Winter Storm in Montana, February 26 to 28, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
1025 PM MST FRI FEB 25 2011

UPDATED AVIATION SECTION

.UPDATE...
CURRENT FORECAST IS ON TRACK...WITH JUST A FEW TWEAKS. MUCH OF THE
REGION WILL REMAIN DRY TONIGHT AS THE AREA IS IN-BETWEEN STORM
SYSTEMS. HOWEVER...A FEW LIGHT SNOW SHOWERS CAN BE EXPECTED IN THE
FAR SOUTH...ESPECIALLY AROUND THE WEST YELLOWSTONE AREA. OTHERWISE
ANOTHER COLD NIGHT IS EXPECTED. HOWEVER...WITH INCREASING WINDS
EXPECTED AFTER MIDNIGHT...TEMPERATURES SHOULD NOT FALL TOO MUCH
MORE OVER THE WESTERN PORTIONS OF NORTH CENTRAL MONTANA...BUT
OTHER LOCATIONS SHOULD STILL SEE A 5 TO 10 DEGREE DROP IN
TEMPERATURES YET TONIGHT. AS THE WINDS PICK UP OVER THE
REGION...WIND CHILLS WILL BE A PROBLEM...THUS THE ADVISORY WILL
CONTINUE. ALSO ADDED SOME PATCHY FOG TO LOW LYING AREAS FOR
TONIGHT.

ANOTHER ISSUE FOR SATURDAY WILL BE THE AMOUNT OF BLOWING SNOW.
WIDESPREAD BLOWING SNOW IS EXPECTED TO AFFECT MUCH OF THE REGION.
THE WINDS COULD BE STRONG ENOUGH THAT WHITE-OUT CONDITIONS COULD
BE POSSIBLE AT TIMES ALONG THE FRONT RANGE. THIS IS BEING WATCHED
CLOSELY. OVERALL...TEMPERATURES SHOULD BEGIN TO WARM UP A BIT ON
SATURDAY...WITH EVEN WARMER TEMPERATURES EXPECTED FOR SUNDAY.
BRUSDA

&&

.AVIATION...
UPDATED 0525Z.
EXPECT GENERALLY VFR CONDITIONS THROUGH SATURDAY EVENING. THERE WILL
BE SOME SNOW SHOWERS NEAR THE IDAHO BORDER THE REST OF TONIGHT WITH
A THREAT OF MVFR CEILINGS AND VISIBILITIES. COULD SEE PATCHY
FREEZING FOG IN THE SOUTHWEST VALLEYS BY LATE TONIGHT WITH MVFR OR
IFR CONDITIONS. OTHERWISE EXPECT MOSTLY CLEAR SKIES TONIGHT.
CEILINGS NEAR AND ABOVE 10000 FEET WILL SPREAD SOUTH OVER THE AREA
LATE TONIGHT THROUGH SATURDAY MORNING. EXPECT TO SEE SCATTERED SNOW
SHOWERS OVER THE MOUTAINS OF THE ROCKY MOUNTAIN FRONT SATURDAY
AFTERNOON AND EVENING WITH AT LEAST LOCAL MOUNTAIN OBSCUREMENT. THE
MAIN FORECAST CONCERN WILL BE INCREASING SOUTHWEST WINDS AND THE
POTENTIAL FOR BLOWING SNOW. CONFIDENT THAT SOUTHWEST WINDS WILL
INCREASE BUT CONFIDENCE IS SOMEWHAT LOW ON THE DETAILS OF THIS
INCREASE. EXPECT AREAS OF VISIBILITIES BELOW 1 MILE IN BLOWING SNOW
OVER THE ROCKY MOUNTAIN FRONT LATE TONIGHT THROUGH SATURDAY. IFR
VISIBILITIES IN BLOWING SNOW WILL SPREAD FARTHER EAST DURING THE DAY
SATURDAY. CONTINUE TO BE FAIRLY CONFIDENT THAT KCTB WILL SEE AT
LEAST OCCASIONAL MVFR/IFR VISIBILITIES IN BLOWING SNOW SO HAVE
CONTINUED THIS IN THE LTEST FORECAST. CONFIDENCE CONTINUES TO BE
RATHER LOW THAT THIS WILL HAPPEN AT KGTF/KHVR/KLWT SO HAVE LEFT THIS
CONDITION OUT OF THOSE PARTICULAR TAF FORECASTS. BLANK

&&

.HYDROLOGY...

