Winter Storm in Montana, February 2 to 3, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREAT FALLS MT
448 PM MST FRI FEB 2 2007

UPDATED AVIATION DISCUSSION

.DISCUSSION...
TONIGHT THROUGH SUNDAY...PERSISTENT BAND OF SNOW EXTENDING FROM CUT
BANK TO JUST EAST OF GREAT FALLS TO LEWISTOWN CONTINUES TO PRODUCE
ACCUMULATING SNOW. BAND IS ASSOCIATED WITH UPPER JET OVER THE AREA
AS WELL AS A SURFACE BOUNDARY ACROSS CENTRAL MONTANA. UPPER JET VERY
SLOW TO MOVE EAST AND HAVE ADJUSTED POP GRIDS TO KEEP SNOW GOING
THROUGH THE EVENING. WILL ALSO EXTEND SNOW AND BLOWING SNOW ADVISORY
FOR CASCADE...JUDITH BASIN AND FERGUS COUNTIES THROUGH THIS EVENING.
CONDITIONS IMPROVE AFTER MIDNIGHT ALTHOUGH FLOW ALOFT REMAINS
NORTHERLY AND WEAK IMPULSES WILL CONTINUE TO MOVE WITH THE FLOW AND
PRODUCE AREAS OF LIGHT SNOW FROM TIME TO TIME. BY SUNDAY...NOSE OF
THE UPPER RIDGE OVER THE PACIFIC NORTHWEST PUSHES INTO WESTERN
MONTANA RESULTING IN A NORTHWEST FLOW ALOFT OVER THE AREA. MOISTURE
MOVING WITHIN THIS FLOW WILL SPREAD OVER THE AREA AND BRING A
CONTINUED CHANCE OF LIGHT SNOW. TEMPERATURES WILL CONTINUE TO WARM
SLOWLY THROUGH THE WEEKEND BUT REMAIN BELOW SEASONAL AVERAGES. EMANUEL

SUNDAY NIGHT THROUGH WEDNESDAY NIGHT...MODELS ARE IN GENERAL
AGREEMENT ON THE OVERALL UPPER LEVEL PATTERN DURING THE EXTENDED
FORECAST PERIOD ALLOWING THE UPPER LEVEL RIDGE ALONG THE WEST
COAST TO GRADUALLY MOVE INLAND WHILE THE CENTRAL/EASTERN NORTH
AMERICAN POLAR VORTEX SLOWLY FILLS AND WEAKENS. THIS PATTERN WILL
MAINTAIN COLD SURFACE HIGH PRESSURE OVER MUCH OF CENTRAL CANADA
AND THE NORTHERN PLAINS STATES WITH WARMING CONDITIONS WEST OF THE
CONTINENTAL DIVIDE. THIS WILL LEAD TO A VERY TRICKY FORECAST OVER
OUR REGION BETWEEN THESE TWO FEATURES AS A FRONTAL BOUNDARY WILL
BE DRAPED NW TO SE ACROSS THE STATE DIVIDING THE COLDER AIR TO THE
EAST FROM WARMER AIR TO THE WEST. SEVERAL DISTURBANCES WILL MOVE
THROUGH THE REGION IN NW FLOW ALOFT...CASING THE BOUNDARY TO
FLUCTUATE AND BRINGING PERIODS OF MAINLY LIGHT PRECIPITATION. AT
THIS POINT...FEEL THAT LOW LEVEL COLD AIR WILL LIKELY DAM UP
AGAINST THE MOUNTAINS...KEEPING COOLER AIR ON THE PLAINS FOR MUCH
OF THE PERIOD...HOWEVER A STRONGER DISTURBANCE ON MONDAY MAY
TEMPORARILY BRING A WARM-UP TO THE PLAINS THAT PERIOD. HAVE KEPT
BROADBRUSH SLIGHT CHANCE TO CHANCE POPS AND NEAR AVERAGE
TEMPERATURES OVER MUCH OF THE AREA THROUGH THE PERIOD AS THESE
FEATURES WILL BE HARD TO TIME AND THE POSITION OF THE FRONTAL
BOUNDARY WILL BE KEY TO PRECIPITATION LOCATION AND TEMPERATURES.
HOENISCH

