Winter Storm in Montana, March 29, 2008

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
317 AM MDT SAT MAR 29 2008

.DISCUSSION...

TODAY THROUGH MONDAY...AN UPPER LEVEL LOW WILL SWEEP ACROSS MY
FORECAST AREA TODAY. A SURFACE LOW PRESSURE SYSTEM IS CURRENTLY
CENTERED OVER SOUTHWEST MONTANA WITH AN INVERTED TROUGH EXTENDING
NORTH TO NORTHWEST ACROSS WESTERN PORTIONS OF MY CWA. THE SURFACE
LOW WILL MOVE EAST TODAY WITH THE INVERTED TROUGH ENDING UP IN AN
EAST-WEST ORIENTATION ACROSS NORTHERN MONTANA BY LATE MORNING.
MODELS ARE NOT IN AGREEMENT WITH LOCATION OF THE SURFACE TROUGH
AND SUBSEQUENT QPF FOOTPRINT. OBSERVATIONS AND SURFACE ANALYSIS
INDICATES THAT THE FURTHER SOUTH GFS MODEL IS PERFORMING BETTER
THAN THE NAM...BUT THE TROUGH MAY END UP A BIT FURTHER SOUTH THAN
EVEN THIS MODEL IS SHOWING. THE SURFACE TROUGH IS THEN EXPECTED TO
SWEEP SOUTH ACROSS CENTRAL MONTANA WITH COLDER CANADIAN AIR
POURING INTO MY CWA ALONG WITH GUSTY NORTH TO NORTHWEST WINDS
CREATING AREAS OF BLOWING SNOW. THIS SCENARIO IS FAVORABLE FOR
THE CURRENT WINTER WEATHER HIGHLIGHTS ACROSS NORTH CENTRAL
MONTANA. HOWEVER...IT DOES APPEAR THAT THE MODELS ARE OVER
ESTIMATING QPF AMOUNTS. AS SUCH I HAVE LOWERED SNOW AMOUNTS IN THE
FORECAST BUT I WILL ALLOW THE HIGHLIGHTS TO CONTINUE FOR NOW. WEAK
SHORTWAVE RIDGING BUILDS OVER MONTANA TONIGHT WITH SNOW DECREASING
RAPIDLY DURING THE EVENING HOURS. BY SUNDAY A SECONDARY BROAD
UPPER LEVEL LOW SWINGS INTO THE NORTHERN ROCKY MOUNTAIN REGION AND
WILL REMAIN OVER MY FORECAST AREA THROUGH MONDAY FOR CONTINUED
UNSETTLED CONDITIONS. TEMPERATURES WILL REMAIN WELL BELOW SEASONAL
NORMALS THROUGH THE SHORT TERM PERIOD. MPJ

MONDAY NIGHT THROUGH THURSDAY NIGHT...A SOMEWHAT UNSETTLED PATTERN
WILL CONTINUE AT LEAST THROUGH THE MIDDLE OF NEXT WEEK AS A BROAD
UPPER LEVEL TROUGH PERSISTS OVER WESTERN NORTH AMERICA...WHICH
GRADUALLY SHIFTS EAST INTO THE PLAINS STATES LATER IN THE WEEK.
MEDIUM RANGE MODELS DIVERGE THROUGH THE PERIOD WITH RESPECT TO THE
STRENGTH AND LOCATION OF SPECIFIC SHORTWAVES EMBEDDED WITHIN THE
FLOW...WHICH LEADS TO INCREASING UNCERTAINTY IN THE DETAILS OF THE
PATTERN AS THE WEEK PROGRESSES.  BETTER CHANCE FOR PRECIP WILL BE
EARLY IN THE PERIOD AS MORE ORGANIZED ENERGY SWINGS THROUGH THE
TROUGH FROM THE NORTHWEST MONDAY NIGHT THROUGH TUESDAY. BROAD
TROUGHING ACROSS THE REGION TUESDAY NIGHT THROUGH WEDNESDAY WILL
PROVIDE ENOUGH INSTABILITY FOR A SLIGHT CHANCE TO CHANCE OF SNOW
SHOWERS THROUGH THE PERIOD WITH DRYING LATE WEDNESDAY NIGHT THROUGH
THURSDAY NIGHT AS THE TROUGH SHIFTS EAST OF THE REGION. BELOW
AVERAGE TEMPERATURES ARE EXPECTED MONDAY NIGHT AND TUESDAY UNDER THE
TROUGH WITH TEMPERATURES WARMING BACK TO NEAR AVERAGE LEVELS BY
THURSDAY. HOENISCH