FOR THE JEFFERSON RIVER...
ICE JAM FLOODING ON THE JEFFERSON RIVER CONTINUES NEAR SILVER
STAR IN NORTHWEST MADISON COUNTY. FLOODING CONTINUES TO AFFECT THE
JEFFERSON ACRES REGION...THUS THE FLOOD WARNING WILL CONTINUE
UNTIL THE FLOOD WATERS HAVE RECEDED.

ADDITIONALLY...A SECOND ICE JAM HAS DEVELOPED UPSTREAM OF THE
FIRST ICE JAM. SHOULD THIS NEW ICE JAM BREAK...IT COULD POSSIBLY
CAUSE THE ORIGINAL ICE JAM TO BREAK AS WELL...CREATING A FLASH
FLOODING POTENTIAL DOWNSTREAM. THUS A FLASH FLOOD WATCH HAS BEEN
ISSUED FOR A PORTION OF THE JEFFERSON RIVER FROM ABOUT 5 MILES
SOUTH OF SILVER STAR...TO WATERLOO. THE WATCH WILL REMAIN IN
PLACE UNTIL THE THREAT FOR FLASH FLOODING HAS CEASED.

FOR THE MISSOURI RIVER...
AS OF FRIDAY EVENING...A NEW ICE JAM HAS DEVELOPED JUST NORTH OF
FORT BENTON ON THE MISSOURI RIVER. MINOR FLOODING HAS BEEN
REPORTED ON THE NORTH SIDE OF FORT BENTON IN LOW LYING
AREAS...THUS A FLOOD WARNING HAS BEEN ISSUED. IN THE PAST
HOUR...THE RIVER GAGE NEAR FORT BENTON HAS LEVELED OFF A
BIT...WHICH IS A GOOD SIGN AT THE MOMENT...BUT OVERALL THE RIVER
HAS RISEN AROUND 8 FEET IN THE PAST 24 HOURS OR SO. WE WILL
CONTINUE TO MONITOR THE SITUATION CLOSELY AND ADDITIONAL FLOOD
HIGHLIGHTS MAY BE REQUIRED SHOULD THE ICE JAM CONTINUE TO GROW
OVER THE NEXT DAY OR SO.

&&

.PREV DISCUSSION...
/ISSUED 455 PM MST FRI FEB 25 2011/

TONIGHT THROUGH SUNDAY...A COLD ARCTIC AIRMASS REMAINS IN PLACE OVER
THE FORECAST THIS EVENING...BUT WILL BEGIN TO MOVE OFF TO THE EAST
LATER TONIGHT. CLEAR SKIES...CALM WINDS AND FRESH SNOW COVER WILL
ALLOW FOR VERY COLD OVERNIGHT LOWS AGAIN TONIGHT. OVER NORTH CENTRAL
MT...LOW TEMPS WILL OCCUR THIS EVENING...BEFORE A SLOW MODERATION OF
TEMPERATURES BEGINS LATER TONIGHT WITH THE DEVELOPMENT OF SOUTH TO
SOUTHWEST WINDS AS A LEE-SIDE SURFACE TROUGH NOSES SOUTHWARD FROM
CANADA ALONG THE EAST SLOPES OF THE ROCKIES. WESTERLY FLOW
ALOFT...AND THE SURFACE LEE-SIDE TROUGH...WILL STRENGTHEN ON
SATURDAY WITH GUSTY SW WINDS SPREADING EAST ACROSS MUCH OF NORTH
CENTRAL MT WITH GUSTS TO 50 MPH POSSIBLE ACROSS PORTIONS OF GLACIER
COUNTY BY SATURDAY AFTERNOON. WINDS AND WARMING ALOFT WILL
SIGNIFICANTLY MODERATE THE AIRMASS ACROSS THE FORECAST AREA WITH
MOST LOCATIONS SEEING MAX TEMPS IN THE TEENS AND TWENTIES BY
SATURDAY AFTERNOON. THERE WILL BE A PERIOD TONIGHT WHEN TEMPS ARE
STILL COLD AS WINDS DEVELOP FOR VERY LOW WIND CHILLS ACROSS MUCH OF
NORTH CENTRAL MT AND WILL HAVE A WIND CHILL ADVISORY FROM MIDNIGHT
TONIGHT THROUGH SATURDAY MORNING. CONCERN THEN SHIFTS TO BLOWING
SNOW POTENTIAL AS WINDS INCREASE FURTHER BY SATURDAY AFTERNOON WITH
SIGNIFICANT BLOWING AND DRIFTING EXPECTED...ESPECIALLY IN THE
GLACIER COUNTY AREA AND WILL HIGHLIGHT THIS WITH A WINTER WEATHER
ADVISORY FOR BLOWING SNOW FOR MOST OF NORTH CENTRAL MT TOMORROW.
WINDS DECREASE BUT WILL REMAIN BREEZY SATURDAY NIGHT INTO SUNDAY
WITH TEMPERATURES CONTINUING TO WARM BUT REMAINING BELOW SEASONAL
AVERAGES. HOENISCH

