM WINDOWS. IF YOU ARE CAUGHT OUTSIDE...MOVE TO A WELL
PROTECTED AREA.

&&

LAT...LON 4821 11392 4723 11373 4723 11464 4807 11478
TIME...MOT...LOC 1927Z 267DEG 32KT 4804 11471 4728 11441

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE MISSOULA MT
200 PM MDT WED MAR 28 2012

MTZ005>007-043-282100-
BITTERROOT/SAPPHIRE MOUNTAINS-BLACKFOOT REGION-BUTTE/PINTLAR
REGION-MISSOULA/BITTERROOT VALLEYS-
200 PM MDT WED MAR 28 2012

...SIGNIFICANT WEATHER ADVISORY FOR NORTHEASTERN RAVALLI...
SOUTHEASTERN LAKE...GRANITE...EASTERN MISSOULA AND NORTHWESTERN
POWELL COUNTIES UNTIL 300 PM MDT...

AT 150 PM MDT...NATIONAL WEATHER SERVICE DOPPLER RADAR WAS TRACKING
STRONG THUNDERSTORMS ALONG A LINE EXTENDING FROM ARLEE TO 6 MILES
SOUTHEAST OF HAMILTON...AND MOVING EAST AT 30 MPH.

WIND GUSTS UP TO 50 MPH ARE EXPECTED WITH THESE STORMS...ALONG WITH
HEAVY RAIN...SMAIL HAIL AND LIGHTNING.

LOCATIONS NEAR THE PATH OF THESE STORMS INCLUDE...BONNER...SEELEY
LAKE...PHILIPSBURG...CONDON...TURAH...CLINTON...QUIGLEY...
POTOMAC...GREENOUGH...CLEARWATER...GARNET AND BEARMOUTH.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

IF THREATENING WEATHER APPROACHES YOUR AREA...GO INDOORS AND STAY
AWAY FROM WINDOWS. IF YOU ARE CAUGHT OUTSIDE...MOVE TO A WELL
PROTECTED AREA.

&&

LAT...LON 4758 11315 4626 11325 4612 11402 4756 11392
TIME...MOT...LOC 1959Z 282DEG 24KT 4717 11393 4617 11398