FRIDAY AND SATURDAY...MODELS INDICATE A WESTERLY FLOW WITH PERIODIC
PACIFIC DISTURBANCES FLOWING THROUGH. A CHANCE FOR SCATTERED SNOW
SHOWERS FOR THE MOUNTAINS AND A SLIGHT CHANCE FOR ISOLATED SHOWERS
ON THE PLAINS. TEMPERATURES ARE EXPECTED TO BE NEAR NORMAL. SAUCIER

&&

.AVIATION...
UPDATED 0515Z.
A STRONG STORM SYSTEM WILL AFFECT THE REGION THROUGH SATURDAY
EVENING. SNOW OVER SOUTHWEST MONTANA WILL SPREAD INTO CENTRAL
AND NORTH CENTRAL MONTANA AFTER 06Z SATURDAY. WIDESPREAD MVFR AND
IFR CONDITIONS ARE ANTICIPATED DUE TO REDUCED VISIBILITIES AND
LOWERED CEILINGS AROUND SNOW...AND SIGNIFICANT MOUNTAIN
OBSCURATIONS ARE EXPECTED. SNOW WILL BECOME MORE SCATTERED OVER
CENTRAL AND SOUTHWEST MONTANA BY SATURDAY MORNING. FURTHER
NORTH...HOWEVER...A PERSISTENT BAND OF HEAVY SNOW IS EXPECTED TO
FORM OVER FAR NORTH CENTRAL MONTANA AFTER 11Z SATURDAY...AFFECTING
AREAS FROM KCTB TO KHVR. WHILE THIS BAND WILL RESULT IN AREAS OF
LIFR CONDITIONS...THE BAND MAY OSCILLATE AROUND THE INTERNATIONAL
BORDER...BRINGING TEMPORARY VISIBILITY AND CEILING IMPROVEMENTS
TO KCTB AND KHVR SATURDAY AFTERNOON. AFTER 00Z SUNDAY...THE BAND
OF SNOW WILL WEAKEN AND SLOWLY SINK SOUTHWARD...BRINGING LIGHT
SNOW TO KGTF AND KLWT. ALSO...A SURFACE TROUGH WILL STRENGTHEN AND
MOVE EASTWARD ACROSS MONTANA THROUGH SATURDAY. EXPECT
SOUTHEASTERLY WINDS SATURDAY MORNING TO BECOME SOUTHERLY THEN
WESTERLY ACROSS MUCH OF THE REGION...BUT WILL BECOME NORTHERLY AND
THEN WESTERLY AROUND KCTB AND KHVR. WIND GUSTS FROM 25 TO 35 KTS
WILL BE POSSIBLE SATURDAY AFTERNOON...WITH BLOWING SNOW A
CONCERN...ESPECIALLY AROUND KHVR. COHEN

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  33  13  35  14 /  80  30  20  30
CTB  31  11  30  12 / 100  20  30  40
HLN  37  17  38  21 /  30  20  20  30
BZN  38  13  37  19 /  40  20  10  50
WEY  29   0  30   9 /  70  40  20  50
DLN  34  13  34  18 /  20  10  10  60
HVR  33  12  34  13 / 100  20  10  30
LWT  32  13  33  12 /  60  60  20  40

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
WINTER WEATHER ADVISORY UNTIL 6 PM MDT THIS AFTERNOON FOR MTZ012-
013-049.