SUNDAY NIGHT THROUGH FRIDAY NIGHT...MODELS ARE IN FAIRLY GOOD
AGREEMENT TONIGHT FOR THIS PERIOD. A MOIST WESTERLY FLOW ALOFT WILL
REMAIN OVER THE TFX CWA SUNDAY NIGHT THROUGH MONDAY NIGHT. A COLD
FRONT WILL DEVELOP ALONG THE CANADIAN BORDER SUNDAY NIGHT...KEEPING
THE BEST CHANCE FOR PRECIPITATION IN THE WESTERN MOUNTAINS AND ALONG
THE FRONTAL BOUNDARY. TEMPERATURES WILL MOSTLY REMAIN NEAR SEASONAL
AVERAGES...EXCEPT FOR 5 TO 10 DEGREE BELOW NORMAL LOWS ALONG THE
FRONTAL BOUNDARY. THIS COLD FRONT WILL THEN MOVE SOUTH OVER THE
PLAINS OF NORTH CENTRAL AND CENTRAL MONTANA MONDAY AND MONDAY
NIGHT...SHIFTING SURFACE WINDS MORE NORTHERLY AND UPSLOPE. THIS WILL
USHER IN MUCH BELOW NORMAL TEMPERATURES FOR THIS AREA BY MONDAY
NIGHT AND TUESDAY...ALONG WITH AN INCREASED CHANCE OF SNOW.
HOWEVER...THE COLD AIR WILL REMAIN EAST OF THE ROCKIES...KEEPING THE
VALLEYS OF SOUTHWEST MONTANA NEAR NORMAL TEMPERATURE-WISE. THE MOIST
WESTERLY FLOW ALOFT WILL LIKELY KEEP SNOW IN THE WESTERN MOUNTAINS
AS WELL DURING THIS TIME...AND THIS SITUATION WILL NEED TO BE
MONITORED FOR POSSIBLE WIND AND/OR WINTER WEATHER HIGHLIGHTS. THE
CHANCE FOR SNOW WILL DECREASE OVERALL TUESDAY AND TUESDAY NIGHT AS
AN UPPER LEVEL RIDGE OF HIGH PRESSURE BUILDS INTO THE AREA. THIS
WILL ALSO MODERATE TEMPERATURES CLOSER TO NORMAL BY WEDNESDAY. AN
UPPER LEVEL TROUGH OF LOW PRESSURE WILL THEN DEEPEN OVER THE PACIFIC
COAST STATES WEDNESDAY NIGHT INTO THURSDAY...FOR AN INCREASING
CHANCE OF SNOW AGAIN OVER THE MOUNTAINS OF WESTERN AND CENTRAL
MONTANA. HOWEVER...TEMPERATURES WILL CONTINUE TO WARM TO
NEAR/SLIGHTLY ABOVE NORMAL ACROSS THE AREA THROUGH THURSDAY. THE
UPPER LEVEL TROUGH WILL THEN MOVE INTO THE AREA THURSDAY NIGHT
THROUGH FRIDAY NIGHT...BRINGING ANOTHER CANADIAN COLD FRONT INTO THE
AREA WITH A CONTINUED CHANCE OF SNOW. TEMPERATURES EAST OF THE
ROCKIES WILL FALL SLIGHTLY BELOW NORMAL AGAIN...WHILE TEMPERATURES
REMAIN NEAR NORMAL ACROSS SOUTHWEST MONTANA.  COULSTON

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF -20  25  15  32 /   0   0  10  10
CTB -21  21  14  28 /   0   0  10  10
HLN -16  22  15  35 /   0   0   0  20
BZN -20  19  10  32 /   0   0  10  20
WEY   2  18  -7  18 /  40  10  10  30
DLN  -5  24  10  30 /   0   0  10  10
HVR -29  19  11  26 /   0  10  10  20
LWT -22  23  12  31 /   0   0  10  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...

WIND CHILL ADVISORY UNTIL 10 AM MST SATURDAY BLAINE...CASCADE...
CENTRAL AND SOUTHERN LEWIS AND CLARK...CHOUTEAU...EASTERN
GLACIER...EASTERN PONDERA...EASTERN TETON...FERGUS...HILL...
JUDITH BASIN...LIBERTY...NORTHERN ROCKY MOUNTAIN FRONT...
SOUTHERN ROCKY MOUNTAIN FRONT...TOOLE.