THURSDAY THROUGH FRIDAY...MODELS NOT IN REAL GOOD AGREEMENT DURING
THIS PERIOD.  I WENT WITH A COMPROMISE SOLUTION OF AN UPPER LEVEL
RIDGE PERSISTING OVER THE PACIFIC NORTHWEST.  THIS IS A DIRTY RIDGE
WITH A SERIES OF DISTURBANCES MOVING THROUGH...IN A FAIRLY MOIST
NORTHWESTERLY FLOW ALOFT.  THIS IS EXPECTED TO RESULT IN MOSTLY
CLOUDY SKIES WITH A CHANCE OF SNOW OVER THE MOUNTAINS AND A SLIGHT
CHANCE OF SNOW FOR MOST OTHER AREAS.  TEMPERATURES SHOULD BE NEAR
SEASONAL AVERAGES ACROSS MUCH OF THE REGION.  EK

&&

.AVIATION...
UPDATED 2348Z.
STRONG NORTHERLY FLOW ALOFT WILL PERSIST OVER THE AREA THROUGH
SATURDAY AFTERNOON. STRONG UPPER LEVEL DYNAMICS DUE THE JET STREAM
OVERHEAD IS CAUSING AN AREA OF SNOW FROM KLWT TO JUST EAST OF KGTF
NORTHWEST THROUGH KCTB AND INTO SOUTHWEST ALBERTA. THE BAND OF SNOW
WILL SLOWLY SHIFT EAST OVERNIGHT AND DISSIPATE BY SATURDAY
AFTERNOON. VISIBILITY WILL RANGE FROM A 1/2 MILE TO 3 MILES IN THE
SNOW WITH CEILINGS AROUND 1000 TO 2500 FEET. OUTSIDE THE SNOW
BAND...VFR CONDITIONS ARE EXPECTED WITH CEILINGS AROUND 5000 FEET.
MEIER

&&

.PRELIMINARY POINT TEMPS/POPS...
GTF  10  26  12  31 /  70  10  10  20
CTB   8  25  10  28 /  50  10   0  10
HLN  -4  22   6  26 /  20  10  10  30
BZN   3  25   5  28 /  20  20  10  40
WEY -20  17 -15  21 /  40  20  30  40
DLN   2  27   8  32 /  10  10  10  30
HVR  -5  16   0  21 /  10  10  10  20
LWT  -2  22   3  25 /  70  20  20  20

&&

.TFX WATCHES/WARNINGS/ADVISORIES...
SNOW AND BLOWING SNOW ADVISORY UNTIL 9 PM MST THIS EVENING FOR
MTZ012-050-051.

&&

SHORT TERM...EMANUEL
LONG TERM...HOENISCH/EK
AVIATION...MEIER

WEATHER.GOV/GREATFALLS

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE GREAT FALLS MT
300 PM MST FRI FEB 2 2007

MTZ008>011-013>015-044>049-052>055-031715-
BEAVERHEAD-NORTHERN ROCKY MOUNTAIN FRONT-EASTERN GLACIER-HILL-
CHOUTEAU-CENTRAL AND SOUTHERN LEWIS AND
CLARK-MADISON-TOOLE-LIBERTY-EASTERN PONDERA-BLAINE-SOUTHERN ROCKY
MOUNTAIN FRONT-EASTERN TETON-JEFFERSON-BROADWATER-MEAGHER-GALLATIN-
300 PM MST FRI FEB 2 2007

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

MTZ012-050-051-031715-
CASCADE-JUDITH BASIN-FERGUS-
300 PM MST FRI FEB 2 2007

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF CENTRAL
MONTANA.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A SNOW AND BLOWING SNOW ADVISORY IS IN EFFECT THROUGH 9 PM MST THIS
EVENING FOR CASCADE...JUDITH BASIN...AND FERGUS COUNTIES.

.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.