HEAVY SNOW WARNING UNTIL 6 PM MDT THIS AFTERNOON FOR MTZ009-010-
048.

WINTER WEATHER ADVISORY FROM 6 AM THIS MORNING TO 6 PM MDT THIS
AFTERNOON FOR MTZ050-051.

WINTER STORM WARNING UNTIL 6 PM MDT THIS AFTERNOON FOR MTZ011-
044>047.

&&

SHORT TERM...MPJ
LONG TERM...HOENISCH
AVIATION...COHEN

WEATHER.GOV/GREATFALLS

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE GREAT FALLS MT
317 PM MDT FRI MAR 28 2008

MTZ009>013-044>051-292130-
NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL-CASCADE-
CHOUTEAU-TOOLE-LIBERTY-EASTERN PONDERA-BLAINE-
SOUTHERN ROCKY MOUNTAIN FRONT-EASTERN TETON-JUDITH BASIN-FERGUS-
317 PM MDT FRI MAR 28 2008

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

A WINTER STORM WARNING IS IN EFFECT FOR THE NORTHERN ROCKIES FROM
THIS EVENING THROUGH SATURDAY. THE HEAVIEST SNOW IS EXPECTED TO
FALL BETWEEN MIDNIGHT AND NOON ON SATURDAY. TOTAL ACCUMULATIONS OF
4 TO 9 INCHES AT LOWER ELEVATIONS AND 8 TO 14 INCHES IN THE
MOUNTAINS ARE EXPECTED. AREAS OF BLOWING AND DRIFTING SNOW ARE
ALSO EXPECTED.

A HEAVY SNOW WARNING IS IN EFFECT FOR EASTERN GLACIER COUNTY FROM
THIS EVENING THROUGH SATURDAY. SNOW WILL SPREAD EAST DURING THE
NIGHT AND THE HEAVY SNOW WARNING WILL INCLUDE MOST PORTIONS OF
NORTH CENTRAL MONTANA AFTER MIDNIGHT. TOTAL SNOW ACCUMULATIONS OF
6 TO 10 INCHES ARE EXPECTED BY SATURDAY. LOCAL BLOWING AND
DRIFTING OF SNOW IS ALSO EXPECTED.

A WINTER WEATHER ADVISORY IS IN EFFECT FOR TETON...CHOTEAU...AND
CASCADE COUNTIES FROM MIDNIGHT TONIGHT THROUGH SATURDAY. TOTAL
SNOW ACCUMULATIONS OF 2 TO 6 INCHES ARE EXPECTED. AREAS OF BLOWING
AND DRIFTING SNOW ARE ALSO EXPECTED.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THE WINTER STORM AND HEAVY SNOW WARNINGS FOR NORTH CENTRAL MONTANA
WILL CONTINUE THROUGH SATURDAY AFTERNOON.

THE WINTER WEATHER ADVISORY FOR TETON...CHOUTEAU...AND CASCADE
COUNTIES CONTINUES THROUGH SATURDAY AFTERNOON.

.SPOTTER INFORMATION STATEMENT...

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

MTZ008-015-055-292130-
BEAVERHEAD-MADISON-GALLATIN-
317 PM MDT FRI MAR 28 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A SNOW AND BLOWING SNOW ADVISORY REMAINS IN EFFECT FROM 6 PM THIS
EVENING TO 6 AM MDT SATURDAY. TOTAL SNOW ACCUMULATIONS OF 1 TO 4
INCHES ARE EXPECTED IN THE VALLEYS...WITH 3 TO 7 INCHES IN THE
MOUNTAINS AND PASSES.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

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

MTZ014-052>054-292130-
CENTRAL AND SOUTHERN LEWIS AND CLARK-JEFFERSON-BROADWATER-MEAGHER-
317 PM MDT FRI MAR 28 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF SOUTHWEST
MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

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