WINTER WEATHER ADVISORY FROM 5 AM TO 8 PM MST SATURDAY BLAINE...
CASCADE...CENTRAL AND SOUTHERN LEWIS AND CLARK...CHOUTEAU...
EASTERN PONDERA...EASTERN TETON...FERGUS...HILL...JUDITH BASIN...
LIBERTY...TOOLE...EASTERN GLACIER...NORTHERN ROCKY MOUNTAIN
FRONT...SOUTHERN ROCKY MOUNTAIN FRONT.

FLASH FLOOD WATCH THROUGH SATURDAY AFTERNOON FOR PORTIONS OF THE
JEFFERSON RIVER IN NORTHERN MADISON COUNTY...FROM NORTH OF TWIN
BRIDGES TO WATERLOO.

FLOOD WARNING UNTIL 10 AM SATURDAY FOR PORTIONS OF THE JEFFERSON
RIVER IN NORTHERN MADISON COUNTY...BETWEEN TWIN BRIDGES AND SILVER
STAR.

FLOOD WARNING UNTIL 630 PM SUNDAY EVENING FOR PORTIONS OF THE
MISSOURI RIVER NEAR FORT BENTON.

&&

WEATHER.GOV/GREATFALLS

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE GREAT FALLS MT
700 PM MST FRI FEB 25 2011

MTZ015-261200-
MADISON-
700 PM MST FRI FEB 25 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
MONTANA.

.DAY ONE...TONIGHT

A FLOOD WARNING REMAINS IN EFFECT ALONG THE JEFFERSON RIVER SOUTH
OF THE TOWN OF SILVER STAR...DUE TO ICE JAM CONDITIONS. A FLASH
FLOOD WATCH IS ALSO IN EFFECT FOR THE JEFFERSON RIVER FROM NORTH
OF TWIN BRIDGES TO WATERLOO DUE TO THE POTENTIAL FOR ICE JAMS TO
BREAK.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

ANOTHER CANADIAN COLD FRONT WILL MOVE THROUGH THE REGION MONDAY AND
MONDAY NIGHT. EXPECT INCREASING CHANCES OF SNOW OVER SOUTHWEST
MONTANA BY MONDAY NIGHT...AND WINTER WEATHER HIGHLIGHTS COULD BE
ISSUED LATER THIS WEEKEND OR EARLY NEXT WEEK FOR PORTIONS OF
SOUTHWEST MONTANA.

ADDITIONALLY...STRONG RIDGE TOP WINDS ARE EXPECTED MONDAY AFTERNOON
THROUGH TUESDAY...AND HIGH WIND HIGHLIGHTS MAY ALSO BE NEEDED FOR
PORTIONS OF SOUTHWEST MONTANA FOR EARLY NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

MTZ008-052>055-261200-
BEAVERHEAD-JEFFERSON-BROADWATER-MEAGHER-GALLATIN-
700 PM MST FRI FEB 25 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
MONTANA.

.DAY ONE...TONIGHT

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER FOR TONIGHT IS
LOW.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

ANOTHER CANADIAN COLD FRONT WILL MOVE THROUGH THE REGION MONDAY AND
MONDAY NIGHT. EXPECT INCREASING CHANCES OF SNOW OVER SOUTHWEST
MONTANA BY MONDAY NIGHT...AND WINTER WEATHER HIGHLIGHTS COULD BE
ISSUED LATER THIS WEEKEND OR EARLY NEXT WEEK FOR PORTIONS OF
SOUTHWEST MONTANA.

ADDITIONALLY...STRONG RIDGE TOP WINDS ARE EXPECTED MONDAY AFTERNOON
THROUGH TUESDAY...AND HIGH WIND HIGHLIGHTS MAY ALSO BE NEEDED FOR
PORTIONS OF SOUTHWEST MONTANA FOR EARLY NEXT WEEK.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

MTZ013-261200-
CHOUTEAU-
700 PM MST FRI FEB 25 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
MONTANA...NORTH CENTRAL MONTANA AND SOUTHWEST MONTANA.

.DAY ONE...TONIGHT

A WIND CHILL ADVISORY HAS BEEN ISSUED FOR MOST OF NORTH CENTRAL
MONTANA FROM LATER TONIGHT THROUGH MID MORNING ON SATURDAY.

A FLOOD WARNING IS IN EFFECT FOR LOCATIONS ALONG THE MISSOURI RIVER
IN THE FORT BENTON AREA.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A FLOOD WARNING REMAINS IN EFFECT LOCATIONS ALONG THE MISSOURI RIVER
IN THE FORT BENTON AREA UNTIL SUNDAY EVENING. PERSONS WHO HAVE
PROPERTY ALONG THE MISSOURI RIVER IN CITY OF FORT BENTON SHOULD
MONITOR THE SITUATION CLOSELY...BECAUSE IF THE ICE JAM CONTINUES TO
BUILD...THE FLOODING COULD BECOME MORE WIDESPREAD.

A WIND CHILL ADVISORY IS IN EFFECT THROUGH MID MORNING SATURDAY.
A BLOWING SNOW ADVISORY IS IN EFFECT FROM SATURDAY MORNING UNTIL
SATURDAY EVENING ACROSS ALL OF NORTH CENTRAL MONTANA.

THE WINDS ARE EXPECTED TO BE STRONG ENOUGH ON SATURDAY...THAT THE
BLOWING SNOW COULD PRODUCE WHITE-OUT CONDITIONS AT TIMES ON
SATURDAY. THUS...THIS SITUATION IS BEING MONITORED CLOSELY FOR
POSSIBLE GROUND BLIZZARD CONDITIONS.

ANOTHER CANADIAN COLD FRONT WILL MOVE THROUGH THE REGION MONDAY AND
MONDAY NIGHT. EXPECT INCREASING CHANCES OF SNOW OVER NORTH CENTRAL
MONTANA BY MONDAY NIGHT. THUS WINTER WEATHER HIGHLIGHTS COULD BE
ISSUED LATER THIS WEEKEND OR EARLY NEXT WEEK FOR PORTIONS OF NORTH
CENTRAL MONTANA.

ADDITIONALLY...STRONG WINDS ARE EXPECTED AT TIMES FROM SATURDAY
AFTERNOON AFTERNOON THROUGH MONDAY NIGHT. THUS HIGH WIND HIGHLIGHTS
MAY ALSO BE NEEDED FOR PORTIONS OF NORTH CENTRAL MONTANA AT TIMES
THROUGH MONDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.

MTZ009>012-014-044>051-261200-
NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL-CASCADE-
CENTRAL AND SOUTHERN LEWIS AND CLARK-TOOLE-LIBERTY-
EASTERN PONDERA-BLAINE-SOUTHERN ROCKY MOUNTAIN FRONT-
EASTERN TETON-JUDITH BASIN-FERGUS-
700 PM MST FRI FEB 25 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
MONTANA...NORTH CENTRAL MONTANA AND SOUTHWEST MONTANA.

.DAY ONE...TONIGHT

A WIND CHILL ADVISORY HAS BEEN ISSUED FOR MOST OF NORTH CENTRAL
MONTANA FROM LATER TONIGHT THROUGH MID MORNING ON SATURDAY.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

A WIND CHILL ADVISORY IS IN EFFECT THROUGH MID MORNING SATURDAY.
A BLOWING SNOW ADVISORY IS IN EFFECT FROM SATURDAY MORNING UNTIL
SATURDAY EVENING ACROSS ALL OF NORTH CENTRAL MONTANA.

THE WINDS ARE EXPECTED TO BE STRONG ENOUGH ON SATURDAY...THAT THE
BLOWING SNOW COULD PRODUCE WHITE-OUT CONDITIONS AT TIMES ON
SATURDAY. THUS...THIS SITUATION IS BEING MONITORED CLOSELY FOR
POSSIBLE GROUND BLIZZARD CONDITIONS.

ANOTHER CANADIAN COLD FRONT WILL MOVE THROUGH THE REGION MONDAY AND
MONDAY NIGHT. EXPECT INCREASING CHANCES OF SNOW OVER NORTH CENTRAL
MONTANA BY MONDAY NIGHT. THE SNOW COULD BE HEAVY AT TIMES EARLY NEXT
WEEK OVER THE ROCKY MOUNTAIN FRONT. THUS WINTER WEATHER
HIGHLIGHTS COULD BE ISSUED LATER THIS WEEKEND OR EARLY NEXT WEEK FOR
PORTIONS OF NORTH CENTRAL MONTANA.

ADDITIONALLY...STRONG WINDS ARE EXPECTED AT TIMES FROM SATURDAY
AFTERNOON AFTERNOON THROUGH MONDAY NIGHT. THUS HIGH WIND HIGHLIGHTS
MAY ALSO BE NEEDED FOR PORTIONS OF NORTH CENTRAL MONTANA AT TIMES
THROUGH MONDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS ACCORDING TO STANDARD OPERATING PROCEDURES.